有关混凝土的毕业生外文翻译
混凝土毕业设计外文翻译--保护,预防,修复,改造和升级
外文文献翻译Protection,prevention,repair,renovation and upgrading（摘自《Management of Deteriorating Concrete Structures》Chapter 7作者George Somerville ）7.1 IntroductionThe need to repair concrete structure is not new. Much of the early work involved making good via patch repairs and crack filling, for aesthetic and serviceability reasons[7.1]. As the concrete infrastructure of the mid-20th century matured, there was also a demand to strengthen or upgrade to meet changes in use or increase in loadings. The need to treat cases of corrosion emerged in the 1950s with post-war prefabricated reinforced concrete housing,and many of the references to Chapter 2 detail examples of corrosion in highway structures as the use of de-icing salts increased rapidly in the early 1960s.Reference[7.2] gives some details of this ,and reference [7.3] is a detailed review of the situation in the UK and France with regard to post-tesioned concrete bridges.As durability concerns became more widespread, and consequences of failure more critical, repair became a growth industry, and options available on the market increased significantly in term of principles and approaches, and the individual solutions within each basic approach. This taining over 200 short papers on all aspects of the problem.The literature is full of individual case studies, describing what has been physically done and giving some reasons for selecting a particular option; it is often diffcult to draw general conclusions from these. Such articles, which are also helpful since they provide website addressers,appear most frequently in concrete-related journals such as Concrete from the Concrete Society in the UK. In North America, the various journals of the American Concrete Institute (ACI) do a similar job, and focus on repair is provided by the International Concrete Repair Institute (ICRI),which publishs a bimonthly Bulletin, and whose website gives details of available publications in the USA; generally, these are either guidance documents, or complications of articles on particular topics.There are aslo guidance documents available on individual repair, protection and upgrading methods, which explain the principles involved and are strong on the “how to …” aspects of the problem. Some examples of these can be obtained from the ICRIwebsite for North America, and reference[7.4-7.9] are similar publications available from the Concrete Society in the UK. The Concrete Society portfolio is augmented by other reports on test methods and diagnosis,and on how to enhance durability in new constructions; Technical Report 61 [7.10] is an example of the latter, where much of the detailed information is transferable to the repair and renovation situation. The Concrete RepairAssocication in the UK also has a website.The above brief rewiew is intended to show that there is quite a lot of information available on repair and renovation methods and also to indicate the nature of that information. It can become dated quite quickly however, as the technology is improved and new techniques are introduced. Moreover,, the nature and format of the information make it difficult to compare the technical and economic merits of alternative approaches- essential information to the owner when making a choice. This situation is now changing, with serious attempts being made to develop a systematic scientific basis for classifying repair and renovation methods, supported by sound specification and test methods. The emergence of EN 1504 is a prime example of that, and will be referred to strongly in later sections of this chapter.The final major missing link from the data bases is the lack of indepth feedback on real performation in the field over relevant periods of time. How does this compare with claims and expectations? Again this is changing, as typified by Figures 2.13-2.16 ,taken from the paper by Tilly [7.11]. Tilly's paper comes from the activities of a European network CONREPNET, which has examined well over 100 case studies in some detail and, apart from providing field data, has forced on developing criteria to permit alterative options to be evaluated to a common base. This information will also be used extensively later in this chapter.Repair and renovation is a huge subject, deserving several books in its own right.This book is about assessment, management and maintenance, and repair is an integral part of that. The emphasis in this chapter is on how it fits into the overall scheme of things, in moving forward from the assessment phase to taking effective action in selecting optimum solutions. This approach leads to the following sequence of subsection.7.2 Performance requirements for repaired structures7.3 Classification of protection, repair,renovation and upgrading options7.4 Performance requirements for repair and remedial measures7.5 Engineering specifications7.6 Moving towards the selection process7.7 Performance of repairs in sevice7.8 Timing of an intervention7.9 Selection a repair option-general7.10 The role of EN 1504 in selection7.11 Selecting a repair option in practice7.12 Concluding remarks Appendix 7.1 and 7.2 Reference7.2 Performance requirements for repaired structuresIn simple terms, the performance requirements for repaired structures are no different from those for new construction. Structurally, the focus will be on the factors listed in Table 4.12. Progressive assessment will have led to a performance time graph, such as that in Figure 3.13, for all relevant Table 4.12 factors. This paints a picture of how the present condition relates both to the performance levels provided in the original design and to the owner's perception of what constitutes minimum acceptable performance, bearing in mind that much more is now known about the structure (the Table 6.2 issue).Complicating the situation is the fact different owners may wish to manage the rehabilitation process differently. Figure 3.3 shows two viable options emanating from the asset management procedures associated with bridge in the UK . The different strategies involved intervention on different timescales, and,most probably, different solutions. Some owners may also wish to take a conservative approach,involving early preventative measures. There are no definitive general rules here, but a need to be aware of what the options are , linked to confidence in their effectiveness.In moving forward, however, it is essential to be clear about the required performance levels. While the basic structural factors in Table 4.12 will remain, there are broader strategies issues involved, some non-technical,which will influence the course which individual owners may choose to follow. Different owners will have different strategic goals, depending, for example, on:•type of ownership – whether private or public sector;•changing statutory requirements;•the type of structure and its function;•future plans for the structure, independent of its current physicall state, due, say, to – a possible change in use;-- improved performance requirements arising from higher user expectations;-- increases in imposed loadings;• a greater emphasis on whole life costing, linked to budgetary plans;•s desire for improved sustainability.In a follow-up project to CONTECVET, a group of parters containing a high proportion of owners from Spain, Sweden and the UK, set out to establish a strategy for the maitenance and rehabilition of concrete structures. As part of this project, acronym REHABCON, a list of general performance requirements was developed. Table 7.1, taken from a REHABCON deliverable [7.12] ,givesdetails. While the majority of the requirements relate to the structure as a whole, some also relate to the selected rehabilitation option and to the renovation process itself.Table 7.1 General performance requirements for rehabilitated structures.Rehabcon [7.12]General performance requirements__________________________________________________________________ Structural safety Ultimate limit state design (same expectations as for newstructures)•Strength•Stability•Robustness•Fatigue•Fire resistance•Earthquake resistanceServiceability Serviceability limit state design (same expectations as fornew structures)•Deformation•Displacement•Vibrations•Watertightness•Slip resistance/roughness•Drainage•Visibility during inclement weather•Comfort/convenience to userOperation and function•Availability, functionability•Minimisation of downtime. While this is important for a rehabilitated structure, it is also important to minimise inconvenience to users during the rehabilitation action,i.e,low low impact on users during operation, maintenance and repair.Aesthetics•Inspectability•Colour•Texture of surface•Durability of aesthetics•Safe-lookingSustainabilityand environmentalfactors•Materials for rehabilitation works tobe sustainable, and environmentally friendlyduring•Manufacture•Construction works•Use•Damage•Demolition•Impact on recycling and reuse•Deposition•Acoustics, noise control•Energy consumption•Harmful effects, such as spillage, leakage, dust or the emission of toxic fumes, either spontaneously or due to situiations such as fire, both duringthe rehabilitation works and afterwardsHeath andSafety•Public safety•Health for humans and nature during all phases in the life-cycle•Evacuation, emergency escape routesDurability•Durability of the original structure and the rehabilitated parts of the structure. Dependability•Reliability of the repair methods•Maitainability•Maintenance supportabilityFlexibility•Ensure that it is possible to meet future requirementEconomy•Reduce or limit whole life costs•Operational costs•Maintenance, repair and rehabilitation costs•Improvement/strengthening costs•Demolition and deposition costs•User cost•Limit loss of income due to insufficient functionality etc Cultureheritage•Structure having cultural or historic value require special treatment保护，预防，修复，改造和升级（摘自《混凝土结构腐蚀恶化的管理》第7章作者乔治·萨默维尔）7.1简介混凝土结构需要修复对我们来说并不陌生。
外文翻译---混凝土,钢筋混凝土和预应力混凝土
Concrete, Reinforced Concrete, andPrestressedConcreteConcrete is a stone like material obtained by permitting a carefully proportioned mixture of cement, sand and gravel or other aggregate, and water to harden in forms of the shape and dimensions of the desired structure. The bulk of the material consists of fine and coarse aggregate. Cement and water interact chemically to bind the aggregate particles into a solid mass. Additional water, over and above that needed for this chemical reaction, is necessary to give the mixture workability that enables it to fill the forms and surround the embedded reinforcing steel prior to hardening. Concretes with a wide range of properties can be obtained by appropriates adjustment of the proportions of the constituent materials. Special cements, special aggregates, and special curing methods permit an even wider variety of properties to be obtained.These properties depend to a very substantial degree on the proportions of the mix, on the thoroughness with which the various constituents are intermixed, and on the conditions of humidity and temperature in which the mix is maintained from the moment it is placed in the forms of humidity and hardened. The process of controlling conditions after placement is known as curing. To protect against the unintentional production of substandard concrete, a high degree of skillful control and supervision is necessary throughout the process, from the proportioning by weight of the individual components, trough mixing and placing, until the completion of curing.The factors that make concrete a universal building material are so pronounced that it has been used, in more primitive kinds and ways than at present, for thousands of years, starting with lime mortars from 12,000 to 600 B.C. in Crete, Cyprus, Greece, and the Middle East. The facility with which , while plastic, it can be deposited and made to fill forms or molds of almost any practical shape is one of these factors. Its high fire and weather resistance are evident advantages. Most of the constituent materials, with the exception of cement and additives, are usually available at low cost locally or at small distances from the construction site. Its compressive strength, like that of natural stones, is high, which makes it suitable for members primarily subject to compression, such as columns and arches. On the other hand, again as in natural stones, it is a relatively brittle material whose tensile strength is small compared with its compressive strength. This prevents its economical use in structural members that ate subject to tension either entirely or over part of their cross sections.To offset this limitation, it was found possible, in the second half of thenineteenth century, to use steel with its high tensile strength to reinforce concrete, chiefly in those places where its low tensile strength would limit the carrying capacity of the member. The reinforcement, usually round steel rods with appropriate surface deformations to provide interlocking, is places in the forms in advance of the concrete. When completely surrounded by the hardened concrete mass, it forms an integral part of the member. The resulting combination of two materials, known as reinforced concrete, combines many of the advantages of each: the relatively low cost , good weather and fire resistance, good compressive strength, and excellent formability of concrete and the high tensile strength and much greater ductility and toughness of steel. It is this combination that allows the almost unlimited range of uses and possibilities of reinforced concrete in the construction of buildings, bridges, dams, tanks, reservoirs, and a host of other structures.In more recent times, it has been found possible to produce steels, at relatively low cost, whose yield strength is 3 to 4 times and more that of ordinary reinforcing steels. Likewise, it is possible to produce concrete 4 to 5 times as strong in compression as the more ordinary concrete. These high-strength materials offer many advantages, including smaller member cross sections, reduced dead load, and longer spans. However, there are limits to the strengths of the constituent materials beyond which certain problems arise. To be sure, the strength of such a member would increase roughly in proportion to those of the materials. However, the high strains that result from the high stresses that would otherwise be permissible would lead to large deformations and consequently large deflections of such member under ordinary loading conditions. Equally important, the large strains in such high-strength reinforcing steel would induce large cracks in the surrounding low tensile strength concrete, cracks that would not only be unsightly but that could significantly reduce the durability of the structure. This limits the useful yield strength of high-strength reinforcing steel to 80 ksi according to many codes and specifications; 60 ksi steel is most commonly used.A special way has been found, however, to use steels and concrete of very high strength in combination. This type of construction is known as prestressed concrete. The steel, in the form of wires, strands, or bars, is embedded in the concrete under high tension that is held in equilibrium by compressive stresses in the concrete after hardening, Because of this precompression, the concrete in a flexural member will crack on the tension side at a much larger load than when not so precompressed. Prestressing greatly reduces both the deflections and the tensile cracks at ordinaryloads in such structures, and thereby enables these high-strength materials to be used effectively. Prestressed concrete has extended, to a very significant extent, the range of spans of structural concrete and the types of structures for which it is suited.混凝土，钢筋混凝土和预应力混凝土混凝土是一种经过水泥，沙子和砂砾或其他材料聚合得到经过细致配比的混合物，在液体变硬使材料石化后可以得到理想的形状和结构尺寸。
混凝土工艺中英文对照外文翻译文献
混凝土工艺中英文对照外文翻译文献混凝土工艺中英文对照外文翻译文献混凝土工艺中英文对照外文翻译文献(文档含英文原文和中文翻译) Concrete technology and developmentPortland cement concrete has clearly emerged as the material of choice for the construction of a large number and variety of structures in the world today. This is attributed mainly to low cost of materials and construction for concrete structures as well as low cost of maintenance.Therefore, it is not surprising that many advancements in concrete technology have occurred as a result of two driving forces, namely the speed of construction and the durability of concrete.During the period 1940-1970, the availability of high early strength portland cements enabled the use of high water content in concrete mixtures that were easy to handle. This approach, however, led to serious problems with durability of structures, especially those subjected to severe environmental exposures.With us lightweight concrete is a development mainly of the last twenty years.Concrete technology is the making of plentiful good concrete cheaply. It includes the correct choice of the cement and the water, and the right treatment of the aggregates. Those which are dug near by and therefore cheap, must be sized, washed free of clay or silt, and recombined in the correct proportions so as to make a cheap concrete which is workable at a low water/cement ratio, thus easily comoacted to a high density and therefore strong.It hardens with age and the process of hardening continues for a long time after the concrete has attained sufficient strength.Abrams’law, perhaps the oldest law of concrete technology, states that the strength of a concrete varies inversely with its water cement ratio. This means that the sand content (particularly the fine sand which needs much water) must be reduced so far as possible. The fact that the sand “drinks” large quantities of water can easily be established by mixing several batches of x kg of cement with y kg of stone and the same amount of water but increasing amounts of sand. However if there is no sand the concrete will be so stiff that it will be unworkable thereforw porous and weak. The same will be true if the sand is too coarse. Therefore for each set of aggregates, the correct mix must not be changed without good reason. This applied particularly to the water content.Any drinkable and many undrinkable waters can be used for making concrete, including most clear waters from the sea or rivers. It is important that clay should be kept out of the concrete. The cement if fresh can usually be chosen on the basis of the maker’s certificates of tensile or crushing tests, but these are always made with fresh cement. Where strength is important , and the cement at the site is old, it should be tested.This stress , causing breakage,will be a tension since concretes are from 9 to 11times as strong in compression as in tension, This stress, the modulus of rupture, will be roughly double the direct tensile breaking stress obtained in a tensile testing machine,so a very rough guess at the conpressive strength can be made by multiplying the modulus of rupture by 4.5. The method can be used in combination with the strength results of machine-crushed cubes or cylinders or tensile test pieces but cannot otherwise be regarded as reliable. With these comparisons,however, it is suitable for comparing concretes on the same site made from the same aggregates and cement, with beams cast and tested in the same way.Extreme care is necessary for preparation,transport,plating and finish of concrete in construction works.It is important to note that only a bit of care and supervision make a great difference between good and bad concrete.The following factors may be kept in mind in concreting works.MixingThe mixing of ingredients shall be done in a mixer as specified in the contract.Handling and ConveyingThe handling&conveying of concrete from the mixer to the place of final deposit shall be done as rapidly as practicable and without any objectionable separation or loss of ingredients.Whenever the length of haul from the mixing plant to the place of deposit is such that the concrete unduly compacts or segregates,suitable agitators shall be installed in the conveying system.Where concrete is being conveyed on chutes or on belts,the free fall or drop shall be limited to 5ft.(or 150cm.) unless otherwise permitted.The concrete shall be placed in position within 30 minutes of its removal from the mixer.Placing ConcreteNo concrete shall be placed until the place of deposit has been thoroughly inspected and approved,all reinforcement,inserts and embedded metal properly security in position and checked,and forms thoroughly wetted(expect in freezing weather)or oiled.Placing shall be continued without avoidable interruption while the section is completed or satisfactory construction joint made.Within FormsConcrete shall be systematically deposited in shallow layers and at such rate as to maintain,until the completion of the unit,a plastic surface approximately horizontal throughout.Each layer shall be thoroughly compacted before placing the succeeding layer.CompactingMethod. Concrete shall be thoroughly compacted by means of suitable tools during and immediately after depositing.The concrete shall be worked around all reinforcement,embedded fixtures,and into the comers of the forms.Every precaution shall be taken to keep the reinforcement and embedded metal in proper position and to prevent distortion.Vibrating. Wherever practicable,concrete shall be internally vibrated within the forms,or in the mass,in order to increase the plasticity as to compact effectively to improve the surface texture and appearance,and to facilitate placing of the concrete.Vibration shall be continued the entire batch melts to a uniform appearance and the surface just starts to glisten.A minute film of cement paste shall be discernible between the concrete and the form and around the reinforcement.Over vibration causing segregation,unnecessary bleeding or formation of laitance shall be avoided.The effect spent on careful grading, mixing and compaction of concrete will be largely wasted if the concrete is badly cured. Curing means keeping the concretethoroughly damp for some time, usually a week, until it has reached the desired strength. So long as concrete is kept wet it will continue to gain strength, though more slowly as it grows older.Admixtures or additives to concrete are materials arematerials which are added to it or to the cement so as to improve one or more of the properties of the concrete. The main types are:1. Accelerators of set or hardening,2. Retarders of set or hardening,3. Air-entraining agents, including frothing or foaming agents,4. Gassing agents,5. Pozzolanas, blast-furnace slag cement, pulverized coal ash,6. Inhibitors of the chemical reaction between cement and aggregate, which might cause the aggregate to expand7. Agents for damp-proofing a concrete or reducing its permeability to water,8. Workability agents, often called plasticizers,9. Grouting agents and expanding cements.Wherever possible, admixtures should be avouded, particularly those that are added on site. Small variations in the quantity added may greatly affect the concrete properties in an undesiraale way. An accelerator can often be avoided by using a rapid-hardening cement or a richer mix with ordinary cement, or for very rapid gain of strength, high-alumina cement, though this is very much more expensive, in Britain about three times as costly as ordinary Portland cement. But in twenty-four hours its strength is equal to that reached with ordinary Portland cement in thirty days.A retarder may have to be used in warm weather when a large quantity of concrete has to be cast in one piece of formwork, and it is important that the concrete cast early in the day does not set before the last concrete. This occurs with bridges when they are cast in place, and the formwork necessarily bends underthe heavy load of the wet concrete. Some retarders permanently weaken the concrete and should not be used without good technical advice.A somewhat similar effect,milder than that of retarders, is obtained with low-heat cement. These may be sold by the cement maker or mixed by the civil engineering contractor. They give out less heat on setting and hardening, partly because they harden more slowly, and they are used in large casts such as gravity dams, where the concrete may take years to cool down to the temperature of the surrounding air. In countries like Britain or France, where pulverized coal is burnt in the power stations, the ash, which is very fine, has been mixed with cement to reduce its production of heat and its cost without reducing its long-term strength. Up to about 20 per cent ash by weight of the cement has been successfully used, with considerable savings in cement costs.In countries where air-entraining cement cement can be bought from the cement maker, no air-entraining agent needs to be mixed in .When air-entraining agents draw into the wet cement and concrete some 3-8 percent of air in the form of very small bubbles, they plasticize the concrete, making it more easily workable and therefore enable the water |cement ratio to be reduced. They reduce the strength of the concrete slightly but so little that in the United States their use is now standard practice in road-building where heavy frost occur. They greatly improve the frost resistance of the concrete.Pozzolane is a volcanic ash found near the Italian town of Puzzuoli, which is a natural cement. The name has been given to all natural mineral cements, as well as to the ash from coal or the slag from blast furnaces, both of which may become cementswhen ground and mixed with water. Pozzolanas of either the industrial or the mineral type are important to civil engineers because they have been added to oridinary Portland cement in proportions up to about 20 percent without loss of strength in the cement and with great savings in cement cost. Their main interest is in large dams, where they may reduce the heat given out by the cement during hardening. Some pozzolanas have been known to prevent the action between cement and certain aggregates which causes the aggregate to expand, and weaken or burst the concrete.The best way of waterproof a concrete is to reduce its permeability by careful mix design and manufacture of the concrete, with correct placing and tighr compaction in strong formwork ar a low water|cement ratio. Even an air-entraining agent can be used because the minute pores are discontinuous. Slow, careful curing of the concrete improves the hydration of the cement, which helps to block the capillary passages through the concrete mass. An asphalt or other waterproofing means the waterproofing of concrete by any method concerned with the quality of the concrete but not by a waterproof skin.Workability agents, water-reducing agents and plasticizers are three names for the same thing, mentioned under air-entraining agents. Their use can sometimes be avoided by adding more cement or fine sand, or even water, but of course only with great care.The rapid growth from 1945 onwards in the prestressing of concrete shows that there was a real need for this high-quality structural material. The quality must be high because the worst conditions of loading normally occur at the beginning of the life of the member, at the transfer of stress from the steel to theconcrete. Failure is therefore more likely then than later, when the concrete has become stronger and the stress in the steel has decreased because of creep in the steel and concrete, and shrinkage of the concrete. Faulty members are therefore observed and thrown out early, before they enter the structure, or at least before it The main advantages of prestressed concrete in comparison with reinforced concrete are :①The whole concrete cross-section resists load. In reinforced concrete about half the section, the cracked area below the neutral axis, does no useful work. Working deflections are smaller.②High working stresses are possible. In reinforced concrete they are not usually possible because they result in severe cracking which is always ugly and may be dangerous if it causes rusting of the steel.③Cracking is almost completely avoided in prestressed concrete.The main disadvantage of prestressed concrete is that much more care is needed to make it than reinforced concrete and it is therefore more expensive, but because it is of higher quality less of it needs to be needs to be used. It can therefore happen that a solution of a structural problem may be cheaper in prestressed concrete than in reinforced concrete, and it does often happen that a solution is possible with prestressing but impossible without it.Prestressing of the concrete means that it is placed under compression before it carries any working load. This means that the section can be designed so that it takes no tension or very little under the full design load. It therefore has theoretically no cracks and in practice very few. The prestress is usually applied by tensioning the steel before the concrete in which it isembedded has hardened. After the concrete has hardened enough to take the stress from the steel to the concrete. In a bridge with abutments able to resist thrust, the prestress can be applied without steel in the concrete. It is applied by jacks forcing the bridge inwards from the abutments. This methods has the advantage that the jacking force, or prestress, can be varied during the life of the structure as required.In the ten years from 1950 to 1960 prestressed concrete ceased to be an experinmental material and engineers won confidence in its use. With this confidence came an increase in the use of precast prestressed concrete particularly for long-span floors or the decks of motorways. Whereever the quantity to be made was large enough, for example in a motorway bridge 500 m kong , provided that most of the spans could be made the same and not much longer than 18m, it became economical to usefactory-precast prestressed beams, at least in industrial areas near a precasting factory prestressed beams, at least in industrial areas near a precasting factory. Most of these beams are heat-cured so as to free the forms quickly for re-use.In this period also, in the United States, precast prestressed roof beams and floor beams were used in many school buildings, occasionally 32 m long or more. Such long beams over a single span could not possibly be successful in reinforced concrete unless they were cast on site because they would have to be much deeper and much heavier than prestressed concrete beams. They would certainlly be less pleasing to the eye and often more expensive than the prestressed concrete beams. These school buildings have a strong, simple architectural appeal and will be a pleasure to look at for many years.The most important parts of a precast prestressed concrete beam are the tendons and the concrete. The tendons, as the name implies, are the cables, rods or wires of steel which are under tension in the concrete.Before the concrete has hardened (before transfer of stress), the tendons are either unstressed (post-tensioned prestressing) or are stressed and held by abutments outside the concrete ( pre-tensioned prestressing). While the concrete is hardening it grips each tendon more and more tightly by bond along its full length. End anchorages consisting of plates or blocks are placed on the ends of the tendons of post-tensioned prestressed units, and such tendons are stressed up at the time of transfer, when the concrete has hardened sufficiently. In the other type of pretressing, with pre-tensioned tendons, the tendons are released from external abutments at the moment of transfer, and act on the concrete through bond or archorage or both, shortening it by compression, and themselves also shortening and losing some tension.Further shortening of the concrete (and therefore of the steel) takes place with time. The concrete is said to creep. This means that it shortens permanently under load and spreads the stresses more uniformly and thus more safely across its section. Steel also creeps, but rather less. The result of these two effects ( and of the concrete shrinking when it dries ) is that prestressed concrete beams are never more highly stressed than at the moment of transfer.The factory precasting of long prestressed concrete beams is likely to become more and more popular in the future, but one difficulty will be road transport. As the length of the beam increases, the lorry becomes less and less manoeuvrable untileventually the only suitable time for it to travel is in the middle of the night when traffic in the district and the route, whether the roads are straight or curved. Precasting at the site avoids these difficulties; it may be expensive, but it has often been used for large bridge beams.混凝土工艺及发展波特兰水泥混凝土在当今世界已成为建造数量繁多、种类复杂结构的首选材料。
预应力混凝土Prestressed-Concrete大学毕业论文外文文献翻译及原文
毕业设计（论文）外文文献翻译文献、资料中文题目：预应力混凝土文献、资料英文题目：Prestressed Concrete文献、资料来源：文献、资料发表（出版）日期：院（部）：专业：班级：姓名：学号：指导教师：翻译日期： 2017.02.14毕业设计（论文）外文资料翻译外文出处：The Concrete structure附件：1、外文原文；2、外文资料翻译译文。
1、外文资料原文Prestressed ConcreteConcrete is strong in compression, but weak in tension: Its tensile strength varies from 8 to 14 percent of its compressive strength. Due tosuch a Iow tensile capacity, fiexural cracks develop at early stages ofloading. In order to reduce or prevent such cracks from developing, aconcentric or eccentric force is imposed in the longitudinal direction of the structural element. This force prevents the cracks from developing by eliminating or considerably reducing the tensile stresses at thecritical midspan and support sections at service load, thereby raising the bending, shear, and torsional capacities of the sections. The sections are then able to behave elastically, and almost the full capacity of the concrete in compression can be efficiently utilized across the entire depth of the concrete sections when all loads act on the structure.Such an imposed longitudinal force is called a prestressing force,i.e., a compressive force that prestresses the sections along the span ofthe structural elementprior to the application of the transverse gravitydead and live loads or transient horizontal live loads. The type ofprestressing force involved, together with its magnitude, are determined mainly on the basis of the type of system to be constructed and the span length and slenderness desired.~ Since the prestressing force is applied longitudinally along or parallel to the axis of the member, the prestressing principle involved is commonly known as linear prestressing.Circular prestressing, used in liquid containment tanks, pipes,and pressure reactor vessels, essentially follows the same basic principles as does linear prestressing. The circumferential hoop, or "hugging" stress on the cylindrical or spherical structure, neutralizes the tensile stresses at the outer fibers of the curvilinear surface caused by the internal contained pressure.Figure 1.2.1 illustrates, in a basic fashion, the prestressing action in both types of structural systems and the resulting stress response. In(a), the individual concrete blocks act together as a beam due to the large compressive prestressing force P. Although it might appear that the blocks will slip and vertically simulate shear slip failure, in fact they will not because of the longitudinal force P. Similarly, the wooden staves in (c) might appear to be capable of separating as a result of the high internal radial pressure exerted on them. But again, because of the compressive prestress imposed by the metal bands as a form of circular prestressing, they will remain in place.From the preceding discussion, it is plain that permanent stresses in the prestressed structural member are created before the full dead and live loads are applied in order to eliminate or considerably reduce the net tensile stresses caused by these loads. With reinforced concrete,it is assumed that the tensile strength of the concrete is negligible and disregarded. This is because the tensile forces resulting from the bending moments are resisted bythe bond created in the reinforcement process. Cracking and deflection are therefore essentially irrecoverable in reinforced concrete once the member has reached its limit state at service load.The reinforcement in the reinforced concrete member does not exert any force of its own on the member, contrary to the action of prestressing steel. The steel required to produce the prestressing force in the prestressed member actively preloads the member, permitting a relatively high controlled recovery of cracking and deflection. Once the flexural tensile strength of the concrete is exceeded, the prestressed member starts to act like a reinforced concrete element.Prestressed members are shallower in depth than their reinforced concrete counterparts for the same span and loading conditions. In general, the depth of a prestressed concrete member is usually about 65 to 80 percent of the depth of the equivalent reinforced concrete member. Hence, the prestressed member requires less concrete, and,about 20 to 35 percent of the amount of reinforcement. Unfortunately, this saving in material weight is balanced by the higher cost of the higher quality materials needed in prestressing. Also, regardless of the system used, prestressing operations themselves result in an added cost: Formwork is more complex, since the geometry of prestressed sections is usually composed of. flanged sections with thin-webs.In spite of these additional costs, if a large enough number of precast units are manufactured, the difference between at least the initial costs of prestressed and reinforced concrete systems is usually not very large.~ And the indirect long-term savings are quite substantial, because less maintenance is needed; a longer working life is possible due to better quality control of the concrete, and lighter foundations are achieved due to the smaller cumulative weight of the superstructure.Once the beam span of reinforced concrete exceeds 70 to 90 feet (21.3 to 27.4m), the dead weight of the beam becomes excessive, resulting in heavier members and, consequently, greater long-term deflection and cracking. Thus, for larger spans, prestressed concrete becomes mandatory since arches are expensive to construct and do not perform as well due to the severe long-term shrinkage and creep they undergo.~ Very large spans such as segmental bridges or cable-stayed bridges can only be constructed through the use of prestressing.Prestressd concrete is not a new concept, dating back to 1872, when P. H. Jackson, an engineer from California, patented a prestressing system that used a tie rod to construct beams or arches from individual blocks [see Figure 1.2.1 (a)]. After a long lapse of time during which little progress was made because of the unavailability of high-strength steel to overcome prestress losses, R. E. Dill of Alexandria, Nebraska, recognized the effect of the shrinkage and creep (transverse material flow) of concrete on the loss of prestress. He subsequently developed the idea that successive post-tensioning of unbonded rods would compensate for the time-dependent loss of stress in the rods due to the decrease in the length of the member because of creep and shrinkage. In the early 1920s,W. H. Hewett of Minneapolis developed the principles of circular prestressing. He hoop-stressed horizontal reinforcement around walls of concrete tanks through the use of turnbuckles to prevent cracking due to internalliquid pressure, thereby achieving watertightness. Thereafter, prestressing of tanks and pipes developed at an accelerated pace in the United States, with thousands of tanks for water, liquid, and gas storage built and much mileage of prestressed pressure pipe laid in the two to three decades that followed.Linear prestressing continued to develop in Europe and in France, in particular through the ingenuity of Eugene Freyssinet, who proposed in 1926--1928 methods to overcome prestress losses through the use of high-strength and high-ductility steels. In 1940, he introduced thenow well-known and well-accepted Freyssinet system.P. W. Abeles of England introduced and developed the concept of partial prestressing between the 1930s and 1960s. F. Leonhardt of Germany, V. Mikhailov of Russia, and T. Y. Lin of the United States also contributed a great deal to the art and science of the design of prestressed concrete. Lin's load-balancing method deserves particular mention in this regard, as it considerably simplified the design process, particularly in continuous structures. These twentieth-century developments have led to the extensive use of prestressing throughoutthe world, and in the United States in particular.Today, prestressed concrete is used in buildings, underground structures, TV towers, floating storage and offshore structures, power stations, nuclear reactor vessels, and numerous types of bridge systems including segn~ental and cable-stayed bridges, they demonstrate the versatility of the prestressing concept and its all-encompassing application. The success in the development and construction of all these structures has been due in no small measures to the advances in the technology of materials, particularly prestressing steel, and the accumulated knowledge in estimating the short-and long-term losses in the prestressing forces.~2、外文资料翻译译文预应力混凝土混凝土的力学特性是抗压不抗拉：它的抗拉强度是抗压强度的8％一14％。
钢筋混凝土中英文对照外文翻译文献
中英文资料对照外文翻译目录1 中文翻译 (1)1.1钢筋混凝土 (1)1.2土方工程 (2)1.3结构的安全度 (3)2 外文翻译 (6)2.1 Reinforced Concrete (6)2.2 Earthwork (7)2.3 Safety of Structures (9)1 中文翻译1.1钢筋混凝土素混凝土是由水泥、水、细骨料、粗骨料（碎石或；卵石）、空气，通常还有其他外加剂等经过凝固硬化而成。
将可塑的混凝土拌合物注入到模板内，并将其捣实，然后进行养护，以加速水泥与水的水化反应，最后获得硬化的混凝土。
其最终制成品具有较高的抗压强度和较低的抗拉强度。
其抗拉强度约为抗压强度的十分之一。
因此，截面的受拉区必须配置抗拉钢筋和抗剪钢筋以增加钢筋混凝土构件中较弱的受拉区的强度。
由于钢筋混凝土截面在均质性上与标准的木材或钢的截面存在着差异，因此，需要对结构设计的基本原理进行修改。
将钢筋混凝土这种非均质截面的两种组成部分按一定比例适当布置，可以最好的利用这两种材料。
这一要求是可以达到的。
因混凝土由配料搅拌成湿拌合物，经过振捣并凝固硬化，可以做成任何一种需要的形状。
如果拌制混凝土的各种材料配合比恰当，则混凝土制成品的强度较高，经久耐用，配置钢筋后，可以作为任何结构体系的主要构件。
浇筑混凝土所需要的技术取决于即将浇筑的构件类型，诸如：柱、梁、墙、板、基础，大体积混凝土水坝或者继续延长已浇筑完毕并且已经凝固的混凝土等。
对于梁、柱、墙等构件，当模板清理干净后应该在其上涂油，钢筋表面的锈及其他有害物质也应该被清除干净。
浇筑基础前，应将坑底土夯实并用水浸湿6英寸，以免土壤从新浇的混凝土中吸收水分。
一般情况下，除使用混凝土泵浇筑外，混凝土都应在水平方向分层浇筑，并使用插入式或表面式高频电动振捣器捣实。
必须记住，过分的振捣将导致骨料离析和混凝土泌浆等现象，因而是有害的。
水泥的水化作用发生在有水分存在，而且气温在50°F以上的条件下。
桥梁工程本科毕业设计外文翻译---混凝土桥梁的结构形式
本科毕业设计外文翻译混凝土桥梁的结构形式院（系、部）名称：专业名称：学生姓名：学生学号：指导教师：The Structure of Concrete BridgePre-stressed concrete has proved to be technically advantageous, economically competitive, and esthetically superior bridges, from very short span structures using standard components to cable-stayed girders and continuous box girders with clear spans of nearly 100aft .Nearly all concrete bridges, even those of relatively short span, are now pre-stressed. Pre-casting, cast-in-place construction, or a combination of the two methods may be used .Both pre-tensioning and post tensioning are employed, often on the same project.In the United States, highway bridges generally must-meet loading ,design ,and construction requirements of the AASHTO Specification .Design requirements for pedestrian crossings and bridges serving other purposes may be established by local or regional codes and specifications .ACI Code provisions are often incorporated by reference .Bridges spans to about 100ft often consist of pre-cast integral-deck units ,which offer low initial cost ,minimum ,maintenance ,and fast easy construction ,with minimum traffic interruption .Such girders are generally pre-tensioned .The units are placed side by side ,and are often post-tensioned laterally at intermediate diaphragm locations ,after which shear keys between adjacent units are filled with non-shrinking mortar .For highway spans ,an asphalt wearing surface may be applied directly to the top of the pre-cast concrete .In some cases ,a cast-in-place slab is placed to provide composite action .The voided slabs are commonly available in depths from 15 to 21 in .and widths of 3 to 4 ft .For a standard highway HS20 loading, they are suitable for spans to about 50 ft, Standard channel sections are available in depths from 21 to 35 in a variety of widths, and are used for spans between about 20 and 60 ft .The hollow box beams-and single-tee girders are intended for longer spans up to about 100 ft.For medium-span highway bridges ,to about 120 ft ,AASHTO standard I beams are generally used .They are intended for use with a composite cast-in-place roadway slab .Such girders often combine pre-tensioning of the pre-cast member with post-tensioning of the composite beam after the deck is placed .In an effort to obtain improved economy ,some states have adopted more refined designs ,such as the State of Washington standard girders.The specially designed pre-cast girders may be used to carry a monorail transit system .The finished guide way of Walt Disney World Monorail features a series of segments, each consisting of six simply supported pre-tensioned beams ,together to from a continuous structure .Typical spans are 100 to 110 ft . Approximately half of the 337 beams used have some combination of vertical and horizontal curvatures and variable super elevation .Allbeams are hollow, a feature achieved by inserting a styro-foam void in the curved beams and by a moving mandrel in straight beam production.Pre-cast girders may not be used for spans much in excess of 120 ft because of the problems of transporting and erecting large, heavy units.On the other hand ,there is a clear trend toward the use of longer spans for bridges .For elevated urban expressways ,long spans facilitate access and minimize obstruction to activities below .Concern for environmental damage has led to the choice of long spans for continuous viaducts . For river crossings, intermediate piers may be impossible because of requirements of navigational clearance.In typical construction of this type, piers are cast-in-place, often using the slip-forming technique .A “hammerhead” section of box girder is often cast at the top of the pier, and construction proceeds in each direction by the balanced cantilever method. Finally, after the closing cast-in-place joint is made at mid-span, the structure is further post-tensioned for full continuity .Shear keys may be used on the vertical faces between segments, and pre-cast are glued with epoxy resin.The imaginative engineering demonstrated by many special techniques has extended the range of concrete construction for bridges far beyond anything that could be conceived just a few years ago .In the United States, twin curved cast-in –place segmental box girders have recently been completed for of span of 310 ft over the Eel River in northern California .Preliminary design has been completed for twin continuous box girders consisting of central 550 ft spans flanked by 390 ft side spans.Another form of pre-stressed concrete bridge well suited to long spans is the cable-stayed box girder .A notable example is the Chaco-Corrientes Bridge in Argentina .The bridges main span of 804 ft is supported by two A-frame towers, with cable stays stretching from tower tops to points along the deck .The deck itself consists of two parallel box girders made of pre-cast sections erected using the cantilever method .The tensioned cables not only provide a vertical reaction component to support the deck ,but also introduce horizontal compression to the box girders ,adding to the post-tensioning force in those members .Stress-ribbon Bridge pioneered many years ago by the German engineer Ulrich Finsterwalder. The stress-ribbon bridge carries a pipeline and pedestrians over the Rhine River with a span of 446 ft .The superstructure erection sequence was to (a) erect two pairs of cables, (b) place pre-cast slabs forming a sidewalk deck and a U under each of the sets of cables, and (c) cast-in-place concrete within the two Us. The pipeline is placed atop supports at railing height, off to one side, which greatly increases the wind speed of the structure.It is appropriate in discussing bridge forms to mention structural esthetics .The time ispast when structures could be designed on the basis of minimum cost and technical advantages alone .Bridge structures in particular are exposed for all to see .To produce a structure that is visually offensive ,as has occurred all too often in the past, is an act professional irresponsibility .Particularly for major spans ,but also for more ordinary structures ,architectural advice should be sought early in conceptual stage of the design process.混凝土梁桥的结构形式事实证明，预应力混凝土结构是在技术上先进、经济上有竞争力、符合审美学的一种先进技术。
毕业论文外文翻译-混凝土的耐久性
Durability of concreteBesides its ability to sustain loads, concrete is also required to be durable .The durability of concrete can be defined as its resistance to deterioration resulting from external and internal causes. The external causes include the effects of environmental and service conditions to which concrete is subjected, such as weathering, particularly chlorides and sulphates, in the constituent materials, interaction between the constituent materials, such as alkali-aggregate reaction, volume changes, absorption and permeability.In order to produce a durable concrete, care should be taken to select suitable constituent materials. It is also important that mix contains adequate quantities of materials in proportions suitable for producing a homogeneous and fully compacted concrete mass.WeatheringDeterioration of concrete by weathering is usually brought about by the disruptive action of alternate freezing and thawing of free water within the concrete and expansion and contraction of the concrete, under restraint, resulting from variations in temperature and alternate wetting and drying.Damage to concrete from freezing and thawing arises from the expansion of pore water during freezing; in a condition of restraint, if repeated a sufficient number of times, this results in the development of hydraulic pressure capable of disrupting concrete. Road Krebs and slabs, dams and reservoirs are very susceptible are very susceptible to frost action.The resistance of concrete to freezing and thawing can be improved by increasing its impermeability. This can be achieved by using a mix with the lowest possible water-cement ratio compatible with sufficient workability for placing and compacting into a homogeneous mass. Durability can be further improved by using air entrainment, an air content of 3 to 6 per cent of the volume of concrete normally being adequate for most applications. The use of air entrained concrete is particularly useful for roads where salts are used for deicing.Chemical Attackin general, concrete has a low resistance to chemical attack.There are several chemical agents which react with concrete but the most common forms of attack are those associated with leaching, carbonation, chlorides and sulphates. Chemical agents essentially react with certain compounds of the hardened cement paste and the resistance of concrete to chemical attack therefore can be affected by the type of cement used. The resistance to chemical attack improves with increased impermeability.WearThe main causes of wear of concrete are the cavitation effects of fast-moving water, abrasive material in water, wind blasting and attrition and impact of traffic. Certain conditions of hydraulic flow result in the formation of cavities between the flowing water and the concrete surface .These cavities are usually filled with water vapor charged with extraordinarily high energy and repeated contact with the concrete surface results in the formation of pits and holes, Known an cavitation erosion. Since even a good-quality concrete will not be able to resist this kind of deterioration, the best remedy is therefore the elimination of cavitation by producing smooth hydraulic flow. Wherenecessary, the critical areas may be lined with materials having greater resistance to cavitation erosion.In general, the resistance of concrete to erosion and abrasion increases with increase in strength. The use of a hard and tough aggregate tends to improve concrete resistance to wear.Alkali-Aggregate ReactionsCertain natural aggregates react chemically with the alkalis present in Portland cement. When this happens these aggregates expand or swell resulting in cracking and disintegration of concrete.Volume ChangesPrincipal factors responsible for volume changes are the chemical combination of water and cement and the subsequent drying of concrete, variations in temperature and alternate wetting and drying. When a change in volume is resisted by internal or external forces this can produce cracking, The greater the imposed restraint, the more severe the cracking. The presence of cracks in concrete reduces its resistance to the action of leaching, corrosion of reinforcement, attack by sulphates and other chemicals, alkali-aggregate reaction and freezing and thawing, all of which may lead to disruption of concrete. Severe cracking can lead to complete disintegration of the concrete surface particularly when this is accompanied by alternate expansion and contraction.V olume changes can be minimized by using suitable constituent materials and mix proportions having due regard to the size of structure. Adequate moist curing is also essential to minimize the effects of any volume changes.Permeability and AbsorptionPermeability refers to the ease with which water can pass through the concrete. This should not be confused with the absorption property of concrete and the two are not necessarily related. Absorption may be defined as the ability of concrete to draw water into its voids. Low permeability is an important requirement for hydraulic structures and in some cases water tightness of concrete may be considered to be more significant than strength although, other conditions being equal, concrete of low permeability will also be strong and durable. A concrete which readily absorbs water is susceptible to deterioration. Concrete is inherently a porous material. This arises from the use of water in excess of that required for the purpose of hydration in order to make the mix sufficiently workable and the difficulty of completely removing all the air from the concrete during compaction. If the voids are interconnected concrete becomes pervious although with normal care concrete is sufficiently impermeable for most purposes. Concrete of low permeability can be obtained by suitable selection of its constituent materials and their proportions followed by careful placing, compaction and curing. In general for a fully compacted concrete, the permeability decreases with decreasing water-cement ratio. Permeability is affected by both the fineness and the chemical composition of cement. Aggregates of low porosity are preferable when concrete with a low permeability is required. Segregation of the constituent materials during placing can adversely affect the impermeability of concrete.混凝土的耐久性混凝土除了承受荷载之外，还需要有一定的耐久性。
土木工程专业钢筋混凝土结构设计毕业论文外文文献翻译及原文
毕业设计（论文）外文文献翻译文献、资料中文题目：钢筋混凝土结构设计文献、资料英文题目：DESIGN OF REINFORCED CONCRETE STRUCTURES 文献、资料来源：文献、资料发表（出版）日期：院（部）：专业：土木工程班级：姓名：学号：指导教师：翻译日期： 2017.02.14毕业设计（论文）外文参考资料及译文译文题目：DESIGN OF REINFORCED CONCRETE STRUCTURES原文：DESIGN OF REINFORCED CONCRETESTRUCTURES1. BASIC CONCERPTS AND CHARACERACTERISTICS OF REINFORCED CONCRETEPlain concrete is formed from hardened mixture of cement, water , fine aggregate , coarse aggregate (crushed stone or gravel ) , air and often other admixtures . The plastic mix is placed and consolidated in the formwork, then cured to accelerate of the chemical hydration of hen cement mix and results in a hardened concrete. It is generally known that concrete has high compressive strength and low resistance to tension. Its tensile strength is approximatelyone-tenth of its compressive strength. Consequently, tensile reinforcement in the tension zone has to be provided to supplement the tensile strength of the reinforced concrete section.For example, a plain concrete beam under a uniformly distributed load q is shown in Fig .1.1(a), when the distributed load increases and reaches a value q=1.37KN/m , the tensile region at the mid-span will be cracked and the beam will fail suddenly . A reinforced concrete beam if the same size but has to steel reinforcing bars (2φ16) embedded at the bottom under a uniformly distributed load q is shown in Fig.1.1(b). The reinforcing bars take up the tension there after the concrete is cracked. When the load q is increased, the width of the cracks, the deflection and thestress of steel bars will increase . When the steel approaches the yielding stress ƒy , thedeflection and the cracked width are so large offering some warning that the compression zone . The failure load q=9.31KN/m, is approximately 6.8 times that for the plain concrete beam.Concrete and reinforcement can work together because there is a sufficiently strong bond between the two materials, there are no relative movements of the bars and the surrounding concrete cracking. The thermal expansion coefficients of the two materials are 1.2×10-5K-1 for steel and 1.0×10-5~1.5×10-5K-1 for concrete .Generally speaking, reinforced structure possess following features :Durability .With the reinforcing steel protected by the concrete , reinforced concreteFig.1.1Plain concrete beam and reinforced concrete beamIs perhaps one of the most durable materials for construction .It does not rot rust , and is not vulnerable to efflorescence .(2)Fire resistance .Both concrete an steel are not inflammable materials .They would not be affected by fire below the temperature of 200℃when there is a moderate amount of concrete cover giving sufficient thermal insulation to the embedded reinforcement bars.(3)High stiffness .Most reinforced concrete structures have comparatively large cross sections .As concrete has high modulus of elasticity, reinforced concrete structures are usuallystiffer than structures of other materials, thus they are less prone to large deformations, This property also makes the reinforced concrete less adaptable to situations requiring certainflexibility, such as high-rise buildings under seismic load, and particular provisions have to be made if reinforced concrete is used.(b)Reinfoced concrete beam(4)Locally available resources. It is always possible to make use of the local resources of labour and materials such as fine and coarse aggregates. Only cement and reinforcement need to be brought in from outside provinces.(5)Cost effective. Comparing with steel structures, reinforced concrete structures are cheaper.(6)Large dead mass, The density of reinforced concrete may reach2400~2500kg/pare with structures of other materials, reinforced concrete structures generally have a heavy dead mass. However, this may be not always disadvantageous, particularly for those structures which rely on heavy dead weight to maintain stability, such as gravity dam and other retaining structure. The development and use of light weight aggregate have to a certain extent make concrete structure lighter.(7)Long curing period.. It normally takes a curing period of 28 day under specified conditions for concrete to acquire its full nominal strength. This makes the progress of reinforced concrete structure construction subject to seasonal climate. The development of factory prefabricated members and investment in metal formwork also reduce the consumption of timber formwork materials.(8)Easily cracked. Concrete is weak in tension and is easily cracked in the tension zone. Reinforcing bars are provided not to prevent the concrete from cracking but to take up the tensile force. So most of the reinforced concrete structure in service is behaving in a cracked state. This is an inherent is subjected to a compressive force before working load is applied. Thus the compressed concrete can take up some tension from the load.2. HISTOEICAL DEVELPPMENT OF CONCRETE STRUCTUREAlthough concrete and its cementitious(volcanic) constituents, such as pozzolanic ash, have been used since the days of Greek, the Romans, and possibly earlier ancient civilization, the use of reinforced concrete for construction purpose is a relatively recent event, In 1801, F. Concrete published his statement of principles of construction, recognizing the weakness if concrete in tension, The beginning of reinforced concrete is generally attributed to Frenchman J. L. Lambot, who in 1850 constructed, for the first time, a small boat with concrete for exhibition in the 1855 World’s Fair in Paris. In England, W. B. Wilkinson registered a patent for reinforced concrete l=floor slab in 1854.J.Monier, a French gardener used metal frames as reinforcement to make garden plant containers in 1867. Before 1870, Monier had taken a series of patents to make reinforcedconcrete pipes, slabs, and arches. But Monier had no knowledge of the working principle of this new material, he placed the reinforcement at the mid-depth of his wares. Then little construction was done in reinforced concrete. It is until 1887, when the German engineers Wayss and Bauschinger proposed to place the reinforcement in the tension zone, the use of reinforced concrete as a material of construction began to spread rapidly. In1906, C. A. P. Turner developed the first flat slab without beams.Before the early twenties of 20th century, reinforced concrete went through the initial stage of its development, Considerable progress occurred in the field such that by 1910 the German Committee for Reinforced Concrete, the Austrian Concrete Committee, the American Concrete Institute, and the British Concrete Institute were established. Various structural elements, such as beams, slabs, columns, frames, arches, footings, etc. were developed using this material. However, the strength of concrete and that of reinforcing bars were still very low. The common strength of concrete at the beginning of 20th century was about 15MPa in compression, and the tensile strength of steel bars was about 200MPa. The elements were designed along the allowable stresses which was an extension of the principles in strength of materials.By the late twenties, reinforced concrete entered a new stage of development. Many buildings, bridges, liquid containers, thin shells and prefabricated members of reinforced concrete were concrete were constructed by 1920. The era of linear and circular prestressing began.. Reinforced concrete, because of its low cost and easy availability, has become the staple material of construction all over the world. Up to now, the quality of concrete has been greatly improved and the range of its utility has been expanded. The design approach has also been innovative to giving the new role for reinforced concrete is to play in the world of construction.The concrete commonly used today has a compressive strength of 20~40MPa. For concrete used in pre-stressed concrete the compressive strength may be as high as 60~80MPa. The reinforcing bars commonly used today has a tensile strength of 400MPa, and the ultimate tensile strength of prestressing wire may reach 1570~1860Pa. The development of high strength concrete makes it possible for reinforced concrete to be used in high-rise buildings, off-shore structures, pressure vessels, etc. In order to reduce the dead weight of concrete structures, various kinds of light concrete have been developed with a density of 1400~1800kg/m3. With a compressive strength of 50MPa, light weight concrete may be used in load bearing structures. One of the best examples is the gymnasium of the University of Illinois which has a span of 122m and is constructed of concrete with a density of 1700kg/m3. Another example is the two 20-story apartment houses at the Xi-Bian-Men in Beijing. The walls of these two buildings are light weight concrete with a density of 1800kg/m3.The tallest reinforced concrete building in the world today is the 76-story Water Tower Building in Chicago with a height of 262m. The tallest reinforced concrete building in China today is the 63-story International Trade Center in GuangZhou with a height a height of 200m. The tallest reinforced concrete construction in the world is the 549m high International Television Tower in Toronto, Canada. He prestressed concrete T-section simply supported beam bridge over the Yellow River in Luoyang has 67 spans and the standard span length is 50m.In the design of reinforced concrete structures, limit state design concept has replaced the old allowable stresses principle. Reliability analysis based on the probability theory has very recently been introduced putting the limit state design on a sound theoretical foundation. Elastic-plastic analysis of continuous beams is established and is accepted in most of the design codes. Finite element analysis is extensively used in the design of reinforced concrete structures and non-linear behavior of concrete is taken into consideration. Recent earthquake disasters prompted the research in the seismic resistant reinforced of concrete structures. Significant results have been accumulated.3. SPECIAL FEATURES OF THE COURSEReinforced concrete is a widely used material for construction. Hence, graduates of every civil engineering program must have, as a minimum requirement, a basic understanding of the fundamentals of reinforced concrete.The course of Reinforced Concrete Design requires the prerequisite of Engineering Mechanics, Strength of Materials, and some if not all, of Theory of Structures, In all these courses, with the exception of Strength of Materials to some extent, a structure is treated of in the abstract. For instance, in the theory of rigid frame analysis, all members have an abstract EI/l value, regardless of what the act value may be. But the theory of reinforced concrete is different, it deals with specific materials, concrete and steel. The values of most parameters must be determined by experiments and can no more be regarded as some abstract. Additionally, due to the low tensile strength of concrete, the reinforced concrete members usually work with cracks, some of the parameters such as the elastic modulus I of concrete and the inertia I of section are variable with the loads.The theory of reinforced concrete is relatively young. Although great progress has been made, the theory is still empirical in nature in stead of rational. Many formulas can not be derived from a few propositions, and may cause some difficulties for students. Besides, due to the difference in practice in different countries, most countries base their design methods on their own experience and experimental results. Consequently, what one learns in one country may be different in another country. Besides, the theory is still in a stage of rapid。
建筑施工混凝土裂缝 毕业论文外文文献翻译
Building construction concrete crackAbstractThe crack problem of concrete is a widespread existence but again difficult in solve of engineering actual problem, this text carried on a study analysis to a little bit familiar crack problem in the concrete engineering. Keyword:Concrete crackForewordConcrete's ising 1 kind is anticipate by the freestone bone, cement, water and other mixture but formation of the in addition material of quality brittleness not and all material.Because the concrete construction transform with oneself, control etc. a series problem, harden model of in the concrete existence numerous tiny hole, spirit cave and tiny crack, is exactly because these beginning start blemish of existence just make the concrete present one some not and all the characteristic of quality.The tiny crack is a kind of harmless crack and accept concrete heavy, defend Shen and a little bit other use function not a creation to endanger.But after the concrete be subjected to lotus carry, difference in temperature etc. function, tiny crack would continuously of expand with connect, end formation we can see without the aid of instruments of macro view the crack be also the crack that the concrete often say in the engineering.Concrete crack creation of the reason be a lot of and have alreadytransformed to cause of crack:Such as temperature variety, constringency, inflation, the asymmetry sink to sink etc. reason cause of crack;Have outside carry the crack that the function cause;Protected environment not appropriate the crack etc. caused with chemical effect.Want differentiation to treat in the actual engineering, work°out a problem according to the actual circumstance.In the concrete engineering the familiar crack and the prevention1.Stem Suo crack and preventionStem the Suo crack much appear after the concrete protect be over of a period of time or concrete sprinkle to build to complete behind of around a week.In the cement syrup humidity of evaporate would creation stem Suo, and this kind of constringency is can't negative.Stem Suo crack of the creation be main is because of concrete inside outside humidity evaporate degree dissimilarity but cause to transform dissimilarity of result:The concrete is subjected to exterior condition of influence, surface humidity loss lead quick, transform bigger, inner part degree of humidity variety smaller transform smaller, bigger surface stem the Suo transform to be subjected to concrete inner part control, creation more big pull should dint but creation crack.The relative humidity is more low, cement syrup body stem Suo more big, stem the Suo crack be more easy creation.Stem the Suo crack is much surface parallel lines form or the net shallow thin crack, width many between 0.05-0.2 mm, the flat surface part much see in the bigphysical volume concrete and follow it more in thinner beam plank short to distribute.Stem Suo crack usually the anti- Shen of influence concrete, cause the durable of the rust eclipse influence concrete of reinforcing bar, under the function of the water pressure dint would creation the water power split crack influence concrete of loading dint etc..Concrete stem the Suo be main with water ash of the concrete ratio, the dosage of the composition, cement of cement, gather to anticipate of the dosage of the property and dosage, in addition etc. relevant.2.The Su constringency crack and preventionSu constringency is the concrete is before condense, surface because of lose water quicker but creation of constringency.The Su constringency crack is general at dry heat or strong wind the weather appear, crack's much presenting in the center breadth, both ends be in the centerthin and the length be different, with each other not coherent appearance.Shorter crack general long 20-30 cm, the longer crack can reach to a 2-3 m, breadth 1-5 mm.It creation of main reason is:The concrete is eventually almost having no strength or strength before the Ning very small, perhaps concrete just eventually Ning but strength very hour, be subjected to heat or compare strong wind dint of influence, the concrete surface lose water to lead quick, result in in the capillary creation bigger negative press but make a concrete physical volume sharply constringency, but at this time the strength of concrete again can't resist its constringency, thereforecreation cracked.The influence concrete Su constringency open the main factor of crack to have water ash ratio, concrete of condense time, environment temperature, wind velocity, relative humidity...etc..3.Sink to sink crack and preventionThe creation which sink to sink crack is because of the structure foundation soil quality not and evenly, loose soft or return to fill soil dishonest or soak in water but result in the asymmetry sink to decline with the result that;Perhaps because of template just degree shortage, the template propped up to once be apart from big or prop up bottom loose move etc. to cause, especially at winter, the template prop up at jelly soil up, jelly the soil turn jelly empress creation asymmetry to sink to decline and cause concrete structure creation crack.This kind crack many is deep enter or pierce through sex crack, it alignment have something to do with sinking to sink a circumstance, general follow with ground perpendicular or present 30 °s-45 ° Cape direction development, bigger sink to sink crack, usually have certain of wrong, crack width usually with sink to decline quantity direct proportion relation.Crack width under the influence of temperature variety smaller.The foundation after transform stability sink to sink crack also basic tend in stability.4.Temperature crack and preventionTemperature crack much the occurrence is in big surface or difference in temperature variety of the physical volume concrete compare the earth areaof the concrete structure.Concrete after sprinkling to build, in the hardening the process, cement water turn a creation a great deal of of water turn hot, .(be the cement dosage is in the 350-550 kg/m 3, each sign square the rice concrete will release a calories of 17500-27500 kJ and make concrete internal thus the temperature rise to reach to 70 ℃or so even higher)Because the physical volume of concrete be more big, a great deal of of water turn hot accumulate at the concrete inner part but not easy send forth, cause inner part the temperature hoick, but the concrete surface spread hot more quick, so formation inside outside of bigger difference in temperature, the bigger difference in temperature result in inner part and exterior hot the degree of the bulge cold Suo dissimilarity, make concrete surface creation certain of pull should dint.When pull should dint exceed the anti- of concrete pull strength extreme limit, concrete surface meeting creation crack, this kind of crack much occurrence after the concrete under construction period.In the concrete of under construction be difference in temperature variety more big, perhaps is a concrete to be subjected to assault of cold wave etc., will cause concrete surface the temperature sharply descend, but creation constringency, surface constringency of the concrete be subjected to inner part concrete of control, creation very big of pull should dint but creation crack, this kind of crack usually just in more shallow scope of the concrete surface creation.ConclusionThe crack is widespread in the concrete structure existence of a kind of phenomenon, it of emergence not only will lower the anti- Shen of building ability, influence building of usage function, and will cause the rust eclipse of reinforcing bar, the carbonization of concrete, lower the durable of material, influence building of loading ability, so want to carry on to the concrete crack earnest research, differentiation treat, adoption reasonable of the method carry on processing, and at under construction adopt various valid of prevention measure to prevention crack of emergence and development, assurance building and Gou piece safety, stability work.建筑施工混凝土裂缝混凝土的裂缝问题是一个普遍存在而又难于解决的工程实际问题，本文对混凝土工程中常见的一些裂缝问题进行了探讨分析。
土木工程专业外语混凝土含翻译
4 Where fresh concrete is placed on hardened concrete, a good bond must be developed.5 The temperature of fresh concrete must be controlled from the time of mixing through final placement, and protected after placement.。
to avoid segregation.Selection of the most appropriate technique for economy depends on jobsite conditions, especially project size, equipment, and the contractor’s experience.In building construction，power-operated buggies; drop bottom buckets with a inclined chutes; flexible and rigid pipe by pumping;which either dry materials and water are sprayed separately or mixed concrete is shot against the forms; and for underwater placing, tremie chutes (closed flexible tubes).side-dump cars on narrow-gageFor pavement, concrete may be placed by bucket from the swinging boom of a paving mixer, directly by dump truck or mixer truck, or7 Even within the specified limits on slump and water-cementitious materials ratio, excess water must be avoided.In this context, excess water is presented for the conditions of placing if evidence of water rise (vertical segregation) or water flow (horizontal segregation) occurs.Excess water also tends to aggravate surface defects by increasedleakage through form openings. The result may be honeycomb, variations in color, or soft spots at the surface.8 In vertical formwork, water rise causes weak planes between each layer deposited. In addition to the deleterious structural effect, such planes, when hardened, contain voids which water may pass through.9 In horizontal elements, such as floor slabs, excess water rises and strength, low high and generallypoor quality.10 The purpose of consolidation is to eliminate voids of air and to ensure intimate complete contact of the concrete with the surfaces of the forms and the reinforcement.Intense vibration, however, may also reduce the volume of desirable entrained air; but this reduction can be compensated by adjustment of the mix proportions11 Powered internal vibrators are usually used to achieve consolidation. For thin slabs, however, high-quality, low-slump concrete can be effectively consolidated, without excess water, by mechanical surface vibrators.For precast elements in rigid external vibration is highly effective. External vibration is also effective with in-place forms, but should not be used unless the formwork is for theimpact of the vibrator.12 Except in certain paving operations, vibration of the reinforcement should be it is effective, thevertical rebars passing into partly set concrete below may be harmful.Note, however, that re-vibration of concrete before the final set, under controlled conditions, can improve concrete strength markedly and reduce surface voids.This technique is too difficult to control for general use on field-cast vertical elements, but it is very effective in finishing slabs with powered vibrating equipment.13 The interior of columns is usually congested; it contains a large volume of reinforcing steel compared with the volume of concrete, and has a large height compared with its cross-sectional dimensions.Therefore, though columns should be continuously cast, the concrete should be placed in 2-to 4-ft-deep increments and consolidated with internal vibrators. These should be lifted after each increment has been vibrated.If delay occurs in concrete supply before a beenWhen the remainder of the column isportion slightly.14 In all columns and reinforced narrow walls, concrete placing should begin with 2 to 4 inches of grout. Otherwise, loose stone will collect at the bottom, resulting in the formation of honeycomb. This grout should be proportioned for about the same slump as the concrete or slightly more, but at the same or lower water-cementitious material ratio.the same proportions of butWhen concrete is placed for walls,the only practicable means to avoid segregation is to place no more than a 24-in layer in one pass. Each layer should be vibrated separately and kept nearly level.15 For walls deeper than 4 ft, concrete should be placed through vertical. The concrete should not fall free more than 4 ft or segregation will occur, with the coarse aggregate ricocheting off thelayers after the initial layer should be penetrated by.can be beneficial (re-vibration), but control under variable jobsite conditions is too uncertain for recommendation of this practice for general use.16 The results of poor placement in walls are frequently observed:slope layer lines; honeycombs, leaking, if water is present; and, if cores are taken at successive heights, up to a 50% reduction in strength from bottom to top. Some precautions necessary to avoid these ill effects are:17 Do not move concrete laterally with vibrators18 For deep, long walls, reduce the slump for upper layers 2 to 3 in below the slump for the starting layer.19 On any placing of layers, vibrate the concrete20 Concrete should be inspected for the owner before, during, and after casting. Before concrete is placed, the formwork must be free of ice and debris and properly coated with bond-breaker oil.The rebars must be in place, properly supported to bear any traffic they will receive during concrete placing.inserts, and other items to be embedded must be inConstruction personnel should be available, usually carpenters, bar placers and other trades, if piping or electrical conduit is to be embedded, to act as form watchers and to reset any rebars, conduit, or piping displaced.21 As concrete is cast, the slump of the concrete must be observed and regulated within prescribed limits, or the specified strengths based on the expected slump may be reduced.An inspector of placing who is also responsible for sampling and making cylinders, should test slump, temperatures, and unit weights, during concreting and should control any field adjustmentThe inspector should also that handling, placing, and finishing procedures that agreed on in advance are properly followed, to avoid segregated concrete.should ensure that any construction joints made necessary by stoppage of concrete supply, rain, or other delays are properly located and made in accordancewith procedures specified or approved by the engineer.22 Inspection is complete only when concrete is cast, finished, protected for curing, and attains full strength.1混凝土适当放置的原则是：2在混合器和放置点之间的所有操作（包括最终固结和精整）期间必须避免分离。
2021年最新混凝土搅拌站毕业论文外文翻译（完整版）
一.外文翻译CONCRETE MIXING PLANTThe apparatus of the present invention relates generally to concrete mixing plants and more specifically to such plants utilized to automatically and continuously mix separate concrete components into a wide range of predetermined quantities or batches.Conventional concrete plants and mixer trucks that can normally only be utilized for mixing single large batches of concrete. Such apparatus often are preset to mix a batch that is too large for a specific job. The remaining concrete must either be dumped or resold. If the remaining concrete is to be resold, it often must be watered down before it reaches the second job site.Conventional truck-mounted mixers are necessarily large in volume, to accommodate the labor cost of the individual driver. Furthermore, the concrete must be used within a fixed time span from its receipt in the truck. Delays in transit or unforeseen delay at the site of usage make it difficult to maintain a constant delivery schedule. Usually excess trucks and drivers must be used to assure a ready supply of concrete.Much greater control of concrete consistency and cost is possible by on-site mixing. However, conventional concrete mixers are designed for large scale batch mixing. The mixer described below fills the need for an on-site mixer readily adjustable to meet the instant demands of the user asto quantity and quality.A further problem is that with a premixed batch, it is difficult or impossible to make last minute adjustments in mixture proportions. This difficulty arises frequently in areas where quick climate changes are common and further, where specific building construction techniques call for different concrete stress characteristics.These problems are realized to a limited degree by the apparatus disclosed in U.S. Pat. Nos. 3,339,898 and 3,469,824 granted to Futtyetal. These patents disclosed mixing methods and mixing truck constructions where in concrete components are supplied to an elongated trough. An elongated shaft is provided within the trough having a plurality of spatially disposed mixing paddles and helical feeding screws. Rotation of the shaft simultaneously mixes the particulate ingredients and moves them toward an output end.U.S. Pat. No. 3,310,293 granted to Zimmerman discloses a concrete mixing and delivery system wherein concrete components are held within a plurality of bins supported on a truck frame. The components are held separately within the bins that provide means for dispensing predetermined amounts of the components onto an elongated conveyor belt. The conveyor delivers the separate components to an external mixing trough where water is applied to the dry components and they are mixed by an elongated auger within the mixing trough.Another patent granted to Futty, U.S. Pat. No. 3,336,011, discloses a system and means for selectively mixing concrete and incorporating additives therein which, like the Zimmerman apparatus, deposits concrete components onto a conveyor and delivers them separately to a mixing trough. Water is added to the components at the mixing trough as an auger is rotated to mix the components together. The principal feature of this invention is the provision of separate water supply systems in which either pure water or an antifreeze solution may be selectively applied to the mixture.A further patent granted to Futty, U.S. Pat. No. 3,623,708 discloses a system and means for selectively mixing concrete and incorporating dry additives therein. The apparatus includes means for delivering dry additives to the concrete batch and incorporates a hopper assembly for holding the dry additives. The hopper contains agitator means for mixing and breaking up the dry additive ingredients. A controlled feed means selectively controls the amount of dry additives passed from the hopper into an enclosed auger arrangement. The additives are conveyed by the auger arrangement into an auxiliary mixing trough where they are incorporated into a concrete batch. U.S. Pat. No. 2,976,025 granted to G. M. Pro discloses a combined mixer and conveyor for concrete components. Individual hoppers are used in the Pro apparatus for storing each concrete component. The apparatus includes means for deliveringsand and cement to a helical conveyor within a trough. The materials are received within the trough and tumbled and agitated as they are moved upwardly.Another U.S. Pat. No. 2,946,597, granted to M. W. Simonsen, discloses a fertilizer mixer and spreader with a partition container wherein fertilizer components are kept separately in longitudinally spaced bins. The bins include bottom openings through which the individual components are placed onto a conveyor and delivered to a fertilizer dispensing impeller. The fertilizer dropped onto the impeller is spread across the ground behind the supporting vehicle.U.S. Pat. No. 796,591 granted to W. B. Martin describes a concrete mixer in which individual concrete components are contained within separate hoppers. The apparatus includes means for removing measured amounts of gravel, stone, cement and sand in predetermined quantities and dropping them gravitationally downwardly into a mixing auger.It may be noted that each of the above-cited patents r elating to an apparatus f or mixing separate c oncrete components utilizes an auger or paddled wheel arrangement as means for mixing the components together. The apparatus of the present invention differs from this art in that the mixing of the components is accomplished by impact and shearing action. Mixing by impact is accomplished as the components are propelled against a stationary abutment surface, while mixing by shearing layers orstrata of the components is affected as the components are delivered from storage bins or fall from the abutment surface onto to second conveyor belt or other receiving conveyor.SUMMARY OF THE INVENTIONA concrete mixing plant is described comprising conveyor means for carrying concrete component mater als along a first direction of travel toa discharge point where they are propelled against an upright abutment surface. Supply means is also provided for placing controlled quantitiesof concrete component materials onto an upwardly facing surface of the conveyor means.It is a first object of my invention to provide a concrete mixing plant that is capable of producing a continuous supply of consistent wet concrete.Another object is to provide such a plant that may be controlled while in operation, to change mixture proportions and the consistency of the concrete produced.It is an additional object of my invention to provide such a concrete mixing plant that is relatively simple in3construction and therefore easy to operate. It can be transported to the job site or used as a central mixing plant.A yet further object is to provide such a mixing plant that includesseparate storage bins for each individual concrete component with a metering and discharge mechanism attached to each bin to facilitate control of the quantity of each individual component supplied to the mixture.These and further objects and advantages will become apparent upon reading the following disclosure which, taken with the accompanying drawings, discloses two preferred forms of the present invention.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a pictorial view of a first embodiment of the mixing plant;FIG. 2 is an enlarged elevational section view taken substantially along line 2—2 in FIG. 1;FIG. 3 is an enlarged elevational section view taken substantially along line 3—3 in FIG. 1;FIG. 4 is an enlarged elevational section view taken substantially along line 4—4 in FIG. 1;FIG. 5 is a fragmentary operational view taken substantially along line 5—5 in FIG. 1;FIG. 6 is a section view illustrating a weighing mechanism utilizedin conjunction with the present invention;FIG. 7 is a plan view of a slurry mixing mechanism incorporated inthe present invention;FIG. 8 is a cross sectional view taken substantially along line 8—8in FIG. 7;FIG. 9 is a plan view of a mixing plant mounted to a truck frame;FIG. 10 is an elevational view of the plant and truck as shown in FIG. 9;FIG. 11 is a sectioned view taken along line 11—11 in FIG. 9; andFIG. 12 is a fragmentary sectioned view taken along lines 12—12 in FIG. 9.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTSA first embodiment of the concrete mixing plant invention is illustrated in FIGS. 1 through 8 of the attached drawings and is generally designated therein by the reference numeral 10. A mixing plant 10 as shown, is supported by a framework 11. A plurality of component bins 12 and a dry cement bin 12a are located on the framework for receiving and storing individual concrete components such as sand, various size aggregate and, of course, dry cement.The component bins are elements of a supply means whereby the individual concrete components are placed in controlled layered quantities on an upwardly facing surface 13 of first and second conveyor means 14 and 26 respectively. In operation, the supply means is utilized to deliver dry concrete components to the first conveyor means 14 which in turn initially moves the components along a first direction of travel to adischarge end 15. The dry components fall from discharge end 15 ontothe second conveyor means 26. A wet cement slurry is added to the components as they move along on the second conveyor means 26 to a second discharge end 33. The components leave the discharge end 33 as a concrete mixture.混凝土搅拌站本发明的装置本发明一般涉及混凝土搅拌站，更具体地说，涉及这样的植物，利用自动连续到范围广泛的预定量或分批混合单独的混凝土构件。
土木工程毕业论文外文翻译---建筑施工混凝土裂缝的预防与处理
Building construction concrete crack ofprevention and processingAbstractThe crack problem of concrete is a widespread existence but again difficult in solve of engineering actual problem, this text carried on a study analysis to a little bit familiar crack problem in the concrete engineering, and aim at concrete the circumstance put forward some prevention, processing measure.Keyword:Concrete crack prevention processingForewordConcrete's ising 1 kind is anticipate by the freestone bone, cement, water and other mixture but formation of the in addition material of quality brittleness not and all material.Because the concrete construction transform with oneself, control etc. a series problem, harden model of in the concrete existence numerous tiny hole, spirit cave and tiny crack, is exactly because these beginning start blemish of existence just make the concrete present one some not and all the characteristic of quality.The tiny crack is a kind of harmless crack and accept concrete heavy, defend Shen and a little bit other use function not a creation to endanger.But after the concrete be subjected to lotus carry, difference in temperature etc. function, tiny crack would continuously of expand with connect, end formation we can see without the aid of instruments of macro view the crack be also the crack that the concrete often say in the engineering.Concrete building and Gou piece usually all take sewer to make of, because of crack of existence and development usually make inner part of reinforcing bar etc. material creation decay, lower reinforced concrete material of loading ability, durable and anti- Shen ability, influence building of external appearance, service life, severity will threat arrive people's life and property safety.A lot of all of crash of engineerings is because of the unsteady development of the crack with the result that.Modern age science research with a great deal of of the concrete engineering practice certificate, in theconcrete engineering crack problem is ineluctable, also acceptable in certainly of the scope just need to adopt valid of measure will it endanger degree control at certain of scope inside.The reinforced concrete norm is also explicit provision:Some structure at place of dissimilarity under the condition allow existence certain the crack of width.But at under construction should as far as possible adopt a valid measure control crack creation, make the structure don't appear crack possibly or as far as possible decrease crack of amount and width, particularly want to as far as possible avoid harmful crack of emergence, insure engineering quality thus.Concrete crack creation of the reason be a lot of and have already transformed to cause of crack:Such as temperature variety, constringency, inflation, the asymmetry sink to sink etc. reason cause of crack;Have outside carry the crack that the function cause;Protected environment not appropriate the crack etc. caused with chemical effect.Want differentiation to treat in the actual engineering, work°out a problem according to the actual circumstance.In the concrete engineering the familiar crack and the prevention1.Stem Suo crack and preventionStem the Suo crack much appear after the concrete protect be over of a period of time or concrete sprinkle to build to complete behind of around a week.In the cement syrup humidity of evaporate would creation stem Suo, and this kind of constringency is can't negative.Stem Suo crack of the creation be main is because of concrete inside outside humidity evaporate degree dissimilarity but cause to transform dissimilarity of result:The concrete is subjected to exterior condition of influence, surface humidity loss lead quick, transform bigger, inner part degree of humidity variety smaller transform smaller, bigger surface stem the Suo transform to be subjected to concrete inner part control, creation more big pull should dint but creation crack.The relative humidity is more low, cement syrup body stem Suo more big, stem the Suo crack be more easy creation.Stem the Suo crack is much surface parallel lines form or the net shallow thin crack, width many between 0.05-0.2 mm, the flat surface part much see in the big physical volume concrete and follow it more in thinner beam plank short to distribute.Stem Suo crack usually the anti- Shen of influence concrete, cause thedurable of the rust eclipse influence concrete of reinforcing bar, under the function of the water pressure dint would creation the water power split crack influence concrete of loading dint etc..Concrete stem the Suo be main with water ash of the concrete ratio, the dosage of the composition, cement of cement, gather to anticipate of the dosage of the property and dosage, in addition etc. relevant.Main prevention measure:While being to choose to use the constringency quantity smaller cement, general low hot water mire and powder ash from stove cement in the adoption, lower the dosage of cement.Two is a concrete of stem the Suo be subjected to water ash ratio of influence more big, water ash ratio more big, stem Suo more big, so in the concrete match the ratio the design should as far as possible control good water ash ratio of choose to use, the Chan add in the meantime accommodation of reduce water.Three is strict control concrete mix blend with under construction of match ratio, use of concrete water quantity absolute can't big in match ratio design give settle of use water quantity.Four is the earlier period which strengthen concrete to protect, and appropriate extension protect of concrete time.Winter construction want to be appropriate extension concrete heat preservation to overlay time, and Tu2 Shua protect to protect.Five is a constitution the accommodation is in the concrete structure of the constringency sew.2.The Su constringency crack and preventionSu constringency is the concrete is before condense, surface because of lose water quicker but creation of constringency.The Su constringency crack is general at dry heat or strong wind the weather appear, crack's much presenting in the center breadth, both ends be in the centerthin and the length be different, with each other not coherent appearance.Shorter crack general long 20-30 cm, the longer crack can reach to a 2-3 m, breadth 1-5 mm.It creation of main reason is:The concrete is eventually almost having no strength or strength before the Ning very small, perhaps concrete just eventually Ning but strength very hour, be subjected to heat or compare strong wind dint of influence, the concrete surface lose water to lead quick, result in in the capillary creation bigger negative press but make a concrete physical volume sharply constringency, but at this time the strength of concrete again can't resist itsconstringency, therefore creation cracked.The influence concrete Su constringency open the main factor of crack to have water ash ratio, concrete of condense time, environment temperature, wind velocity, relative humidity...etc..Main prevention measure:One is choose to use stem the Suo value smaller higher Huo sour salt of the earlier period strength or common the Huo sour brine mire.Two is strict the control water ash ratio, the Chan add to efficiently reduce water to increment the collapse of concrete fall a degree and with easy, decrease cement and water of dosage.Three is to sprinkle before building concrete, water basic level and template even to soak through.Four is in time to overlay the perhaps damp grass mat of the plastics thin film, hemp slice etc., keep concrete eventually before the Ning surface is moist, perhaps spray to protect etc. to carry on protect in the concrete surface.Five is in the heat and strong wind the weather to want to establish to hide sun and block breeze facilities, protect in time.3.Sink to sink crack and preventionThe creation which sink to sink crack is because of the structure foundation soil quality not and evenly, loose soft or return to fill soil dishonest or soak in water but result in the asymmetry sink to decline with the result that;Perhaps because of template just degree shortage, the template propped up to once be apart from big or prop up bottom loose move etc. to cause, especially at winter, the template prop up at jelly soil up, jelly the soil turn jelly empress creation asymmetry to sink to decline and cause concrete structure creation crack.This kind crack many is deep enter or pierce through sex crack, it alignment have something to do with sinking to sink a circumstance, general follow with ground perpendicular or present 30 °s-45 °Cape direction development, bigger sink to sink crack, usually have certain of wrong, crack width usually with sink to decline quantity direct proportion relation.Crack width under the influence of temperature variety smaller.The foundation after transform stability sink to sink crack also basic tend in stability.Main prevention measure:One is rightness loose soft soil, return to fill soil foundation a construction at the upper part structure front should carry on necessity of Hang solid with reinforce.Two is the strength that assurance template is enough andjust degree, and prop up firm, and make the foundation be subjected to dint even.Three is keep concrete from sprinkle infusing the foundation in the process is soak by water.Four is time that template tore down to can't be too early, and want to notice to dismantle a mold order of sequence.Five is at jelly soil top take to establish template to notice to adopt certain of prevention measure.4.Temperature crack and preventionTemperature crack much the occurrence is in big surface or difference in temperature variety of the physical volume concrete compare the earth area of the concrete structure.Concrete after sprinkling to build, in the hardening the process, cement water turn a creation a great deal of of water turn hot, .(be the cement dosage is in the 350-550 kg/m 3, each sign square the rice concrete will release a calories of 17500-27500 kJ and make concrete internal thus the temperature rise to reach to 70 ℃or so even higher)Because the physical volume of concrete be more big, a great deal of of water turn hot accumulate at the concrete inner part but not easy send forth, cause inner part the temperature hoick, but the concrete surface spread hot more quick, so formation inside outside of bigger difference in temperature, the bigger difference in temperature result in inner part and exterior hot the degree of the bulge cold Suo dissimilarity, make concrete surface creation certain of pull should dint.When pull should dint exceed the anti- of concrete pull strength extreme limit, concrete surface meeting creation crack, this kind of crack much occurrence after the concrete under construction period.In the concrete of under construction be difference in temperature variety more big, perhaps is a concrete to be subjected to assault of cold wave etc., will cause concrete surface the temperature sharply descend, but creation constringency, surface constringency of the concrete be subjected to inner part concrete of control, creation very big of pull should dint but creation crack, this kind of crack usually just in more shallow scope of the concrete surface creation.The alignment of the temperature crack usually none settle regulation, big area structure the crack often maneuver interleave;The size bigger structure of the beam plank length, the crack run parallel with short side more;Thorough with pierce through sex of temperature crack general and short side direction parallelism or closeparallelism, crack along long side cent the segment appear, in the center more airtight.Crack width the size be different, be subjected to temperature variety influence more obvious, winter compare breadth, summer more narrow.The concrete temperature crack that the heat inflation cause is usually in the center the thick both ends be thin, but cold Suo crack of thick thin variety not too obvious.The emergence of the this kind crack will cause the rust eclipse of reinforcing bar, the carbonization of concrete, the anti- jelly which lower concrete melt, anti- tired and anti- Shen ability etc..Main prevention measure:One is as far as possible choose to use low hot or medium hot water mire, like mineral residue cement, powder ash from stove cement...etc..Two is a decrease cement dosage, cement dosage as far as possible the control is in the 450 kg/m 3 following.Three is to lower water ash ratio, water ash of the general concrete ratio control below 0.6.Four is improvement the bone anticipate class to go together with, the Chan add powder ash from stove or efficiently reduce water etc. to come to reduce cement dosage and lower water to turn hot.Five is an improvement concrete of mix blend to process a craft, lower sprinkle of concrete to build temperature.Six is the in addition that the Chan add a have of fixed amount to reduce water and increase Su, slow Ning etc. function in the concrete, improvement the concrete mix to match a thing of mobility, protect water, lower water to turn hot, postpone hot Feng of emergence time.Seven is the heat season sprinkle to build can the adoption take to establish to hide sun plank etc. assistance measure control concrete of Wen Sheng, lower to sprinkle temperature of build the concrete.Eight is the temperature of big physical volume concrete should the dint relate to structure size, concrete structure size more big, temperature should dint more big, so want reasonable arrangement construction work preface, layering, cent the piece sprinkle to build, for the convenience of in spread hot, let up control.Nine is at great inner part constitution of the physical volume concrete cool off piping, cold water perhaps cold air cool off, let up concrete of inside outside difference in temperature.Ten is the supervision which strengthen concrete temperature, adopt to cool off in time, protection measure.11 is to reserve temperature constringency to sew.12 is to let up to control, sprinkle proper before building concrete in the Ji rock and old concrete top build a 5 mm or so sand mat a layer or usage asphalt etc. materialTu2 Shua.13 is to strengthen concrete to protect, the concrete after sprinkle build use moist grass Lian in time, hemp slice's etc. overlay, and attention sprinkle water to protect, appropriate extension protect time, assurance the concrete surface be slow-moving cool off.At the cold season, concrete surface should constitution heat preservation measure, in order to prevent cold wave assault.14 is the allocation be a little amount in the concrete of reinforcing bar perhaps add fiber material concrete of temperature crack control at certain of scope inside.5.Crack and prevention that the chemical reaction causeAlkali bone's anticipating the crack that reaction crack and reinforcing bar rust eclipse cause is the most familiar in the reinforced concrete structure of because of chemical reaction but cause of crack.The concrete blend a future reunion creation some alkalescence ion, these ion with some activity the bone anticipate creation chemical reaction and absorb surroundings environment in of water but the physical volume enlarge, make concrete crisp loose, inflation open crack.In this kind of crack general emergence concrete structure usage period, once appear very difficult remediable, so should at under construction adopt valid the measure carry on prevention.Main of prevention measure:While being to choose to anticipate with the alkali activity small freestone bone.Two is the in addition which choose to use low lye mire with low alkali or have no alkali.Three is the Chan which choose to use accommodation with anticipate to repress an alkali bone to anticipate reaction.Because the concrete sprinkle to build, flap Dao bad perhaps is a reinforcing bar protection layer thinner, the harmful material get into concrete to make reinforcing bar creation rust eclipse, the reinforcing bar physical volume of the rust eclipse inflation, cause concrete bulge crack, the crack of this kind type much is a crack lengthways, follow the position of reinforcing bar ually of prevent measure from have:One is assurance reinforcing bar protection the thickness of the layer.Two is a concrete class to go together with to want good.Three is a concrete to sprinkle to note and flap Dao airtight solid.Four is a reinforcing bar surface layer Tu2 Shua antisepsis coating.Crack processingThe emergence of the crack not only would influence structure of whole with just degree, return will cause the rust eclipse of reinforcing bar, acceleration concrete of carbonization, lower durable and anti- of concrete tired, anti- Shen ability.Therefore according to the property of crack and concrete circumstance we want differentiation to treat, in time processing, with assurance building of safety usage.The repair measure of the concrete crack is main to have the following some method:Surface repair method, infuse syrup, the Qian sew method, the structure reinforce a method, concrete displacement method, electricity chemistry protection method and imitate to living from heal method.Surface repair the method be a kind of simple, familiar of repair method, it main be applicable to stability and to structure loading the ability don't have the surface crack of influence and deep enter crack of processing.The processing measure that is usually is a surface in crack daubery cement syrup, the wreath oxygen gum mire or at concrete surface Tu2 Shua paint, asphalt etc. antisepsis material, at protection of in the meantime for keeping concrete from continue under the influence of various function to open crack, usually can adoption the surface in crack glue to stick glass fiber cloth etc. measure.1, infuse syrup, the Qian sew methodInfuse a syrup method main the concrete crack been applicable to have influence or have already defend Shen request to the structure whole of repair, it is make use of pressure equipments gum knot the material press into the crack of concrete, gum knot the material harden behind and concrete formation one be whole, thus reinforce of purpose.The in common use gum knot material has the cement the syrup, epoxy, A Ji C Xi sour ester and gather ammonia ester to equalize to learn material.The Qian sew a method is that the crack be a kind of most in common use method in, it usually is follow the crack dig slot, the Qian fill Su in the slot or rigid water material with attain closing crack of purpose.The in common use Su material has PVC gum mire, plastics ointment, the D Ji rubber etc.;In common use rigid water material is thepolymer cement sand syrup.2, the structure reinforce a methodWhen the crack influence arrive concrete structure of function, will consideration adopt to reinforce a method to carry on processing to the concrete structure.The structure reinforce medium in common use main have the following a few method:The piece of enlargement concrete structure in every aspect accumulate, outside the Cape department of the Gou piece pack type steel, adoption prepare should the dint method reinforce, glue to stick steel plate to reinforce, increase to establish fulcrum to reinforce and jet the concrete compensation reinforce.3, concrete displacement methodConcrete displacement method is processing severity damage concrete of a kind of valid method, this method be first will damage of the concrete pick and get rid of, then again displacement go into new of concrete or other material.The in common use displacement material have:Common concrete or the cement sand syrup, polymer or change sex polymer concrete or sand syrup.4, the electricity chemistry protection methodThe electricity chemistry antisepsis is to make use of infliction electric field in lie the quality of electricity chemical effect, change concrete or reinforced concrete the environment appearance of the place, the bluntness turn reinforcing bar to attain the purpose of antisepsis.Cathode protection method, chlorine salt's withdrawing a method, alkalescence to recover a method is a chemistry protection method in three kinds of in common use but valid method.The advantage of this kind of method is a protection method under the influence of environment factor smaller, apply reinforcing bar, concrete of long-term antisepsis, since can used for crack structure already can also used for new set up structure.5, imitate to living from legal moreImitate to living from heal the method be a kind of new crack treatment, its mimicry living creature organization secrete a certain material towards suffering wound part auto, but make the wound part heal of function, join some and special composition(such as contain to glue knot of the liquid Xin fiber or capsule) in the concrete of the traditionthe composition, at concrete inner part formation the intelligence type imitate to living from heal nerve network system, be the concrete appear crack secrete a parts of liquid Xin fiber can make the crack re- heal.ConclusionThe crack is widespread in the concrete structure existence of a kind of phenomenon, it of emergence not only will lower the anti- Shen of building ability, influence building of usage function, and will cause the rust eclipse of reinforcing bar, the carbonization of concrete, lower the durable of material, influence building of loading ability, so want to carry on to the concrete crack earnest research, differentiation treat, adoption reasonable of the method carry on processing, and at under construction adopt various valid of prevention measure to prevention crack of emergence and development, assurance building and Gou piece safety, stability work.From《CANADIAN JOURNAL OF CIVIL ENGINEERING》建筑施工混凝土裂缝的预防与处理混凝土的裂缝问题是一个普遍存在而又难于解决的工程实际问题，本文对混凝土工程中常见的一些裂缝问题进行了探讨分析，并针对具体情况提出了一些预防、处理措施。
建筑毕业设计外文翻译---建筑材料—混凝土与砂浆
CONCRETE AND MORTAR1. Early History of Cement and ConcreteShelter from the very beginning of man/ existence, has demanded the application Of the best , available technology of the contemporary era. In the earliest ages, structures consisted of rammed earth, or stone blocks laid one on another without benefit of any bonding or cementing medium. Stability of the stone structures depended on the regular setting of the heavy stones , The earliest masonry probably consisted of sun-dried clay bricks, set in regular courses in thin layers of moist mud. When the moist mud dried, a solid clay wall resulted. Construction: of this kind was common in the dry desert areas of the world.Burnt gypsum as a cementing material was developed early in the Egyptian period and was apparently used in construction of some of the pyramids. Later the Greeks and Romans discovered methods of burning limestone to produce quicklime which was subsequently slaked for use in making mortar. Both the Greeks and the Romans learned that certain fine soil or earth, when mixed with the lime and the sand, produced a superior cementing material. The Greek material, a volcanic tuff from the island of Santorin , is still used in that part Of the world. The best of the materials used by the Romans was a tuff or ash from the vicinity of Pozzuoli near Mt. V esuvius, hence the name “pozzolan”used to identify a certain type of mineral admixture used in concrete today.The cement produced by the Romans was a hydraulic cement, that is, it had the capability of hardening under water. Many of the Roman structures were constructed of a form of concrete, using these materials, and stone masonry was bonded with a mortar similarly composed.During the Middle Ages of history, the art of making good mortar was nearly lost, the low point having been reached in about the llth century, when much inferior material was used. Quality of the lime started to improve at this time and in the 14th century or later the use of pozzolans was again practised.One of the most famous projects of the comparatively recent period was the construction of the new Eddystone Lighthouse off the coast of England in 1757--59. John Smeaton, the engineer and designer of the structure, investigated many materials and methods of bonding the stones for the building.Engineering and scientific development was beginning to move rapidly at this time, and many researchers in several countries were investigating cementing agents made from gypsum, limestoneand other natural materials. One discovery was a method of making a cement by burning a naturally occurring mixture of lime and clay. properties of the natural cement were very erratic because of variations in the proportions in the natural material, although use of this natural cement continued for many years.In 1824 Joseph Aspdin , a brickmason of Leeds, England, took out a patent on a material he called Portland cement, so called because concrete made with it was supposed to resemble the limestone quarried near Portland, England. Aspdin is generally credited with inventing a method of proportioning limestone and clay, burning the mixture at high temperature to produce clinkers, then grinding the clinkers to produce a hydraulic cement. His small kiln, producing about 16 tons of clinker at a time, required several days/or each burn. Expansion and development of cement manufacturing was slow for a number of years. About 1850, however, the industry had become well established not only in England, but also in Germany and Belgium.Shipments to the United States were started in 1868 and reached a peak about 1895, at which time production was well under way in the United States.Meanwhile the United States production of natural cement had been started early in the 19th century as a result of the demand for cement for construction of the Erie Canal and related works. Subsequent development of the rotary kiln led to large scale production of cement throughout the world.The use of concrete was expanded by the construction of railroads, bridges ,buildings and street pavements. Research in reinforcing concrete with steel rods had been started in France, and the year 1875 saw first use of reinforced concrete in the United States. Much'of the concrete at this time contained barely enough water to enable the concrete to be rammed into place by the application of much hand labor. There then ensued a period of wet concrete in which the concrete was flowed into place. Many users of concrete, however, realized the folly of wet mixes, and about 1920 Duff Abrams revealed the results of his research and observations. He stated that the quality of concrete was directly affected by the amount of water in relation to the amount of cement ; within reasonable limits, the quality of the concrete decreases as the water-cement ratio goes up. This has become one of the basic laws of concrete technology.2. Advantages and Disadvantages of Concrete and Its Water-Cement RatioConcrete is a mixture of Portland cement, water, sand, and crushed gravel or stone. The waterand cement form a cement paste in which the sand and stone or gravel are mixed. The sand and stone or gravel together make up the aggregate of a concrete mixture. The aggregate serves no structural function. It is merely ,a filler that adds low-cost bulk to the cement paste; it usually makes up about 75 percent of a given mass of concrete, by volume, although a poor aggregate can reduce the strength of a batch of concrete considerably, good aggregate adds only slightly to the strength of the cement.The two principal advantages of concrete as a construction material are its relative cheapness and the ease with which it can be handled and placed while it is in the plastic state.The principal structural advantages of concrete are its great compressive strength and its durability , Concrete can withstand very high compressive loads. This is what makes concrete so suitable for the foundations, walls, and columns of buildings, and for driveways and walks as well.The principal structural disadvantage of concrete is its poor tensile strength. That is, it cannot withstand pulling or bending loads without cracking or breaking. For this reason, steel rods, or reinforcement steel, are often embedded in concrete, the reinforcement steel providing the tensile strength the concrete lacks. Concrete with reinforcement steel embedded in it is reinforced concrete.In addition to its poor tensile strength, concrete, like most construction materials, expands in hot weather and when wet and contracts in cold weather and as it dries out. Unless these movements are allowed for during construction, the concrete will crack.And, contrary to common belief, solid concrete is not impervious to water. Some moisture will migrate into the best-made concrete. But if the concrete should be excessively porous ,which can happen if too much water has been used in mixing it, moisture can easily enter the concrete after it has cured. If this moisture should be present within the concrete when cold weather comes, the moisture may freeze, which may result in serious frost damage to the structure.Despite these limitations, concrete is an inherently strong and durable construction material. If the proportions of water, cement, and aggregate are carefully calculated and if the concrete is placed and allowed to cure according to simple but definite rules, it is possible to obtain from the concrete all the strength and durability that is inherent in it.The ratio of water to cement in a batch of concrete is the principal determinant of the concrete's final strength. At one time the instructions for preparing a batch of concrete would have contained proportions such as 1:2:4, indicating that 1 part of Portland cement to 2 parts of sand to 4 parts of gravel by volume were to be mixed together, after which sufficient water was to be added to obtain aworkable mixture. This procedure ignored entirely the importance of the water-cement ratio. It also resulted very often in the preparation or a very weak concrete, since the natural tendency is to add enough water to make placement of the concrete as easy as possible-the sloppier the better, as far as the workmen are concerned. This manner of specifying the proportions of concrete is obsolete and should never be followed.In theory, it takes only 3 gal of water to hydrate completely 1 cu ft of cement. (A sack of cement contains 1 cu ft exactly, and the sack weighs 94 lb). But this water-cement ratio produces a mixture that is too stiff to be worked. In practice, therefore, additional water, between 4 and 8 gal per sack of cement, is used to obtain a workable mixture.But the greater the proportion of water in a water-cement ratio, the weaker the final concrete will be. The additional water that is necessary to achieve a workable batch will only evaporate from the concrete as the concrete sets, and it will leave behind in the concrete innumerable voids. This is the reason there will always be some porosity in concrete. When an excessive amount of water has been used, there will be an excessive number of voids, which may cause the concrete to leak badly. If these voids should be filled with moisture when cold weather comes, they will cause the frost damage alluded to above.As a general rule, therefore, 6 gal of water per sack of cement should be the maximum amount used for making concrete; and the less the amount of water that is used, the stronger the concrete will be. Also included in the 6 gal is whatever surface moisture is contained in the sand that is part of the aggregate.3.MortarMortar is a mixture of a cementitious material (which may be portland cement or lime or both) and sand. When water is added to these ingredients, the result is a plastic substance that is used to bind together bricks, tiles, concrete blocks, and other kinds of masonry units. After the mortar has set, the masonry units are bound together by the ,mortar in such a way that they form a single structural unit.Mortar is closely related to other cementitious materials such as concrete, plaster, and stucco, but it would be a mistake to confuse mortar with these other materials or attempt to use them as a substitute for mortar; the properties required of each are distinctive and differ from the others.By a mistaken analogy with a chain and its weakest link, it is a common belief that for anymasonry construction to be strong, the mortar must be strong also. V ery often, for example, a person who is familiar with concrete will infer that mortar, being a cementitious material like concrete, should have properties similar to those of concrete and be mixed and used in much the same way. w Since, for example, concrete has, or should have, a high compressive strength, mortar should have a high compressive strength also. But the primary function of mortar is to bind the masonry units together, not to resist compressive loads or add to the strength of the masonry units.A great many tests have been made of brick walls built with mortars having a wide range of strength characteristics. ~ These tests show uniformly that a brick wall is strongest when the mortar used to bind the brick is weaker than the brick. Indeed, the mortar can be substantially weaker than the brick Without much affecting the overall strength of the construction. As long as the mortar is strong enough to resist the erosive effects of the weather and of freezing water, it is strong enough for use in the ordinary exterior wall.But suppose for the sake of argument that a brick wall has been built using a mortar that does have a compressive strength greater than that of the brick. ~Any stress this wall may be subjected to-the result of the settlement of the soil under the wall, say-will cause the brick to fracture along the line of greatest stress. This fracture will run in a single jagged crack right through the brick, from the top of the wall to the bottom.But when the mortar is weaker than the brick, as it should be, any stresses in the construction will be absorbed entirely by the mortar. The mortar will absorb these stresses in the form of a multitude of minute cracks invisible to the eye that leaves the basic strength of the construction unimpaired. The overall appearance of the wall and its structural integrity will be unchanged.Masonry constructions can, however, suffer from another type of failure. Sometimes stresses are relieved by a separation of the mortar from the brick. The result is a zig-zag crack through the mortar that follows the brick pattern. What has happened here is that the bond between the brick and the mortar was too weak, a consequence either of ignorance or poor workmanship, or both, since the last thing that should happen in a well-made masonry wall is for there to be a poor bond between the masonry units and the mortar. Either the mortar was incorrectly proportioned and mixed or it was improperly applied to the brick, or both,Freshly prepared mortar in which the cement, lime, and sand are accurately proportioned and mixed with the requited amount of water has a quality called workability or, sometimes, plasticity. Workability is as difficult to describe in words as the consistency of pancake batter or soft butter, butfresh mortar that doesn't have this quality will be incapable of bonding masonry units together as tightly as they should be, A workable mortar can be spread with a trowel smoothly, evenly, and without effort. The mortar has a cohesive quality that enables it to hold its shape and keeps it from falling of its own weight when it is troweled onto the side of a brick. A workable mortar has a give to it that enables a bricklayer to bed masonry units solidly into place. One can say that on a microscopic scale a workable mortar makes such intimate contact with the surface of a masonry unit that the bond between the mortar and the masonry unit is as strong as possible.建筑材料—混凝土与砂浆一、水泥与混凝土的早期历史自从人类开始存在时起，人的住处一直要求应用每个时代所能提供的最好的技术。
毕业设计外文资料翻译——翻译译文
毕业设计外文资料翻译（二）外文出处：Jules Houde 《Sustainable development slowed down by bad construction practices and natural and technological disasters》2、外文资料翻译译文混凝土结构的耐久性即使是工程师认为的最耐久和最合理的混凝土材料，在一定的条件下，混凝土也会由于开裂、钢筋锈蚀、化学侵蚀等一系列不利因素的影响而易受伤害。
近年来报道了各种关于混凝土结构耐久性不合格的例子。
尤其令人震惊的是混凝土的结构过早恶化的迹象越来越多。
每年为了维护混凝土的耐久性，其成本不断增加。
根据最近在国内和国际中的调查揭示，这些成本在八十年代间翻了一番，并将会在九十年代变成三倍。
越来越多的混凝土结构耐久性不合格的案例使从事混凝土行业的商家措手不及。
混凝土结构不仅代表了社会的巨大投资，也代表了如果耐久性问题不及时解决可能遇到的成本，更代表着，混凝土作为主要建筑材料，其耐久性问题可能导致的全球不公平竞争以及行业信誉等等问题。
因此，国际混凝土行业受到了强烈要求制定和实施合理的措施以解决当前耐久性问题的双重的挑战，即：找到有效措施来解决现有结构剩余寿命过早恶化的威胁。
纳入新的结构知识、经验和新的研究结果，以便监测结构耐久性，从而确保未来混凝土结构所需的服务性能。
所有参与规划、设计和施工过程的人，应该具有获得对可能恶化的过程和决定性影响参数的最低理解的可能性。
这种基本知识能力是要在正确的时间做出正确的决定，以确保混凝土结构耐久性要求的前提。
加固保护混凝土中的钢筋受到碱性的钝化层(pH值大于12.5)保护而阻止了锈蚀。
这种钝化层阻碍钢溶解。
因此，即使所有其它条件都满足(主要是氧气和水分)，钢筋受到锈蚀也都是不可能的。
混凝土的碳化作用或是氯离子的活动可以降低局部面积或更大面积的pH值。
当加固层的pH值低于9或是氯化物含量超过一个临界值时，钝化层和防腐保护层就会失效，钢筋受腐蚀是可能的。
土木工程类外文文献翻译---钢筋混凝土可编辑
土木工程类外文文献翻译---钢筋混凝土外文文献翻译院系_________________________班级_________________________姓名_________________________指导教师_________________________2012年2月20 日2 外文翻译21 Reinforced ConcretePlain concrete is formed from a hardened mixture of cement water fine aggregate coarse aggregate crushed stone or gravel air and often other admixtures The plastic mix is placed and consolidated in the formwork then cured to facilitate the acceleration of the chemical hydration reaction lf the cementwater mix resulting in hardened concrete The finished product has high compressive strength and low resistance to tension such that its tensile strength is approximately one tenth lf its compressive strength Consequently tensile and shear reinforcement in the tensile regions of sections has to be provided to compensate for the weak tension regions in the reinforced concrete elementIt is this deviation in the composition of a reinforces concrete section from the homogeneity of standard wood or steel sections that requires a modified approach to the basic principles of structural design The two components of the heterogeneous reinforced concrete section are to be so arranged and proportioned that optimal use is made of the materials involved This is possible because concrete can easily be givenany desired shape by placing and compacting the wet mixture of the constituent ingredients are properly proportioned the finished product becomes strong durable and in combination with the reinforcing bars adaptable for use as main members of any structural system The techniques necessary for placing concrete depend on the type of member to be cast that is whether it is a column a bean a wall a slab a foundation a mass columns or an extension of previously placed and hardened concrete For beams columns and walls the forms should be well oiled after cleaning them and the reinforcement should be cleared of rust and other harmful materials In foundations the earth should be compacted and thoroughly moistened to about 6 in in depth to avoid absorption of the moisture present in the wet concrete Concrete should always be placed in horizontal layers which are compacted by means of high frequency power-driven vibrators of either the immersion or external type as the case requires unless it is placed by pumping It must be kept in mind however that over vibration can be harmful since it could cause segregation of the aggregate and bleeding of the concreteHydration of the cement takes place in the presence of moisture at temperatures above 50°F It is necessary to maintain such a condition in order that the chemical hydration reaction can take place If drying is too rapid surface cracking takes place This would result in reduction of concrete strength due to cracking as well as the failure to attain full chemical hydrationIt is clear that a large number of parameters have to be dealt with in proportioning a reinforced concrete element such as geometrical widthdepth area of reinforcement steel strain concrete strain steel stress and so on Consequently trial and adjustment is necessary in the choice of concrete sections with assumptions based on conditions at site availability of the constituent materials particular demands of the owners architectural and headroom requirements the applicable codes and environmental reinforced concrete is often a site-constructed composite in contrast to the standard mill-fabricated beam and column sections in steel structuresA trial section has to be chosen for each critical location in a structural system The trial section has to be analyzed to determine if its nominal resisting strength is adequate to carry the applied factored load Since more than one trial is often necessary to arrive at the required section the first design input step generates into a series of trial-and-adjustment analysesThe trial-and –adjustment procedures for the choice of a concrete section lead to the convergence of analysis and design Hence every design is an analysis once a trial section is chosen The availability of handbooks charts and personal computers and programs supports this approach as a more efficient compact and speedy instructional method compared with the traditional approach of treating the analysis of reinforced concrete separately from pure design22 EarthworkBecause earthmoving methods and costs change more quickly than those in any other branch of civil engineering this is a field where there are real opportunities for the enthusiast In 1935 most of the methods now inuse for carrying and excavating earth with rubber-tyred equipment did not exist Most earth was moved by narrow rail track now relatively rare and the main methods of excavation with face shovel backacter or dragline or grab though they are still widely used are only a few of the many current methods To keep his knowledge of earthmoving equipment up to date an engineer must therefore spend tine studying modern machines Generally the only reliable up-to-date information on excavators loaders and transport is obtainable from the makersEarthworks or earthmoving means cutting into ground where its surface is too high cuts and dumping the earth in other places where the surface is too low fills Toreduce earthwork costs the volume of the fills should be equal to the volume of the cuts and wherever possible the cuts should be placednear to fills of equal volume so as to reduce transport and double handlingof the fill This work of earthwork design falls on the engineer who lays out the road since it is the layout of the earthwork more than anything else which decides its cheapness From the available maps ahd levels the engineering must try to reach as many decisions as possible in the drawing office by drawing cross sections of the earthwork On the site when further information becomes available he can make changes in jis sections and layoutbut the drawing lffice work will not have been lost It will have helped him to reach the best solution in the shortest timeThe cheapest way of moving earth is to take it directly out of the cut and drop it as fill with the same machine This is not always possible but when it canbe done it is ideal being both quick and cheap Draglinesbulldozers and face shovels an do this The largest radius is obtained with the draglineand the largest tonnage of earth is moved by the bulldozer though only over short distancesThe disadvantages of the dragline are that it must dig below itself it cannot dig with force into compacted material it cannot dig on steep slopws and its dumping and digging are not accurate Face shovels are between bulldozers and draglines having a larger radius of action than bulldozers but less than draglines They are anle to dig into a vertical cliff face in a way which would be dangerous tor a bulldozer operator and impossible for a dragline Each piece of equipment should be level of their tracks and for deep digs in compact material a backacter is most useful but its dumping radius is considerably less than that of the same escavator fitted with a face shovelRubber-tyred bowl scrapers are indispensable for fairly level digging where the distance of transport is too much tor a dragline or face shovel They can dig the material deeply but only below themselves to a fairly flat surface carry it hundreds of meters if need be then drop it and level it roughly during the dumping For hard digging it is often found economical to keep a pusher tractor wheeled or tracked on the digging site to push each scraper as it returns to dig As soon as the scraper is fullthe pusher tractor returns to the beginning of the dig to heop to help the nest scraperBowl scrapers are often extremely powerful machinesmany makers build scrapers of 8 cubic meters struck capacity which carry 10 m 3 heaped The largest self-propelled scrapers are of 19 m 3 struck capacity 25 m 3 heaped and they are driven by a tractor engine of 430 horse-powersDumpers are probably the commonest rubber-tyred transport since they can also conveniently be used for carrying concrete or other building materials Dumpers have the earth container over the front axle on large rubber-tyred wheels and the container tips forwards on most types though in articulated dumpers the direction of tip can be widely varied The smallest dumpers have a capacity of about 05 m 3 and the largest standard types are of about 45 m 3 Special types include the self-loading dumper of up to 4 m 3 and the articulated type of about 05 m 3 The distinction between dumpers and dump trucks must be remembered dumpers tip forwards and the driver sits behind the load Dump trucks are heavy strengthened tipping lorries the driver travels in front lf the load and the load is dumped behind him so they are sometimes called rear-dump trucks23 Safety of StructuresThe principal scope of specifications is to provide general principles and computational methods in order to verify safety of structures The safety factor which according to modern trends is independent of the nature and combination of the materials used can usually be defined as the ratio between the conditions This ratio is also proportional to the inverse of the probability risk of failure of the structureFailure has to be considered not only as overall collapse of the structure but also as unserviceability or according to a more precise Common definition As the reaching of a limit state which causes the construction not to accomplish the task it was designed for There are two categories of limit state1 Ultimate limit sate which corresponds to the highest value of the load-bearing capacity Examples include local buckling or global instability of the structure failure of some sections and subsequent transformation of the structure into a mechanism failure by fatigue elastic or plastic deformation or creep that cause a substantial change of the geometry of the structure and sensitivity of the structure to alternating loads to fire and to explosions2 Service limit states which are functions of the use and durability of the structure Examples include excessive deformations and displacements without instability early or excessive cracks large vibrations and corrosionComputational methods used to verify structures with respect to the different safety conditions can be separated into1 Deterministic methods in which the main parameters are considered as nonrandom parameters2 Probabilistic methods in which the main parameters are considered as random parametersAlternatively with respect to the different use of factors of safety computational methods can be separated into1 Allowable stress method in which the stresses computed under imum loads are compared with the strength of the material reduced by given safety factors2 Limit states method in which the structure may be proportioned on the basis of its imum strength This strength as determined by rational analysis shall not be less than that required to support a factored loadequal to the sum of the factored live load and dead load ultimate state The stresses corresponding to working service conditions with unfactored live and dead loads are compared with prescribed values service limit state From the four possible combinations of the first two and second two methods we can obtain some useful computational methods Generally two combinations prevail1 deterministic methods which make use of allowable stresses2 Probabilistic methods which make use of limit statesThe main advantage of probabilistic approaches is that at least in theory it is possible to scientifically take into account all random factors of safety which are then combined to define the safety factor probabilistic approaches depend upon1 Random distribution of strength of materials with respect to the conditions of fabrication and erection scatter of the values of mechanical properties through out the structure2 Uncertainty of the geometry of the cross-section sand of the structure faults and imperfections due to fabrication and erection of the structure3 Uncertainty of the predicted live loads and dead loads acting on the structure4 Uncertainty related to the approximation of the computational method used deviation of the actual stresses from computed stresses Furthermore probabilistic theories mean that the allowable risk can be based on several factors such as1 Importance of the construction and gravity of the damage byits failure2 Number of human lives which can be threatened by this failure3 Possibility andor likelihood of repairing the structure4 Predicted life of the structureAll these factors are related to economic and social considerations such as1 Initial cost of the construction2 Aortization funds for the duration of the construction3 Cost of physical and material damage due to the failure of the construction4 Adverse impact on society5 Moral and psychological viewsThe definition of all these parameters for a given safety factor allows construction at the optimum cost However the difficulty of carrying out a complete probabilistic analysis has to be taken into account For such an analysis the laws of the distribution of the live load and its induced stresses of the scatter of mechanical properties of materials and of the geometry of the cross-sections and the structure have to be known Furthermore it is difficult to interpret the interaction between the law of distribution of strength and that of stresses because both depend upon the nature of the material on the cross-sections and upon the load acting on the structure These practical difficulties can be overcome in two ways The first is to apply different safety factors to the material and to the loads without necessarily adopting the probabilistic criterion The second is an approximate probabilistic method which introduces some simplifyingassumptions semi-probabilistic methods1 中文翻译11钢筋混凝土素混凝土是由水泥水细骨料粗骨料碎石或卵石空气通常还有其他外加剂等经过凝固硬化而成将可塑的混凝土拌合物注入到模板内并将其捣实然后进行养护以加速水泥与水的水化反应最后获得硬化的混凝土其最终制成品具有较高的抗压强度和较低的抗拉强度其抗拉强度约为抗压强度的十分之一因此截面的受拉区必须配置抗拉钢筋和抗剪钢筋以增加钢筋混凝土构件中较弱的受拉区的强度由于钢筋混凝土截面在均质性上与标准的木材或钢的截面存在着差异因此需要对结构设计的基本原理进行修改将钢筋混凝土这种非均质截面的两种组成部分按一定比例适当布置可以最好的利用这两种材料这一要求是可以达到的因混凝土由配料搅拌成湿拌合物经过振捣并凝固硬化可以做成任何一种需要的形状如果拌制混凝土的各种材料配合比恰当则混凝土制成品的强度较高经久耐用配置钢筋后可以作为任何结构体系的主要构件浇筑混凝土所需要的技术取决于即将浇筑的构件类型诸如柱梁墙板基础大体积混凝土水坝或者继续延长已浇筑完毕并且已经凝固的混凝土等对于梁柱墙等构件当模板清理干净后应该在其上涂油钢筋表面的锈及其他有害物质也应该被清除干净浇筑基础前应将坑底土夯实并用水浸湿6英寸以免土壤从新浇的混凝土中吸收水分一般情况下除使用混凝土泵浇筑外混凝土都应在水平方向分层浇筑并使用插入式或表面式高频电动振捣器捣实必须记住过分的振捣将导致骨料离析和混凝土泌浆等现象因而是有害的水泥的水化作用发生在有水分存在而且气温在50°F以上的条件下为了保证水泥的水化作用得以进行必须具备上述条件如果干燥过快则会出现表面裂缝这将有损与混凝土的强度同时也会影响到水泥水化作用的充分进行设计钢筋混凝土构件时显然需要处理大量的参数诸如宽度高度等几何尺寸配筋的面积钢筋的应变和混凝土的应变钢筋的应力等等因此在选择混凝土截面时需要进行试算并作调整根据施工现场条件混凝土原材料的供应情况业主提出的特殊要求对建筑和净空高度的要求所用的设计规范以及建筑物周围环境条件等最后确定截面钢筋混凝土通常是现场浇注的合成材料它与在工厂中制造的标准的钢结构梁柱等不同因此对于上面所提到的一系列因素必须予以考虑对结构体系的各个部位均需选定试算截面并进行验算以确定该截面的名义强度是否足以承受所作用的计算荷载由于经常需要进行多次试算才能求出所需的截面因此设计时第一次采用的数值将导致一系列的试算与调整工作选择混凝土截面时采用试算与调整过程可以使复核与设计结合在一起因此当试算截面选定后每次设计都是对截面进行复核手册图表和微型计算机以及专用程序的使用使这种设计方法更为简捷有效而传统的方法则是把钢筋混凝土的复核与单纯的设计分别进行处理12土方工程由于和土木工程中任何其他工种的施工方法与费用相比较土方挖运的施工方法与费用的变化都要快得多因此对于有事业心的人来说土方工程是一个可以大有作为的领域在1935年目前采用的利用轮胎式机械设备进行土方挖运的方法大多数还没有出现那是大部分土方是采用窄轨铁路运输在这目前来说是很少采用的当时主要的开挖方式是使用正铲反铲拉铲或抓斗等挖土机尽管这些机械目前仍然在广泛应用但是它们只不过是目前所采用的许多方法中的一小部分因此一个工程师为了使自己在土方挖运设备方面的知识跟得上时代的发展他应当花费一些时间去研究现代的机械一般说来有关挖土机装载机和运输机械的唯一可靠而又最新的资料可以从制造厂商处获得土方工程或土方挖运工程指的是把地表面过高处的土壤挖去挖方并把它倾卸到地表面过低的其他地方填方为了降低土方工程费用填方量应该等于挖方量而且挖方地点应该尽可能靠近土方量相等的填方地点以减少运输量和填方的二次搬运土方设计这项工作落到了从事道路设计的工程师的身上因为土方工程的设计比其他任何工作更能决定工程造价是否低廉根据现有的地图和标高道路工程师应在设计绘图室中的工作也并不是徒劳的它将帮助他在最短的时间内获得最好的方案费用最低的运土方法是用同一台机械直接挖方取土并且卸土作为填方这并不是经常可以做到的但是如果能够做到则是很理想的因为这样做既快捷又省钱拉铲挖土机推土机和正铲挖土机都能做到这点拉铲挖土机的工作半径最大推土机所推运的图的数量最多只是运输距离很短拉铲挖土机的缺点是只能挖比它本身低的土不能施加压力挖入压实的土壤内不能在陡坡上挖土而且挖卸都不准确正铲挖土机介于推土机和拉铲挖土机的之间其作用半径大于推土机但小于拉铲挖土机正铲挖土机能挖取竖直陡峭的工作面这种方式对推土机司机来说是危险的而对拉铲挖土机则是不可能的每种机械设备应该进行最适合它的性能的作业正铲挖土机不能挖比其停机平面低很多的土而深挖坚实的土壤时反铲挖土机最适用但其卸料半径比起装有正铲的同一挖土机的卸料半径则要小很多在比较平坦的场地开挖如果用拉铲或正铲挖土机运输距离太远时则装有轮胎式的斗式铲运机就是比不可少的它能在比较平的地面上挖较深的土但只能挖机械本身下面的土需要时可以将土运至几百米远然后卸土并在卸土的过程中把土大致铲平在挖掘硬土时人们发现在开挖场地经常用一辆助推拖拉机轮式或履带式对返回挖土的铲运机进行助推这种施工方法是经济的一旦铲运机装满助推拖拉机就回到开挖的地点去帮助下一台铲运机斗式铲运机通常是功率非常大的机械许多厂家制造的铲运机铲斗容量为8 m3满载时可达10 m3最大的自行式铲运机铲斗容量为19立方米满载时为25 m3由430马力的牵引发动机驱动翻斗机可能是使用最为普遍的轮胎式运输设备因为它们还可以被用来送混凝土或者其他建筑材料翻斗车的车斗位于大橡胶轮胎车轮前轴的上方尽管铰接式翻斗车的卸料方向有很多种但大多数车斗是向前翻转的最小的翻斗车的容量大约为05立方米而最大的标准型翻斗车的容量大约为45m3特殊型式的翻斗车包括容量为4 m3的自装式翻斗车和容量约为05 m3的铰接式翻斗车必须记住翻斗车与自卸卡车之间的区别翻斗车车斗向前倾翻而司机坐在后方卸载因此有时被称为后卸卡车13结构的安全度规范的主要目的是提供一般性的设计原理和计算方法以便验算结构的安全度就目前的趋势而言安全系数与所使用的材料性质及其组织情况无关通常把它定义为发生破坏的条件与结构可预料的最不利的工作条件之比值这个比值还与结构的破坏概率危险率成反比破坏不仅仅指结构的整体破坏而且还指结构不能正常的使用或者用更为确切的话来说把破坏看成是结构已经达到不能继续承担其设计荷载的极限状态通常有两种类型的极限状态即1强度极限状态它相当于结构能够达到的最大承载能力其例子包括结构的局部屈曲和整体不稳定性某此界面失效随后结构转变为机构疲劳破坏引起结构几何形状显著变化的弹性变形或塑性变形或徐变结构对交变荷载火灾和爆炸的敏感性2使用极限状态它对应着结构的使用功能和耐久性器例子包括结构失稳之前的过大变形和位移早期开裂或过大的裂缝较大的振动和腐蚀根据不同的安全度条件可以把结构验算所采用的计算方法分成1确定性的方法在这种方法中把主要参数看作非随机参数2概率方法在这种方法中主要参数被认为是随机参数此外根据安全系数的不同用途可以把结构的计算方法分为1容许应力法在这种方法中把结构承受最大荷载时计算得到的应力与经过按规定的安全系数进行折减后的材料强度作比较2极限状态法在这种方法中结构的工作状态是以其最大强度为依据来衡量的由理论分析确定的这一最大强度应不小于结构承受计算荷载所算得的强度极限状态计算荷载等于分别乘以荷载系数的活载与恒载之和把对应于不乘以荷载系数的活载和恒载的工作使用条件的应力与规定值使用极限状态相比较根据前两种方法和后两种方法的四种可能组合我们可以得到一些实用的计算方法通常采用下面两种计算方法确定性的方法这种方法采用容许应力概率方法这种方法采用极限状态至少在理论上概率法的主要优点是可以科学的考虑所有随机安全系数然后将这些随机安全系数组合成确定的安全系数概率法取决于1制作和安装过程中材料强度的随机分布整个结构的力学性能数值的分散性2截面和结构几何尺寸的不确定性由结构制作和安装造成的误差和缺陷而引起的对作用在结构上的活载和恒载的预测的不确定性所采用的近似计算方法有关的不精确性实际应力与计算应力的偏差此外概率理论意味着可以基于下面几个因素来确定允许的危险率例如建筑物的重要性和建筑物破坏造成的危害性2由于建筑物破坏使生活受到威胁的人数3修复建筑的可能性4建筑物的预期寿命所有这些因素均与经济和社会条件有关例如1建筑物的初始建设费2建筑物使用期限内的折旧费3由于建筑物破坏而造成的物质和材料损失费4在社会上造成的不良影响5精神和心理上的考虑就给定的安全系数而论所有这些参数的确定都是以建筑物的最佳成本为依据的但是应该考虑到进行全概率分析的困难对于这种分析来说应该了解活载及其所引起的盈利的分布规律材料的力学性能的分散性和截面的结构几何尺寸的分散性此外由于强度的分布规律和应力的分布规律之间的相互关系是困难的这些实际困难可以采用两种方法来克服第一种方法对材料和荷载采用不同的安全系数而不需要采用概率准则第二种方法是引入一些而简化假设的近似概率方法半概率方法1建筑工程学院土木工程系土木084班。
英文介绍混凝土的作文
英文介绍混凝土的作文英文：Concrete is a versatile and durable building material that is widely used in construction projects around the world. It is made up of a mixture of cement, water, and aggregates such as sand, gravel, or crushed stone.One of the main advantages of concrete is its strength and durability. It can withstand a great deal of weight and pressure, making it ideal for use in buildings, bridges, and other structures that need to be able to support heavy loads. Additionally, concrete is resistant to fire, water, and weather damage, making it a good choice for structures that need to be able to withstand harsh environmental conditions.Another advantage of concrete is its versatility. It can be molded into a variety of shapes and sizes, making it ideal for use in a wide range of construction projects. Forexample, it can be used to create walls, floors, and ceilings, as well as decorative elements such as statues, fountains, and other outdoor features.Despite its many advantages, concrete does have some drawbacks. For one thing, it can be quite heavy, which can make it difficult to transport and install. Additionally, it can be prone to cracking and other forms of damage if it is not properly maintained.Overall, however, concrete is an excellent choice for construction projects of all kinds. Its strength, durability, and versatility make it a valuable building material that is sure to continue to be used for many years to come.中文：混凝土是一种多功能且耐用的建筑材料，广泛应用于全球各地的建筑项目中。
钢筋混凝土中英文资料外文翻译文献
钢筋混凝土中英文资料翻译1 外文翻译1.1 Reinforced ConcretePlain concrete is formed from a hardened mixture of cement ,water ,fine aggregate, coarse aggregate (crushed stone or gravel),air, and often other admixtures. The plastic mix is placed and consolidated in the formwork, then cured to facilitate the acceleration of the chemical hydration reaction lf the cement/water mix, resulting in hardened concrete. The finished product has high compressive strength, and low resistance to tension, such that its tensile strength is approximately one tenth lf its compressive strength. Consequently, tensile and shear reinforcement in the tensile regions of sections has to be provided to compensate for the weak tension regions in the reinforced concrete element.It is this deviation in the composition of a reinforces concrete section from the homogeneity of standard wood or steel sections that requires a modified approach to the basic principles of structural design. The two components of the heterogeneous reinforced concrete section are to be so arranged and proportioned that optimal use is made of the materials involved. This is possible because concrete can easily be given any desired shape by placing and compacting the wet mixture of the constituent ingredients are properly proportioned, the finished product becomes strong, durable, and, in combination with the reinforcing bars, adaptable for use as main members of anystructural system.The techniques necessary for placing concrete depend on the type of member to be cast: that is, whether it is a column, a bean, a wall, a slab, a foundation. a mass columns, or an extension of previously placed and hardened concrete. For beams, columns, and walls, the forms should be well oiled after cleaning them, and the reinforcement should be cleared of rust and other harmful materials. In foundations, the earth should be compacted and thoroughly moistened to about 6 in. in depth to avoid absorption of the moisture present in the wet concrete. Concrete should always be placed in horizontal layers which are compacted by means of high frequency power-driven vibrators of either the immersion or external type, as the case requires, unless it is placed by pumping. It must be kept in mind, however, that over vibration can be harmful since it could cause segregation of the aggregate and bleeding of the concrete.Hydration of the cement takes place in the presence of moisture at temperatures above 50°F. It is necessary to maintain such a condition in order that the chemical hydration reaction can take place. If drying is too rapid, surface cracking takes place. This would result in reduction of concrete strength due to cracking as well as the failure to attain full chemical hydration.It is clear that a large number of parameters have to be dealt with in proportioning a reinforced concrete element, such as geometrical width, depth, area of reinforcement, steel strain, concrete strain, steel stress, and so on. Consequently, trial and adjustment is necessary in the choice of concrete sections, with assumptions based on conditions at site, availability of the constituent materials, particular demands of the owners, architectural and headroom requirements, the applicable codes, and environmental reinforced concrete is often a site-constructed composite, in contrast to the standard mill-fabricated beam and column sections in steel structures.A trial section has to be chosen for each critical location in a structural system. The trial section has to be analyzed to determine if its nominal resisting strength is adequate to carry the applied factored load. Since more than one trial is often necessary to arrive at the required section, the first design input step generates into a series of trial-and-adjustment analyses.The trial-and –adjustment procedures for the choice of a concrete section lead to the convergence of analysis and design. Hence every design is an analysis once a trial section is chosen. The availability of handbooks, charts, and personal computers and programs supports this approach as a more efficient, compact, and speedy instructionalmethod compared with the traditional approach of treating the analysis of reinforced concrete separately from pure design.1.2 EarthworkBecause earthmoving methods and costs change more quickly than those in any other branch of civil engineering, this is a field where there are real opportunities for the enthusiast. In 1935 most of the methods now in use for carrying and excavating earth with rubber-tyred equipment did not exist. Most earth was moved by narrow rail track, now relatively rare, and the main methods of excavation, with face shovel, backacter, or dragline or grab, though they are still widely used are only a few of the many current methods. To keep his knowledge of earthmoving equipment up to date an engineer must therefore spend tine studying modern machines. Generally the only reliable up-to-date information on excavators, loaders and transport is obtainable from the makers.Earthworks or earthmoving means cutting into ground where its surface is too high ( cuts ), and dumping the earth in other places where the surface is too low ( fills). Toreduce earthwork costs, the volume of the fills should be equal to the volume of the cuts and wherever possible the cuts should be placednear to fills of equal volume so as to reduce transport and double handlingof the fill. This work of earthwork design falls on the engineer who lays out the road since it is the layout of the earthwork more than anything else which decides its cheapness. From the available maps ahd levels, the engineering must try to reach as many decisions as possible in the drawing office by drawing cross sections of the earthwork. On the site when further information becomes available he can make changes in jis sections and layout,but the drawing lffice work will not have been lost. It will have helped him to reach the best solution in the shortest time.The cheapest way of moving earth is to take it directly out of the cut and drop it as fill with the same machine. This is not always possible, but when it canbe done it is ideal, being both quick and cheap. Draglines, bulldozers and face shovels an do this. The largest radius is obtained with the dragline,and the largest tonnage of earth is moved by the bulldozer, though only over short distances.The disadvantages of the dragline are that it must dig below itself, it cannot dig with force into compacted material, it cannot dig on steep slopws, and its dumping and digging are not accurate.Face shovels are between bulldozers and draglines, having a larger radius of action than bulldozers but less than draglines. They are anle to dig into a vertical cliff face in a way which would be dangerous tor a bulldozer operator and impossible for a dragline.Each piece of equipment should be level of their tracks and for deep digs in compact material a backacter is most useful, but its dumping radius is considerably less than that of the same escavator fitted with a face shovel.Rubber-tyred bowl scrapers are indispensable for fairly level digging where the distance of transport is too much tor a dragline or face shovel. They can dig the material deeply ( but only below themselves ) to a fairly flat surface, carry it hundreds of meters if need be, then drop it and level it roughly during the dumping. For hard digging it is often found economical to keep a pusher tractor ( wheeled or tracked ) on the digging site, to push each scraper as it returns to dig. As soon as the scraper is full,the pusher tractor returns to the beginning of the dig to heop to help the nest scraper.Bowl scrapers are often extremely powerful machines;many makers build scrapers of 8 cubic meters struck capacity, which carry 10 m ³ heaped. The largest self-propelled scrapers are of 19 m ³ struck capacity ( 25 m ³ heaped )and they are driven by a tractor engine of 430 horse-powers.Dumpers are probably the commonest rubber-tyred transport since they can also conveniently be used for carrying concrete or other building materials. Dumpers have the earth container over the front axle on large rubber-tyred wheels, and the container tips forwards on most types, though in articulated dumpers the direction of tip can be widely varied. The smallest dumpers have a capacity of about 0.5 m ³, and the largest standard types are of about 4.5 m ³. Special types include the self-loading dumper of up to 4 m ³and the articulated type of about 0.5 m ³. The distinction between dumpers and dump trucks must be remembered .dumpers tip forwards and the driver sits behind the load. Dump trucks are heavy, strengthened tipping lorries, the driver travels in front lf the load and the load is dumped behind him, so they are sometimes called rear-dump trucks.1.3 Safety of StructuresThe principal scope of specifications is to provide general principles and computational methods in order to verify safety of structures. The “ safety factor ”, which according to modern trends is independent of the nature and combination of the materials used, can usually be defined as the ratio between the conditions. This ratio is also proportional to the inverse of the probability ( risk ) of failure of the structure.Failure has to be considered not only as overall collapse of the structure but also as unserviceability or, according to a more precise. Common definition. As the reaching of a “limit state ” which causes the construction not to accomplish the task it was designedfor. There are two categories of limit state :(1)Ultimate limit sate, which corresponds to the highest value of the load-bearing capacity. Examples include local buckling or global instability of the structure; failure of some sections and subsequent transformation of the structure into a mechanism; failure by fatigue; elastic or plastic deformation or creep that cause a substantial change of the geometry of the structure; and sensitivity of the structure to alternating loads, to fire and to explosions.(2)Service limit states, which are functions of the use and durability of the structure. Examples include excessive deformations and displacements without instability; early or excessive cracks; large vibrations; and corrosion.Computational methods used to verify structures with respect to the different safety conditions can be separated into:(1)Deterministic methods, in which the main parameters are considered as nonrandom parameters.(2)Probabilistic methods, in which the main parameters are considered as random parameters.Alternatively, with respect to the different use of factors of safety, computational methods can be separated into:(1)Allowable stress method, in which the stresses computed under maximum loads are compared with the strength of the material reduced by given safety factors.(2)Limit states method, in which the structure may be proportioned on the basis of its maximum strength. This strength, as determined by rational analysis, shall not be less than that required to support a factored load equal to the sum of the factored live load and dead load ( ultimate state ).The stresses corresponding to working ( service ) conditions with unfactored live and dead loads are compared with prescribed values ( service limit state ) . From the four possible combinations of the first two and second two methods, we can obtain some useful computational methods. Generally, two combinations prevail:(1)deterministic methods, which make use of allowable stresses.(2)Probabilistic methods, which make use of limit states.The main advantage of probabilistic approaches is that, at least in theory, it is possible to scientifically take into account all random factors of safety, which are then combined to define the safety factor. probabilistic approaches depend upon :(1) Random distribution of strength of materials with respect to the conditions offabrication and erection ( scatter of the values of mechanical properties through out the structure );(2) Uncertainty of the geometry of the cross-section sand of the structure ( faults and imperfections due to fabrication and erection of the structure );(3) Uncertainty of the predicted live loads and dead loads acting on the structure;(4)Uncertainty related to the approximation of the computational method used ( deviation of the actual stresses from computed stresses ).Furthermore, probabilistic theories mean that the allowable risk can be based on several factors, such as :(1) Importance of the construction and gravity of the damage by its failure;(2)Number of human lives which can be threatened by this failure;(3)Possibility and/or likelihood of repairing the structure;(4) Predicted life of the structure.All these factors are related to economic and social considerations such as：(1) Initial cost of the construction;(2) Amortization funds for the duration of the construction;(3) Cost of physical and material damage due to the failure of the construction;(4) Adverse impact on society;(5) Moral and psychological views.The definition of all these parameters, for a given safety factor, allows construction at the optimum cost. However, the difficulty of carrying out a complete probabilistic analysis has to be taken into account. For such an analysis the laws of the distribution of the live load and its induced stresses, of the scatter of mechanical properties of materials, and of the geometry of the cross-sections and the structure have to be known. Furthermore, it is difficult to interpret the interaction between the law of distribution of strength and that of stresses because both depend upon the nature of the material, on the cross-sections and upon the load acting on the structure. These practical difficulties can be overcome in two ways. The first is to apply different safety factors to the material and to the loads, without necessarily adopting the probabilistic criterion. The second is an approximate probabilistic method which introduces some simplifying assumptions ( semi-probabilistic methods ) 。
(完整版)土木工程毕业设计外文文献翻译
外文文献翻译Reinforced ConcreteConcrete and reinforced concrete are used as building materials in every country. In many, including the United States and Canada, reinforced concrete is a dominant structural material in engineered construction. The universal nature of reinforced concrete construction stems from the wide availability of reinforcing bars and the constituents of concrete, gravel, sand, and cement, the relatively simple skills required in concrete construction, and the economy of reinforced concrete compared to other forms of construction. Concrete and reinforced concrete are used in bridges, buildings of all sorts underground structures, water tanks, television towers, offshore oil exploration and production structures, dams, and even in ships.Reinforced concrete structures may be cast-in-place concrete, constructed in their final location, or they may be precast concrete produced in a factory and erected at the construction site. Concrete structures may be severe and functional in design, or the shape and layout and be whimsical and artistic. Few other building materials off the architect and engineer such versatility and scope.Concrete is strong in compression but weak in tension. As a result, cracks develop whenever loads, or restrained shrinkage of temperature changes, give rise to tensile stresses in excess of the tensile strength of the concrete. In a plain concrete beam, the moments about the neutral axis due to applied loads are resisted by an internal tension-compression couple involving tension in the concrete. Such a beam fails very suddenly and completely when the first crack forms. In a reinforced concrete beam, steel bars are embedded in the concrete in such a way that the tension forces needed for moment equilibrium after the concrete cracks can be developed in the bars.The construction of a reinforced concrete member involves building a from of mold in the shape of the member being built. The form must be strong enough to support both the weight and hydrostatic pressure of the wet concrete, and any forces applied to it by workers, concrete buggies, wind, and so on. The reinforcement is placed in this form and held in placeduring the concreting operation. After the concrete has hardened, the forms are removed. As the forms are removed, props of shores are installed to support the weight of the concrete until it has reached sufficient strength to support the loads by itself.The designer must proportion a concrete member for adequate strength to resist the loads and adequate stiffness to prevent excessive deflections. In beam must be proportioned so that it can be constructed. For example, the reinforcement must be detailed so that it can be assembled in the field, and since the concrete is placed in the form after the reinforcement is in place, the concrete must be able to flow around, between, and past the reinforcement to fill all parts of the form completely.The choice of whether a structure should be built of concrete, steel, masonry, or timber depends on the availability of materials and on a number of value decisions. The choice of structural system is made by the architect of engineer early in the design, based on the following considerations:1. Economy. Frequently, the foremost consideration is the overall const of the structure. This is, of course, a function of the costs of the materials and the labor necessary to erect them. Frequently, however, the overall cost is affected as much or more by the overall construction time since the contractor and owner must borrow or otherwise allocate money to carry out the construction and will not receive a return on this investment until the building is ready for occupancy. In a typical large apartment of commercial project, the cost of construction financing will be a significant fraction of the total cost. As a result, financial savings due to rapid construction may more than offset increased material costs. For this reason, any measures the designer can take to standardize the design and forming will generally pay off in reduced overall costs.In many cases the long-term economy of the structure may be more important than the first cost. As a result, maintenance and durability are important consideration.2. Suitability of material for architectural and structural function.A reinforced concrete system frequently allows the designer to combine the architectural and structural functions. Concrete has the advantage that it is placed in a plastic condition and is given the desired shapeand texture by means of the forms and the finishing techniques. This allows such elements ad flat plates or other types of slabs to serve as load-bearing elements while providing the finished floor and / or ceiling surfaces. Similarly, reinforced concrete walls can provide architecturally attractive surfaces in addition to having the ability to resist gravity, wind, or seismic loads. Finally, the choice of size of shape is governed by the designer and not by the availability of standard manufactured members.3. Fire resistance. The structure in a building must withstand the effects of a fire and remain standing while the building is evacuated and the fire is extinguished. A concrete building inherently has a 1- to 3-hour fire rating without special fireproofing or other details. Structural steel or timber buildings must be fireproofed to attain similar fire ratings.4. Low maintenance.Concrete members inherently require less maintenance than do structural steel or timber members. This is particularly true if dense, air-entrained concrete has been used for surfaces exposed to the atmosphere, and if care has been taken in the design to provide adequate drainage off and away from the structure. Special precautions must be taken for concrete exposed to salts such as deicing chemicals.5. Availability of materials. Sand, gravel, cement, and concrete mixing facilities are very widely available, and reinforcing steel can be transported to most job sites more easily than can structural steel. As a result, reinforced concrete is frequently used in remote areas.On the other hand, there are a number of factors that may cause one to select a material other than reinforced concrete. These include:1. Low tensile strength.The tensile strength concrete is much lower than its compressive strength ( about 1/10 ), and hence concrete is subject to cracking. In structural uses this is overcome by using reinforcement to carry tensile forces and limit crack widths to within acceptable values. Unless care is taken in design and construction, however, these cracks may be unsightly or may allow penetration of water. When this occurs, water or chemicals such as road deicing salts may cause deterioration or staining of the concrete. Special design details are required in such cases. In the case of water-retaining structures, special details and /of prestressing are required to prevent leakage.2. Forms and shoring. The construction of a cast-in-place structure involves three steps not encountered in the construction of steel or timber structures. These are ( a ) the construction of the forms, ( b ) the removal of these forms, and (c) propping or shoring the new concrete to support its weight until its strength is adequate. Each of these steps involves labor and / or materials, which are not necessary with other forms of construction.3. Relatively low strength per unit of weight for volume.The compressive strength of concrete is roughly 5 to 10% that of steel, while its unit density is roughly 30% that of steel. As a result, a concrete structure requires a larger volume and a greater weight of material than does a comparable steel structure. As a result, long-span structures are often built from steel.4. Time-dependent volume changes. Both concrete and steel undergo-approximately the same amount of thermal expansion and contraction. Because there is less mass of steel to be heated or cooled, and because steel is a better concrete, a steel structure is generally affected by temperature changes to a greater extent than is a concrete structure. On the other hand, concrete undergoes frying shrinkage, which, if restrained, may cause deflections or cracking. Furthermore, deflections will tend to increase with time, possibly doubling, due to creep of the concrete under sustained loads.In almost every branch of civil engineering and architecture extensive use is made of reinforced concrete for structures and foundations. Engineers and architects requires basic knowledge of reinforced concrete design throughout their professional careers. Much of this text is directly concerned with the behavior and proportioning of components that make up typical reinforced concrete structures-beams, columns, and slabs. Once the behavior of these individual elements is understood, the designer will have the background to analyze and design a wide range of complex structures, such as foundations, buildings, and bridges, composed of these elements.Since reinforced concrete is a no homogeneous material that creeps, shrinks, and cracks, its stresses cannot be accurately predicted by the traditional equations derived in a course in strength of materials forhomogeneous elastic materials. Much of reinforced concrete design in therefore empirical, i.e., design equations and design methods are based on experimental and time-proved results instead of being derived exclusively from theoretical formulations.A thorough understanding of the behavior of reinforced concrete will allow the designer to convert an otherwise brittle material into tough ductile structural elements and thereby take advantage of concrete’s desirable characteristics, its high compressive strength, its fire resistance, and its durability.Concrete, a stone like material, is made by mixing cement, water, fine aggregate ( often sand ), coarse aggregate, and frequently other additives ( that modify properties ) into a workable mixture. In its unhardened or plastic state, concrete can be placed in forms to produce a large variety of structural elements. Although the hardened concrete by itself, i.e., without any reinforcement, is strong in compression, it lacks tensile strength and therefore cracks easily. Because unreinforced concrete is brittle, it cannot undergo large deformations under load and fails suddenly-without warning. The addition fo steel reinforcement to the concrete reduces the negative effects of its two principal inherent weaknesses, its susceptibility to cracking and its brittleness. When the reinforcement is strongly bonded to the concrete, a strong, stiff, and ductile construction material is produced. This material, called reinforced concrete, is used extensively to construct foundations, structural frames, storage takes, shell roofs, highways, walls, dams, canals, and innumerable other structures and building products. Two other characteristics of concrete that are present even when concrete is reinforced are shrinkage and creep, but the negative effects of these properties can be mitigated by careful design.A code is a set technical specifications and standards that control important details of design and construction. The purpose of codes it produce structures so that the public will be protected from poor of inadequate and construction.Two types f coeds exist. One type, called a structural code, is originated and controlled by specialists who are concerned with the proper use of a specific material or who are involved with the safe design of a particular class of structures.The second type of code, called a building code, is established to cover construction in a given region, often a city or a state. The objective of a building code is also to protect the public by accounting for the influence of the local environmental conditions on construction. For example, local authorities may specify additional provisions to account for such regional conditions as earthquake, heavy snow, or tornados. National structural codes genrally are incorporated into local building codes.The American Concrete Institute ( ACI ) Building Code covering the design of reinforced concrete buildings. It contains provisions covering all aspects of reinforced concrete manufacture, design, and construction. It includes specifications on quality of materials, details on mixing and placing concrete, design assumptions for the analysis of continuous structures, and equations for proportioning members for design forces.All structures must be proportioned so they will not fail or deform excessively under any possible condition of service. Therefore it is important that an engineer use great care in anticipating all the probable loads to which a structure will be subjected during its lifetime.Although the design of most members is controlled typically by dead and live load acting simultaneously, consideration must also be given to the forces produced by wind, impact, shrinkage, temperature change, creep and support settlements, earthquake, and so forth.The load associated with the weight of the structure itself and its permanent components is called the dead load. The dead load of concrete members, which is substantial, should never be neglected in design computations. The exact magnitude of the dead load is not known accurately until members have been sized. Since some figure for the dead load must be used in computations to size the members, its magnitude must be estimated at first. After a structure has been analyzed, the members sized, and architectural details completed, the dead load can be computed more accurately. If the computed dead load is approximately equal to the initial estimate of its value ( or slightly less ), the design is complete, but if a significant difference exists between the computed and estimated values of dead weight, the computations should be revised using an improved value of dead load. An accurate estimate of dead load is particularly important when spans are long, say over 75 ft ( 22.9 m ),because dead load constitutes a major portion of the design load.Live loads associated with building use are specific items of equipment and occupants in a certain area of a building, building codes specify values of uniform live for which members are to be designed.After the structure has been sized for vertical load, it is checked for wind in combination with dead and live load as specified in the code. Wind loads do not usually control the size of members in building less than 16 to 18 stories, but for tall buildings wind loads become significant and cause large forces to develop in the structures. Under these conditions economy can be achieved only by selecting a structural system that is able to transfer horizontal loads into the ground efficiently.钢筋混凝土在每一个国家，混凝土及钢筋混凝土都被用来作为建筑材料。
混凝土毕业设计论文中英文对照资料外文翻译文献
外文文献及译文目录•1历史•2组成o水泥2.1o 2.2水o 2.3骨料o 2.4化学外加剂o 2.5掺合料和水泥混合o 2.6纤维•3搅拌混凝土•4个特点o 4.1和易o 4.2固化o 4.3强度o 4.4弹性o 4.5扩张和收缩o 4.6开裂▪ 4.6.1收缩裂缝▪ 4.6.2拉裂o 4.7蠕变•5损伤模式o 5.1火灾o 5.2总量扩张o 5.3海水效果o 5.4细菌腐蚀o 5.5化学武器袭击▪ 5.5.1碳化▪ 5.5.2氯化物▪ 5.5.3硫酸盐o 5.6浸出o 5.7人身损害•6种混凝土o 6.1普通混凝土o 6.2高强混凝土o 6.3高性能混凝土o 6.4自密实混凝土o 6.5喷浆o 6.6透水性混凝土o 6.7混凝土蜂窝o 6.8软木复合水泥o 6.9碾压混凝土o 6.10玻璃混凝土o 6.11沥青混凝土•7混凝土测试•8混凝土回收•9使用混凝土结构o9.1大体积混凝土结构o9.2钢筋混凝土结构o9.3预应力混凝土结构•10参见•11参考•12外部链接历史在塞尔维亚,仍然是一个小屋追溯到5600bce已经发现,同一个楼层发红色石灰,沙子和砾石。
金字塔陕西中建千多年前,含有石灰和火山灰.或粘土。
碎石水和泥浆僵硬和发展实力超过时间。
为了确保经济实用的解决方案,既罚款又粗骨料使用,以弥补大部分的混凝土混合物。
砂,天然砾石及碎石,主要用于这一目的。
不过,现在越来越普遍,再生骨料(由建筑,拆卸和挖掘废物)被用作局部代替天然骨料,而一些生产总量包括风冷高炉炉渣和粉煤灰也是不允许的。
装饰石材等石英岩,潆石块或玻璃破碎,有时添加到混凝土表面进行装饰性"的总暴露"完成,流行景观设计师。
化学外加剂化学外加剂现形式的材料粉末或液体,补充了混凝土给它的某些特性没有可与普通混凝土混合物。
在正常情况下使用,外加剂剂量均低于5%的大量水泥,并补充了混凝土当时的配料/混合.最常见的外加剂有:加速器加速水化(硬化)的混凝土。
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Xxxx工程学院毕业设计外文资料翻译系（院）：专业：姓名：学号：混凝土的浇筑与养护摘要：根据一般承认的惯例看,巴基斯坦的混凝土结构建筑物在结构上的质量，效用和安全需要上都留下了很多值得关注的问题。
当2005 年10月8日发生在巴基斯坦北部的一个7.6级地震的时候，这些施工技术上的缺点袒露无遗了,破坏了数以千计建筑物、桥梁, 而且造成估计79,000人的死亡。
在巴基斯坦这种十分低质量的混凝土施工技术是造成这次极广破坏的主要原因。
关键字：混凝土浇筑养护混凝土浇筑若混凝土在地面上浇筑，地面应该具有足够的含水量以避免它吸收混凝土中的水分。
如果新混凝土将被浇筑在已经凝固的混凝土上或其旁边，已浇混凝土表面应该彻底清除干净，最好使用高压空气、高压水流或钢丝刷。
其表应潮湿，但不应有集水，应当在整个范围内刷上少量的水泥浆，然后立即铺上一层厚度为1/2in的砂浆。
新混凝土应铺筑在砂浆上或其旁边。
为减少混凝土在浇筑后由于运输导致的离析，混凝土的制备应该尽可能靠近最后浇筑的地方。
它应该分层浇筑以使每层可被均压实。
每层浇筑间隔的时间应该限制在能够保证新浇筑的混凝土与前面浇筑的有良好的结合。
当向较深的模板中浇筑混凝土时，就应该使用一根导管来限制混凝土的自由降落高度不超过3或4ft，以防止混凝土离析。
这种导管是由轻金属制成的管子，具有可调节的长度而且被连接到储存的混凝土的罐的底部。
当模板被浇筑满后，就可以抽出管节。
混凝土一浇筑完成，应立即用手提振捣器或机器振捣器进行捣密后就应该移走，否则就会发生骨料离析。
一般来说，振捣器不应该集中在先前提起的混凝土上。
振捣主要优点是它允许使用较干的混凝土，由于减少了混凝土的含水量，这种混凝土有较高的强度。
振捣混凝土的优点如下：1、水分的减少允许水泥和细集料的用量，因为这时需要较少的水泥浆。
2、较低的含水量可减少收缩和空隙。
3、较干的混凝土减少混凝土表面处理的费用。
4、机械振捣可代替3—8个手持振捣棒。
5、较低的含水量可提高混凝土的强度。
6、较干的混合料允许较早地拆除一些模板，这样可降低模板的造价。
混凝土的养护若混凝土想要获得最高强度或其它必要特性，则应该对其用足够的水分和适当的温度进行养护。
如果没能提供这些条件，则会导致劣质的混凝土。
混凝土中最初的水分足够所有水泥的水化反应，只要在使用前没有被蒸发。
这可以用多种方法来实现，例如把模板留在混凝土中，保持表面潮湿，或在混凝土表面覆盖一层液体养生化合物，它可以形成一种不透水的隔膜来阻止混凝土中的水分遗失。
养生化合物可以用刷子或压力喷嘴加到混凝土表面。
一加仑可以覆盖200—300ft2。
混凝土应该在40°F以上或80°F以下进行浇筑。
低温会降低凝结速度，而高温会降低混凝土的极限强度。
寒冷天气下的混凝土浇筑当混凝土在寒冷天气下浇筑时，通常有必要预先加热水、骨料或两者同时预热，以便使其初始温度能够保证混凝土的初凝并获得强度。
对水进行预热是提供必要的温度最有效的方法。
出于这一目的，蓄水池应该安装一个通有蒸气的蛇形管或将蒸气可以直接通到水中，这是可以使用多个排气口以提供良好的热量分布。
当混合料的温度已知，一些专用图可以用来计算混凝土的温度。
一条直线穿过所有三种比例，通过任意两个已知温度，就可以确定出第三个温度。
如果砂的表面干燥，则应使用实线计算混凝土的温度。
然而，如果砂含有3%的水分，则应使用虚线。
规范通常要求新浇筑的混凝土在浇筑后应保持3天温度不低于70°F或5天不低于50°F。
当预计有寒冷天气时必须提供一些适当的方法来保持要求的温度。
用于混凝土中的钢筋与混凝土相比，钢是一种高强度材料。
普通钢筋在抗拉和抗压时可以利用的强度，即屈服强度，约为普通的结构混凝土抗压强度的1.5倍，而且超过抗拉强度的100倍。
另一方面，与混凝土相比，钢材的成本要高得多。
所以，两种材料最好的结合使用是混凝土用于抵抗压应力。
因此，在钢筋混凝土梁内，混凝土抵抗压应力，纵向钢筋配置在靠近受拉面处以抵抗拉应力，通常还附加配有一些钢筋，抵抗梁内的剪应力所引起的斜向拉应力。
然而，钢材也可以用于抵抗应力，主要是为了减小受压构件的截面尺寸，例如用于多层建筑的下部楼层柱。
即使不存在这种必要性，所有受压构件也要配置最少数量的钢筋，以保证这些构件在偶然出现的小弯矩作用下的安全性，在这情况下，不加钢筋的混凝土构件可能会开裂，甚至破坏。
使配筋最有效的发挥作用的基本条件是钢筋和混凝土的变形要一致，即这两种材料间要有足够强的黏结力，以确保钢筋和其周围混凝土间不发生相对移动。
这种黏结力是由钢筋-混凝土结合面上较强的化学粘合作用，热轧钢筋表面层的固有粗糙度，以及间距较小的肋形表面变形等所构成的。
钢筋的边面并行为两种材料间提供了很高的咬合作用。
钢材以两种不同方式应用于混凝土中：普通钢筋和预应力钢筋。
普通钢筋在浇筑混凝土之前先置于模板内。
钢筋中的应力，与硬化混凝土中的应力一样，除了由收缩或类似原因造成的附加应力外，仅仅是由结构上作用的荷载引起的，比较起来，在预应力混凝土结构中，在钢筋与混凝土共同工作承受外部荷载之前，对钢筋已施加了很大的拉力。
最常见的钢筋的形式为圆棒状。
现在可以使用的钢筋的直径范围很大，在一般的应用中从10到35毫米，两种大型钢筋的尺寸为44和57毫米。
对这些钢筋表面进行了变形处理，其目的是增加钢筋与混凝土之间的抗滑能力。
对这些变形的最低要求已经通过实验研究予以确定。
不同的钢筋制造厂家采用不同的变形花纹，他们全部都能够满足这些要求。
为了对钢筋进行拼接，或者便于制作置于模板内的钢筋骨架所进行的焊接，可能会引起金相的变化而降低材料的强度和延性，因此，必须对所有钢材的类型和焊接规程加以特殊的限制。
ASTM中的A706的条款是专门使用于焊接的。
长期以来，在钢筋混凝土领域明显的趋向于高强度材料，包括钢筋和混凝土。
屈服强度为40KSI的钢筋，在20年前几乎是标准的盲目前大部分已由屈服强度为60钢筋所取代。
因为后者更为经济，而且使用他们可以减少模板内钢筋的拥挤状况。
ACI规范允许使用强度FY=80KSI的钢筋。
这类高强度钢筋通常是逐渐屈服的没有屈服平台。
在这种情况下，ACI规范要求在规定的最小屈服强度时的总应变不应超过0.0035。
这是将现行的设计方法应用于这类高强度钢筋时必须遵守的。
现行的设计方法是按钢材突然屈服，而且有屈服平台的情况而制定的。
ASTM规范中没有关于屈服强度高于60KSI的变形钢筋的条款，但是在实际中可能使用这种钢筋，根据ACI规范，他们可以在根据上述的要求的情况下使用。
在特殊情况下，例如高层建筑的下部楼层的柱子，使用这一高强度范围内的钢筋就非常适合。
在恶劣的环境田间下，例如受除冰化学剂侵蚀的荞麦内，要求使用镀锌或环氧树脂涂层的钢筋，以便使钢筋的腐蚀和随之发生的混凝土的剥落减至最小。
混凝土结构的修复钢筋混凝土是非常耐用的结构材料，它需要的修复工作很少。
然而，它的耐用性受很多因素的影响。
这包括那些设计和施工的失误，使用劣质材料和在侵蚀性环境下暴露。
修复的必要性主要取决于对破坏程度的诊断。
如果某项工程不只需要作装饰性处理，好的工作技巧很重要。
1、修复系统的功能要求通过对事故的仔细诊断并找到损坏的原因之后，下一步是考虑修复方法的要求，这样会我到一个解决问题的有效方法。
（参看图）①耐久性选择有相当耐久性的修复材料非常重要。
修复工作所用的材料最起码也要像基层混凝土那样耐用。
②钢筋的保护对加劲钢筋的保护机理取决于所使用的修复材料的类型。
例如，粘性材料能促使混凝土碱性增加，其抑制作用能保护钢筋免受更深的侵蚀，而环氧树脂砂浆可防止氧气、水分和其它有害物的侵人。
③基片粘结使用基片粘结可进行完整的修复，它可防止水分和大气从界面进人。
大多数的修复材料，通过使用合适的粘合手段，其粘合性能已大大地改善了，如环氧树脂系统使用未填充的环氧底漆，普通水泥修复系统使用普通水泥稀浆加上任何一种乳胶添加剂。
所要采用的预防措施是：对即将被粘结的表面，必须先清理其上面的疏松和易碎的物质。
④尺寸稳定性在养护期间，材料的收缩要保持到最小，为了防止修复失败、材料的尺寸变化应与基层材料相当接近。
⑤对环境引起的损伤的早期防护一些开始就暴露在外的情况会引起修复的过早损坏。
例如，热天会阻碍水泥的水合作用从而使局部修复的普通水泥发生变质，为了防止发生这种情况，养护期间应对其作特别的保护。
⑥操作方便材料应当易混合和方便使用，这样可以随时填到裂缝和孔隙里去，材料最好是不粘工具，用泥刀修平时不剥落，填筑后不坍塌。
⑦外观修复材料与现有混凝土的匹配程度取决于所修补的结构和业主的要求。
当外观很重要或钢筋的保护层很薄时，要求采用镶面处理。
2、修复方法的选择适当的修复就是消除与结构使用有关的所有缺陷。
认真考虑选择正确的方法和某一特定操作所用的材料，弄清到底是要满足强度、耐用性的特定要求还是满足其它的长期或短期的性能要求。
这些因素包括：1.损伤的性质如果活动裂缝里填的是刚性材料，那么不但填补材料会断裂，而且旧裂缝周围也会产生新的裂缝，修复活动裂缝的方法是要么采用柔性材料以适应结构位移，要么在修复之前采取一定措施消除结构位移。
2．断裂的部位依靠材料重力填充裂缝技术在水平面上裂缝修补中的成功率较高，但在竖直面上裂缝修补中效果很差。
3．环境如果裂缝里有水气、水和杂物时，要先补好漏洞。
如果结构还处于工作状态并且环境潮湿时，会使得堵住漏洞这一工作更加困难。
4.工艺工人所采用的修复工艺是另一个与修复有关的因素，有时它意味着水久性修复或者修复材料过早损坏。
5．成本与为修复工作提供通路、做准备工作和实际劳力的成本相比，所用的修复材料的成本是相当小的。
6.外观修复部位的表面可能很难看，特别是当它处于建筑物显眼的地方时。
在这种情况下，修复工作系统就要包括对整个表面进行某种处理。
Concrete Placing CuringAbstractViewed in terms of accepted practices, concrete construction operations leave much to be desired with respect to the quality, serviceability, and safety of completed structures. The shortcomings of these operations became abundantly clear when a magnitude 7.6 earthquake struck northern Paki-stan on October 8, 2005, destroying thousands of buildings, damaging bridges, and killing an esti-mated 79,000 people. The unusually low quality of construction operations prevalent was a major cause of the immense devastation.Keywords: Concrete Placing CuringPlacing ConcreteIf concrete is placed in the surface, the surface should be filled with water sufficiently to prevent it from absorbing the concrete of its water.If fresh concrete is to be placed on or nearby to concrete that has solidified, the surface of the placed concrete should be cleaned absolutely, preferably with a high-pressure air or water jetor steel-wire brushes. The surface should be wet, but there should be no much water. A little quantity of cement grout should be brushed over the whole area, and then followed immediately with the application of a 1/2-in Layer of mortar. The fresh concrete should be placed on or against the mortar.In order to decrease the disintegration resulting from carriage after it is placed. The concrete should be placed as nearly as probably in its final point. It should be placed in layers to permit uniform compaction. The time interval between the placing of layers should be limited to assure perfect bond between the fresh and previously placed concrete.In placing concrete in deeper patters, a vessel should be used limit thefree fall to not over 3 or 4 ft, in order to prevent concrete disintegration. The vessel is a pipe made of lightweight metal, having adjustable lengths and attached to the bottom of a hopper into which the concrete is deposited. As the patters are filled, sections of the pipe may be removed.Immediately after the concrete is placed, it should be compacted by hand pudding or a mechanical vibrator to eliminate voids. The vibrator should be left in one position only long enough to reduce the concrete around it to a plastic mass; then the vibrator should be moved, or disintegration of the aggregate will occur. In general, the vibrator should not be permitted to penetrate concrete in the prior lift.The mainly advantage of vibrating is that it permits the use of a drier concrete, which has a higher strength because of the reduced water content. Among the advantages of vibrating concrete are the following:1. The decreased water permits a reduction in the cement and fine aggregate because less cement paste is needed.2. The lower water content decreases shrinkage and voids.3. The drier concrete decreases the cost of finishing the surface.4. Mechanical vibration may replace three to eight hand puddles.5. The lower water content increases the strength of the concrete.6. The drier mixture permits the removal of some patters more quickly, which may reduce the cost of patters.Curing ConcreteIf concrete is to gain its maximum strength and other desirable properties, it should be cured with adequate moisture and at a favorable temperature. Failure to provide these conditions may result in an inferior concrete. The initial moisture in concrete is adequate to hydrate all the cement, provided it is not should replace the moisture that does evaporate. This may be accomplished by many methods, such as leaving the patters in place,keeping the surface wet, or covering the surface with a liquid .curing compound, which comes being to a water-tight membrane that prevents the escape of the initial water. Curing compounds may be applied by brushes or pressure sprayers. A gallon will cover 200 to 300 sq ft.Concrete should be placed at a temperature not less than 40 or more than 80°F.A lower temperature will decrease the rate of setting, while a higher temperature will decrease the ultimate strength.Placing Concrete in Cold WeatherWhen the concrete is placed during cold weather, it is usually necessary to preheat the water, the aggregate, or both in order that the initial temperature will assure an initial set and gain in strength .Preheating the water is the most effective method of providing the necessary temperature. For this purpose a water reservoir should be equipped with pipe coils through which steam can be passed, or steam may be discharged directly into the water, several outlets being used to given better distribution of the heat. When the temperatures of the mixtures are known, some specific charts may be used to calculate the temperature of concrete. A straight line pass all three scales, passing through every two known temperatures, will assure the determination of the third temperature. If the surface of sand is dry, the fact lines of the scales giving the temperature of concrete should be used. However, if the sand contains about 3 percent moisture, the dotted lines should be used.Specifications usually demand that freshly placed concrete shall be kept at a temperature of not less than 70°F for 3 days or 50°F for 5 days after it is placed. Some proper method must be provided to keep the demanded temperature when the cold weather is estimated.Reinforcing steels for concreteCompared with concrete, steel is a high strength material. The useful strength of ordinary reinforcing steels in tension as well as compression,i.e., the yield strength, is about 15 times the compressive strength of common structural concrete, and well over 100 times its tensile strength. On the other hand, steel is a high-cost material compared with concrete. It follow that the two materials are the best used in combination if the concrete is made to resist the compressive stresses and the compressive force, longitudinal steel reinforcing bars are located close to the tension face to resist the tension force., and usually additional steel bars are so disposed that they resist the inclined tension stresses that are caused by the shear force in the beams. However, reinforcement is also used for resisting compressive forces primarily where it is desired to reduce the cross-sectional dimensions of compression members, as in the lower-floor columns of multi-story buildings. Even if no such necessity exits , a minimum amount of reinforcement is placed in all compression members to safeguard them against the effects of small accidental bending moments that might crack and even fail an unreinforced member.For most effective reinforcing action, it is essential that steel and concrete deform together, i.e., that there be a sufficiently strong bond between the two materials to ensure that no relative movements of the steel bars and the surrounding concrete occur. This bond is provided by the relatively large chemical adhesion which develops at the steel-concrete interface, by the natural roughness of the mill scale of hot-rolled reinforcing bars , and by the closely spaced rib-shaped surface deformations with which reinforcing bars are furnished in order to provide a high degree of interlocking of the two materials.Steel is used in two different ways in concrete structures: as reinforcing steel and as prestressing steel .reinforcing steel is placed in the forms prior to casting of the concrete. Stresses in the steel, as in the hardened concrete, are caused only by the loads on the structure, except for possible parasitic stresses from shrinkage or similar causes. In contrast, in priestesses concrete structures large tension forces are applied to thereinforcement prior to letting it act jointly with the concrete in resisting external.The most common type of reinforcing steel is in the form of round bars, sometimes called rebars, available in a large range of diameters, from 10 to 35 mm for ordinary applications and in two heavy bar sizes off 44 and 57 mm these bars are furnished with surface deformations for the purpose of increasing resistance to slip between steel and concrete minimum requirements for these deformations have been developed in experimental research. Different bar producers use different patterns, all of which satisfy these requirements.Welding of rebars in making splices, or for convenience in fabricating reinforcing cages for placement in the forms, may result in metallurgical changes that reduce both strength and ductility, and special restrictions must be placed both strength and ductility, and special restrictions must be placed both on the type of steel used and the welding procedures the provisions of ASTM A706 relate specifically to welding.In reinforced concrete a long-time trend is evident toward the use of higher strength materials, both steel and concrete. Reinforcing bars with 40ksi yield stress , almost standard 20 years ago , have largely been replaced by bars with 60ksi yield stress , both because they are more economical and because their use tends to reduce congestion of steel in the forms .The ACI Code permits reinforcing steels up to Fy=80ksi. Such high strength steels usually yield gradually but have no yield plateau in this situation the ACI Code requires that at the specified minimum yield strength the total strain shall not exceed 0.0035 this is necessary to make current design methods, which were developed for sharp-yielding steels with a yield plateau, applicable to such higher strength steels. there is no STM specification for deformed bars may be used , according to the ACI Code , providing they meet the requirements stated under special circumstances steel in thishigher strength range has its place, e.g., in lower-story columns of high-rise buildings.In order to minimize corrosion of reinforcement and consequent spelling of concrete under sever exposure conditions such as in bridge decks subjected to deicing chemicals , galvanized or epoxy-coated rebars may be specified.Repair of Concrete StructuresReinforced concrete is generally a very durable structural material and very little repair work is usually needed. However, its durability can be affected by a variety of causes, including those of design and construction faults, use of inferior materials and exposure to aggressive environment. The need for a repair is primarily dictated by the severity of the deterioration as determined from the diagnosis. Good workmanship is essential if anything more than just a cosmetic treatment to the creation is required.1. performance requirements of repair systemHaving established the causes of the defect by carefully diagnosing the distress, the next step should be to consider the requirements of the repair method that will offer an effective solution to the problem (see fig.).①DurabilityIt is important to select repair materials that provide adequate durability. Materials used for the repair job should be at least as durable as the substrate concrete to which it is applied.②Protection of steelThe mechanism of protection provided to the reinforcing depends on the type of repair materials used. For example, cementations materials can protect the steel from further corrosion by their inhibitive effect of increasing the alkalinity of the concrete, whereas epoxy resin mortars can give protection against the ingress of oxygen, moisture and other harmful agents.③Bond with substrateThe bond with the substrate must produce an integral repair to prevent entry of moisture and atmospheric gases at the interface. With most repair materials, the bond is greatly enhanced with the use of a suitable bonding aid such as an unfilled epoxy resin systems and slurry of Portland cement, plus any latex additives for a Portland cement-based repair system. Precautions should also be taken to remove all loose and friable materials from the surfaces to be bonded.④Dimensional StabilityShrinkage of materials during curing should be kept to a minimum. Subsequent dimensional change should be very close in the substrate inorder to prevent failure⑤Initial Resistance to Environmentally Induced DamageSome initial exposure conditions may lead to premature damage lo repairs. For example, partially cured Portland cement repairs can deteriorate from hot weather preventing full hydration of the cement. To prevent this from happening extra protection during curing time may be necessary.⑥Ease of ApplicationMaterials should be easily mixed and applied so that they can be worked readily into small crevices and voids. Ideally, the material should not stick to tools, and should not shear while being trowel led nor slump after placement.⑦AppearanceThe degree to which the repair material should match the existing concretewill depend on the use of the structure and the client' s requirements. A surface coating may be required when appearance is important or when cover to reinforcement is small.2. Selection of Repair MethodsA suitable repair counteracts all the deficiencies which are relevant to the use of the structure. The selection of tile correct method and material for a particular, application requires careful consideration, whether to meet special requirements for placing strength, durability or other short-or long-term properties. These considerations include:1. Nature of the DistressIf alive crack is filled with a rigid material, then either the repair material will eventually fail or some new cracking will occur adjacent to the original crack. Repairs to live cracks must either use flexible materials to accommodate movements or else steps must be taken prior to the repair to eliminate the movement.2. Position of the CrackTechniques which rely on gravity to introduce the material into the crack are more successfully carried out on horizontal surfaces but are rarely effective on vertical ones.3. EnvironmentIf moisture, water or contaminants are found in the crack, then it is necessary to rectify the leaks Repair to slop leaks may be further complicated by the need to make the repairs while the structure is in service and the environment is damp.4. WorkmanshipThe skill the operatives available to carry put the repairs is another relevant factors. Sometimes this can mean the difference between a permanent repair and premature failure of the repair material.5. CostThe cost of repair materials is usually small compared with the costs ofproviding access, preparation and actual labor.6. AppearanceThe repair surface may be unsightly, particularly when it appears on a prominent part of the building. In this case, the repair system will include some form of treatment over the entire surface.Reference[1] Philip Jodidio, Contemporary European Architecture, Taschen, Koln, pp.148-153[2] Ann Breen & Dick Rigby, Waterfronts, McGraw-Hill, Inc. New York, 1994, pp.297-300[3] Ann Breen & Dick Rigby, The New Waterfront, Thames and Hudson, London, 1996, pp.118-120[4] Ann Breen & Dick Rigby, The New Waterfront, Thames and Hudson, London, 1996, pp.52-55[5] Robert Holden, International Landscape Design, Laurence King Publishing, London, 1996, pp.10-27[6] A new concept in refrigerant control for heat pumps ,J.R.Harnish,IIR Conference Paper,Cleveland,Ohio.May,1996[7] Carrier Corporation-Catalog 523 848, 1997[8] Waste Heat Management Handbook, National Bureau of Standardc Handbook 121, Publication PB 264959, February,1997[9] Ten design principles for air to air heat pumps,Allen Trask,ASHRAE Journal,July,1997。