混凝土英语论文
The durability of concrete 英文版混凝土论文
The durability of concreteIn civil engineering, concrete is the most widely used and the amount of one of the largest building materials. Over the past century, the concrete strength to continuously improve its main development trends. China's large population, the urgent need for housing.Structural Design not only to meet the requirements of safe and reliable indicators, but also consider the durability requirements.The durability of concrete issues, refers to the structure in the environment and cause long-term evolution of the structure due to internal or external reasons, the concrete has to lose the ability to use. That for durability failure, the durability of many reasons, have antifreeze failure, failure of alkali - aggregate reaction, chemical corrosion failure. Part of the concrete structure in the environment below freezing, water in the pores will freeze, resulting in volume expansion of cold water migration, the formation of various pressures, when the pressure reaches a certain level, resulting in the destruction of the concrete.Alkali - aggregate reaction of concrete chemical reactions that occur by the active component of the alkali in the concrete aggregates, causing the expansion of the concrete, cracking, or even destroy. Response factors in the concrete, and its harmful effects are often not the root of the rule is a big hidden in the concrete works. Concrete structures in aggressive media environment, will cause the cement paste to a series of chemical, physical, and materialized change gradually been eroded, cement strength to reduce serious, as well as destruction. In concrete engineering in order to meet the requirements of concrete construction work, that is, water consumption, water-cement ratio is high, resulting in high porosity of the concrete, durability reduce. Also, the lack of hydrate stability in the cement paste will have an impact on the durability.Therefore, to improve the durability of concrete, must reduce the porosity of the concrete, especially the capillary porosity, the most important method is to reduce the concrete mixing water. But if we simply reduce the amount of water, the concrete decreases, will lead to tamping forming a total of difficulties, the same result in the concrete structure is not dense, and even cellular and macroscopic defects such as, not only reduce the strength of concrete, and the durability of concrete also reduced. To improve the durability of concrete basic There are several ways: First, the strength of the material and engineering properties of cement cement is hardening formed by the condensation of the cement mortar, cement paste, once damaged, the durability of concrete is damaged, the choice of cement should pay attention to the specific performance of the varieties of cement, select alkali content, low heat of hydration, shrinkage of a small, heat resistance, water resistance, corrosion resistance, good frost resistance of cement and in the circumstances to choose . The strength of cement is not the sole criterion to determine the concrete strength and performance, such as lower grade cement can also be the preparation of high-grade concrete. Therefore, the project select the strength of cement at the same time, the need to consider the engineering performance, and sometimes, its engineering performance is more important than the strength. Aggregates and admixtures choice of the aggregate consideration should be given its alkali activity to prevent the harm caused by alkali-aggregate reaction, corrosion resistance and water absorption of the aggregate, reasonable choice of gradation, to improve the workability of the concrete mixture to increase concrete density; a large number of studies have shown that the doped fly ash, slag, silica fume, etc. the mixed caineng effectively improve the performance of the concrete, to improve the pore structure of concrete, filling the internal voids, and to increase the density, high-ash concrete can inhibition of alkali-aggregate reaction, and thus doped hybrid materials of concrete, is to improve the durability of concrete and effective measures. Development in recent years, high-performance concrete. Second, the rational design of concrete mix mix design meet the concrete strength, work should be considered to minimize the amount of cement and water consumption, lower heat of hydration, reduce shrinkage cracks, and to increase the density, and reasonable water reducer and air entraining agent, to improve the internal structure of concrete, mixed with a sufficient amount of mixture to improve concrete durability. Structural members shall use the environmental design of the concrete cover thickness, to prevent the outside media to penetrate the internal corrosion of reinforced. Node structural design of the structure should also be considered a component to the overallendurance capacity after partial damage. The structural design shall also control the crack width of concrete cracks. Third, the incorporation of an appropriate amount of admixtures, water-reducing agent such as: liquidity needed to ensure that concrete mixture at the same time, minimizing water consumption, reduce water-cement ratio, so that the total porosity of the concrete, in particular, the capillary porosity substantially reduced. 4, the incorporation of the hydrate stability, lack of efficient activity of mineral admixtures: ordinary Portland cement concrete, cement paste is another major factor in the concrete can not be super durable.To eliminate the structure of the concrete itself disruptive factor: In addition to concrete structural damage caused by environmental factors, some of the concrete itself, physical and chemical factors may also cause serious damage of the concrete structure, resulting in concrete failure. To ensure the strength of concrete: strength and durability is a different concept, but is closely related to the nature of links between them is based on the internal structure of the concrete with water-cement ratio, this factor is directly related.Concrete construction should also consider the durability of concrete mixing and maximize the use of the second mixing method, wrap the sand method, wrapped in the process of gravel law, improve the workability of the concrete mixing materials, water retention and improve the concrete strength, reduce water consumption; pouring mass concrete vibrators shall control the temperature of concrete cracks, shrinkage cracks, construction cracks, concrete pouring and vibrating system, to improve concrete density and impermeability, attention to the process of the surface after the concrete vibratorsand enhance the conservation, in order to reduce the concrete cracks. Concrete construction process control component appearance of cracks, construction cracks is essential and should strengthen the construction quality management, the special season of construction of concrete structures, there should be to take special measures.So, we want to develop the new concrete, such as high performance concrete.Therefore, to improve the durability of concrete is the inevitable trend of development of the concrete.。
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％。
对商品混凝土养护几点看法论文
对商品混凝土养护的几点看法摘要:简叙了目前商品混凝土养护的现状，早期混凝土养护的重要性。
及时充分的对商品混凝土进行湿养护和二次抹压的重要性。
关键词:商品混凝土；养护时间；湿养护；二次抹压abstract: the present concrete products jane syria maintenance, the current situation of the importance of early concrete curing. the goods in time to fully concrete curing and secondary wipe wet the importance of pressure.keywords: concrete products; maintenance time; wet maintenance; secondary wipe pressure中图分类号：tu37 文献标识码：a文章编号：1.前言商品混凝土，又称预拌混凝土，简称为“商砼”，俗称灰或料：是由水泥、骨料、水及根据需要掺入的外加剂、矿物掺合料等组分按照一定比例，在搅拌站经计量、拌制后出售并采用运输车，在规定时间内运送到使用地点的混凝土拌合物。
商品混凝土的实质就是把混凝土从过去的施工现场搅拌流离出来，由专门生产混凝的公司集中搅拌，并以商品的性质向需方供应。
商品混凝土搅拌站设置在城市边缘地区，相对于施工现场搅拌的传统工艺减少了粉尘、噪音、污水等污染。
这是一种特殊的建筑材料，交货时是塑性、流态状得半成品。
在所有权转以后，还需要使用方继续尽一定的质量义务，才能达到最终的设计要求。
由于商品混凝土搅拌站是一个专业性的混凝土生产企业，管理模式基本定型且比较单一，设备配置先进，不仅产量大、生产周期短，而且几率较为准确，搅拌较为均匀，生产工艺相对简洁、稳定，生产人员有比较丰富的经验，而且实现全天候生产，质量相对施工现场搅拌的混凝土更稳定可靠，提高了工程质量，有效的节约资源和能用。
什么是钢筋混凝土英语作文
什么是钢筋混凝土英语作文What is Reinforced Concrete?Reinforced concrete is a type of building material that is widely used in construction projects. It is composed of two main components: concrete and steel reinforcement. Concrete is a mixture of cement, water, and aggregates such as sand and gravel. Steel reinforcement, commonly known as rebar, is a steel bar or mesh that is embedded in the concrete to provide additional strength and support.The use of reinforced concrete has become increasingly popular in recent years due to its strength, durability, and versatility. It can be used to construct a wide variety of structures, including buildings, bridges, tunnels, and dams. It is also a cost-effective building material, as it can be produced in large quantities and is relatively easy to work with.The process of constructing a reinforced concretestructure typically involves several steps. First, the foundation is excavated and prepared. Next, the steel reinforcement is placed in the desired location and secured in place. Then, the concrete is poured into the mold and allowed to cure. Finally, the finished structure is inspected and tested to ensure that it meets the necessary safety and quality standards.One of the main advantages of reinforced concrete isits ability to withstand a wide range of environmental conditions. It is resistant to fire, water, and corrosion, making it ideal for use in areas that are prone to natural disasters, such as earthquakes and hurricanes. Additionally, it is a low-maintenance material that requires little upkeep over time.In conclusion, reinforced concrete is a versatile and durable building material that is widely used inconstruction projects around the world. Its strength, durability, and resistance to environmental conditions make it an ideal choice for a wide variety of structures. As technology continues to advance, it is likely that the useof reinforced concrete will only continue to grow in popularity and importance.。
混凝土项目描述范文
混凝土项目描述范文英文回答：Concrete is a versatile construction material that is widely used in various projects. It is composed of amixture of cement, aggregates, water, and sometimes additional additives. The use of concrete in construction offers several advantages. Firstly, it has excellent compressive strength, making it suitable for supporting heavy loads. For example, in the construction of high-rise buildings, concrete is used to create strong and stable foundations and columns. Secondly, concrete is highly durable and resistant to weathering and fire. This makes it a preferred choice for outdoor structures such as bridges and pavements. Additionally, concrete can be molded into different shapes and sizes, allowing for flexibility in design. For instance, decorative concrete can be used to create aesthetically pleasing facades or flooring. Moreover, concrete has good thermal properties, helping to regulate temperature in buildings. This can contribute to energyefficiency and reduce heating and cooling costs. Therefore, concrete is a reliable and versatile material for construction projects.中文回答：混凝土是一种多功能的建筑材料，广泛应用于各种项目中。
混凝土的英文作文
混凝土的英文作文英文：Concrete is a versatile and durable building material that is widely used in construction. It is composed of a mixture of cement, water, and aggregates, such as sand, gravel, or crushed stone. The mixture is then poured into molds or forms and allowed to harden and cure.One of the key benefits of concrete is its strength and durability. It can withstand heavy loads and harsh weather conditions, making it ideal for use in foundations, walls, and floors. Additionally, concrete is fire-resistant and can help to prevent the spread of flames in the event of a fire.Another advantage of concrete is its versatility. It can be molded into various shapes and sizes, allowing for a wide range of design possibilities. It can also be colored or textured to create a unique look and feel.However, there are some drawbacks to using concrete. It can be expensive and time-consuming to install, and it is not always the most environmentally friendly option. Additionally, concrete can crack and deteriorate over time, requiring maintenance and repair.Overall, concrete is a reliable and durable building material that has been used for centuries. With proper installation and maintenance, it can last for many yearsand provide a solid foundation for any structure.中文：混凝土是一种多功能且耐用的建筑材料，在建筑中被广泛使用。
混凝土产品介绍范文
混凝土产品介绍范文英文回答：Concrete is a versatile and widely used construction material that offers numerous benefits. It is a composite material made up of cement, aggregates (such as sand and gravel), and water. Concrete products are used in various applications, including buildings, roads, bridges, and infrastructure projects.One of the key advantages of concrete is its strength and durability. It can withstand heavy loads and resist the effects of weathering, making it ideal for structural applications. For example, concrete is commonly used in the construction of high-rise buildings, where it provides the necessary support and stability.In addition to its strength, concrete also offers excellent fire resistance. Unlike other materials, such as wood, concrete does not burn or contribute to the spread offire. This makes it a safe choice for buildings and structures where fire protection is a priority.Concrete is also known for its thermal properties. It has the ability to absorb and store heat, which helps regulate indoor temperatures. This can result in energy savings and increased comfort in buildings. For instance, concrete floors can provide natural cooling during hot summer months and retain warmth during colder seasons.Furthermore, concrete is a sustainable and environmentally friendly material. It is produced from readily available resources and can be recycled and reused. By using recycled concrete, we can reduce the demand for new materials and minimize waste. This contributes to the conservation of natural resources and reduces the carbon footprint of construction projects.Concrete products come in various forms, such as precast elements, ready-mix concrete, and decorative finishes. Precast elements, such as beams, columns, and panels, are manufactured off-site and then transported tothe construction site for assembly. This method offers time and cost savings, as well as improved quality control.Ready-mix concrete is a popular choice for large-scale projects, as it is delivered in a ready-to-use form. It is produced in a batching plant and then transported to the site in transit mixers. This eliminates the need for on-site mixing and ensures consistent quality and performance.Lastly, decorative finishes can be applied to concrete surfaces to enhance their appearance. This includes techniques such as stamping, staining, and polishing. These finishes can mimic the look of natural materials, such as stone or wood, while offering the durability and strength of concrete.中文回答：混凝土是一种多功能且广泛使用的建筑材料，具有许多优点。
碳纤维材料混凝土桥梁论文中英文资料外文翻译文献
中英文资料外文翻译文献外文资料Structural Rehabilitation of Concrete Bridges with CFRPComposites-Practical Details and Applications ABSTRACT: Many old existing bridges are still active in the various highway transportation networks, carrying heavier and faster trucks, in all kinds of environments. Water, salt, and wind have caused damage to these old bridges, and scarcity of maintenance funds has aggravated their conditions. One attempt to restore the original condition; and to extend the service life of concrete bridges is by the use of carbon fiber reinforced polymer (CFRP) composites. There appear to be very limited guides on repair of deteriorated concrete bridges with CFRP composites. In this paper, guidelines for nondestructive evaluation (NDE), nondestructive testing (NDT), and rehabilitation of deteriorated concrete bridges with CFRP composites are presented. The effect of detailing on ductility and behavior of CFRP strengthened concrete bridges are also discussed and presented.KEYWORDS: Concrete deterioration, corrosion of steel, bridge rehabilitation, CFRP composites.1 IntroductionThere are several destructive external environmental factors that limit the service life of bridges. These factors include but not limited to chemical attacks, corrosion of reinforcing steel bars, carbonation of concrete, and chemical reaction of aggregate. If bridges were not well maintained, these factors may lead to a structural deficiency, which reduces the margin of safety, and may result in structural failure. In order to rehabilitate and/or strengthen deteriorated existing bridges, thorough evaluation should be conducted. The purpose of the evaluation is to assess the actual condition of any existing bridge, and generally to examine the remaining strength and load carry capacity of the bridge.One attempt to restore the original condition, and to extend the service life ofconcrete bridges is by the use of carbon fiber reinforced polymer (CFRP) composites.In North America, Europe and Japan, CFRP has been extensively investigated and applied. Several design guides have been developed for strengthening of concrete bridges with CFRP composites. However, there appear to be very limited guides on repair of deteriorated concrete bridges with CFRP composites. This paper presents guidelines for repair of deteriorated concrete bridges, along with proper detailing. Evaluation, nondestructive testing, and rehabilitation of deteriorated concrete bridges with CFRP composites are presented. Successful application of CFRP composites requires good detailing as the forces developed in the CFRP sheets are transferred by bond at the concrete-CFRP interface. The effect of detailing on ductility and behavior of CFRP strengthened concrete bridges will also be discussed and presented.2 Deteriorated Concrete BridgesDurability of bridges is of major concern. Increasing number of bridges are experiencing significant amounts of deterioration prior to reaching their design service life. This premature deterioration considered a problem in terms of the structural integrity and safety of the bridge. In addition, deterioration of a bridge has a considerable magnitude of costs associated with it. In many cases, the root of a deterioration problem is caused by corrosion of steel reinforcement in concrete structures. Concrete normally acts to provide a high degree of protection against corrosion of the embedded reinforcement. However, corrosion will result in those cases that typically experience poor concrete quality, inadequate design or construction, and harsh environmental conditions. If not treated a durability problem, e.g. corrosion, may turn into a strength problem leading to a structural deficiency, as shown in Figure1.Figure1 Corrosion of the steel bars is leading to a structural deficiency3 Non-destructive Testing of Deteriorated Concrete Bridge PiersIn order to design a successful retrofit system, the condition of the existing bridge should be thoroughly evaluated. Evaluation of existing bridge elements or systems involves review of the asbuilt drawings, as well as accurate estimate of the condition of the existing bridge, as shown in Figure2. Depending on the purpose of evaluation, non-destructive tests may involve estimation of strength, salt contents, corrosion rates, alkalinity in concrete, etc.Figure2 Visible concrete distress marked on an elevation of a concrete bridge pier Although most of the non-destructive tests do not cause any damage to existing bridges, some NDT may cause minor local damage (e.g. drilled holes & coring) that should be repaired right after the NDT. These tests are also referred to as partial destructive tests but fall under non-destructive testing.In order to select the most appropriate non-destructive test for a particular case, the purpose of the test should be identified. In general, there are three types of NDT toinvestigate: (1) strength, (2) other structural properties, and (3) quality and durability. The strength methods may include; compressive test (e.g. core test/rebound hammer/ ultrasonic pulse velocity), surface hardness test (e.g. rebound hammer), penetration test (e.g. Windsor probe), and pullout test (anchor test).Other structural test methods may include; concrete cover thickness (cover-meter), locating rebars (rebar locator), rebar size (some rebar locators/rebar data scan), concrete moisture (acquameter/moisture meter), cracking (visual test/impact echo/ultrasonic pulse velocity), delamination (hammer test/ ultrasonic pulse velocity/impact echo), flaws and internal cracking (ultrasonic pulse velocity/impact echo), dynamic modulus of elasticity (ultrasonic pulse velocity), Possion’s ratio (ultrasonic pulse velocity), thickness of concrete slab or wall (ultrasonic pulse velocity), CFRP debonding (hammer test/infrared thermographic technique), and stain on concrete surface (visual inspection).Quality and durability test methods may include; rebar corrosion rate –field test, chloride profile field test, rebar corrosion analysis, rebar resistivity test, alkali-silica reactivity field test, concrete alkalinity test (carbonation field test), concrete permeability (field test for permeability).4 Non-destructive Evaluation of Deteriorated Concrete Bridge PiersThe process of evaluating the structural condition of an existing concrete bridge consists of collecting information, e.g. drawings and construction & inspection records, analyzing NDT data, and structural analysis of the bridge. The evaluation process can be summarized as follows: (1) Planning for the assessment, (2) Preliminary assessment, which involves examination of available documents, site inspection, materials assessment, and preliminary analysis, (3) Preliminary evaluation, this involves: examination phase, and judgmental phase, and finally (4) the cost-impact study.If the information is insufficient to conduct evaluation to a specific required level, then a detailed evaluation may be conducted following similar steps for the above-mentioned preliminary assessment, but in-depth assessment. Successful analytical evaluation of an existing deteriorated concrete bridge should consider the actual condition of the bridge and level of deterioration of various elements. Factors, e.g. actual concrete strength, level of damage/deterioration, actual size of corroded rebars, loss of bond between steel and concrete, etc. should be modeled into a detailed analysis. If such detailed analysis is difficult to accomplish within a reasonable period of time, then evaluation by field load testing of the actual bridge in question may be required.5 Bridge Rehabilitation with CFRP CompositesApplication of CFRP composite materials is becoming increasingly attractive to extend the service life of existing concrete bridges. The technology of strengthening existing bridges with externally bonded CFRP composites was developed primarily in Japan (FRP sheets), and Europe (laminates). The use of these materials for strengthening existing concrete bridges started in the 1980s, first as a substitute to bonded steel plates, and then as a substitute for steel jackets for seismic retrofit of bridge columns. CFRP Composite materials are composed of fiber reinforcement bonded together with a resin matrix. The fibers provide the composite with its unique structural properties. The resin matrix supports the fibers, protect them, and transfer the applied load to the fibers through shearing stresses. Most of the commercially available CFRP systems in the construction market consist of uniaxial fibers embedded in a resin matrix, typically epoxy. Carbon fibers have limited ultimate strain, which may limit the deformability of strengthened members. However, under traffic loads, local debonding between FRP sheets and concrete substrate would allow for acceptable level of global deformations before failure.CFRP composites could be used to increase the flexural and shear strength of bridge girders including pier cap beams, as shown in Figure3. In order to increase the ductility of CFRP strengthened concrete girders, the longitudinal CFRP composite sheets used for flexural strengthening should be anchored with transverse/diagonal CFRP anchors to prevent premature delamination of the longitudinal sheets due to localized debonding at the concrete surface-CFRP sheet interface. In order to prevent stress concentration and premature fracture of the CFRP sheets at the corners of concrete members, the corners should be rounded at 50mm (2.0 inch) radius, as shown in Figure3.Deterioration of concrete bridge members due to corrosion of steel bars usually leads in loss of steel section and delamination of concrete cover. As a result, such deterioration may lead to structural deficiency that requires immediate attention. Figure4 shows rehabilitation of structurally deficient concrete bridge pier using CFRP composites.Figure3 Flexural and shear strengthening of concrete bridge pier with FRP compositesFigure4 Rehabilitation of deteriorated concrete bridge pier with CFRP composites6 Summary and ConclusionsEvaluation, non-destructive testing and rehabilitation of deteriorated concrete bridges were presented. Deterioration of concrete bridge components due to corrosion may lead to structural deficiencies, e.g. flexural and/or shear failures. Application of CFRP composite materials is becoming increasingly attractive solution to extend the service life of existing concrete bridges. CFRP composites could be utilized for flexural and shear strengthening, as well as for restoration of deteriorated concrete bridge components. The CFRP composite sheets should be well detailed to prevent stress concentration and premature fracture or delamination. For successful rehabilitation of concrete bridges in corrosive environments, a corrosion protection system should be used along with the CFRP system.碳纤维复合材料修复混凝土桥梁结构的详述及应用摘要：在各式各样的公路交通网络中，许多现有的古老桥梁，在各种恶劣的环境下，如更重的荷载和更快的车辆等条件下，依然在被使用着。
土木工程材料(混凝土)适合发表论文的SCI刊物
CEMENT CONCRETE RES 0008-8846 9293 2.187 2.553 0.351 191 8.9 0.01907 0.974 COMPUT CONCRETE 1598-8198 114 0.763 0.637 0.278 36 3.1 0.00066 0.231 INT J CIV ENG 1735-0522 49 0.547 0.194 31 0.00011MAG CONCRETE RES 0024-9831 807 0.52 0.601 0.171 82 >10.0 0.00217 0.33 MATER STRUCT 1359-5997 1901 0.85 1.091 0.16 119 9.3 0.00595 0.565 J MATER CIVIL ENG 0899-1561 1291 0.677 0.956 0.071 155 7.1 0.00415 0.425 CONSTR BUILD MATER 0950-0618 2791 1.366 1.57 0.163 325 3.7 0.01217 0.537 J ADV CONCR TECHNOL 1346-8014 221 0.573 0.074 27 4.9 0.00125MATER RES-IBERO-AM J 1516-1439 535 0.429 0.013 79 6.2 0.0015MATER CONSTRUCC 0465-2746 161 0.646 0.591 0.098 41 4.9 0.00055 0.19 CEMENT AND CONCRETE RESEARCH 《水泥与混凝土研究》英国MonthlyISSN: 0008-8846PERGAMON-ELSEVIER SCIENCE LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND, OX5 1GB1.Science Citation Index2.Science Citation Index Expanded/wps/find ... ome/352/descriptionMAGAZINE OF CONCRETE RESEARCH 《混凝土研究杂志》英国BimonthlyISSN: 0024-9831THOMAS TELFORD PUBLISHING, THOMAS TELFORD HOUSE, 1 HERON QUAY, LONDON, ENGLAND, E14 4JD1.Science Citation Index2.Science Citation Index Expanded/macr/MATERIALS AND STRUCTURES 《材料与结构》荷兰MonthlyISSN: 1359-5997SPRINGER, VAN GODEWIJCKSTRAAT 30, DORDRECHT, NETHERLANDS, 3311 GZ1.Science Citation Index Expanded/materials/mechanics/journal/11527JOURNAL OF MATERIALS IN CIVIL ENGINEERING 《土木工程材料杂志》美国MonthlyISSN: 0899-1561ASCE-AMER SOC CIVIL ENGINEERS, 1801 ALEXANDER BELL DR, RESTON, USA, VA, 20191-44001.Science Citation Index Expanded/mto/CEMENT & CONCRETE COMPOSITES 《水泥与混凝土复合材料》英国BimonthlyISSN: 0958-9465ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND, OXON, OX5 1GB1. Science Citation Index Expanded/cement-and-concrete-composites/COMPUTERS AND CONCRETE 《计算机与混凝土》韩国BimonthlyISSN: 1598-8198TECHNO-PRESS, PO BOX 33, YUSEONG, DAEJEON, SOUTH KOREA, 305-6001.Science Citation Index Expandedhttp://technopress.kaist.ac.kr/?journal=cac&subpage=6JOURNAL OF ADVANCED CONCRETE TECHNOLOGY 《混凝土先进技术杂志》日本Tri-annual （注：2008年开始被SCI收录）ISSN: 1346-8014JAPAN CONCRETE INST, SOGO HANZOMON BLDG 12F, NO 7, KOJIMACHI 1-CHOME, CHIYODA-KU, JAPAN, TOKYO,102-00831.Science Citation Index Expandedhttp://www.jstage.jst.go.jp/browse/jactCONSTRUCTION AND BUILDING MATERIALS 《建筑与建筑材料》英国BimonthlyISSN: 0950-0618ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND, OXON, OX5 1GB1.Science Citation Index Expanded/wps/find ... ription#descriptionMATERIALES DE CONSTRUCCION 《建筑材料》西班牙QuarterlyISSN: 0465-2746INST CIENCIAS CONSTRUCCION EDUARDO TORROJA, SERRANO GALVACHE, 4, MADRID, SPAIN, 280331.Science Citation Index Expandedhttp://materconstrucc.revistas.csic.es/index.php/materconstruccMaterials Research-Ibero-american Journal of Materials 《材料研究》巴西QuarterlyISSN：1516-1439UNIV FED SAO CARLOS, DEPT ENGENHARIA MATERIALS, LABORATORIA DE MATERIAIS VITREOS, CAIXA POSTAL 676, SAO CARLOS, BRAZIL, 13565-905SP1.Science Citation Index Expandedhttp://www.scielo.br/scielo.php?script=sci_serial&pid=1516-1439&lng=en&nrm=isoCEMENT WAPNO BETON 《水泥、石灰、混凝土》波兰Bimonthly （注：2008年开始被SCI收录）ISSN: 1425-8129STOWARZYSZENIE PRODUCENTOW CEMENTU, UL LUBELSKA 29 LOK 4-5, KRAKOW, POLAND, 30-0031.Science Citation Index Expandedwww.cementwapnobeton.pl/INTERNATIONAL JOURNAL OF CIVIL ENGINEERING《国际土木工程学报》伊朗Quarterly1735-0522IRAN UNIV SCI & TECHNOL, COLL CIVIL ENG, PO BOX 16765-163, NARMAK, IRAN, TEHRAN, 16844 http://ijce.iust.ac.ir/index.php?slc_lang=en&slc_sid=11.Science Citation Index Expandedhttp://www.iust.ac.ir/ijce/index.php?slc_lang=en&slc_sid=1。
公路桥梁混凝土施工技术论文
浅谈公路桥梁混凝土施工技术【摘要】本文主要介绍普通混凝土施工技术应用及存在的问题，简述高性能混凝土技术在公路、桥梁建设方面的应用及施工工艺，提出相应的公路、桥梁加固技术措施，以期对我国的公路、桥梁工程建设有所裨益。
【关键词】公路；桥梁；混凝土；施工技术abstract: this paper mainly introduces the construction technology of common concrete application and existing problems, this paper describes the high performance concrete technology in roads and bridges, the application of construction and the construction technology, put forward the corresponding highway, bridge reinforcement technique measures for our country to highway, bridge engineering construction at presentkey words: highway; bridge; concrete; construction technology中图分类号：x734 文献标识码：a 文章编号：前言百年大计，质量第一。
随着国家的基础设施建设的深入推进,混凝土工程建设项目逐年递增,混凝土结构的质量关系到整个建筑的安全。
混凝土主要由水泥、水、砂石骨料等建筑材料搅拌而成的非均质材料，其在硬化成型后容易产生裂缝、气穴以及孔隙等问题，这些问题会影响到混凝土的质量，进而影响到建筑物的质量，基于此，采取必要的混凝土施工工艺防止混凝土质量问题的出现迫在眉睫。
公路、桥梁普通混凝土施工中存在的问题随着交通基础设施建设步伐的加快,普通混凝土在公路、桥梁建设中广泛使用，然而实践表明，在公路、桥梁等高指标、高使用率的建筑项目中,普通混凝土施工容易出现裂缝、气穴、孔隙等质量问题，对工程的整体安全性及质量造成重大影响，严重的甚至会发生公路、桥梁坍塌等安全事故。
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。
土木工程混凝土论文中英文资料外文翻译文献
土木工程混凝土论文中英文资料外文翻译文献外文资料STUDIES ON IMPACT STRENGTH OF CONCRETESUBJECTED TO SUSTAINEDELEVATED TEMPERATUREConcrete has a remarkable fire resisting properties. Damage in concrete due to fire depends on a great extent on the intensity and duration of fire. Spalling cracking during heating are common concrete behaviour observed in the investigation of the fire affected structures. Plenty of literature is available on the studies of concrete based on time temperature cures. In power, oil sectorsand nuclear reactors concrete is exposed to high temperature for considerable period of time. These effects can be reckoned as exposure to sustained elevated temperature. The sustained elevated temperature may be varying from a few hours to a number of years depending upon practical condition of exposures. The knowledge on properties under such conditions is also of prime importance apart from the structures subjected to high intensity fire. Impact studies of structure subjected to sustained elevated temperature becomes more important as it involves sensitive structures which is more prone to attacks and accidents. In this paper impact studies on concrete subjected to sustained elevated temperature has been discussed. Experiments have been conducted on 180 specimens along with 180 companion cube specimens. The temperatures of 100°C, 200°C and 300°C for a duration of exposure of 2 hours 4 hours and 6 hours has been considered in the experiments. The results are logically analyzed and concluded.1. INTRODUCTIONThe remarkable property of concrete to resist the fire reduces the damage in a concrete structure whenever there is an accidental fire. In most of the cases the concrete remains intact with minor damages only. The reason being low thermal conductivity of concrete at higher temperatures and hence limiting the depth of penetration of firedamage. But when the concrete is subjected to high temperature for long duration the deterioration of concrete takes place. Hence it is essential to understand the strength and deformation characteristics of concrete subjected to temperature for long duration. In this paper an attempt has been made to study the variation in Impact Strength of concrete when subjected to a temperature range 100oC, 200oC and 300oC sustained for a period of 2 hrs, 4 hrs and 6 hrs.The review of the literature shows that a lot of research work [1 – 3] has taken place on the effect of elevated temperature on concrete. All these studies are based on time –temperature curves. Hence an attempt has been made to study the effect of sustained elevated temperature on impact strength of concrete and the results are compared with the compressive strength. The experimental programme has been planned for unstressed residual strength test based on the available facilities. Residual strength is the strength of heated and subsequently cooled concrete specimens expressed as percentage of the strength of unheated specimens.2. EXPERIMENTAL INVESTIGATION2.1. TEST SPECIMEN AND MATERIALSA total of 180 specimens were tested in the present study along with 180 companion cubes. An electric oven capable of reaching a maximum temperature of 300oC has been used for investigation. Fine and coarse aggregates conforming to IS383 has been used to prepare the specimen with mix proportions M1 = 1:2.1:3.95 w/c = 0.58, M2 = 1:1.15:3.56 w/c = 0.53, M3 = 1:0.8:2.4 w/c = 0.4.2.2 TEST VARIABLESThe effects of the following variables were studied.2.2.1 Size sSize of Impact Strength Test Specimen was 150 mm dial and 64 mm thickness and size of companion cube 150 x 150 x 150 mm.2.2.2 Maximum TemperatureIn addition to room temperature, the effect of three different temperatures (100oC, 200oC and 300oC) on the compressive strength was investigated.2.2.3 Exposure Time at Maximum TemperatureThree different exposure times were used to investigate the influence of heat on compressive strength; they are 2 hrs, 4 hrs and 6 hrs.2.2.4 Cooling MethodSpecimens were cooled in air to room temperature.3. TEST PROCEDUREAll the specimens were cast in steel moulds as per IS516 and each layer was compacted. Specimens were then kept in their moulds for 24 hours after which they were decoupled and placed into a curing tank until 28 days. After which the specimens were removed and were allowed to dry in room temperature. These specimens were kept in the oven and the required target temperature was set. Depending on the number of specimen kept inside the oven the time taken to reach the steady state was found to vary. After the steady state was reached the specimens were subjected to predetermined steady duration at the end of which the specimens are cooled to room temperature and tested.ACI drop weight impact strength test was adopted. This is the simplest method for evaluating impact resistance of concrete. The size of the specimen is 150 mm dial and 64 mm thickness. The disc specimens were prepared using steel moulds cured and heated and cooled as. This consists of a standard manually operated 4.54 kg hammer with 457 mm drop. A 64 mm hardened steel ball and a flat base plate with positioning bracket and lugs. The specimen is placed between the four guides pieces (lugs) located 4.8 mm away from the sample. A frame (positioning bracket) is then built in order to target the steel ball at the centre of concrete disc. The disc is coated at the bottom with a thin layer of petroleum jelly or heavy grease to reduce the friction between the specimen and base plate. The bottom part of the hammer unit was placed with its base upon the steel ball and the load was applied by dropping weight repeatedly. The loading was continued until the disc failed and opened up such that it touched three of the four positioning lugs. The number of blows that caused this condition is recorded as the failure strength. The companion cubes were tested for cube compression strength (fake).4. ANALYSIS AND RESULTS4.1 RESIDUAL COMPRESSIVE STRENGTH VS. TEMPERATUREFrom Table 1, at 100°C sustained elevated temperature it is seen that the residual strength of air cooled specimens of mixes M1, M2 and M3 has increased in strength 114% for M1 mix, 109% for M2 mix and 111% for M3 mix for 6 hours duration of exposure. When the sustained elevated temperature is to 200°C for air cooled specimens there is a decrease in strength up to 910% approximately for M1 mix for a duration of 6 hours, but in case of M2 mix it is 82% and for M3 mix it is 63% maximum for 6 hours duration of exposure. When the concrete mixes M1, M2 and M3 are exposed to 300°C sustained temperature there is a reduction in strength up to 78% for M1 mix for 6 hour duration of exposure.4.2 RESIDUAL COMPRESSIVE STRENGTH VS DURATION OF EXPOSUREFrom Table 1, result shows that heating up to 100°C for 2 hours and 4 hours, the residual strength of mix M1 has decreased where as the residual strength of mix M2 and M3 has increased. The residual strength is further increased for 6 hours duration of exposure in all the three mixes M1, M2 and M3 even beyond the strength at room temperature. When the specimens of mixes M1, M2 and M3 are exposed to 200°C for 2,4 and 6 hours of duration, it is observed that the residual strength has decreased below the room temperature and has reached 92% for M1 mix, 82 and 73% for M2 and M3 mix respectively. Concrete cubes of mixes M1, M2 and M3 when subjected to 300°C temperature for 2,4 and 6 hours the residual strength for mix M1 reduces to 92% for 2 hours up to 78% for six hours duration of exposure, for M2 mix 90% for 2 hours duration of exposure up to 76% for six hour duration of exposure, for M3 mix 88% up to 68% between 2 and 6 hours of duration of exposure.5. IMPACT STRENGTH OF CONCRETE5.1 RESIDUAL IMPACT STRENGTH VS TEMPERATUREFrom the table 1, it can be observed that for the sustained elevated temperature of 100°C the residual impact strength of all the specimens reduces and vary between 20 and 50% for mix M1, 15 to 40% for mix M2 and M3. When the sustained elevated temperature is 200°C the residual impact strength of all the mixes further decreases. The reduction is around 60-70% for mix M1, 55 to 65% for M2 and M3 mix. When the sustained elevated temperature is 300°C it is observed that the residual impact strength reduces further and vary between 85 and 70% for mix M1 and 85 to 90% for mix M2 and mix M3.5.2 RESIDUAL IMPACT STRENGTH VS DURATION OF EXPOSUREFrom the Table 1 and Figures 1 to 3, it can be observed that there is a reduction in impact strength when the sustained elevated temperature is 100°C for 2 hrs, 4 hrs and 6 hrs, and its range is 15 to 50% for all the mixes M1, M2 and M3. The influence of duration of exposure is higher for mix M1 which decreases more rapidly as compared to mix M2 and mix M3 for the same duration of exposure. When the specimens are subjected to sustained elevated temperature of 200°C for 2,4 and 6 hour of duration, further reduction in residual impact strength is observed as compared to at 100°C. The reduction is in the range of 55-70% for all the mixes. The six hour duration of exposure has a greater influence on the residual impact strength of concrete. When the sustained elevated temperature is 300°C for 2,4 and 6 hours duration of exposure the residualimpact strength reduces. It can be seen that both temperature and duration of exposure have a very high influence on the residual impact strength of concrete which shows a reduction up to 90% approximately for all the mixes.6. CONCLUSIONThe compressive strength of concrete increases at 100oC when exposed to sustained elevated temperature. The compressive strength of concrete decreases when exposed to 200°C and 300°C from 10 to 30% for 6 hours of exposure. Residual impact strength reduces irrespective of temperature and duration. Residual impact strength decreases at a higher rate of 20% to 85% as compared to compressive strength between 15% and 30 % when subjected to sustained elevated temperature. The impact strength reduces at a higher rate as compared to compressive strength when subjected to sustained elevated temperature.混凝土受持续高温影响的强度的研究混凝土具有显着的耐火性能。
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。
高性能混凝土论文
高性能混凝土论文高性能混凝土(High Performance Concrete, HPC) 是现代建筑工程领域中的一项重要技术。
其具有优异的力学特性、耐久性和施工性能等优点，能够在工程建设过程中发挥重要作用。
本文将对高性能混凝土论文进行深入探讨，并对其应用进行分析。
一、高性能混凝土的定义高性能混凝土是指具有高强度、高密实、高耐久性和高可塑性等性能的混凝土，其强度等级一般为C60 及以上，其水胶比一般不大于0.35，且具有一定的抗裂性能和耐久性能。
高性能混凝土的主要特点是强度高、柔韧性好、抗渗透性能好、抗裂性能好、耐久性好等。
二、高性能混凝土的主要组成高性能混凝土的主要组成部分有水泥、粉煤灰、粗骨料、细骨料和适量的掺合料等。
其中，水泥是混凝土的主要固化材料，粉煤灰的掺入可以提高混凝土的强度和耐久性，在掺合料方面，一般采用硅粉、多孔玻璃微珠等加入掺合料，以提高混凝土的抗渗透性、抗冻融性等性能，以提高混凝土的性能。
三、高性能混凝土的应用高性能混凝土在各类工程、如大型基础工程、高层建筑、特种桥梁等领域得到广泛应用。
在建筑工程方面，高性能混凝土可以用于地下工程中的外壁混凝土、桩、基础、隧道等构筑物；同时也广泛应用于建筑助力结构中的梁、柱、板、墙体等构件中。
在道路建设领域，高性能混凝土可用于高速公路、隧道、桥梁等方面。
在水利工程方面，高性能混凝土可以用于坝墙、水闸、管道等建筑物的施工。
四、高性能混凝土的设计方法高性能混凝土设计方法需要根据设计要求，考虑各项因素共同确定设计参数。
首先，需要确定使用场所、相应的强度等级和耐久性参数，以及工程建设条件和其他相关要求，然后根据这些信息综合来确定高性能混凝土的配合比、水胶比、骨料比等，并进行试模试验、构件试验及现场施工试验，以确保高性能混凝土的设计实用性和可靠性。
五、高性能混凝土的问题和解决措施高性能混凝土在实际施工过程中会出现如抗裂性能不足、翻浆现象、骨料配合不均匀等问题。
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。
混凝土英文论文
Development of Green High Performance Concrete for SustainableDevelopment0706121 29 刘海庆Abstract: With the fast development of society and economy an important factor that affects social and economicdevelopment is environmental pollution. In face of reduction of the natural resources and the growing problem ofenvironmental pollution, the ordinary concrete has not been fit with the need of the social economy; the perfor-mances of concrete are required improvement. So the development of the concrete materials is generally considered with environmental protection, energy conservation, resource saving and the green high performance concrete is developed. The green high performance concrete that is developed in recent years is a new building material. The concept and features of green high performance concrete are introduced, then the categories and current application of it are analyzed and exist problems are proposed, finally it is concluded that the development of green high per-formance concrete is the only way for the sustainable development of the concrete materials.Keywords:green high performance concrete; environmental pollution; sustainable development CLC: TU528 Document code: A Article ID: 1672-2132(2010)Suppl.-0432-040 IntroductionConcrete is the most widely used and the greatest amount of building materials in the con-struction area. However, extensive use of concrete has destroyed unprecedented natural resources so that resources and energy appear crisis. Concrete in the 21st.century not only meets with the re-quirements of the structure, but also minimizes asmuch as possible the damage to the ecological envi-ronment to the need of sustainable development.So, developing the green high performance con-crete is the need of the sustainable develop-ment.1 Connotation and features of green high performance concretenWu Zongwei, academician of Chinese academy of engineering, first proposed the concept of con-crete and he pointed out the green high perfor-mance concrete was the direction of concrete devel-opment. Researchers consider the green high performance concrete should follow conditions as follows:(1) Cement used must be green cement. Sand and stone should be exploited orderly and withoutdamaging the environment.(2) Cement consumption should be saved tothe greatest extent in order to reduce by-products during the course of producing cement, for exam-ple, CO2, SO2, and NO2and so on.(3) Agricultural and industrial waste residueprocessed should be mixed more, such as, ground-ed slag, high-quality fly ash, silica fume and rice husk, to reduce cement, protect environment and improve concrete durability.(4) Industrial waste liquid should be used a lot, especially; water reducing agent made by black paper waste liquid and other composite addi-tive developed should be mixed to help dealing with other liquid.(5) Concrete should be mixed in the mixing station to reduce waste, dust and waster water of mixing concrete in site and waste and water recy-cling should be strengthened.(6) Through enhancing the strength, reduc-ing cross-sectional area or volume of structure, re-ducing concrete volume, cement, sand and stone can be saved. By improving durability of concrete,service life of structure can be lengthened and re-pair and reconstruction cost are further saved andthe indiscriminate use of natural resources will be reduced.(7) A lot of demolition waste should be recy-cled and recycled aggregate concrete should be de-veloped.The concept of green high performance con-crete is to strengthen people′s green awareness and to play an important role of energy saving and en-vironmental protection. It is concluded that the de-velopment of green high performance concrete is the only way for the sustainable development of concrete.2 Classification of the green high performance concrete2.1 Ecological environment-friendly concreteTo meet with the requirements of high strength and high durability, traditional concrete is always in pursuit of its compactness, which will cause concrete structures (lots of buildings and rigid pavement and so on) lack of permeability and permeability, exacerbate urban heat island effect,deteriorate human living environment. So rainwa-ter can not penetrate so that it lowers ground-wa-ter table in the city and affects growth of the sur-face plant, in a result, causes urban ecological sys-tem disorder. Because concrete color is gray, living space built in concrete gives a rough, hard, cold,dark feeling. So it is concluded that the develop-ment of ecological environment-friendly concrete is the only way to solve these problems. Another, e-cological environment-friendly concrete can be di-vided into plant concrete and water-permeability concrete according to different functions.2.2 Recycled aggregate concreteConcrete from the old buildings or structures can be divided into coarse and fine aggregate through breaking and this aggregate take place of some sand and gravel. So this is considered as re-cycled aggregate concrete. The use of recycled ag-gregate has been viewed as one of main measures in the development of green concrete.2.3 High-volume fly ash high performance con-creteFly ash mixed can improve concrete’s strength, impermeability and frost resistance,lower shrinkage; inhibit the effect of the alkali-ag-gregate reaction. High performance concrete which is mixed a great deal of fly ash and the morphologi-cal effects, micro-aggregate effects, volcanic ash effects of fly ash are used fully will lead to greater economic and environmental benefits.2.4 Environmentally mitigatable concrete(1) Environment-protecting concrete: the dif-ferences in composition between this concrete and traditional concrete are that a lot of solid waste,industrial waste residue, waste brick, concrete and solid rubbish and so on and additive produced through industrial waste liquid are mixed by taking certain technical measures to achieve all kinds of waste recycling and reduce environment pollution.(2) Energy-saving concrete: high temperature calcinations siliceous materials (clay or shale) and calcium raw material are needed in the course of ce-ment production, which will consume a large amount of energy. If concrete are prepared through non-burned cement, energy consumption can be reduced significantly.(3) Self-compacting concrete: self-compacting concrete is vibrated and compacted through self-weight. Because of this concrete has sufficient co-hesion so as to ensure disengagement in theprocess of pouring, a large amount of powder are required.3 Engineering application of green high performance concreteThe history of green high performance con-crete is not long, but it has obvious advantages and is paid attention to at home and abroad. Because concrete has been used widely as structural materi-al to date, appearance of green high performance concrete will become the main building structure materials in the 21st.century. Concrete strength in Chicago′s 311 South-walker Building in America with 295m height and 71 layers was C95. 40 mil-lion m3high performance concrete was used in both anchor piers of Akashi Kaikyo Bridge which was the longest suspension bridge at that time.The use of high green performance concretewas started late in China, especially the serious de-fects of the overpass in the Beijing and Tianjin re-gion arouse great concern in the engineering area.Research and application of green high perfor-mance concrete are increasing little by little.C80 high performance concrete are used in high-rise buildings and Jingan Center Building in Shang-hai.4 Existing problems of green high performance concrete4.1 Cost issuesThe cost of concrete is increased by 50% or more because used raw materials, the production and management level and production lines are raised. For example, collecting and preparing re-cycling aggregate must cost a certain machinery and equipment and manpower for recycled con-crete. From the point of economic indicators, the production of recycled aggregate is few profits, no profit, even deficit. If the production of recycled aggregate maintains a certain profit, its retail price will inevitably higher than the natural aggregate.Therefore, it is difficult to be accepted by users.4.2 Early crackingIn recent years cracking of concrete has be-come a hot topic at home and abroad and high per-formance concrete is no exception. That is, crackof concrete is very common. Many factors that in-fluence early cracking of concrete are as follows:self-shrinkage, drying shrinkage, earl y elastic modulus, tensile strength, ultimate tensile strain,creep, water evaporation rate, structural con-straint degree and so on.4.3 Mix problemThe same absolute volume is used with con-ventional concrete. After mixes of various compo-nents are determined, the performance require-ments are proved through experiments. The mix design of green high performance concrete is more difficult than that of common concrete. Comparing with mix design of conventional concrete, the mix design parameters of green high performance con-crete are smaller, such as, less than 0.4~0.42 water-cement ratio, less than 25mm the largest stone diameter (less than 20 mm or even 15 mm),2.6~3.0 sand fineness modulus, 42.5 concretes trength grade (ISO). So mix design will be sim-plified.5 ConclusionThe research of the green high performance technology in China is still in primary stage and the current research is not enough to conclude the laws that directly guide production. So the research and development of green high performance concrete should be increased greatly andquality standards and production specifications should be drawn up.In a word, we should attach great importance to green issues of concrete because these are related to our human survival and development. Through constant exploration and research, it is firmly be-lieved that the green high performance concrete is the only way for the sustainable development of the concrete materials.Reference:[1] CEB-FIP. Environment Design [R]. Lausanne: [s.n.],2004.[2]Malhotra V M. Introduction: Sustainable develop-ment and concrete technology [J].Concrete interna-tional,2002, 24(7):22.[3]吴中伟.绿色高性能混凝土——混凝土的发展方向[J].混凝土与水泥制品,1998,(1):3-6.[4]鄢朝勇.混凝土材料的可持续发展与粉煤灰绿色高性能混凝土[J].国外建材科技,2005,(4):5-7.[5] 王立久,汪振双,赵善宇.绿色生态混凝土技术的研究现状与发展[J].混凝土. 2009,(7):1-3.[6] Kumar M P. Reducing the environmental impact of concrete [J]. Concrete International,2001, 23(10):61-66.[7] Kumar M P. Greening of the concrete industry for sustainable development [J]. ConcreteInternational,2002, 24(7):23-28.[8] 王淑萍,王思远,张春,等.高性能混凝土的研究现状和发展应用[J].北方交通,2007,(4):47-50.[9]周士琼,李益进,尹健,等.复合超细粉煤灰与特种混凝土技术的开发与应用[J].铁道科学与工程学报,2004,(2):39-45.。
混凝土裂缝论文中英文资料对照外文翻译文献综述
混凝土裂缝论文中英文资料对照外文翻译文献综述Causes and control measures of concrete cracks study the problemKeywords: Causes prevention of concrete cracksAbstract: At present, paid close attention to the problem of concrete cracks, this crack in the concrete on the basis of classification, analysis of the causes of different cracks, and proposed measures to crack prevention and treatment.1.IntroductionIs the maximum amount of concrete as a building material, widely used in industrial and civil construction, agriculture and forestry with urban construction, water conservancy works in the harbor. However, many concrete structures occurs during the construction and use of different degrees and different forms of fracture. This not only affects the appearance of the building, but also endanger the normal use of buildings and structures durability.Therefore, the cracks become people concerns. In recent years, with the ready-mixed concrete and vigorously promote the use and structure become increasingly large, complex, making the problem even more prominent.However, cracks in concrete structures is a fairly common phenomenon, large number of engineering practice and modern science on the concrete strength of micro studies show that the structures of the crack is inevitable, which is a property of the material. Therefore, the scientific treatment of cracks in the crack problem is to classify on the basis, adopt effective measures to harmful levels of crack control to the extent permitted. This concrete structure will cause cracks in common, control measures and the repair method to analyze some light.2.Classification of concrete cracks2.1 Divided by Crack According to the causes of concrete cracks, structural cracks and can be divided into two major categories of non-structural cracks.(1) Structural cracks Caused by a variety of external loads cracks, also called load cracks. It includes the external loads caused by the direct stress cracks and the structure under external loads caused by secondary stress cracks.(2) Non-structural cracks Deformation caused by the change from a variety of cracks. It includes temperature, shrinkage and swelling caused by factors such as differential settlement cracks. Such cracks in the structure when the deformation is restricted due to the stress caused. Research data from abroad and a large number of engineering practice, non-structural cracks in the works in the majority, about 80%, which led to shrinkage cracks.2.2Divided by the time the cracks(1)Cracks during construction Including plastic shrinkage cracks, settlement shrinkage cracking, drying shrinkage cracks, shrinkage cracks itself, the temperature cracks, the cracks were improper construction operations, the role of early frost, and some irregular cracks caused by cracks.(2)Use of crack during Including the expansion of steel corrosion cracks generated, salt and acid erosion type liquid medium caused by cracks, the cracks caused by freezing and thawing, alkali aggregate reaction, and cracks caused by cyclic loading cumulative damage caused by cracks.2.3Classification of fractured by cracks in the shape of the shape can be divided by:(1)Longitudinal cracks parallel to the bottom component, the distribution along tendons, mainly caused by the role of steel corrosion(2)Transverse cracks perpendicular to the bottom component mainly by the loading, temperature effects caused(3)Shear cracks due to displacement caused by vertical load or vibration(4)Diagonal cracks eight shaped or herringbone cracks, common in the wall of concrete beams, mainly due to the uneven foundation settlement, and thermal effects caused by(5)X-shaped cracks common in the framework of beams, columns and walls on the ends, due to the impact effect, or moment loads caused by earthquake(6)All kinds of irregular cracks such as repeated freezing and thawing, or fires caused by cracksIn addition, concrete mixing and transport time for long cracks due to mesh, squareappears floor slab or plate surface radial cracks appear in the cross cracks and so on.2.4 The development of the state divided by cracksAccording to fracture the movement in which the state and development trends, can be divided into the following categories:(1)Stable crack This crack does not affect the persistence of applications, including two types.One is in motion the process of self-healing of fractures could be common in a number of new water projects, this is because the crack of cement particles in the leakage of water further compounds the process, precipitate Ca (OH) 2 crystal and part of the Ca ( OH) 2 has dissolved in the water with CO2 carbonation reaction to form CaCO3 crystallization occurs, both the formation of cracks in the gel material will be glued closed, and thus stop the leakage, cracks to heal. The other is in a stable movement of the cracks, such as the periodic load generated by the cyclical expansion and closure of cracks.(2)Unstable crack This will result in instability of crack extension, affecting the sustainable use of structures, should be considered part of its expansion, to take corresponding measures.3.Causes of cracks in concrete and control measures3.1 Shrinkage cracks Shrinkage cracks are caused by the humidity, it accounts for non-structural cracks in concrete in the main part. We know that concrete is a cement as the main cementing material to natural sand, stone aggregate mixing water, after casting molding, hardens and the formation of artificial stone.In the construction, in order to ensure its workability, often adding cement hydration than water needed for 4 to 5 times more water. More of these water to free state exists, and the gradual evaporation of the hardening process, resulting in the formation of large pores inside the concrete, voids or holes, resulting in volume shrinkage of concrete. In addition, the hardening process of concrete hydration and carbonation of concrete volume will lead to shrinkage. According to the experimental determination of the ultimate shrinkage of concrete is about 0104% ~ 0106%.Shows that shrinkage is the inherent physical properties of concrete, in general, the larger water-cement ratio, the higher the concrete strength, aggregate less, the higher the temperature, surface water loss is larger, the larger the value of its contract, the more easily shrinkage cracks. According to the formation of shrinkage cracks and formation mechanism of the time, works in the common shrinkage cracksare mainly plastic shrinkage cracks, settlement shrinkage cracking and drying shrinkage cracks in three categories, in addition to their contract (chemical shrinkage) cracks and carbonation shrinkage cracks.3.1.1Plastic shrinkage cracks Plastic shrinkage cracks in concrete plastic stage, before the final set. The cause of this is concrete paste and quickly evaporating water flow to the surface, with the increase in water loss, capillary negative pressure generated by contraction of the concrete surface of the drastic volume shrinkage. Strength of concrete at a time has not yet formed, which resulted in cracking of the concrete surface.This multi-cracks in dry weather, hot and windy, the fracture shallow, intermediate width, both ends of the fine, of different lengths, and disconnected.3.1.2 Settlement shrinkage cracking Settlement shrinkage cracks in concrete pouring about half an hour after the occurrence and hardening stops. The cause of this is occurring after the slurry in the Pouring uneven sink, sinking of coarse aggregate, cement grout float, when the settlement was inhibited (such as steel or embedded parts of the block) is due to shearing and cracking of the concrete. In addition, floating in the plasma layer formed on the surface will be a result of bleeding and cracking.This multi-cracks in the concrete surface, and pass along the long direction of the reinforcement, or the stirrups the distribution width of both ends of the narrow middle, is a common early cracks, especially in the pump construction is more common.3.1.3 Drying shrinkage cracks Drying shrinkage cracks in the concrete curing only appeared after completion. Its formation was mainly due to the concrete to harden, the water evaporation caused by shrinkage of the concrete surface, when the shrinkage deformation of concrete by internal constraint, have a greater tensile stress to crack the concrete surface is pulled.Shrinkage cracks on the surface generally produces very shallow location, multi-component along the short direction of distribution, were parallel, linear, or mesh, can be severe throughout the member section.3.1.4 Self-shrinkage cracks Shrinkage cracks itself has nothing to do with the outside humidity, but because of the hydration reaction of cement clinker in the process, the reaction resultant of the average density of smaller volume shrinkage caused by system (called chemical shrinkage) due. Mainly due to hydration products of free water into a part of it39;s specific volume reduced by 1 / 4 (ie 0125cm3Pg).Therefore, the chemical shrinkage of the sizeof the reduction depends on the chemical combination of cement hydration products in the amount of water.3.1.5 Carbonation shrinkage cracking Carbonation carbonation shrinkage cracks are free ions generated by water evaporation, causing shrinkage in the slurry. Carbonation is atmospheric CO2 conditions in the water reacts with the hydration product of CaCO3, alumina, silica and water free state, this part of the volume shrinkage of concrete caused by water evaporation (known as carbonation shrinkage), and its essence is the carbonate of the cement corrosion.General alkalinity of cement hydration products and the higher the concentration of CO2 in air and moderate humidity (50%), the more prone to carbonation. Therefore, this crack propagation in alternating wet and dry environment, and dry or water saturated environment, there is not easy; and because the crack of carbide precipitation will form a gel product, stop the CO2 into, it usually only occurs on the surface.Prevention of shrinkage cracks on the above can take the following measures:(a) mixed with superplasticizer, pumping agent to minimize water consumption; construction, cutting should not be too fast, and the vibration compacting.(b) For the prevention of early shrinkage cracking, in addition to strengthening the early conservation, the final setting of concrete should be conducted before the second wiping pressure, the material can be mixed with coagulant, and the appropriate use of high early strength and good water holding capacity of ordinary Portland cement; for the prevention of shrinkage cracks, can be appropriately extended curing time, the material should use fly ash in cement and other cement or shrinkage rate of small species.(c) minimize the amount of cement, coarse aggregate content increases, and limestone as the coarse aggregate should be chosen because of its superior shrinkage cracking resistance andesite and sandstone; should strictly control the sand content of aggregate, sand ratio should not be too big, should have good aggregate grading.(d) reduce their shrinkage cracking effective way is to use a low C3A content of cement, as C3A Portland cement clinker in the greatest chemical shrinkage reduction is a C2 S 3 times, C4AF of 5 times.(e) to prevent the carbonation shrinkage cracks key is to reduce the resultant alkalinity, good for fresh concrete wet water conservation, and the use of which the concrete structure to stay as dry as other corrosive gases in the high CO2 environment to good anti-corrosionmeasures.(f) pouring concrete trowel promptly after the straw with the wet or plastic film cover, the wind should be set up wind facility construction season.3.2 Crack Crack is the concrete difference in temperature, or seasonal temperature changes and the formation of excessiveIn the concrete pouring process, the cement hydration reaction will release a lot of heat (generally 502J per gram of cement can release heat), so that the internal temperature of concrete at a certain age there temperature peak, then declined.Since the slow cooling inside the concrete surface, fast heat, will form in the temperature difference between inside and outside, for the coordination of the temperature deformation, the concrete surface will have a tensile stress (ie thermal stress), when after more than make the cracking of concrete tensile strength. Such cracks are mostly cross-cutting and deep, severely reducing the overall stiffness of the structure; usually a few months after the end of the construction. In addition, concrete curing period, if the invasion by the cold will cause cracks in the concrete surface, but the lighter, smaller and harmful. Control of temperature cracks start mainly from the lower temperature, can take the following preventive measures:(a) the materials are advised to use fly ash or cement C3A and C3 S low-low-heat cement, to minimize the amount of cement can be mixed with superplasticizer; on the concrete, can be properly mixed with stones ; in the mixing water and aggregate were mixed and ice water cooling.(b) During the construction, the construction process should be reasonable arrangements to improve the construction process, such as pouring a large volume of concrete, pipes laid in concrete or block cyclic thermal stratification placement; improve the structure of constraints, such as a long structure to be set temperature, joints or back strip, when poured on bedrock, to shop 50 ~ 100 mm sand to remove the embedded solid role.(c) in the design, calculation of thermal stress is mainly good, according to temperature stress may have taken the appropriate structural measures, such as proper temperature reinforced configuration, shared concrete temperature stress.(d) In addition, still need to strengthen the concrete curing, good surface insulation measures (such as water conservation or covering wet straw, etc.), an appropriate extension of time for form removal to the slow cooling of the concrete surface; for the concrete, control ofentry mold temperature, and for temperature tracking, control the temperature difference between inside and outside of concrete in less than 25 ℃.3.3 Subsidence cracks Subsidence cracks is all part of the building after completion caused by differential settlement occurs, mostly cross-cutting, its location and settlement in the same direction. Eight-shaped wall buildings or herringbone cracks is a typical settlement pacted backfill without treatment, formation of soft layer containing the building was in use during the ground water (rain, water, etc.) long-term immersion and other factors will cause uneven settlement of the building to crack. The foundation also works in the new construction, if not make the necessary measures (such as the set of retaining walls, diaphragm walls) to prevent soil or groundwater intrusion instability will undermine the foundations of the adjacent old building capacity, resulting in building subsidence cracking. In concrete construction, due to insufficient template rigidity, support spacing is too large, too early form removal and other factors, there will be settlement cracks.Subsidence cracks are often severely affected structures, and endanger the durability of the structure, control measures to prevent its formation are:(a) in the basic design to ensure the bearing capacity of the bearing layer of uniform strength and foundation, in the story and the different parts of the junction of old and new buildings set the settlement joint.(b) In construction, the template should have sufficient strength and rigidity, and support reliable; Also, pay attention to the construction sequence, such as after the first high-rise low-rise, after the first of the main podium.(c) Geological Survey of pre-construction work to do, as far as possible a good choice of the bearing layer, after the completion of the foundation to avoid being soaked in rainwater.3.4 Other crack In addition to these cracks, the construction process in the structure will be various forms of construction cracks; in the structure will appear during use of different types of corrosion cracks.(1) Construction of crack Construction is due to cracks in the construction of improper operation or component itself, not the stiffness of such factors.If PC project, improper tension will form a component due to strength or strength not been made insufficient cracking; template project, if the concrete form removal or bonding with the template template upgrade easily to concrete crack; hoisting project, because of lateral reinforcement component lessstiffness of poor or incorrect lifting point on factors such as cracks. The key is to prevent such cracks in strict accordance with construction specifications, such as prestressed tension must be over 75% component intensity when, brushing between the template and concrete release agent, form removal, or sliding, the first uniform loose, and then slow detachment or upgrade.(2) corrosion cracks Corrosion cracking is due to structure a long period caused by corrosive liquid environment, which includes the corrosion of concrete and its reinforcement corrosion. Such cracks are often caused by the concrete is not dense, they are usually associated with shrinkage cracks, joint action of temperature cracks, leading to crack expanding and eventually weaken the structure of durability.Control measures are mainly doing the concrete surface and reinforcing steel corrosion protection, cracks should be repaired in time. In addition, if the existing concrete aggregate base active ingredient, cement high MgO content (> 5%) or UEA expansive agent such as too much content, alkali aggregate reaction will occur, or because of the hydration reaction of MgO to produce expansion of the gel, resulting in concrete expansion cracks, formed mostly mesh or irregular cracks.Such cracks tend to occur several years after completion of the structure, because the chemical reaction is extremely slow. The key to prevention is to eliminate or reduce the concrete in the presence of such substances.4. Treatment of crack Once the cracking of concrete structures should be identified on the basis of immediately take appropriate measures. At present, the commonly used methods of surface sealing repair, pressure grouting and filling blocking method.4.1 Surface sealing Less than 012mm for the width of the micro-cracks can be polymers of cement paste, permeability of flexible sealant or waterproofing agent brushing on the crack surface, to restore its water resistance and durability. The construction method is simple, but only superficial cracks.(1) process: the surface of the bristles and wash →embedding surface defect (available epoxy cement mortar or latex) →selection of coating compound.(2) construction elements;(a) As the coating is thin and should use strong adhesive material and not aging;(b) Cracks on the activities, should be greater flexibility in material elongation;(c) Tufu uniform, not a bubble.4.2 Pressure Grouting Width and depth greater than 013mm for the larger cracks can be chemical grouting material (such as polyurethane, epoxy or cement slurry) injected by pressure grouting equipment to deep cracks in order to restore structural integrity, water resistance and durability.(1) process:cutting grooves →laid slurry seal mouth →sealing →Check →→filling →preparation of slurry sealing →grouting quality control.(2) Construction of main points:(a) grouting materials should use strong adhesive resin can be irrigated with good material, usually used epoxy resin;(b) For large crack width is greater than 2mm, cement-like material can be used for active cracks should adopt the diluted epoxy resin or polyurethane;(c) chemical grouting pressure control in the 012 ~ 014MPa, pressure control of cement grouting in the 014 ~ 018MPa, increasing the pressure does not improve the filling rate, is not conducive to filling effect;(d) after grouting, when grout without leakage when the initial setting before grouting remove mouth (boxes, tubes).4.3 Complete blocking law Width greater than 015mm for the large cracks or cracks in steel corrosion can crack the concrete digged along the "U" type or "V" groove, and then filling them with repair materials to restore the water resistance, durability or part of the restoration of structural integrity .(1) process:cutting grooves →primary treatment (decontamination of concrete, steel rust) →brushing binder (epoxy grout) →→workmanship surface repair material handling.(2) Construction of main points:(a) Filling them with materials to choose depending on the particular epoxy resin, epoxy mortar, polymer cement mortar, PVC, clay or asphalt ointment;(b) For the corrosion cracks, the first completely rust on steel, and then cover rust paint. 5．SummaryConcrete Crack is a technical problem, long plagued engineering. In recent years, with high early strength cement is widely used as commercial concrete pumping vigorously promote the construction of the concrete strength grade increase, the emergence of mass concrete, to achieve results in the crack problem, while also more prominent, and even become Concretequality focus.The present concrete shrinkage cracks are mainly caused by deformation and deformation temperature, control of these cracks in addition to the general construction in the design and construction take appropriate measures, also need researchers have developed as quickly as possible to reduce shrinkage and hydration heat of cement efficient materials, which will crack the problem reduced to minimum.混凝土裂缝成因和防治措施问题的研究探讨摘要：目前混凝土裂缝问题倍受关注,本文在对混凝土裂缝进行分类的基础上,分析了不同裂缝的形成原因,并提出了裂缝防治的措施及处理方法。
混凝土施工技术论文(1)
关于混凝土施工技术的探讨摘要: 混凝土工程包括钢筋工程、模板工程和混凝土工程，是建筑施工中的主导工种工程，无论在人力、物力消耗和对工期的影响方面都占非常重要的地位。
本文结合工作实践经验，本文主要阐述了在建筑工程中混凝土配合比设计施工及控制养护方面等方面进行浅析，可供同行参考。
关键词：混凝土；施工；技术abstract: the concrete engineering including reinforcing bar engineering, template engineering and concrete engineering, is the leading engineering construction work, no matter in the human, material consumption and time limit for the influence of all accounts for a very important position. based on the working practice, this paper mainly expounds the concrete in the construction engineering mix proportion design of construction and control in theguide-subject aspects such as maintenance, available for reference to fellow.keywords: concrete; the construction; technology中图分类号：tu74 文献标识码：a文章编号：1 工程简介对某工程建筑面积9500m2，中地下室1层，基坑开挖深度7.5 m，地上12层。
该工程基础底板属于大体积混凝土，同时混凝土强度等级与抗渗等级高。
混凝土英语论文
0734-743X/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PII: S 0 7 3 4 - 7 4 3 X ( 9 9 ) 0 0 0 7 1-8
182
R. Destefanis et al. / International Journal of lmpact Engineering 23 (1999) 181-192
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ROBERTO D E S T E F A N I S , M O R E N O F A R A U D , and M A R C O T R U C C H I
Alenia Aerospazio, Divisione Spazio, C.so Marche 41, 10146 Turin, Italy Phone: 39-11-7180320, Fax: 39-11-7180028, Email: rdestefa@to.alespazio.it Summary--An extensive Light Gas Gun test campaign has been performed to develop a high resistance shielding to protect the Columbus module - the European laboratory attached to the International Space Station - against the threat posed by orbital debris. In a 3-year period from Summer '95 to Summer '98 -more than 100 hypervelocity impact tests have been made on a 3-wall shield system, based on an aluminium Whipple Shield plus an intermediate bumper made of Nextel fabric and a KevlarTM-Epoxy TM plate. Two shielding configurations have been selected, which both reported excellent ballistic performance against aluminium spherical projectiles impacting with velocities between 3 and 7 km/s and angles between 0 and 60 degrees. The results showed that the response of a 3-wall system to hypervelocity impacts is more complex than expected. For instance - in the test range - the shielding resistance does not increase linearly with the velocity but shows non-monotonic variations; the ballistic limit shows little oscillations with the increase of the impact angle in the 0 - 45 degrees range as well. The projectile fragmentation level is shown to play a key role in the target failure process. A thorough analysis of the impacted target is on going to gain insight into the complex damage mechanism with particular attention paid to the X-ray pictures taken of the debris cloud formation and evolution. The present paper summarizes the activities performed and the results obtained so far, focusing on the more recently performed experiments.© 1999 Elsevier Science Ltd. All rights reserved.
水泥和混凝土的制作流程英文作文
水泥和混凝土的制作流程英文作文English:The production process of cement and concrete involves several steps. First, limestone and clay are crushed and mixed together in a crusher to form a raw meal. This raw meal is then heated in a rotating kiln at a temperature of around 1450 degrees Celsius, resulting in the formation of clinker. The clinker is then ground into a fine powder along with gypsum to produce cement. To make concrete, cement is mixed with aggregates such as sand and gravel, along with water and sometimes additives like fly ash or slag to enhance certain properties. The mixture is then poured into molds or formwork to set and harden, resulting in a durable construction material widely used in the building industry.Translated content:水泥和混凝土的制作流程涉及几个步骤。
首先，石灰石和黏土在破碎机中被粉碎并混合在一起形成生料。
然后，这种生料在旋转窑中以约1450摄氏度的温度加热，形成熟料。
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IMPACT ENGINEERING
PERGAMON International Journal of Impact Engineering 26 (2001) 865-877 /locate/ijimpeng
VIDEO IMAGING OF DEBRIS CLOUDS FOLLOWING PENETRATION OF LIGHTWEIGHT SPACECRAds: Hypervelocityimpact, spacecraft shielding, orbital debris, multi-layer insulation,
aluminum foam, debris clouds, high speed video. INTRODUCTION With the increasing number of satellites in orbit, governments and commercial enterprises rely heavily upon protection o f these valuable assets from the growing meteoroid/orbital debris (M/OD) environment. By the year 2000, the U.S. Space Command estimates that the U.S will spend more than $250 billion in space efforts, and an additional 1,800 satellites will be in orbit by the end o f the next decade [1 ]. As the monetary cost o f space utilization increases, insurance companies are interested in assuring that the satellites have sufficient protection from M/OD so the likelihood o f a large claim is reduced. At the same time, the cost to place any additional weight aboard satellites, such as increased protection systems, is very great. These two factors drive the need for greater understanding o f the efficiency and utility o f various satellite protection systems. A key to this understanding is an accurate model for the evolution and propagation o f debris clouds following orbital debris penetration. This also has direct impact on the satellite contamination environment. With the rapid growth in earth observing satellites for resource management, satellites incorporating optical elements such as cameras and telescopes can be adversely affected by deposition o f such contaminants. O f special interest are satellites utilizing lightweight materials, such as multi-layer insulation (MLI), Nextel, aluminum foam, etc. for both thermal shielding and collision protection. A number o f reports have been generated to predict the damage resulting in them from hyperveloeity impact, such as those by Robinson [2] and Rule 0734-743X/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII: S07 3 4 - 7 4 3 X ( 0 1)00 1 3 8-5
J O E L WILLIAM_SEN" a n d E R I C HOWARD** *University of Denver Research Institute, Denver, CO USA; **Opsci Incorporated, Colorado Springs, CO USA Abstract--The structure of debris clouds following hypervelocity penetration of thin materials is of special interest to spacecraft designers-it forms the basis for damage equations from meteoroids, orbital debris, and other kinetic energy threats. Today, video imaging offers the experimenter a new view into the structure and development of debris clouds following penetration of these thin materials. This technique is of special interest in its application to lightweight, thin, or other low density target materials whereflash x-ray experimental imaging has proven difficult to apply, including fibrous materials (such as Nextel and Kevlar), multi-layer insulation (MLI), aluminum foam, and so on. This paper has two purposes: (1) to describe new developments in video imagingof debris clouds using high-speed multi-frame cameras (with frame rates of up to one million flames per second) and still video cameras with extremely high shutter speeds (as short as 3 nanoseconds), and (2) to present video images of debris clouds from light gas gun testing of aluminum and nylon spheres penetrating at 5 to 7 kin/see through thin aluminum plates, aluminum foam, and multi-layer insulation materials. The paper then compares the video images results to previous flash x-ray images (Piekutowski, 1997) and comments on similarities and new features that may be observed using this improved experimentaltechnique. © 2001 Elsevier Science Ltd. All rights reserved.
866 J. Williamsen, E. Howard/International Journal of Impact Engineering 26 (2001) 865-877 [3]. However, these materials are so lightweight that conventional flash x-rays may be unsuited to typify their associated debris cloud when penetrated. For these materials, high-speed video may offer technical advantages, both in their image resolution of small particles and in their digital nature, which makes possible the use of computerized evaluation in determining the mass, velocity, and materials distribution in debris clouds following orbital debris penetration through programs such as MATLAB. This research paper presents results from four recen