外文翻译

毕业设计外文资料翻译题目工程项目成本_学院土建学院专业土木工程班级土木0711学生_ 韩明_学号20070601033 _指导教师扈萍二〇一一年三月一日摘要：混凝土的裂缝是建筑工程中存在的普遍问题。

关键字：裂缝，配合比，降温，浇捣，混凝土养护，预应力张拉。

下面就混凝土裂缝的成因与控制进行简单探讨。

一、裂缝的成因裂缝产生的形式和种类很多，要根本解决混凝土中裂缝问题，还是需要从混凝土裂缝的形成原因人手。

正确判断和分析混凝土裂缝的成因是有效地控制和减少混凝土裂缝产生的最有效的途径。

（一）设计原因1．设计结构中的断面突变而产生的应力集中所产生的构件裂缝。

2．设计中对构件施加预应力不当，造成构件的裂缝（偏心、应力过大等）。

3．设计中构造钢筋配置过少或过粗等引起构件裂缝（如墙板、楼板）。

4．设计中未充分考虑混凝土构件的收缩变形。

5．设计中采用的混凝土等级过高，造成用灰量过大，对收缩不利。

（二）材料原因1．粗细集料含泥量过大，造成混凝土收缩增大。

集料颗粒级配不良或采取不恰当的间断级配，容易造成混凝土收缩的增大，诱导裂缝的产生。

2．骨料粒径越细、针片含量越大，混凝土单方用灰量、用水量增多，收缩量增大。

3．混凝土外加剂、掺和料选择不当、或掺量不当，严重增加混凝土收缩。

4．水泥品种原因，矿渣硅酸盐水泥收缩比普通硅酸盐水泥收缩大、粉煤灰及矾土水泥收缩值较小、快硬水泥收缩大。

5．水泥等级及混凝土强度等级原因：水泥等级越高、细度越细、早强越高对混凝土开裂影响很大。

混凝土设计强度等级越高，混凝土脆性越大、越易开裂。

（三）混凝土配合比设计原因1.设计中水泥等级或品种选用不当。

2．配合比中水灰比（水胶比）过大。

3．单方水泥用量越大、用水量越高，表现为水泥浆体积越大、坍落度越大，收缩越大。

4．配合比设计中砂率、水灰比选择不当造成混凝土和易性偏差，导致混凝土离淅、泌水、保水性不良，增加收缩值。

5．配合比设计中混凝土膨胀剂掺量选择不当。

（四）施工及现场养护原因1．现场浇捣混凝土时，振捣或插入不当，漏振、过振或振捣棒抽撤过快，均会影响混凝土的密实性和均匀性，诱导裂缝的产生。

2．高空浇注混凝土，风速过大、烈日暴晒，混凝土收缩值大。

3．对大体积混凝土工程，缺少两次抹面，易产生表面收缩裂缝。

4．大体积混凝土浇注，对水化计算不准、现场混凝土降温及保温工作不到位，引起混凝土内部温度过高或内外温差过大，混凝土产生温度裂缝。

5．现场养护措施不到位，混凝土早期脱水，引起收缩裂缝。

6．现场模板拆除不当，引起拆模裂缝或拆模过早。

7．现场预应力张拉不当（超张、偏心），引起混凝土张拉裂缝。

（五）使用原因（外界因素）1．构筑物基础不均匀沉降，产生沉降裂缝。

2．使用荷载超负。

3．野蛮装修，随意拆除承重墙或凿洞等，引起裂缝。

4．周围环境影响，酸、碱、盐等对构筑物的侵蚀，引起裂缝。

5．意外事件，火灾、轻度地震等引起构筑物的裂缝。

二、裂缝的控制措施（一）设计方面1．设计中的‘抗’与‘放’。

在建筑设计中应处理好构件中‘抗’与‘放’的关系。

所谓‘抗’就是处于约束状态下的结构，没有足够的变形余地时，为防止裂缝所采取的有力措施，而所谓‘放’就是结构完全处于自由变形无约束状态下，有足够变形余地时所采取的措施。

设计人员应灵活地运用‘抗一放’结合、或以‘抗’为主、或以‘放’为主的设计原则。

来选择结构方案和使用的材料。

2.设计中应尽量避免结构断面突变带来的应力集中。

如因结构或造型方面原因等而不得以时，应充分考虑采用加强措施。

3．积极采用补偿收缩混凝土技术：在常见的混凝土裂缝中，有相当部分都是由于混凝土收缩而造成的。

要解决由于收缩而产生的裂缝，可在混凝土中掺用膨胀剂来补偿混凝土的收缩，实践证明，效果是很好的。

4．重视对构造钢筋的认识：在结构设计中，设计人员应重视对于构造钢筋的配置，特别是于楼面、墙板等薄壁构件更应注意构造钢筋的直径和数量的选择。

5．对于大体积混凝土，建议在设计中考虑采用60天龄期混凝土强度值作为设计值，以减少混凝土单方用灰量，并积极采用各类行之有效的混凝土掺合料。

（二）材料选择和混凝土配合比设计方面1．根据结构的要求选择合适的混凝土强度等级及水泥品种、等级，尽量避免采用早强高的水泥。

2．选用级配优良的砂、石原材料，含泥量应符合规范要求。

3．积极采用掺合料和混凝土外加剂。

掺合料和外加剂目标已作为混凝土的第五、六大组份，可以明显地起到降低水泥用量、降低水化热、改善混凝土的工作性能和降低混凝土成本的作用。

4．正确掌握好?昆凝土补偿收缩技术的运用方法。

对膨胀剂应充发考虑到不同品种、不同掺量所起到的不同膨胀效果。

应通过大量的试验确定膨胀剂的最佳掺量。

5．配合比设计人员应深入施工现场，依据施工现场的浇捣工艺、操作水平、构件截面等情况，合理选择好混凝土的设计坍落度，针对现场的砂、石原材料质量情况及时调整施工配合比，协助现场搞好构件的养护工作。

（三）现场3~-T-操作方面1．浇捣工作：浇捣时，振捣捧要快插慢拔，根据不同的混凝土坍落度正确掌握振捣时间，避免过振或漏振，应提倡采用二次振捣、二次抹面技术，以排除泌水、混凝土内部的水分和气泡。

2．混凝土养护：在混凝土裂缝的防治工作中，对新浇混凝土的早期养护工作尤为重要。

以保证混凝土在早期尽可能少产生收缩。

主要是控制好构件的湿润养护，对于大体积混凝土，有条件时宜采用蓄水或流水养护。

养护时间为14—28天。

3．混凝土的降温和保温工作：对于厚大体积混凝土，施工时应充分考虑水泥水化热问题。

采取必要的降温措施（埋设散热孔、通水排热等），避免水化热高峰的集中出现、降低峰值。

浇捣成型后，应采取必要的蓄水保温措施，表面覆盖薄膜、湿麻袋等进行养护，以防止由于混凝土内外温差过大而引起的温度裂缝。

4．避免在雨中或大风中浇灌混凝土。

5．对于地下结构混凝土，尽早回填土，对减少裂缝有利。

6．夏季应注意混凝土的浇捣温度，采用低温人模、低温养护，必要时经试验可采用冰块，以降低混凝土原材料的温度。

总结：综上所述，对于混凝土裂缝的控制是一个综合性的问题，需要经过设计、监理、施工及使用方等多方面的配合。

随着当今我们对混凝土耐久性研究的不断深入，材料科学的不断发展和建筑技术水平的不断提高，相信混凝土裂缝问题将会逐渐得以圆满地解决。

Summary: Concrete crack exists in the construction of common problem. Now I will discuss the causes and management of concrete cracks briefly.Key words: cracks, mixing proportion, temperature reduction, casting and compacting, concrete curing, stretch-draw.1. The causes of cracks.Cracks have many formations and physics, to fundamentally solve problems of concrete’s crack, we should start from the causes of formation of concrete cracks. The correct judgments and analysis of the causes of concrete cracks are the most efficient way of effectively control and reducing concrete cracks.(1) Design.1. In the process of the structure design, the stress is produced by the section mutation give rise to component cracks.2. In the process of design, structural crack is caused by the stress which is threw to the construction is improper（eccentricity，too much stress etc.)3. In the design process some people did not fully consider the contraction distortion of concrete structures.4. In the design process structure reinforced configuration too little or too thick caused component cracks (such as wall, floor)5. In the design process, the high rank of concrete is used causes toomuch ash using which is harmful to shrink.(2) Materials.1. Different kinds of aggregate have too much mud make concrete shrink too much. The bad aggregate grading or taking inappropriate discontinuous gradation easily make concrete shrink too much, so induce cracks producing.2. Aggregate size is much thinner, and the amount of faller is larger, ash and water consumption is more and the amount of shrinkage is larger.3. Improper selection of concrete additive, or the improper amount of mixed strengthen the shrink of concrete seriously.4. Resent of cement style, Slag Portland cement more contraction than ordinary Portland cement contraction, fly ash and alumina cement shrinkage is smaller, fast hard cement contraction.5. Cement and concrete strength grade level reason: the higher grades of cement, the thinner, the higher influence of early strength of concrete cracking. Concrete design strength grade, the higher the concrete brittleness bigger, easier to crack.(3)Concrete mix ratio1. In the process of design the rank or sort of cement is selected improperly.2. In mix proportion water cement ratio is too large.3. Unilaterally dosage of cement bigger, water consumption, the higherthe performance for the slurry volume is larger, the greater the shrinkage is bigger.4. Mixed proportion design medium sand rate, water-lime ratio options improper concrete workability deviation, resulting in concrete from xi resembles, secrete water, the water is bad, the increase shrinkage5. Mix proportion design of concrete expansive agent to the admixture of improper selection.(4)Resents of construction and site maintenance1. When stirring concrete at the scene, vibrating or insert undeservedly, leakage for vibration, vibration or vibrating great smoke uninstall too fast, all can affect the concrete of course aggregates and uniformity, then induce occurring cracks.2. While depositing concrete aloft, speed of wind being too high, insolating in the sun, make the shrinkage larger.3. For mass concrete engineering, lack of two precautions, being easily to generate surface shrinkage crack.4.For mass concrete casting, the false calculation of hydration, inappropriate cooling and heat preservation making the temperature of concrete too high or temperature range too large lead to temperature cracks.5. Measures of site maintenance not reaching the designated position, concrete dehydrating in the early time, causes shrinkage crack.6. On-site form being dismantled undeservedly, cause mould cracks or dismantle detaching the mold premature.7. Site tensing improperly (splaying overly, eccentric), causes tension cracking of concrete.(5) Usage reasons (external factors)1. The asymmetric drop of structural base makes sedimentary cracks.2. Using excess load.3. Savage decoration, removing main wall or digging holes arbitrarily makes cracks.4. Influence of the surroundings, erosion of acid, alkali, salt and so on to structures caused cracks.5. Accidents, fire, mild earthquake caused structures cracks. Second, cracking control measures2. Design1. Design of "resistance" and "release".In architectural design we should handle component in 'resistance "and" put "relationship. The so-called "resistance" is in the structure of constraint condition, not enough room to prevent deformation cracks, take effective measures, the so-called "put 'is structure is completely in free deformation without constraint, measures are taken when there is enough room for deformation.Design personnel should be flexibly 'resistance to a put' union, or giving priority to the "resistance" , or make 'put ' as mainly designprinciples to choose structure scheme and the materials used.2. In design process we should avoid structure cross-section resulting stress as possible as we can. If because of the structure or model respect etc, and we have due regard to adopt measures of strengthen structure.3. Actively adopting technology of compensating shrinking concrete: Among common concrete cracks, there are some cracks be due to shrinkage of concrete and then be made. To solve the problem that cracks made for shrinkage, concrete can be mixed with expanding agent which used to compensate for concrete's shrinkage, in fact, the effect is very good actually.4. Emphasis on understanding of tectonic reinforced: In structural design, design personnel should attach importance to reinforced configuration of structures, especially for thin-walled structure such as the floor. wall plate etc. should be paid more attention to on choices of the diameter and number of distributing bars.5. For mass concrete Suggestions in design, design value is consider using a 60 days ages concrete strength value, in order to reduce usage of ash for concrete unilaterally, and actively adopt various effective concrete admixtures.(2) The selection of materials and concrete proportioning1. According to the structural requirement and choosing the appropriate strength grade of concrete and cement type, level, avoiding using early,strong, high cement.2. Choosing the fine gradation sand, run-of-pit, hydraulic sand should conform to the standard.3. Actively adopting additive and concrete admixtures. The goal of admixtures and admixture, has been made as the fifth, six components of concrete, it can obviously reduce the dosage of cement, hydration heat, improve the working function and reduce concrete cost.4. Properly understanding the method of technology that concrete compensates shrinkage. Different effect for different style, different dosage of expanding agent should be allowed for. We should make the large number of experiments to determine the optimum content of expansive agent5.Personnel who design mixed proportion should penetrate into constructive site, on the basis of the construction site of pouring process, operative level and component section etc, reasonably choosing a good design of concrete slump, aiming at the scene of the sand, run-of-pit material quality condition adjusting technologies of construction proportioning, assist improving component maintenance work on-site.(3)3 ~ T operating on the scene1. Watering beaten work: when we are pouring and watering, vibrate bar should be pulled slowly and inserted quickly. According to the different concrete slump and correctly grasp vibrating time, personnel should avoidexcessive vibration or leak vibration. We advocate adopting twice vibration, twice maintain technology, to exclude secrete water, concrete internal water and air bubbles.2. Concrete curing:Among the work of preventing concrete crack, it is important to conserve fresh concrete in the early time, so that shrinkage is ensured to be reduced in the early time. Above all personnel should control the structural maintenance of moist, to the mass concrete if it is allowed personnel should be better to adopt maintenance of impounding or flowing. The time of maintenance is 14 to 28 days. Curing time is for 14-28 days.3. Concrete cooling and heat preservation work:To thick mass concrete, in the construction workers should give full consideration to questions of cement hydration. When the concrete shaping up after cooling works should take the necessary measures of impoundment insulation, the surface coverage film, wet sack etc, to prevent the maintenance temperature due to excessive internal and external causes of concrete temperature crack.4. Avoiding watering concrete in rain or high winds.5. For underground structure concrete, personnel should put back the soil as soon as possible to reduce cracks.6. In summer workers should pay attention to the temperature of pouringand watering concrete, adopt low-temperature person mold, low temperature curing, if necessary, after the test workers can use ice to reduce the temperature of the raw materials.Conclusion:Above all, the concrete cracking control is a comprehensive problem, which is needed to pass the design, supervision, construction and using square, and other aspects of cooperation.With penetrating into studying the durableness of concrete currently, materials science development and the construction technology level unceasing enhancement, we believe concrete crack problems will gradually be solved.。