外文翻译---浅谈混凝土的施工过程中温度与裂缝控制
建筑施工混凝土裂缝的预防与处理外文翻译
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南京理工大学紫金学院毕业设计(论文)外文资料翻译系:机械系专业:土木工程外文出处:《 CANADIAN JOURNAL OF CIVI ENGINEERING 》(用外文写)附件: 1.外文资料翻译译文;2.外文原文。
指导教师评语:签名:年月日注:请将该封面与附件装订成册。
附件1:外文资料翻译译文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。
关键词:混凝土裂缝预防处理前言混凝土是一种由砂石骨料、水泥、水及其他外加材料混合而形成的非均质脆性材料。
由于混凝土施工和本身变形、约束等一系列问题,硬化成型的混凝土中存在着众多的微孔隙、气穴和微裂缝,正是由于这些初始缺陷的存在才使混凝土呈现出一些非均质的特性。
微裂缝通常是一种无害裂缝,对混凝土的承重、防渗及其他一些使用功能不产生危害。
但是在混凝土受到荷载、温差等作用之后,微裂缝就会不断的扩展和连通,最终形成我们肉眼可见的宏观裂缝,也就是混凝土工程中常说的裂缝。
混凝土建筑和构件通常都是带缝工作的,由于裂缝的存在和发展通常会使内部的钢筋等材料产生腐蚀,降低钢筋混凝土材料的承载能力、耐久性及抗渗能力,影响建筑物的外观、使用寿命,严重者将会威胁到人们的生命和财产安全。
很多工程的失事都是由于裂缝的不稳定发展所致。
近代科学研究和大量的混凝土工程实践证明,在混凝土工程中裂缝问题是不可避免的,在一定的范围内也是可以接受的,只是要采取有效的措施将其危害程度控制在一定的范围之内。
钢筋混凝土规范也明确规定:有些结构在所处的不同条件下,允许存在一定宽度的裂缝。
但在施工中应尽量采取有效措施控制裂缝产生,使结构尽可能不出现裂缝或尽量减少裂缝的数量和宽度,尤其要尽量避免有害裂缝的出现,从而确保工程质量。
混凝土裂缝产生的原因很多,有变形引起的裂缝:如温度变化、收缩、膨胀、不均匀沉陷等原因引起的裂缝;有外载作用引起的裂缝;有养护环境不当和化学作用引起的裂缝等等。
浅谈混凝土的施工温度与裂缝
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浅谈混凝土的施工温度与裂缝混凝土裂缝威胁着工程质量,文章通过阐述裂缝产生的原因,分析温度应力,提出控制温度和预防裂缝的措施,以及防止裂缝对混凝土进行早期养护,从混凝土裂缝的角度为工程安全提出参考依据。
标签:温度裂缝养护0 引言长期以来,混凝土在建筑施工中始终发挥着举足轻重的作用。
但是混凝土裂缝问题也是长期困扰建筑、施工单位的一大难题,桥梁工程裂缝问题尤为严重。
尽管在施工阶段已采取了防治措施,但裂缝仍时有发生。
在混凝土施工中,温度应力和温度控制对裂缝防治意义重大,具体体现在:一是混凝土结构的整体性和耐久性受温度产生的裂缝的影响较大;另一方面结构的应力状态受温度变化的影响明显。
1 裂缝产生的原因在混凝土施工中,原材料的选择、温湿度变化、混凝土的脆性和不均匀性、地基发生不均匀沉陷等等诸多因素都有可能引发混凝土裂缝,因此在施工中要加强各环节、各工序的质量控制。
由于混凝土水花作用会产生大量水化热,致使混凝土内、外部形成温度差,进而导致混凝土表面产生拉应力。
降温时,基础混凝土与旧混凝土相互制约,导致混凝土的内部出现大于混凝土本身抗裂能力的拉应力,进而引发结构裂缝。
混凝土作为一种脆性材料,抗拉强度不均匀,在混凝土的内部存在许多抗拉能力低、极易出现裂缝的薄弱部位。
另外,由于原材料拌合不均匀,水灰比不稳定,以及混凝土出现离析现象,在混凝土内部由钢筋承担拉应力,混凝土只承受压应力。
但是在钢筋混凝土的边缘和素混凝土内部,这部分拉应力职能由混凝土本身承担。
因此,浇筑过程中,要严格控制浇筑质量,尽量避免混凝土构件产生拉应力。
但是在施工过程中,由于混凝土温度的变化,导致混凝土内部产生拉应力。
为了确保结构设计的合理性,熟悉温度应力的变化规律。
2 温度应力的分析形成温度应力过程分为早期、中期、晚期三个阶段:①早期:大约需要30天,是指从开始浇筑混凝土到水泥完成放热。
此时混凝土表现出两个特征:一是弹性模量发生急剧变化;二是水泥产生大量水化热。
浅谈混凝土的施工温度与裂缝的成因与控制
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浅谈混凝土的施工温度与裂缝的成因与控制【摘要】在如今的工程建设中,混凝土构件占有相当大的比重。
但因为混凝土的抗拉强度比较低,所以在混凝土构件中会经常会出现一些裂缝,而这些裂缝的存在会严重影响混凝土构件的使用效能,甚至会造成一定的安全危害。
这些裂缝主要是因为混凝土温度应力的变化而引起的。
本文将结合察汗乌苏水电站大坝工程对混凝土的施工温度和裂缝的成因与控制进行探讨。
【关键词】混凝土;施工温度;裂缝;成因;控制1.引言混凝土广泛应用于现代工程建设当中,混凝土裂缝问题是混凝土施工过程当中常见的问题。
混凝土裂缝的出现会导致混凝土浸水而腐蚀内部构件,从而降低混凝土材料的耐久性、抗渗透性以及承载力,同时还会影响混凝土结构的使用寿命以及外观,严重的甚至会对人们的生命财产安全产生危害。
在混凝土施工过程中,施工人员通常会采取各种办法防止混凝土裂缝的产生,但混凝土裂缝问题仍会出现。
这主要是由于不重视对混凝土的温度应力的控制。
混凝土的体积一般比较大,会产生大量的水化热,但混凝土的内部结构和外部结构散热速度不一致以及混凝土会受到各种约束,从而会在混凝土内部产生较大的温度应力,进而导致混凝土裂缝的产生。
这些裂缝的存在是很严重的质量隐患。
因而,在混凝土施工过程中,对混凝土的施工温度控制是控制混凝土裂缝产生的关键。
2.工程概况趾板砼设计宽度有6m、8m、10m,厚度有60cm、80cm、100cm、130cm,共分42个浇筑块,砼方量共计4898m3。
趾板锚筋(Φ28)长分别有5.2m、4.9m、4.85m、4.7m,锚筋深入基岩4m。
右岸在1600m高程以上设计有高趾墙,左岸在1646.500m高程以上设计有高趾墙。
趾板混凝土标号为C25W12F300,级配为二级配。
砼浇筑严格执行DL/T5144-2001,施工坍落度控制在3~7cm。
施工方案:趾板砼浇筑顺序为先河床段,后岸坡段,岸坡段趾板砼随坝体升高超前8~10m浇筑。
趾板砼共分为42个浇筑块,施工时由上而下依次跳仓浇筑,各道工序穿插进行,流水作业。
英文翻译-混凝土裂缝成因及控制
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山东交通学院2015届毕业生毕业论文外文翻译院别交通土建工程学院专业土木工程班级土木111学号姓名指导教师二○一五年六月混凝土裂缝成因及控制摘要: 针对目前建筑混凝土的裂缝问题, 分别从温度应力、原材料质量、收缩形变、钢筋锈蚀以及施工工艺质量几个方面论述了开裂原因, 并提出了相应的控制措施。
关键词: 混凝土; 裂缝; 原因; 控制混凝土出现裂缝的原因多种多样, 通常情况下,裂缝的存在不会影响构件的正常使用( 宽度< 0. 05 mm ) , 但如果裂缝过大就会降低结构的安全性和耐久性, 本文主要针对后者进行讨论。
1 混凝土裂缝成因1. 1 温度裂缝当外部温度或结构内部温度发生变化, 混凝土将发生形变, 若变形受到约束, 结构内将产生应力,当应力超过混凝土抗拉强度时将产生温度裂缝。
通常情况下, 温度应力主要有3 种形成方式:1) 大体积混凝土(厚度超过2 m ) 浇注之后由于水泥水化放热产生温度应力; 此外, 由于混凝土弹性模量的急剧变化也会在其内部形成残余应力;2) 当水泥放热基本结束后, 由于混凝土的冷却以及外界气温变化引起温度应力;3) 在使用过程中, 由于突发降水、冷空气侵袭或日落等致使混凝土结构外表面温度突然下降, 内部温降相对较慢而产生温度应力。
1. 2 原材料质量引起的裂缝配制混凝土时所采用原材料质量不合格, 也可能导致结构出现裂缝。
1. 2. 1 水泥如果水泥安定性不合格, 其中的游离氧化钙含量超标, 则由于氧化钙在凝结过程中水化很慢, 在混凝土凝结后仍然继续起水化作用, 可破坏已硬化的水泥石, 使混凝土抗拉强度下降。
若水泥出厂时强度不足, 水泥受潮或过期, 亦可能使混凝土强度不足, 导致混凝土开裂。
1. 2. 2 砂、石集料1) 砂石的粒径、级配、杂质含量如果砂石粒径太小、级配不良, 将导致水泥和拌和水用量加大, 使混凝土收缩加大, 影响混凝土的强度; 如果使用超出规定的特细砂, 后果将更加严重。
浅谈混凝土的施工温度与裂缝控制
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浅谈混凝土的施工温度与裂缝控制混凝土是一种常见的建筑材料,在建筑工程中使用广泛。
混凝土的施工温度是混凝土在浇筑和养护过程中的温度。
混凝土施工温度对混凝土的力学性能、耐久性以及裂缝控制起着重要的作用。
一、混凝土施工温度对混凝土性能的影响混凝土的强度及其它力学性能受施工温度的影响较大。
施工温度过高或过低均会影响混凝土的强度和耐久性。
1.施工温度过高当混凝土浇筑时,由于施工温度过高,混凝土内部的水分蒸发过快,使混凝土失去一定的流动性,使混凝土浇筑成型品质降低,甚至会导致表面龟裂、脱落等现象。
当混凝土在热天时间内浇筑施工时,混凝土表面干燥速度过快,由于混凝土内部空隙温度差异而产生的收缩留下很强的甚至是深层龟裂,好比新鲜的面团刚刚加水和发酵,如果太阳直射整个盆,开裂就是不可避免的。
同时,高温还会降低混凝土的强度和耐久性,减缓和延长混凝土的硬化时间,以及增加混凝土表面和内部的温度差异。
这些问题都会对混凝土的性能造成负面影响。
2.施工温度过低当混凝土浇筑时,如果温度过低,将会延缓混凝土的硬化时间,影响混凝土的强度的形成。
还会影响混凝土的耐久性,导致混凝土易龟裂、渗漏、变形等现象的产生,降低混凝土的使用寿命。
施工温度过高或过低,均会影响混凝土的强度和耐久性,因此,在混凝土的施工中,需要注意施工温度的控制。
二、混凝土的裂缝控制混凝土的裂缝问题一直是一个难解决的问题,在施工中常常因为温度问题而导致混凝土裂缝,这种问题会降低混凝土的强度和水密性。
在混凝土浇筑时,需要注意以下几点,从而控制混凝土的裂缝。
1. 控制施工温度在混凝土施工中,需要适当控制施工温度。
混凝土的施工温度应该在适宜的范围内,户外施工建议在混凝土浇筑前,首先确定好混凝土温度,以便掌握室内水泥浆料温度。
混凝土表层蒸发记录、养护天数以及养护时段都是需要记录的任务。
2. 减少温度温跃变化在混凝土浇筑时,避免热、冷交替引起的温度温跃变化,可以采用以下几种方式:确保混凝土内温度均匀,使用适当的混凝土配合比例控制水灰比,加有机物超塑剂、熟石灰等减少水泥对混凝土的影响,以减少液体表面张力。
外文翻译---浅谈混凝土的施工过程中温度与裂缝控制
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外文翻译---浅谈混凝土的施工过程中温度与裂缝控制外文翻译一、原文Discuss the construction temperature andcrack of the concrete lightlyThe summary: In order to prevent the owners of the concrete work of claims, we must do a good job in the construction process in the temperature and crack control, through observation live for many years, through consulting the monograph about stress within the concrete, explain to concrete temperature reason, on-the-spot concrete control and measure, prevention of crack of temperature that crack produce. Keyword Concrete Temperature stress Crack Control1. The concrete occupies the important position in modern engineering construction. But today, the crack of the concrete is comparatively general, the cracks are nearly omnipresent in the science of bridge building. Though we take various kinds of measures in constructing, careful, but the crack still occurs now and then. Tracing it to its cause, it is one of them incompletely that our change to concrete temperature stress pays attention to. In the large volume concrete, temperature stress and temperature control are significant. This is mainly because of the reason of two respects. First of all, concrete often appear the temperature crack in not constructing, influence the globality and durability of the structure. Secondly, in the course of operating, the temperature change has remarkable influence that can't be ignored on the stress state of the structure. We meet to construct temperature crack in mainly, so only to origin cause of formation and treatment measure, concrete of crack make a discussion in constructing this text.Reason of a crackIt has many kinds of reasons to produce the crack in the concrete, it is mainly the changes of temperature and humidity, fragility and disparity of the concrete, and the structure is unreasonable, the raw materials is not up to standard (if the alkali aggregate react), the template is out of shape, the foundation does not subside etc. evenly. The cement emits a large amount of heat of hydration when the concrete is hardened, inside temperature is rising constantly, cause the stress of drawing on the surface. In the course of lowering the temperature, is it congeal foundation pay restrain to mix always later stage, will present the stress of drawing within the concrete. Reducing of temperature can surface cause heavy stress of drawing very in concretetoo. When these draw the stress and go beyond resisting the ability of splitting of concrete, namely will present the crack. A lot of inside humidity of concrete change very light or change relatively slow, surface humidity might change heavy the violent change takes placing. Such as maintaining thoroughly, when getting wetter when not doing, contract surface there aren't deformation doing, often cause the crack too. The concrete is a kind of fragility material, tensile strength is about 1/10 of the compression strength, is it carry on one's shoulder or back limit when draw out of shape to have (0.6~1.0)×104 only, is it carry on one's shoulder or back limit location when stretch out of shape to there is(1.2~2.0)×104 to add for a long time to add a short time. Because raw materials even, water dust than unstable, transport and build phenomenon of emanating of course, its tensile strength is not even in the same concrete, a lot of resist the ability of drawing very low, it is apt to present the weak position of the crack. Among armored concrete, draw stress to undertake by reinforcing bar mainly, concrete bear stress of keeping just. Or reinforcing bar mix if edge position gone to congeal presents the stress of drawing in the structure in plain concrete must rely on the concrete oneself to bear. Require avoiding the stress of drawing or only very small stress of drawing appears of the general design. But the concrete is cooled from maximum temperature to the steady temperature of operating period in constructing, often cause sizable to draw the stress within the concrete. The temperature stress can exceed other outsides and load the stresses caused sometimes, know change law, temperature of stress for carry on reasonable structural design and construct extremely important.Analysis of 2 temperature stressesIt can be divided into following three stages according to the forming process of the temperature stress:(1)It is early: It needs generally 30 day from beginning building concrete to finishing sending out heat basically by cement. There are two characteristics at this stage, first, the cement emits a large amount of heat of hydration, second, mix and congeal the changing sharply of elastic model quantity. Because of the change of elastic model quantity, form the remaining stress in the concrete in this period.(2)Middle period: Up till the concrete is cooled until stability temperature from cement send out heat function basically when expiring, in this period, the temperature stress is mainly because the cooling of the concrete and external temperature change cause, these stresses and remnants stresses that is formed in early days are superposed, mix and congeal the elastic mould amount that goes to and does not change much during this period.(3)Later period: Operation period after the complete cooling of concrete. Temperature stress whether external temperature change causes mainly, these stresses and first two kinds of remnants stresses are changed and added.It can be divided into two kinds according to the reason why the temperature stress causes:(1)Spontaneous stress: There are not any restraints or totally static structure at the border, if inside temperature is non-linear distribution, temperature stress appearing because structure restrains from each other. For example, the body of mound of the bridge, the physical dimension is relatively large, surface temperature is low when the concrete is cooled, inside temperature is high, present the stress of drawing on the surface, present the stress of pressing in the middle.(2)Restrain the stress: All of the structure ones or it restrain external one some border, can't out of shape and stress not cause not free. Such as case beam roof concrete and guardrail concrete.These two kinds of temperature stresses draw back stresses caused to act on with the doing of concrete together frequently. It is a more complicated job to want to analyse the distribution, size of the temperature stress accurately according to known temperature. In case of great majority, need to rely on the model test or the number value to calculate. To is it make temperature stress have sizable limp to creep concrete, at the stress accounting temperature, must consider the influence that creep, calculate concretely that no longer states thinly here.Control and preventing the measure of the crack of 3 temperatureFor prevent crack, lighten temperature stress can from control temperature and is it is it set about to restrain terms from two to improve.The measure of controlling temperature is as follows:(1)Is it improve aggregate grade mix, is it do rigid concrete to spend, mix mixture to adopt, is it guide angry pharmaceutical or plastification pharmaceutical, etc. measure in order to reduce cement consumption of concrete to add;(2)Add water or the water to cool the broken stone in order to reduce the temperature of building of the concrete while mixing and shutting the concrete;(3)Reduce the thickness of building while building the concrete on hot day, utilize and build the aspect to dispel the heat;(4)Bury the water pipe underground in the concrete, enter the cold water to lower the temperature openly;(5)Stipulate rational form removal time, the temperature keeps warm the surface while lowering suddenly, in case that the rapid temperature gradient takes place in the concrete surface;(6)The concrete with medium and long-term and exposed construction builds a piece of surface or thin wall structure, take the measure of keeping warm in cold season;The measure of improving condition of restraining is:(1)Divide and sew and divide one rationally;(2)Prevent the foundation from rising and falling too big;(3)Rational arrangement construction process, prevent the too big discrepancy in elevation and side from exposing for a long time;In addition, improve the performance of the concrete and improve and resist the ability of splitting, strengthen maintenance, prevent the surface from being done and contracted, especially guarantee the quality of the concrete is very important to preventing the crack, should pay special attention to avoiding producing and running through the crack, the globality resumed its structure after appearing is very difficult, so should rely mainly on preventing the emergence of the running through crack while constructing.In construction of concrete, for raise turnover rate of template, demand concrete form removal as soon as possible that build newly often. Should consider form removal time properly when concrete temperature is higher than the temperature, so as not to cause the superficial early crack of concrete. Building the early form removal newly, cause very large stress of drawing on the surface, the phenomenon that "temperature is assaulted" appears. Build initial stage in concrete, because heat of hydration is sent out, the surface causes sizable to draw the stress, surface temperature is also higher than temperature at this moment, remove the template at this moment, surface temperature is lowered suddenly, must cause temperature gradient, thus add and draw the stress on the surface, change and add with the heat of hydration stress, in addition, the concrete dries and contracts, the superficial stress of drawing reaches very great number value, have danger of causing the crack, but cover a light-duty heat insulator with on the surface in time after removing the template, for instance foam sponge, etc. , for prevent concrete surface from produce the too big stress of drawing, have remarkable results.Add muscle influence to large volume temperature stress of concrete very light, because large volume concrete include muscle to be rate very much low. Just have influence on the general armored concrete. On terms that temperature is not very high and the stress is less than limit of surrendering, every performance of the steel is steady, and have nothing to do with stress state, time and temperature. Line bloated coefficient of steel and concrete line bloated coefficient difference very light, take place little internal stress very only between the two while changing in temperature. Because elastic mould amount of steel concrete elastic mould 7~15 of quantity, reach as interior concrete stress tensile strength and when fracturing, the stress of the reinforcing bar will not exceed 10000kg/cm2. So is it is it prevent tiny appearance difficulty very much of crack from to make use of reinforcing bar to want among concrete. But the crack in the structure generally becomes numerous, the interval is little, the width and depth are smaller after adding the muscle. And if diameter of reinforcing bar detailed and when interval dense, to improve concrete resist result of person who split better.Concrete and surface, armored concrete of structure can take place detailed and shallow crack often, among them the great majority belong to and do and draw back the crack. Though this kind of crack is generally all relatively light, it stills have certain influence on the intensity and durability of the structure.In order to guarantee concrete project quality, prevent fracturing, improve the durability of the concrete, use the admixture to reduce one of the measures that fractures correctly. Whether is it reduce water is it split pharmaceutical to defend, I summarize his main function in practice to use.(1)There is a large number of capillary in the concrete, produce capillary tension in the capillary after water is evaporated, make concrete is it contract out of shape to do. Increasing the thin aperture of hair can reduce the capillary surface tension, but will make the intensity of concrete reduce. This surface tension theory has already been confirmed in the world as far back as the sixties.(2)Water dust than influence important factor that concrete shrink, is it reduce water is it split pharmaceutical can make concrete water consumption reduce by 25% to defend to use.(3)Cement consumption important factor, concrete of person who shrink too, is it add and subtract water is it split concrete reducible 15% of the cement consumption on terms that keep the intensity of concrete of pharmaceutical to defend to mix, its volume is supplemented by increasing aggregate consumption.(4)Reduce water is it split pharmaceutical can improve consistency of grout, reduce concrete secrete ink to defend, reduce and sink and draw back deforming.(5)Improve gluing the strength of forming of the grout and aggregate, the concrete improved resists the performance of splitting.(6)Concrete is it produce stress of drawing to restrain from while shrinking, crack when drawing the stress and is greater than concrete tensile strength can produce. Reduce water is it split pharmaceutical effective concrete tensile strength of improvement very to defend, improve resisting the performance of splitting of concrete by a wide margin.(7)It can make the concrete density good to add the admixture to mix, can improve resisting carbonization of concrete effectively, reduce carbonization to shrink.(8)Is it reduce water is it split slow coagulation time proper concrete under pharmaceutical to defend, on the basis of preventing the fast water of cement from sending out heat effectively to mix, prevent the plasticity shrink that brings because the cement is not congealed for a long time from increasing.(9)Mix admixture concrete and getting easy and kind, surface easy to feel flat, form little membrane, reduce the moisture to evaporate, reduce drily and shrink. A lot of admixtures all have the functions of slow coagulation, increasing and apt, improvement plasticity, the experiment that we should carry on in this respect more inthe project practice is compared with and studied, than lean against not improving terms more simple, may getting simple and more direct, economy.Early maintenance of 4 concretePractice has proved, the common crack of concrete , most is the surface crack of different depth, main reason its whether temperature gradient cause cold temperature of area lower too easy to form crack suddenly. So say the warm-keeping of the concrete is especially important to preventing the early crack of surface.From the viewpoint of temperature stress, should reach and require keeping warm following:1)Prevent concrete internal and external temperature poor and concrete surface gradient from, prevent the surface crack.2)Prevent concrete from to be ultra and cold , should is it is it make the minimum temperature is not lower than the steady temperature of concrete service time construction time in concrete to try to try one's best.3)Prevent the old concrete subcooling, in order to reduce the restraint among the old and new concrete.The early maintenance of the concrete, the main purpose lies in keeping the suitable warm and humid condition, in order to get the result of two respects, on the other hand make the concrete avoid the invasion and attack of the unfavorable and warm, humidity out of shape, the ones that prevent from harmfully are cold to contract and do to contract. On one hand make cement water function go on smoothly, is in the hope of reaching the intensity designed and resisting the ability of splitting.The suitable warm damp condition is interrelated. Mix warm-keeping measure paid to congeal often protects wet results too. Analyse, water concrete include moisture can meet demand, cement of water have enough and to spare newly theoretically. But because the reason of evaporating etc. often causes losses of the moisture, thus postpone or hinder water of the cement from, the surface concrete receives this kind of adverse effect easiestly and directly. Key period when maintained in initial a few days after so the concrete is built should pay attention to conscientiously in constructing.2. Quality control of waterproof concrete constructionCombined with experience, from formwork design, fabrication and installation, assembling reinforcement, pouring and curing of concrete and other aspects construction technology of fair-faced concrete is introduced as well as quality control measures and standards in order to reduce engineering cost to acquire satisfied economic and social benefits.The factors of influencing waterproof-concrete quality are very many. Any links does not pay attention to the water-proof concrete of field loss hinders the water function without exception jointly with degree. Engineering construction in the basement adopts secondary form board fabrication and installation, reinforced barfabrication and bind, concrete stirring and mixing system and transport, concrete covibration beat with a stick, construction joint practice, concrete curing and dismantle model and being ready for backfill and so on aspects. These are very critical to quality method to ensure that water-proof concrete self water-proof, and the way of practice has wan out.Method being under construction2.1 Fabrication and InstallationAccording to the concert of closely knit, demand of reason why to form board since the water-proof also concrete have made and have assembled corresponding rise is special, be to require that not leaving out thick fluid, firm closely knit block of wood deformation, water absorption Character should be small and ought to give priority to select and using bamboo slab rubber form board or the steel form.. Strict control form board room gap size, necessary exceeding 2 mms uses foam rubber or plastic to squeeze a crack in, porous form board nonutility without exception to board face Be ready for wall post at the same time rotting the prevention and cure job adopt the cement mortar pouring same, indicia in before the root segment sticking the foam rubber or plastic strip, the bottom puts on a cement mortar, concrete a concrete, first 5cm~10cm. Since water-proof, concrete structure wall thickness is mostly more infertile. Be to ensure that component geometry dimension, Chang adopt the inside and outside bolt to pull the measure meeting attention to, responds to on play receive bolt centre interpose stop water iron plate, to prevent water from forming pilotage passage along bolt leakage.2.2 Assembling reinforcementWater-proof concrete structure has demanding as follows to the reinforced bar:1)Reinforced bar should adopt twisted steel as far as possible, increases by hold wrap a force composing in reply a water ability2)Reinforced bars connect should try one's best to adopt to solder connection, stop using and being needless to bind connection to the full3)When binding a reinforced bar, the iron wire head responds to inner bending.4)Strict control reinforced bars protective layer thickness.Minimal thickness of water-proof concrete reinforced bar protective layer is not smaller than 25mms, the protective layer welcoming water surface especially inadmissibility to disappoint error. The iron wire and reinforced bar that application buries in advance within mortar piece while using mortar heel block as protective layer, are bound solid. When the cavalry puts up the fixed reinforced bar if adopt a reinforced bar, also need to increase solders water iron plate or fixation just goes ahead, to strengthen water-proof effect in the heel block. This project uses new materials nylon to have fixed there is an effect's had guarded against reinforced bar protective layer deviation piece big mass common failings.2.3 The concrete stirring and mixing makes and transportsSince the water-proof concrete requires that higher closely knit, reason why stir and mix system also need to have the fairly good homogeneity, should be ready for burning as follows almost for this purpose:1)Ensures that mixing time, mixing at every time are secondary jump into a expect the general ejection of compact block of wood less than 2mins.2)Should use the apposition agent, the solution queen who should manufacture certain thickness from apposition agent adds the mixer inner, the dried powder or high concentration solution will add an agent extra not to adds the mixer inner directly, prevent from mixing is uneven but part concentrates, both lose the apposition agent effect, and affect concrete mass.3)Responds to the assured source of life degree having a spot test on the admeasurement concrete at the regular intervals collapsing in the process being under construction, construction is middle if Yu rains or other cause, respond to the ratio determining whose water ratio, and adjusting the composition being under construction in time when change happened in sandstone moisture content.4)Project uses the commodity concrete, has boundary have raised a concrete stirring mass and of all kinds effect apposition agent adulterating falls when amounts, the water ash having controlled a concrete strictly collapsing.5)Concretes adopt a pump to have given handicraft, effective avoiding a concrete producing the phenomenon isolating bleeding and leaving out thick fluid in the process of transportation.2.4 Matters needing attention in being under construction1)Construction school assignment soft and floury is divided. Water-proof concreting should stratify strictly being in progress, and a continuous construction is completed The front and back and high and low connect between the tier should subjugate within the cement initial setting time, For this purpose, with handling a worker dividing into several, at the same time each other, school assignment group faces or it is all right for each other, carry on the back.2)Achieve strictly fixed point determines the amounts of the components of a substance material down According to the vehicle capacities stratifying concrete altitude and the means of transport, the quantify carrying out fixed point strictly is able to go down one important ring expecting that this is to improve water-proof concreting mass.3)Concretes vibrating beat one important ring being to ensure that the concrete is closely knit, defend against to seep with a stick. Also, should adopt fixed point vibrating, handle meticulously on basis expecting that under determining the amounts of the components of a substance homogeneously in fixed point. Pay attention to high and low tier of linking up. Now that needing to prevent from miss and vibrating, notvibrating enough, being going to prevent a fault from vibrating again, Need to forbid using prying the method coming to aid to vibrate moving a reinforced bar or shaking a reinforced bar especially, such separates to making the front already concrete the reinforced bar and concrete shaking the reality part, causes serious consequences.4)Being ready for the assured source of life degree taking over thick fluid measure, and adjusting in time to collapse seriously. Average water-proof concrete structure construction, the construction joint being under construction respectively, composing namely on erecting wall sells be bottom board and vertical wall at reduced prices. Should irrigate thick a layer of 5cm~10cms surname indicia cement mortars in seam place first linking up closely knitting tier, in order to ensuring that the seam place vibrates when concrete vertical wall. Simultaneous, improve step by step with concrete an altitude, should fall off step by step with the water yield, diminish collapsing to fall degree prevent from concrete insist to be short but the cement paste is partial to much phenomenon to aggregate appearing on upper part.2.5 Dismantling model and curing of concreteThe water-proof concreting queen maintains goodness and badness working, not only affecting the intensity arriving at a concrete, moreover the impervious function affecting to the concrete. Evidence, water-proof concrete early phase dehydration or curing process lack for water, will reduce whose impervious function by a wide margin. Water-proof concrete curing responds to the block of wood less than 14ds. The water-proof concrete dismantles a model demanding to be unable to compare high, dismantle model time unsuitable untimely, respond to when dismantling a model handle meticulously, prevent an iron rod from using to pry stiffly, that the sledgehammer is knocked suddenly and forcibly pries, uses a concrete meet with destroy.2.6 Do good well at backfillWater-proof architectural backfill is a final working procedure, it be sometimes ignored, this is a very big faults in fact under the ground. When the water-proof structure job is over queen responds to the construction carrying out backfill immediately. Most important, we should take backfill seriously self mass; Secondly, backfill varia and ponding should clear up the pit bottom in the front, respond to densification with layers when backfill. Water-proof structure vicinity layer pounds true backfill, self is a reliable and economical as well water proofing drapery under the ground. In project basement engineering construction Shanghai, since organizing water proofing down to earth strictly with all above seven passes, the concrete is under construction, effect is comparatively ideal. The percolating water phenomenon does not appear.ConclusionsConstruction temperature and relation of crack in concrete the above carry onpreliminary discussion of theory and practice, though the academia has different theories to origin cause of formation and computing technology of the concrete crack, but to concrete prevention and improving the measure suggestion to relatively unify, application in practice result fine too at the same time, concrete to is it observe, compare more by us to want in constructing, analyse more, summarize more after going wrong, combine many kinds of prevention and deal with the measure, the crack of the concrete can be avoided.一、翻译浅谈混凝土的施工过程中温度与裂缝控制摘要为了防止业主对混凝土工程的索要赔偿,我们就必须做好过程中的温度与裂缝控制。
土木工程混凝土论文中英文资料外文翻译文献
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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。
浅析混凝土施工过程中的温度及裂缝控制
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浅析混凝土施工过程中的温度及裂缝控制混凝土在工程施工中扮演着重要的角色,它广泛应用于建筑、桥梁、道路等工程中。
混凝土的温度和裂缝控制一直是工程施工中需要重点考虑的问题。
温度和裂缝对混凝土结构的安全和耐久性都具有重要影响,因此在混凝土施工过程中,需要合理控制温度并采取有效措施来防止裂缝的产生。
一、混凝土施工中的温度控制1. 温度的影响混凝土的温度对混凝土的强度、收缩、开裂等性能都会有影响。
一般来说,混凝土的温度过高会导致混凝土强度降低,收缩率增加,易裂性增加;温度过低也会影响混凝土的强度和耐久性。
在混凝土施工过程中,需要合理控制混凝土的温度,以保证混凝土的质量和工程的安全。
2. 控制温度的措施在混凝土施工中,常用的控制温度的措施有:水泥的选择、水泥用量的控制、控制拌合料温度、加入减水剂等。
水泥的选择和用量的控制是最为关键的。
不同种类的水泥适用的温度范围不同,因此在选择水泥时需要根据施工环境和要求来选择合适的水泥。
控制水泥的用量也是非常重要的,过多或过少的水泥用量都会对混凝土的温度产生影响。
控制拌合料的温度也是需要重点考虑的问题,因为拌合料的温度会直接影响混凝土的温度。
在炎热的夏季,需要采取措施来控制拌合料的温度,以保证混凝土的质量。
2. 控制裂缝的措施在混凝土施工中,控制裂缝的措施有很多种,常用的措施包括:合理设计梁板结构、采用预应力混凝土、使用增强混凝土等。
合理设计梁板结构是防止裂缝产生的最为基本的措施。
在设计结构时,需要合理设置构件的截面积和配筋,以及设置适当的支撑和支座,以避免混凝土受到过大的内力和变形而产生裂缝。
采用预应力混凝土和增强混凝土也是控制裂缝的有效措施。
预应力混凝土能够在混凝土中设置预应力钢筋,使混凝土在受力时产生一定的压应力,从而减小混凝土的张应力,减少裂缝的产生;而增强混凝土则是利用增强材料来提高混凝土的抗拉强度和抗裂性能,降低混凝土的裂缝宽度和数量。
外文翻译混凝土裂缝的成因预防及处理
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The causes, prevention and treatment of cracks in concrete Abstract:In the building construction concrete cracks a quality common problem, the causes of cracks in concrete, prior prevention, as well as after the repair process is a more common phenomenon in the process of building production, should be taken seriously enough. The concrete is a brittle material of a gravel aggregate, cement, water and other additional material formed by mixing a non-homogeneous. Concrete construction and deformation constraints and a series of problems, there are a large number of micro-porosity, cavitation and micro-cracks in the concrete hardening molding. The author combines his engineering work experience, summed up the cracks in concrete causes and prevention measures.Keywords: causes of cracks in concrete preventive treatmentIn building construction, concrete cracks is a widespread problem, cracks solution is a more difficult problem. Cracks in concrete reasons are manifold, deformation: such as contraction, expansion, settlement and other causes cracks; external load caused by: improper maintenance of concrete; cracks caused by the external additive problems.Concrete cracks, if not prevention measures to solve, extending its further development will lead to the internal reinforcement corrosive, reducing the carrying capacity of the reinforced concrete structure, impermeability, durability useful life, and even affect people's lives and property safety . Crack is impossible to completely eliminate the engineering specification expressly provides some structure in which the different conditions, allowing the existence of a certain width and depth of the crack. But in the construction process should be as far as possible to take effective preventive and technical safeguards to effectively control the cracks, as little as possible or minimize crack width, depth, and in particular to avoid in key positions or harmful cracks.1.Causes and types of concrete cracksThe concrete is a brittle material of a gravel aggregate, cement, water and other additional material formed by mixing a non-homogeneous. Hardening molding concrete concrete construction and deformation constraints there are a large number of micro-porosity, cavitation and micro-cracks, precisely because of the existence of these initial defects before the concrete showing some heterogeneity characteristics . Micro-cracks is usually a harmless cracks on concrete load-bearing, seepage and use the function does not cause harm. But in the concrete under load, temperature effects, the micro-cracks will continue to expand and connectivity, and ultimately the formation of visible macro cracks, the cracks is often said that the concrete works.Many cracks in concrete cracks caused by deformation: such as temperature change, shrinkage, expansion, uneven subsidence caused cracks; external load induced cracks; cracks caused by improper conservation of the environment and chemical action, etc. .Common cracks in the concrete are the following: (1) shrinkage cracks; ②plastic shrinkage cracking; (3) settlement cracks; ④temperature cracks; ⑤chemical reaction caused by cracks.2.Concrete cracks and prevention2.1 Shrinkage cracks and prevention ofShrinkage cracks appear in a week or so after the end of the concrete curing period of time or after concrete pouring. The evaporation of the water in the slurry will produce shrinkage, and the shrinkage is irreversible. Drying shrinkage cracks are mainly caused due to the different degree of evaporation of the moisture inside and outside the concrete result of deformation of the type: concrete affected by the influence of external conditions, excessive surface moisture loss, large deformation, internal humidity changes smaller deformation smaller, the larger the surface shrinkage deformation by concrete internal constraints, have a greater tensile stress cracks. The lower the relative humidity, the greater the shrinkage of cement paste shrinkage cracks are easy to produce. Shrinkage cracks parallel to the surface of the linear or reticular light fine cracks, width of more than 0.05 to 0.2 mm between the flat parts more common in mass concrete, thin flat-slab along the short to distribution. Shrinkage cracks usually affect the impermeability of concrete, causing corrosion of steel affect the durability of concrete, water pressure will produce hydraulic fracturing affecting concrete bearing capacity. The concrete shrinkage main and to the water-cement ratio of the concrete, cement component, the amount of cement used, thenature and amount of aggregate, the amount of admixture.The main preventive measures:(1)Selection of a smaller amount of shrinkage cement, commonly used in low heat cement and fly ash cement, reduce the amount of cement.(2)Concrete shrinkage by water-cement ratio, the greater the water-cement ratio, the greater the shrinkage in the concrete mix design should try to control the selection of a good water-cement ratio, while mixing the water-reducing agent .(3)Strict control than with concrete mixing and construction, concrete water consumption must not be greater than the amount of water given by the mixture ratio design.(4)To strengthen the early curing of concrete and appropriate to extend the concrete curing time. Appropriate to extend the winter construction concrete insulation cover, and brushing curing agent curing.(5) Set the appropriate contraction joints in concrete structures2.2 Plastic shrinkage cracks and preventionThe plastic shrinkage refers to the before condensation, the concrete surface due to rapid dehydration resulting contraction. Plastic shrinkage cracking is generally hot and dry or windy weather, the cracks mostly wide in the middle, both ends of the thin and vary in length, non-coherentstate. Short cracks as long as 20 to 30cm the longer cracks of up to 2 to 3 m, width of 1 to 5 mm. Main causes: the concrete before the final setting almost no strength or intensity is very small or just the final setting concrete small strength, high temperature or a larger wind, the concrete surface excessive water loss, resulting in capillary have a greater negative pressure of the concrete volume of a sharp contraction, but this time the strength of the concrete can not resist its own contraction, resulting in cracking. The main factors affecting the plastic shrinkage cracking water-cement ratio, the setting time of the concrete, the ambient temperature, wind speed, relative humidity, and so on.The main preventive measures:(1) Selection of shrinkage values smaller high early strength Portland cement or ordinary Portland cement.(2) Strict control of water-cement ratio, to increase the slump and workability of the concrete, to reduce the amount of cement and water mixed with superplasticizer.(3) Pouring concrete before watering the grass roots and templates evenly soaked.(4) Timely covered by plastic film or wet straw, hemp sheet to maintain final setting of concrete the moist front surface or the surface of the concrete spraying curing agent for conservation.To set the sun and wind facilities .(5) At high temperatures and windy weather, timely conservation.2.3 subsidence cracks and preventionSubsidence cracks caused by structural foundation soil is uneven, soft, or backfill or flooding due to uneven settlement; template stiffness, the template support spacing is too large or the bottom of the support as a result of loose, especially in the template support winter on the frozen ground, permafrost thaw uneven settlement, resulting in the concrete structure cracks. Such cracks are deep into or through the cracks, toward subsidence, generally along the perpendicular to the ground or in the form of an angle of 30 °to 45 °direction, subsidence cracks tend to have a certain amount of dislocation, crack width is often and is proportional to the amount of the settlement. Crack width was less affected by temperature changes. Ground deformation stability, subsidence cracks basically stabilized.The main preventive measures:(1)on the soft soil, filling foundation should be carried out prior to the construction of the superstructure necessary compaction and reinforcement.(2)to ensure that the template has a sufficient strength and stiffness, and firmly support the foundation uniform force.(3) prevent the process of concreting the foundation is immersed inwater.(4) template removal time can not be too early, and pay attention to the order form removal.(5) in the erection of the template on the permafrost to take certain precautions.2.4 Temperature cracks and preventionTemperature cracks occurred in mass concrete surface or larger changes in temperature regions in concrete structures. Concrete pouring, in the hardening process of cement hydration reaction to produce large amounts of heat of hydration (when the amount of cement per cubic meter of concrete will release 17,500 27500kJ heat at 350 to 550 kg/m3, so that the internal temperature of the concrete SITA about 70 °C or higher). Cause the internal temperature to rise sharply due to the larger volume of concrete, the accumulation of a large amount of heat of hydration within the concrete and easy to distribute, and rapid cooling of the surface of the concrete, thus forming a larger temperature difference inside and outside, the larger the temperature difference caused by the internal and external different degrees of thermal expansion and contraction of the concrete surface tensile stress (Practice has proved that when the temperature difference between inside and outside of the concrete itself is 25 ° C to 26 °C, will produce roughly about10MPa concrete tensile stress). When the tensile stress exceeds the ultimate tensile strength of the concrete, the concrete surface cracks, cracks occurred in the concrete construction in the late. Concrete construction when the temperature changes, or concrete attacked by the cold wave will lead to concrete surface temperature sharp decline, and contraction, contraction of the concrete surface bound by internal concrete, will produce large tensile stress. cracks, such cracks are generated in the the shallow concrete surface within the range of usually only.The trend of temperature cracks usually certain rules, often criss-cross a large area of structural cracks; the length of the beam and plate size larger structures, cracks parallel to the short side; deep and penetrating temperature cracks are generally parallel or nearly parallel to the direction of the short side , cracks along the longest edge segments appear more dense middle. Crack width sizes, affected by temperature changes more obvious, summer, winter wide narrow. The high temperature expansion caused by the concrete temperature is usually middle coarse fine at both ends, while the the shrink cracks thickness less obvious changes. The emergence of such cracks can cause corrosion of steel, concrete carbonation, reduce freeze-thaw resistance of concrete, anti-fatigue and impermeability.The main preventive measures:(1) try to use low heat or moderate heat cement, slag cement, fly ash cement.(2) reduce the amount of cement to try to control the amount of cement 450kg/m3.(3) reduce the water-cement ratio, generally water-cement ratio of concrete is controlled below 0.6.(4) improve the aggregate gradation, fly ash or superplasticizer to reduce the amount of cement, lower heat of hydration.(5) improve the concrete mixing process, "secondary air" traditional "cold" on the basis of new technology, reduce the temperature of concrete pouring.(6)a certain amount of concrete admixture having less water, plasticizers, retarding admixture role to improve the fluidity of the concrete mixture, water retention, reduce the heat of hydration, delaying the time of occurrence of the thermal peak.(7)hot season puts up visor and other auxiliary measures to control the temperature rise of the concrete pouring, to reduce pouring concrete temperature.(8)mass concrete temperature stress associated with the structure size, the larger the size of the concrete structure, the greater the temperature stress, so reasonable arrangements for the construction process, hierarchical, block pouring, to facilitate cooling, reducingconstraints.2.5 chemical reaction caused cracks and preventionAlkali-aggregate reaction cracks and steel corrosion cracks caused by the most common due to the chemical reaction caused by cracks in the reinforced concrete structure. Concrete mixing will produce some of the alkaline ions, these ions produce a chemical reaction with certain reactive aggregate and absorbs water in the surrounding environment and the volume increases, resulting in concrete crisp, expansion cracking. Such cracks usually appear in the concrete structure during use, in the event difficult to remedy, should take effective measures to prevent it in the construction. Concrete pouring poor vibrators or reinforced protective layer is thin, harmful substances into the concrete reinforcing bars from corrosion, the corroded reinforcement volume expansion, leading to concrete Splitting the cracks of this type of longitudinal cracks along the location of reinforcement .The main preventive measures:(1) selection of the alkali reactivity of small sand and gravel aggregate.(2) selection of low-alkali cement and admixtures of low-alkali or alkali.(3) selection of a suitable admixture AAR with.3 crack treatmentCracks in concrete remedial measures mainly the following methods: surface repair method, grouting, caulking closure method, structural reinforcement, concrete replacement method, electrochemical protection and legal bionic self-healing.3.1 Surface repair methodSurface repair method is a simple, common repair method, the action is in the cracks in the surface of the painting grout, epoxy mortar or concrete surface coating paint, anti-corrosion materials such as asphalt, concrete protection at the same time in order to prevent various The Effect of cracking, usually can paste in cracks in the surface of the glass fiber cloth and other measures.3.2 grouting, caulking closure methodThe grouting method is the use of pressure equipment cementing material is pressed into the cracks in the concrete, the cementing material hardened concrete to form a whole, and thus play the purpose of plugging consolidation. Top cementing material grout, epoxy, methacrylate, polyurethane and other chemical materials. The filleting gouges along the cracks in the tank filled, the plastic or rigid sealing material, in order to achieve the purpose of closed cracks. Commonly used plastic materialsare PVC, clay, plastic ointment, butyl rubber, etc.; rigid sealing material is a polymer cement mortar.3.3 Structural reinforcement methodWhen the the cracks impact on the performance of concrete structures, to take structural reinforcement concrete structure. Commonly used in the following ways: structural reinforcement to increase the cross-sectional area of the concrete structure, corner in the component outsourcing steel, prestressed Reinforcing paste the steel reinforcement, additional the fulcrum reinforcement and shotcrete reinforcement.3.4 Concrete replacement methodThe concrete substitution method is an effective method for dealing with serious damage to the concrete, this method is deteriorated concrete is removed first, and then replaced into the new concrete or other materials. Top replacement materials: of Ordinary concrete or cement mortar, polymer or polymer modified concrete or mortar.3.5 electrochemical Protection ActCathodic protection, chloride extraction, alkaline recovery method, the use of the electrochemical action of the applied electric field in the medium, to change concrete or reinforced concrete in which the state of the environment, passivated steel, in order to achieve the purpose ofanti-corrosion.3.6 biomimetic self-healing legalBionic self-healing legitimate the traditional components of the concrete in some special components such as liquid-core fibers or capsules containing binder, formed within the concrete the intelligent bionic self-healing neural network system, when the concrete cracks secreted part of the liquid core fiber cracks can heal again. Conclusion:Cracks is a common phenomenon in the concrete structure, its appearance will not only reduce the impermeability of the building, affect the use of the building, and would lead to corrosion of steel, concrete carbonation, reduce the durability of the materials, the impact the carrying capacity of the building, so to carefully study the concrete cracks, be treated differently, using a reasonable method for processing to take effective preventive measures to prevent the emergence and development of cracks in the construction, to ensure the safety of buildings and structures and stable work.混凝土裂缝的成因、预防及处理摘要:在建筑工程施工中混凝土裂缝的产生是一项质量通病,因此对混凝土裂缝的成因分析、事先预防,以及产生后的修补处理是建筑生产过程中较为普遍的现象,应引起足够的重视。
外文翻译--论建筑工程中混凝土裂缝的预防与处理
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中文5153字附录A论建筑工程中混凝土裂缝的预防与处理作者:阿西夫·哈米德摘要:混凝土裂缝是建筑工程中普遍存在的一种不良现象,它直接影响到混凝土结构的使用功能和耐久性。
对建筑工程中一些常见的混凝土裂缝进行了分类探讨,并对具体情况提出了一些预防和处理措施。
关键词:混凝土;裂缝;预防;处理1 前言建筑工程施工中,如果混凝土构件出现裂缝,就会影响混凝土构件的刚度和建筑物结构的整体抵抗能力,即使裂缝的出现不会导致混凝土构件的破坏或建筑物的倒塌,也会影响到建筑外观,当裂缝宽度超出一定限度时,也会造成钢筋锈蚀,影响结构构件的耐久性能。
本文介绍混凝土工程施工中几种常见裂缝的预2 常见裂缝分类混凝土裂缝产生的原因是多方面的,情况较为复杂,综合因素较多。
对于某种裂缝的出现,人们很难给予一个准确明晰的原因分析。
工程实践证明,裂缝形成的原因主要来自三个方面:变形、荷载以及不均匀沉降。
一般由温差、收缩、不均匀沉降等引起的变形赞成的裂缝约占80%,荷载等造成的约占20%,当然还需要考虑其综合原因。
根据这些主要影响因素,人们常把混凝土裂缝归纳为收缩裂缝、温度裂缝、沉降裂缝、徐变裂缝、应力裂缝和施工裂缝等几大类。
3 常见裂缝分析及预防3.1混凝土塑性收缩裂缝及预防塑性收缩是指混凝土在凝结前期。
表面因失水过快而产生的收缩。
一般在干热和大风天气裂缝较为常见,形状多为中间宽、两端细、互不连贯且长短不一,较长的裂缝可达2m-3m,宽度可达0.5cm,严重影响混凝土的抗渗性和耐久性。
主要预防措施:一是选用干缩值较小、早期强度较高的硅酸盐或普通硅酸盐水泥。
二是严格控制水灰比,在保证混凝土施工所需坍落度和和易性的前提下尽量减少水的用量,必要时掺入减水剂。
三是浇筑混凝土之前,将基层和模板均匀浇水湿透。
四是及时覆盖握料薄膜或者潮湿的草垫、麻片等,保持混凝土凝结前表面湿润,或者在混凝土表面喷洒养护剂等进行养护。
3.2 沉陷裂缝及预防沉陷裂缝的产生主要是由于结构地基浸水、土质不匀或回填土不密实等原因引起不均匀沉降所致;另外在混凝士硬化过程中由于模板刚度不足或支撑底部不牢固也会引起沉陷裂缝。
论混凝土的施工温度与结构裂缝外文翻译
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On the construction of concrete temperature and cracks1. the causes of the cracksCracks in concrete are a variety of reasons, mainly temperature and humidity changes, brittle and uneven concrete, as well as the structure is irrational, failure of raw materials (such as alkali-aggregate reaction), template deformation, and so on the basis of differential settlement.The concrete to harden off a large number of cement during the hydration heat, the internal temperature rising on the surface caused by tensile stress. Late in the cooling process, due to coagulation on the basis of or be bound by the old, will emerge in the concrete tensile stress. Lower temperatures in the concrete surface will be a lot of tensile stress. When the tensile stress beyond the capacity of concrete crack, the cracks will appear. A number of concrete changes in the internal humidity or changes very little slow, but possible changes in surface humidity or more dramatic changes. Such as conservation, failed to keep dry when wet, surface shrinkage deformation of concrete subject to internal constraints, but also often leads to cracks. Short-term loading at the time of ultimate tensile deformation only (0.6 ~ 1.0) × 104, the limit of long-term loading spaces when the only stretch deform ation (1.2 ~ 2.0) × 104. Unevenly as a result of raw materials, water-cement ratio of instability, and transportation and pouring in the process of segregation phenomena, in the same piece of concrete in the tensile strength is uneven, there are many low tensile capacity, easy to fracture in a weak position. In reinforced concrete, the tensile stress is mainly borne by the steel, concrete is subject to compressive stress. In plain concrete or reinforced coagulation on the edge of the site if the structure of the tensile stress appears to be relying on its own concretecommitment.2. thermal stress analysisAccording to the formation of thermal stress can be divided into the following three stages:(1)early: Since the beginning of pouring concrete to cement the end of exothermic basic general about 30 days. Two characteristics of this stage, first, to release a large number of cement hydration heat, and the other is the elastic modulus of coagulation dramatic changes. Modulus of elasticity as a result of changes within this period in the formation of residual stress in the concrete.(2) medium-term: from the basic role of cement heat until the end of the stable temperature of the concrete cooling time, during this period, the temperature stress was mainly due to cooling and the outside concrete caused by temperature changes, stress and early formation of these residual stress superposition phase, during which the coagulation of the elastic modulus changed little.(3) late: concrete completely cooling period after the operation. Thermal stress is mainly caused by external temperature changes, the stress and the first two-phase superposition of residual stress.Under the thermal stress caused by the reasons can be divided into two categories:(1) self-stress: there is no constraint on the border or completely static structure, if the internal temperature distribution is nonlinear, due to structural constraints arising from their co-temperature stress. For example, the conversion layer of its relatively larger size, concrete cooling surface temperature low, the internal temperatures are high, the surface tensile stress, compressive stress appears in the middle.(2) bound by stress: the structure of all or part of the boundary bound by the outside world can not be free-form deformation caused by stress. Roof box,such as concrete and concrete barrier.Both the temperature and the concrete stress is often caused by shrinkage of the combined effect of stress.Known to be in accordance with an accurate analysis of the temperature of the thermal stress distribution, size is a more complex task. In most cases, the need to rely on model test or numerical calculation. Creep of concrete so that the temperature there is considerable stress relaxation, thermal stress calculation, we must consider the effects of creep, is no longer calculated in detail here.3. temperature control and measures to prevent the cracksIn order to prevent cracking, reduce the thermal stress can control the conditions of temperature and to improve the binding of two aspects.Temperature control measures are as follows:(1) used to improve the aggregate gradation, dry hard concrete, mixed mixture, add air-entraining agent or plasticizer, etc. measures to reduce the amount of cement concrete;(2) mixing concrete by adding water or cooling water will be gravel and pouring concrete to reduce the temperature;(3) pouring hot days to reduce the pouring of concrete thickness, the use of pouring heat levels;(4) laid in concrete water pipes, access to cold water to cool;(5) the provisions of reasonable time, the temperature drop when the surface insulation, concrete surface in order to avoid a sharp temperature gradient;(6) Construction of long-term exposure to block the surface of the concrete pouring, or thin-walled structures, thermal insulation in the cold season to take measures;Measures to improve the constraints are:(1) a reasonable sub-block joints;(2) basis to avoid too much ups and downs;(3) reasonable arrangements for the construction process, to avoid excessive side elevation and long-term exposure;In addition, to improve the performance of concrete to improve the anti-cracking ability, to strengthen the conservation, to prevent surface drying, in particular, is to ensure the quality of concrete is very important to prevent cracks, should pay special attention to avoid cross-cracks appears to restore the integrity of its structure it is very difficult, so the construction should be to prevent the occurrence of cross-cutting the main crack.In concrete construction, in order to increase the turnover rate of the template, often require new pouring concrete as soon as possible. When the concrete temperature is higher than the temperature should be appropriate to consider time, so as to avoid the early cracks in the concrete surface. New pouring early, a lot of the surface tensile stress, a "temperature shock" phenomenon. Concrete pouring in the early heat of hydration as a result of the dissemination of the surface caused by a large tensile stress, when the surface temperature is higher than the temperature at this time to remove the template, a sharp fall in surface temperature is bound to lead to temperature gradient, so an additional one on the surface tensile stress, thermal stress superposition and hydration, coupled with the shrinkage of concrete,Tensile stress to reach the surface of great value, there is the danger of lead to cracks, but if in a timely manner after the removal of the template on the surface coverage of a light insulating material, such as foam sponge and so on, have a concrete surface to prevent excessive tensile stress, with significant results.Reinforced concrete on the large volume of thermal stress has little effect because the large volume of concrete reinforced with a very low rate. Only onthe general impact of reinforced concrete. Not too high in temperature and stress below the yield limit under the condition of the properties of steel is stable, and with the stress, time and temperature has nothing to do. Linear expansion coefficient of steel and concrete linear expansion coefficient difference between the small changes in temperature between the two with only a very small stress. Since the modulus of elasticity of steel to concrete elastic modulus of 7 ~ 15-fold, when the stress reached the tensile strength of concrete and cracking, the steel stress will not exceed 100 ~ 200kg/cm2 .. So, Want to use in reinforced concrete to prevent the emergence of small cracks is difficult. However, after the reinforced structure of the number of cracks in general has become more than a small distance, a smaller width and depth. And if the diameter of steel thin and close spacing, the crack resistance of concrete to enhance the effect of better. Concrete and reinforced concrete structure of the surface often occur cracks in thin and shallow, most of them belonging to shrinkage cracks. While this is generally shallow cracks, but its strength and durability of the structure is still a certain impact.In order to ensure the quality of concrete to prevent cracking and improve the durability of concrete, the proper use of admixtures is also one of the measures to reduce cracking. Such as the use of anti-cracking agent and water, in practice, its major role in concluding as follows:(1) the existence of a large number of pores in the concrete that, after evaporation of water generated by capillary capillary tension, deformation of the concrete shrinkage. Pores increased capillary diameter can reduce the surface tension, but would reduce the strength of concrete.(2) the impact of water-cement ratio is an important factor for concrete shrinkage, the use of anti-cracking agent can reduce water consumption reduced by 25% concrete.(3) the amount of cement concrete is also an important factor in shrinkage,water addition and subtraction mixed concrete cracking agent in maintaining the strength of concrete under the condition of 15 percent can reduce the amount of cement, aggregate size, by increasing the amount to supplement.(4) anti-cracking agent and water can improve the consistency of cement slurry to reduce the bleeding of concrete, reduce shrinkage deformation Shen.(5) to improve and cement bonded aggregate, and enhance the anti-cracking performance of concrete.(6) concrete bound in the contraction produced by tensile stress, when the tensile stress is greater than the tensile strength of concrete will be produced when the cracks. Water-reducing agent can be an effective anti-cracking of the concrete tensile strength to increase, a substantial increase in anti-cracking performance of concrete.(7) mixing-compacting concrete admixtures can, and can effectively improve the carbonation resistance of concrete to reduce the carbonation shrinkage.(8)-doped water-reducing agent after the concrete cracking retardation time due, in the effective prevention of the rapid hydration heat of cement based on cement to avoid long-term result of non-condensable increase plastic shrinkage.(9)-doped workability of concrete admixtures, and easy to find flat surfaces to form a micro-membrane to reduce evaporation and reduce drying shrinkage.Many have a retarding admixture to increase the workability and improve the function of plasticity, we in engineering practice in this area should be more contrast and research experiments than simply relying on external conditions to improve may be even more simple and economic.4. early concrete conservationPractice has proved that the common concrete cracks, the majority of surface cracks at different depths, mainly because of the temperature gradient caused by the cold temperature region is also vulnerable to a sharp fall in the formationof cracks. Insulation so that the concrete surface to prevent early cracking is particularly important.Thermal stress from the point of view, the insulation should meet the following requirements:(1) to prevent the concrete inside and outside the concrete surface temperature difference and gradient, to prevent surface cracks.(2) to prevent the concrete super-cold, it should be possible to make concrete the construction period of not less than the minimum temperature of concrete used for the stability of the temperature.(3) to prevent cold-old concrete in order to reduce the concrete between the old and new constraints.Early concrete conservation, the main objective is to maintain the appropriate temperature and humidity conditions in order to achieve the effect of two aspects, on the one hand, the concrete from adverse temperature and humidity deformation invasion to prevent the harmful and drying shrinkage. On the one hand, to enable the smooth progress of cement hydration, with a view to meet the design capacity of the strength and crack resistance.Appropriate conditions of temperature and humidity are interrelated. Coagulation on the insulation often has the effect of moisture.Theoretical analysis of fresh concrete contained in the water fully meets the requirements of cement hydration and more than. However, due to evaporation and other factors often cause water loss, thereby delay or prevent the hydration of cement, concrete surface and most likely to be directly affected by such a negative impact. Concrete pouring, therefore the first few days after the critical period of conservation in the construction should pay attention to.5. concluding remarksAbove the temperature of concrete and cracks in the construction of therelation between theory and practice of the preliminary study, although the academic community about the causes of cracks in concrete and calculation methods are different theories, but specific measures to prevent and improve the opinion it is quite uniform At the same time, the application in practice is also a relatively good effect, concrete construction and more depends on our observation, and more, when compared to multi-issue analysis, and more sum up, combined with a wide range of prevention measures, the cracks in the concrete is completely avoided.论混凝土的施工温度与结构裂缝1.裂缝的原因混凝土中产生裂缝有多种原因,主要是温度和湿度的变化,混凝土的脆性和不均匀性,以及结构不合理,原材料不合格(如碱骨料反应),模板变形,基础不均匀沉降等。
浅析混凝土施工过程中的温度及裂缝控制
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浅析混凝土施工过程中的温度及裂缝控制混凝土是施工中常用的一种材料,它在施工中需要控制的一个关键因素就是温度及裂缝。
混凝土对于温度的敏感度较高,在施工过程中温度的变化可能造成材料本身的变形或者不均匀收缩,导致混凝土内部产生应力,甚至出现裂缝,影响结构的使用寿命和安全性。
本文将从温度和裂缝控制两个方面浅析混凝土施工过程中的相关问题。
一、温度控制混凝土施工过程中的温度控制是非常重要的,可以从以下两个角度来考虑:1. 混凝土的配合比混凝土的配合比直接关系到混凝土的性能,包括强度、抗渗、抗裂和耐久性等。
但不同的配合比所需使用的水泥和混凝土内含量可能不同,因而在施工中受温度影响的程度也会不同。
通常情况下,水泥含量较高的混凝土抗温度变化强,但其施工时的温度变形也相对较大;而水泥含量较少的混凝土则变形较小,但受温度变化的影响较大。
因此,确定合理的配合比可以有效地控制混凝土的温度问题。
2. 施工环境施工环境是影响混凝土施工中温度变化的另一个重要因素。
气温、湿度以及风、日等外界因素都会对混凝土的温度产生影响。
在施工过程中,应根据气候条件和当地的季节特点,采取一些措施来减小温度变化的影响。
例如,在高温季节,可以在混凝土表面覆盖遮光布防止晒伤、适当增加养护时间等措施。
二、裂缝控制混凝土在施工中容易出现裂缝现象,其发生原因多种多样,包括混凝土内部收缩、外部荷载作用以及温度变化等。
控制混凝土裂缝有以下几种方法:1. 控制施工温度如前所述,在施工过程中合理控制温度,避免温度变化对混凝土的影响,是控制裂缝发生的有效手段之一。
2. 采用高强度的混凝土采用高强度的混凝土可以提高混凝土的抗裂性能,降低混凝土出现裂缝的可能性。
3. 施工中掌握好浇筑时间混凝土从浇筑到硬化需要一定的时间,如果在硬化初期就接受外界荷载,容易导致混凝土内部产生应力,从而出现裂缝问题。
通常在浇筑完成后,应等待混凝土达到一定的强度后再进行下一步施工或荷载作用。
4. 在混凝土中加入适量的缩微剂合理加入缩微剂可以有效地减小混凝土收缩率,从而降低混凝土出现裂缝的可能性。
浅析混凝土施工过程中的温度及裂缝控制
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浅析混凝土施工过程中的温度及裂缝控制混凝土作为建筑工程中常用的材料,其施工过程中温度和裂缝控制是十分重要的环节。
温度的控制对混凝土的强度和耐久性有着直接的影响,而裂缝的产生则直接关系到混凝土结构的安全和使用寿命。
本文将从温度和裂缝两个方面对混凝土施工过程中的控制进行浅析,希望对相关行业有所帮助。
一、温度控制1. 温度对混凝土的影响混凝土在温度变化的环境下会产生体积变化,这对混凝土的强度和耐久性都有着直接的影响。
在混凝土初凝和硬化过程中,如果受到较大的温度影响,就容易产生裂缝和变形,从而影响混凝土结构的使用性能。
控制混凝土施工过程中的温度十分重要。
2. 控制方法(1)选择合适的季节和时间进行施工,避免在高温或寒冷的环境下进行混凝土浇筑。
(2)采用冷却水对混凝土进行降温处理,可以有效控制混凝土温度的升高。
(3)可以在混凝土配合比中加入缓凝剂,延长混凝土的凝固时间,从而减缓温度的升高。
(4)在混凝土初凝和硬化过程中可以采用覆盖材料对混凝土进行保温处理,防止温度急剧下降。
3. 温度监测在混凝土施工过程中需要对温度进行及时监测,一方面可以及时采取措施控制温度的变化,另一方面也可以为后续施工工序提供参考。
常用的温度监测方法有表面温度监测和内部温度监测两种,根据具体施工情况选择合适的监测手段进行温度控制。
二、裂缝控制1. 裂缝的产生原因混凝土结构在施工和使用过程中会受到各种外部力的作用,从而产生应力,当应力超过混凝土的承受能力时就容易产生裂缝。
在混凝土的龄期初期和末期都容易出现裂缝,因为这两个阶段混凝土的强度较低,抗裂性也较弱。
(1)合理设计和施工,避免因为结构设计不合理或者施工缺陷等原因导致裂缝的产生。
(2)采用预应力混凝土结构,提高混凝土结构的抗裂性能。
(3)在混凝土配合比中加入裂缝控制剂,改善混凝土的抗裂性能。
(4)在混凝土结构中设置缝隙,避免裂缝的产生对整体结构的影响。
3. 裂缝监测和修补在混凝土结构施工完毕后需要对裂缝进行监测,一旦发现裂缝需要及时进行修补,防止裂缝扩大影响结构的安全性。
浅谈混凝土的施工温度与裂缝
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浅谈混凝土的施工温度与裂缝摘要:通过多年的现场观察,通过查阅有关混凝土强度增长的关系,对混凝土温度裂缝产生的原因、现场混凝土温度的控制和预防裂缝的措施进行等进行阐述。
关键词:混凝土施工温度裂缝控制Abstract: Through years of on-site observation, through the consult about concrete strength growth, the temperature of the concrete cracks, the concrete temperature control and crack prevention measures are expounded.Keywords: concrete construction temperature and crack control混凝土在现代工程建设中占有重要地位。
而在今天,混凝土的裂缝较为普遍,在桥梁工程中裂缝几乎无所不在。
尽管我们在施工中采取各种措施,小心谨慎,但裂缝仍然时有出现。
究其原因,我们对混凝土施工温度的变化注意不够是其中之一。
在大体积混凝土中,施工温度控制具有重要意义。
这主要是由于两方面的原因。
首先,在施工中混凝土常常出现温度裂缝,影响到结构的整体性和耐久性。
其次,在运转过程中,施工温度变化对混凝土强度具有显著的不容忽视的影响。
我们遇到的主要是施工中的温度裂缝,因此本文仅对施工中混凝土裂缝的成因和处理措施做一探讨。
1混凝土施工温度与混凝土强度增长的关系混凝土强度增长快慢与温度高低有直接的关系,混凝土在凝结过程中由于水泥的水化升温,有助于混凝土强度增长,混凝土在较高温度和湿度下可以迅速达到要求的强度。
如低温时,混凝土造冻,拌合水结冰,其体积也会增加9%。
水泥的水化作用会停止,混凝土强度增长也会停止。
因此在混凝土施工时,混凝土抗压强度不得低于抗冻零界强度。
2 裂缝的原因温度裂缝多发生在大体积混凝土表面或温度变化较大地区的混凝土结构中。
建筑施工混凝土裂缝的预防与处理毕业论文中英文资料对照外文翻译文献
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建筑施⼯混凝⼟裂缝的预防与处理毕业论⽂中英⽂资料对照外⽂翻译⽂献建筑施⼯混凝⼟中英⽂资料对照外⽂翻译⽂献1,⽂献原⽂: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 the concrete 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 relativehumidity 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 muchsee 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 the durable of the rust eclipse influence concrete of reinforcing bar, under the function of the water pressure dint would creation the water power split crack influence concrete of loading dint etc..Concrete stem the Suo be main with water ash of the concrete ratio, the dosage of the composition, cement of cement, gather to anticipate of the dosage of the property and dosage, in addition etc. relevant.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 creationbigger negative press but make a concrete physical volume sharply constringency, but at this time the strength of concrete again can't resist its constringency, 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 and just degree, and prop up firm, and make the foundation be subjected to dint even.Three is keep concrete from sprinkle infusingthe 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 shoulddint.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 close parallelism, 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 willcause 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. material Tu2 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 /doc/7711103392.htmlually 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 reinforcingbar 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 healmethod.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 the polymer 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:Commonconcrete 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 tradition the 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 theanti- 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》2,译⽂: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。
浅析混凝土施工过程中的温度及裂缝控制
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浅析混凝土施工过程中的温度及裂缝控制1. 引言1.1 介绍混凝土作为建筑工程中常见的一种建筑材料,在施工过程中温度及裂缝控制问题一直备受关注。
温度是影响混凝土施工质量的重要因素之一,合理控制混凝土在施工过程中的温度,可以有效避免裂缝的生成,从而保证工程的安全和持久性。
深入研究混凝土施工过程中的温度及裂缝控制问题,对于提高工程质量具有重要的意义。
1.2 研究背景混凝土施工是建筑工程中非常重要的一环,而在混凝土施工过程中,温度及裂缝控制是一个十分关键的问题。
温度的控制不仅影响着混凝土的强度和耐久性,还与混凝土裂缝的产生有着密切的关系。
深入研究混凝土施工过程中的温度及裂缝控制对于保证工程质量和安全具有重要意义。
在实际施工中,由于混凝土在硬化过程中会释放热量,在环境温度变化的影响下混凝土会发生体积变化,这些因素都会对混凝土结构造成影响。
而裂缝的出现往往是由于温度变化引起的混凝土内部应力造成的。
合理控制混凝土施工过程中的温度,有效预防裂缝的产生,对于保证工程质量至关重要。
通过深入研究混凝土施工过程中的温度及裂缝控制,可以为工程施工提供指导,提高工程质量,降低工程风险。
对于混凝土施工中的温度及裂缝控制进行深入的研究具有重要的现实意义。
1.3 目的本文的目的是探讨混凝土施工过程中的温度及裂缝控制问题,分析温度和裂缝控制之间的关系,总结不同方法对温度和裂缝的影响,以及解决施工中常见的温度及裂缝控制问题。
通过对这些问题深入了解和分析,能够帮助施工人员更好地掌握混凝土施工过程中的技术要点,提高施工质量,确保工程的稳定性和耐久性。
本文也旨在引起施工行业人员对温度及裂缝控制的重视,促进更多关于此方面的研究和实践,为混凝土施工的发展和改进提供有益参考。
通过本文的研究,希望能够为混凝土施工中的温度及裂缝控制问题提供一定的解决思路和方法,推动施工行业的不断发展和进步。
2. 正文2.1 混凝土施工过程中的温度控制混凝土施工过程中的温度控制是非常重要的一环。
浅析混凝土施工过程中的温度及裂缝控制
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浅析混凝土施工过程中的温度及裂缝控制混凝土是建筑工程中常用的一种材料,其施工过程中温度和裂缝控制是非常重要的环节。
在混凝土施工过程中,由于混凝土的收缩和温度变化等因素,容易产生裂缝,影响工程质量和使用性能。
合理控制施工过程中的温度和裂缝对于保障工程质量和延长工程寿命具有重要意义。
本文将对混凝土施工过程中的温度和裂缝控制进行浅析。
一、混凝土施工过程中的温度控制(一)温度对混凝土的影响在混凝土的施工过程中,温度是直接影响混凝土性能的重要因素之一。
一方面,随着温度的升高,混凝土的抗压强度和抗拉强度会逐渐降低;温度的变化会导致混凝土产生收缩,从而引起裂缝的产生。
合理控制混凝土施工过程中的温度,对于保障混凝土的强度和防止裂缝的产生具有非常重要的意义。
(二)温度控制的方法1.控制混凝土的初始温度:混凝土的初始温度是指混凝土拌合完毕后的温度。
控制混凝土的初始温度,可以通过在拌合前对原材料进行预冷或预热的处理,以及在拌合过程中控制水泥浆的温度等方式进行。
在夏季高温施工时,可以考虑采用低温水稀释控制混凝土浆体温度的方法,以减缓混凝土的初凝和凝结速度,降低混凝土温度。
2.控制混凝土的散热速度:混凝土的散热速度是指混凝土在施工后逐渐散发热量并冷却的速度。
一般来说,混凝土的散热速度与环境温度、风速、湿度等因素有关。
为了控制混凝土的散热速度,可以采用覆盖保温、喷水养护等方法,延缓混凝土的温度下降速度,减缓混凝土的收缩。
3.控制混凝土的环境温度:在混凝土浇筑后,应尽量避免混凝土受到外界高温或低温的影响。
一般来说,当环境温度较高时,可以采用遮阳、喷水等方式进行降温;当环境温度较低时,可以采用加热、覆盖等方式进行保温。
这样可以有效地减缓混凝土的温度变化速度,降低混凝土的收缩和裂缝的产生。
二、混凝土施工过程中的裂缝控制(一)裂缝的产生原因1.混凝土的收缩:混凝土在凝固和硬化的过程中会发生收缩,由于混凝土的收缩会受到外界约束而产生拉应力,从而引起裂缝的产生。
浅谈混凝土施工中的温度与裂缝控制
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浅谈混凝土施工中的温度与裂缝控制摘要:作为工程项目施工中最不可缺少的基础材料,混凝土具有成本低、韧性强等优势,已广泛应用于各大项目建设中。
但由于混凝土自身特性原因,温度裂缝问题经常会出现在施工中,对混凝土使用寿命及整体强度造成了严重影响,如何更好地控制混凝土施工中的裂缝与温度已成为当前各大建设企业单位最亟需解决的重点问题。
基于此,本文将进一步分析控制混凝土施工中温度与裂缝的有效措施,仅供相关人士参考。
关键词:混凝土施工;温度;裂缝;控制前言:随着城镇化进程的加快,大量工程项目投入建设,人们对于工程安全与质量的要求愈加严格,在此情况下,控制与完善施工工艺至关重要。
现阶段,混凝土结构已广泛应用于各大工程中,尤其是大跨度与高净空的工程项目,但混凝土的脆性在很大程度上制约了该材料的发展,在施工过程中极易出现裂缝问题。
当混凝土裂缝宽度过大时,就会影响工程的安全性,阻碍工程的施工进程,因此,对于各大建设企业及单位而言,亟需重点研究如何做好混凝土施工中温度及裂缝的控制,这样才能保证工程的顺利完成,提升项目整体质量。
1混凝土施工裂缝形成的主要原因分析1.1温度所导致的裂缝在混凝土施工时,完成混凝土的浇筑操作后,混凝土会有一段时间的硬化过程,在这一过程中,混凝土中的水泥材料会出现水化反应,并生成水化热,一旦水化热过量,就会导致在大体积混凝土内部形成热量聚集,从而致使混凝土内部的温度出现明显的上升。
对于混凝土结构外部而言,其表面具有较好的散热性能,由此就会导致混凝土内部和外部的较大的温差,并因不同的热胀冷缩系数而使混凝土内部出现较大的拉应力。
相关负责人需要严格控制拉应力大小,并将其和混凝土的抗拉强度相对比,一旦超过抗拉强度,就会导致裂缝在混凝土表面产生。
1.2收缩导致的裂缝在混凝土结构裂缝中,收缩裂缝也是较为常见的裂缝之一。
分析导致收缩裂缝出现的成因可知,湿度变化是主要的诱因,当混凝土内、外部的湿度出现变化时,就会引发混凝土结构的非结构性裂缝,收缩裂缝是主要的表现之一。
浅谈混凝土温度裂缝及其处理措施(5篇)
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浅谈混凝土温度裂缝及其处理措施(5篇)第一篇:浅谈混凝土温度裂缝及其处理措施论文关键词:混凝土;温度应力;裂缝;控制论文摘要:文章对混凝土温度裂缝产生的原因、现场混凝土温度的的控制和预防裂缝的措施等进行阐述。
引言混凝土在现代工程建设中占有重要地位。
而在今天,混凝土的裂缝较为普遍,在桥梁工程中裂缝几乎无所不在。
尽管我们在施工中采各种措施,小心谨慎,但裂缝仍然时有出现。
究其原因,我们对混凝土温度应力的变化注意不够期中之一。
在大体积混凝土中,温度应力及温度控制具有重要意义。
这主要是由于两方面的原因。
首先,在施工中混凝土常常出现温度裂缝,影响到结构的整体性和耐久性;其次,在运转过程中,温度变化对结构的应力状态具有显著的不容忽视的影响。
本文对施工中混凝土裂缝的成因和处理措施作一探讨。
混凝土施工裂缝成因及其处理措施2.1 裂缝的成因混凝土中产生裂缝有多种原因,主要是温度和湿度的变化,混凝土的脆性和不均匀性,以及结构不合理,原材料不合格(如碱骨料反应),模板变形,基础不均匀沉降等。
混凝土硬化期间水泥放出大量水化热,内部温度不断上升,在表面引起拉应力。
后期在降温过程中,由于受到基础或老混凝土的约束,又会在混凝土内部出现拉应力。
气温的降低也会在混凝土表面引起很大的拉应力。
当这些拉应力超出混凝土的抗裂能力时,即会出现裂缝。
许多混凝土的内部湿度变化很小或变化较慢,但表面湿度可能变化较大或发生剧烈变化。
如养护不周、时干时湿,表面干缩变形受到内部混凝土的约束,也往往导致裂缝。
混凝土是一种脆性材料,抗拉强度是抗压强度的1/10左右。
由于原材料不均匀,水灰比不稳定,及运输和浇筑过程中的离析现象,在同一块混凝土中其抗拉强度又是不均匀的,存在着许多抗拉能力很低,易于出现裂缝的薄弱部位。
在钢筋混凝土中,拉应力主要是由钢筋承担,混凝土只是承受拉应力。
在素混凝土内或钢筋混凝土的边缘部位如果结构内出现了拉应力,则须依靠混凝土自身承担。
一般设计中均要求不出现拉应力或者出现很小的拉应力,但是在施工中混凝土由最高温度冷却到运转时期的稳定温度,往往在混凝土内部引起相当大的拉应力。
混凝土施工裂缝原因及防治外文翻译
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外文翻译资料Construction cracks in concretecauses and preventionConstruction cracks in concrete, causes and preventionConstruction cracks of concrete reason for the external and internal. The initial mainly refers to the internal defects of concrete in early concrete, its internal hardening process will exist numerous micro-pores, air-pocket and micro cracks, External refers to the load reason: temperature crack, dry shrinkage effect etc. In these, can produce various forms of concrete cracks. To grasp the construction process of raw materials, in pouring process configuration of progress and thickness, grasp timely maintenance work well, which can avoid concrete cracks. A, The cause of the tear1.The initial defects of concreteConcrete is composed of cement, sand aggregate, mixed with water and other materials and formation of heterogeneity brittle materials. In the beginning, because hardened concrete construction and deformation, a series of problems, such as constraint in the concrete shape sclerosis will exist numerous micro-pores, air-pocket and micro cracks of concrete that usually called initial defects. Micro cracks is usually a cracks in the concrete, bearing, and some other function not harm. But under load, temperature of concrete, shrinkage and function, micro cracks will be expanded and connectivity, and finally form the visible cracks of concrete, macroscopic crack, said it was the use of concrete structure, properties and durability of adverse effects.2.The load factorDue to the tensile strength of concrete structure or structures, small as a part of the external effects of stress than concrete tensile strength, will crack. Therefore, the concrete in the load and the load, can produce a crack. To load the crack, can produce by reasonable design and construction to prevent. For the load of crack, due to reasons, it is hardto handle and prevent. The more common than load factors have temperature, dry shrinkage, settling contraction deformation, plastic shrinkage deformation, etc, in these function, can make concrete inside tensile stress.3.Big volume concrete crack formation reasonsMassive concrete cracking reasons can be divided into two types: one is the structural cracks, is caused by external load, 2 it is material of crack is not caused by the changes of deformation and temperature stress and is mainly composed of concrete's shrinkage. This article mainly discussed type materials. One specific reasons are as follows: The temperature stress caused by fracture (temperature crack) temperature cracks in the main reason is caused by temperature difference. Temperature can be divided into three types: early concrete pouring, produce large amounts of the hydration heat, due to the concrete is a poor conductor of heat accumulation in concrete, the hydration heat to send out, often make internal temperatures rise, concrete and reinforced concrete surface temperature for outdoor environment temperature, it is formed, the temperature and temperature inside of condensate in early concrete tensile stress when more than concrete compressive strength, will cause cracking in concrete, In addition, in the dismantling formwork, surface temperature and reduce the temperature caused by fast, and will cause cracking. When the concrete temperature, maximum heat radiates to the minimum temperature, temperature, or use them with the highest temperature difference is the internal temperature, These three temperature will produce temperature crack. In these three temperature, is mainly caused by hydration heat and the temperature.Shrinkage crack contraction there are many causes, including drying shrinkage, plastic shrinkage, shrinkage, carbonation contraction, etc. Here mainly introduces drying shrinkage and plastic shrinkage.After drying shrinkage of concrete sclerosis, in dry environment, the water concrete to the loss caused by inside extroversion, concrete the shrinkage deformation cracks.The plastic shrinkage of cement and concrete in the activity of higher temperature, or in low water-cement condition exacerbate cause craze. When the concrete surface water obviously decreased, lactation evaporation of water cannot get the timely supplements, then concrete is still in a state of plastic, by a concrete surface tension, uneven distribution will appear the cracks of concrete cracks, and further intensify the moisture inside body, and further expansion crack Second, the measures to prevent cracksFrom the above analysis, the crack is mainly caused by temperature difference and contraction, so in order to prevent the cracks of, will maximize reduce temperature and reduce the shrinkage of concrete, specific measures as follows.1. Optimizing raw materials(1)Cement. The cement should be chosen according to the engineering properties, construction condition, climate and other technical requirements, comprehensive consideration, to meet the strength and durability of concrete design requirements. When the choice should be labeled with cement concrete design match the label. For full strength of cement, cement, cement save from the label for concrete label 1.5 to 2 times as appropriate.(2) aggregate. (a) coarse aggregate. The coarse aggregate concrete rubble is close-grained, must have the enough strength, hard to expand the coarse aggregate size. To ensure the concrete pouring dao close-grained, coarse aggregate maximum diameter less than the minimum size of the structural sections 1/4, also not greater than the minimum distance between steel net for thickness 3/4, in 10 centimeters and concrete, allowing adoptsmaximum diameter 1 1/2 of the aggregate number, but it shall not exceed 25%. (b) fine aggregate. Sand particle gradation of technical properties of concrete influence, requests the porosity and total surface area small, small need total surface on the surface of the gravel package will reduce quantity of cement slurry, can reduce the dosage of cement hydration heat, reduce to prevent cracks. On the other hand is to control the hydraulic sand, the content of 5% in concrete, "the contraction deformation, the hydraulic and larger crack, fine aggregate to use clean in the sand.(3) admixtures. (a) water-reducing agent. Jianshuiji belongs to the surface active substances, is a kind of cement dispersant. Its main function of improving concrete workability, reduce the consumption of concrete mixture, reduce water-cement ratio increases, and improve the liquidity of concrete strength of concrete or keep in concrete cement strength must decrease, while the water-cement ratio, the dosage of cement to prevent cracking is reduced. (b) retarder. Retarder is delaying the role of concrete exothermic peak time, 2 it is to improve workability, and reduce the loss of collapsbillity. (c) air-entraining agent. In the application of concrete air-entraining agent for improving the concrete workability, can pump, improving the concrete durability is very favorable. In a certain extent increase anti-cracking performance of concrete.(4) mass concrete chooses raw materials should pay attention to the following:①The coarse aggregate gradation, appropriate USES continuous fine aggregate ZhongSha should be adopted.②Admixtures appropriate USES retarder, water-reducer, Admixtures appropriate USES fly ash, slag powder etc.③In mass concrete strength of concrete and the slump and the requirements of the premise, should improve mixing and aggregate content,in order to reduce the dosage of cement concrete alone.④ Should try to choose cement hydration heat low, setting time is long, the cement, low thermal Portland cement slag silicate cement, cement, slag dam Portland cement, coal ash Portland cement, volcanic gray Portland cement, etc.However, the slag cement hydration heat low water cement ratio of chromatography in other large, casting lots of water surface layer. This phenomenon is not only affect lactation water, also influence the construction speed and quality of construction. Because the water gathered in separation between the two casting concrete surface layer, change, and water-cement ratio in the water and took out some of the mortar, thus forming a layer of interlining content, destroyed the cohesive force of concrete and holistic. The size of the water concrete lactation with water water, water, lactation; And with the temperature, water separation of time with temperature completely and shortening, In addition, also with the composition and fineness of cement. Therefore, in selecting slag cement should be chosen when the varieties, and lactation shall be adding water-reducing agent in concrete, to reduce the consumption. During construction, should be in water or mixing some tomography uniform rolling cement casting in water, with 3-degrees vibration compaction, continue again after a concrete casting.2.the reasonable construction method(1) The concrete mixing and transportation. (a) white, accurate grasp of concrete proportion, especially the strict control of water consumption, the determination of sand. Records of every block water cement, sand and gravel, specific quantity, the application must be accurate to scale, by mixing. Good control of concrete slump and general shoulds not be too big, in 120 ± 20 mm. To minimize the mouth 3 concrete temperature. (b) concrete mixing in a storehouse after good transportprocess, to prevent to produce separation, lactation water, mortar loss should shorten transportation time, concrete loading not too full. (2)Concrete pouring and open mode. Pouring process may be close-grained, vibration to vibration time should be uniform in surface functional plasma advisable, uniform spacing, vibrating force scope affected overlap 1/2 advisable, after casting, compaction, surface must, in order to prevent the surface crack. Try to avoid in the solar radiation, high time due to the needs of the project if pouring in summer construction, avoid noon pouring temperature period, try to arrange at night. Time should be removed, according to air temperature and strength. In the actual temperature curing of the concrete conditions of strength, strength design of concrete center and 75%, the lowest temperature control surface in 25 degrees Celsius, expected the concrete surface temperature drop more than 9 degrees Celsius above does not allow removed.(3) Do surface insulation protection of mass concrete temperature crack, is mainly caused by excessive temperature. Concrete pouring, due to internal heat faster, more surface temperature will form the internal and external surface by internal restraint, contraction, but the tensile stress, not more than usually have small tensile strength and the concrete cracks. But if the air raid, or by excessive ventilation cooling, make the surface temperature will easily lead to excessive temperature crack in the concrete, and so on, especially after dismantling formwork, low season in the immediate surface protection. To prevent excessive temperature crack, cause surface. In addition, the average day temperature in 2 ~ 3d consecutive decline not less than 6 ~ 8 degrees Celsius, 28d age concrete surface must surface within the protection.(4) Of the mass concrete casting:Construction scheme, besides should satisfy each place of concrete in early before a new concrete are covered and rammed finished outside,still should consider structure size, steel pipe, buries the bolts and leave, concrete and hydration heat supply, the influence of factors such as the commonly used method has the following kinds:Comprehensive stratified:In the first layer after pouring all comprehensive casting, casting back second, should make the first layer of concrete yet, so early, continuous casting until completion by far. Using this scheme, applicable to the general structure of planar size shoulds not be too big, when construction from the short side began to push along the long side, is more appropriate. When necessary, can be divided into two sections from middle to both ends to or from the middle and construction.Section 2 layer:Concrete casting, starting from scratch, casting a certain distance to the second floor, so after pouring in other layers on casting. Due to the total number of layers, therefore, after the first layer top pouring concrete yet at the end of the beginning of the second period, and can turn from layered casting. This scheme is applicable to units within the time required, the supply of concrete less like the first option on that. This scheme is applicable to structure is too big and thickness of large area or length.Incline stratified:Requirements of slope not greater than cant 1/3, applicable to greatly exceed the length of the structure of the thickness of the three times. From the bottom layer of concrete casting, gradually move.3.maintenance measuresMaintenance of mass concrete construction is a vital work. Maintain proper maintenance is mainly to control temperature and humidity, temperature, promote concrete outside the normal development of the strength of concrete and prevent the cracks of concrete and development.According to the specific circumstances of should as far as possible much maintenance period of time, after dismantling formwork should immediately, covering protection to prevent recent climate, sudden cold temperature, prevent and control in early concrete cracks and medium. The massive concrete curing, not only to satisfy the need that still should increase by artificial temperature control, due to temperature caused by deformation of the concrete cracking. After the completion of the concrete curing time to keep the concrete surface spraying maintenance, such as reducing often humid heat outside pour cans, and prevent dry crack and promote the stable growth of concrete strength. In general 18h 12 ~ after pouring in immediately start maintenance, maintenance time not less than 28d or design age.4 CooledIf in the high-temperature seasonal construction, should be in early general refrigeration adopted to reduce the water temperature, but the peak of concrete, water cannot too long, for a long time can cause excessive temperature range of temperature stress caused by large. In order to cut inside and outside, still should temperature in summer jiamoqiuchu undertake metaphase is cooled by water, river, general middle water lasted about two months. Later, water is made concrete cylindrical blocks the necessary measures to juncture grouting, generally USES water and cooling water through the combination scheme.Third, the conclusionConcrete crack, especially large volume concrete crack is currently scholars and engineering is an important problem of attention, through the above analysis, the material of mass concrete crack is mainly composed of temperature stress and concrete's shrinkage, the author thinks carefully select material, and in the use of reasonable construction method, can effectively prevent the cracks.混凝土施工裂缝原因及防治混凝土施工裂缝原因不外乎外因和内因。
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外文翻译一、原文Discuss the construction temperature andcrack of the concrete lightlyThe summary: In order to prevent the owners of the concrete work of claims, we must do a good job in the construction process in the temperature and crack control, through observation live for many years, through consulting the monograph about stress within the concrete, explain to concrete temperature reason, on-the-spot concrete control and measure, prevention of crack of temperature that crack produce.Keyword Concrete Temperature stress Crack Control1. The concrete occupies the important position in modern engineering construction. But today, the crack of the concrete is comparatively general, the cracks are nearly omnipresent in the science of bridge building. Though we take various kinds of measures in constructing, careful, but the crack still occurs now and then. Tracing it to its cause, it is one of them incompletely that our change to concrete temperature stress pays attention to. In the large volume concrete, temperature stress and temperature control are significant. This is mainly because of the reason of two respects. First of all, concrete often appear the temperature crack in not constructing, influence the globality and durability of the structure. Secondly, in the course of operating, the temperature change has remarkable influence that can't be ignored on the stress state of the structure. We meet to construct temperature crack in mainly, so only to origin cause of formation and treatment measure, concrete of crack make a discussion in constructing this text.Reason of a crackIt has many kinds of reasons to produce the crack in the concrete, it is mainly the changes of temperature and humidity, fragility and disparity of the concrete, and the structure is unreasonable, the raw materials is not up to standard (if the alkali aggregate react), the template is out of shape, the foundation does not subside etc. evenly. The cement emits a large amount of heat of hydration when the concrete is hardened, inside temperature is rising constantly, cause the stress of drawing on the surface. In the course oflowering the temperature, is it congeal foundation pay restrain to mix always later stage, will present the stress of drawing within the concrete. Reducing of temperature can surface cause heavy stress of drawing very in concrete too. When these draw the stress and go beyond resisting the ability of splitting of concrete, namely will present the crack. A lot of inside humidity ofconcrete change very light or change relatively slow, surface humidity might change heavy the violent change takes placing. Such as maintaining thoroughly, when getting wetter when not doing, contract surface there aren't deformation doing, often cause the crack too. The concrete is a kind of fragility material, tensile strength is about 1/10 of the compression strength, is it carry on one's shoulder or back limit when draw out of shape to have (0.6~1.0)×104 only, is it carry on one's shoulder or back limit location when stretch out of shape to there is(1.2~2.0)×104 to add for a long time to add a short time. Because raw materials even, water dust than unstable, transport and build phenomenon of emanating of course, its tensile strength is not even in the same concrete, a lot of resist the ability of drawing very low, it is apt to present the weak position of the crack. Among armored concrete, draw stress to undertake by reinforcing bar mainly, concrete bear stress of keeping just. Or reinforcing bar mix if edge position gone to congeal presents the stress of drawing in the structure in plain concrete must rely on the concrete oneself to bear. Require avoiding the stress of drawing or only very small stress of drawing appears of the general design. But the concrete is cooled from maximum temperature to the steady temperature of operating period in constructing, often cause sizable to draw the stress within the concrete. The temperature stress can exceed other outsides and load the stresses caused sometimes, know change law, temperature of stress for carry on reasonable structural design and construct extremely important.Analysis of 2 temperature stressesIt can be divided into following three stages according to the forming process of the temperature stress:(1)It is early: It needs generally 30 day from beginning building concrete to finishing sending out heat basically by cement. There are two characteristics at this stage, first, the cement emits a large amount of heat of hydration, second, mix and congeal the changing sharply of elastic model quantity. Because of the change of elastic model quantity, form the remaining stress in the concrete in this period.(2)Middle period: Up till the concrete is cooled until stability temperature from cement send out heat function basically when expiring, in this period, the temperature stress is mainly because the cooling of the concrete and external temperature change cause, these stresses and remnants stresses that is formed in early days are superposed, mix and congeal the elastic mould amount that goes to and does not change much during this period.(3)Later period: Operation period after the complete cooling of concrete. Temperature stress whether external temperature change causes mainly, these stresses and first two kinds of remnants stresses are changed and added.It can be divided into two kinds according to the reason why the temperature stress causes:(1)Spontaneous stress: There are not any restraints or totally static structure at the border, if inside temperature is non-linear distribution, temperature stress appearing because structure restrains from each other. For example, the body of mound of the bridge, the physical dimension is relatively large, surface temperature is low when the concrete is cooled, inside temperature is high, present the stress of drawing on the surface, present the stress of pressing in the middle.(2)Restrain the stress: All of the structure ones or it restrain external one some border, can't out of shape and stress not cause not free. Such as case beam roof concrete and guardrail concrete.These two kinds of temperature stresses draw back stresses caused to act on with the doing of concrete together frequently. It is a more complicated job to want to analyse the distribution, size of the temperature stress accurately according to known temperature. In case of great majority, need to rely on the model test or the number value to calculate. To is it make temperature stress have sizable limp to creep concrete, at the stress accounting temperature, must consider the influence that creep, calculate concretely that no longer states thinly here.Control and preventing the measure of the crack of 3 temperatureFor prevent crack, lighten temperature stress can from control temperature and is it is it set about to restrain terms from two to improve.The measure of controlling temperature is as follows:(1)Is it improve aggregate grade mix, is it do rigid concrete to spend, mix mixture to adopt, is it guide angry pharmaceutical or plastification pharmaceutical, etc. measure in order to reduce cement consumption of concrete to add;(2)Add water or the water to cool the broken stone in order to reduce the temperature of building of the concrete while mixing and shutting the concrete;(3)Reduce the thickness of building while building the concrete on hot day, utilize and build the aspect to dispel the heat;(4)Bury the water pipe underground in the concrete, enter the cold water to lower the temperature openly;(5)Stipulate rational form removal time, the temperature keeps warm the surface while lowering suddenly, in case that the rapid temperature gradient takes place in the concrete surface;(6)The concrete with medium and long-term and exposed construction buildsa piece of surface or thin wall structure, take the measure of keeping warm in cold season;The measure of improving condition of restraining is:(1)Divide and sew and divide one rationally;(2)Prevent the foundation from rising and falling too big;(3)Rational arrangement construction process, prevent the too big discrepancy in elevation and side from exposing for a long time;In addition, improve the performance of the concrete and improve and resist the ability of splitting, strengthen maintenance, prevent the surface from being done and contracted, especially guarantee the quality of the concrete is very important to preventing the crack, should pay special attention to avoiding producing and running through the crack, the globality resumed its structure after appearing is very difficult, so should rely mainly on preventing the emergence of the running through crack while constructing.In construction of concrete, for raise turnover rate of template, demand concrete form removal as soon as possible that build newly often. Should consider form removal time properly when concrete temperature is higher than the temperature, so as not to cause the superficial early crack of concrete. Building the early form removal newly, cause very large stress of drawing on the surface, the phenomenon that "temperature is assaulted" appears. Build initial stage in concrete, because heat of hydration is sent out, the surface causes sizable to draw the stress, surface temperature is also higher than temperature at this moment, remove the template at this moment, surface temperature is lowered suddenly, must cause temperature gradient, thus add and draw the stress on the surface, change and add with the heat of hydration stress, in addition, the concrete dries and contracts, the superficial stress of drawing reaches very great number value, have danger of causing the crack, but cover a light-duty heat insulator with on the surface in time after removing the template, for instance foam sponge, etc. , for prevent concrete surfacefrom produce the too big stress of drawing, have remarkable results.Add muscle influence to large volume temperature stress of concrete very light, because large volume concrete include muscle to be rate very much low. Just have influence on the general armored concrete. On terms that temperature is not very high and the stress is less than limit of surrendering, every performance of the steel is steady, and have nothing to do with stress state, time and temperature. Line bloated coefficient of steel and concrete line bloated coefficient difference very light, take place little internal stress very only between the two while changing in temperature. Because elastic mould amount of steel concrete elastic mould 7~15 of quantity, reach as interior concrete stress tensile strength and when fracturing, the stress of the reinforcing bar will not exceed 10000kg/cm2. So is it is it prevent tiny appearance difficulty very much of crack from to make use of reinforcing bar to want among concrete. But the crack in the structure generally becomes numerous, the interval is little, the width and depth are smaller after adding the muscle. And if diameter of reinforcing bar detailed and when interval dense, to improve concrete resist result of person who split better. Concrete and surface, armored concrete of structure can take place detailed and shallow crack often, among them the great majority belong to and do and draw back the crack. Though this kind of crack is generally all relatively light, it stills have certain influence on the intensity and durability of the structure.In order to guarantee concrete project quality, prevent fracturing, improve the durability of the concrete, use the admixture to reduce one of the measures that fractures correctly. Whether is it reduce water is it split pharmaceutical to defend, I summarize his main function in practice to use.(1)There is a large number of capillary in the concrete, produce capillary tension in the capillary after water is evaporated, make concrete is it contract out of shape to do. Increasing the thin aperture of hair can reduce the capillary surface tension, but will make the intensity of concrete reduce. This surface tension theory has already been confirmed in the world as far back as the sixties.(2)Water dust than influence important factor that concrete shrink, is it reduce water is it split pharmaceutical can make concrete water consumption reduce by 25% to defend to use.(3)Cement consumption important factor, concrete of person who shrink too, is it add and subtract water is it split concrete reducible 15% of the cement consumption on terms that keep the intensity of concrete of pharmaceutical to defend to mix, its volume is supplemented by increasing aggregate consumption.(4)Reduce water is it split pharmaceutical can improve consistency of grout, reduce concrete secrete ink to defend, reduce and sink and draw back deforming.(5)Improve gluing the strength of forming of the grout and aggregate, the concrete improved resists the performance of splitting.(6)Concrete is it produce stress of drawing to restrain from while shrinking, crack when drawing the stress and is greater than concrete tensile strength can produce. Reduce water is it split pharmaceutical effective concrete tensile strength of improvement very to defend, improve resisting the performance of splitting of concrete by a wide margin.(7)It can make the concrete density good to add the admixture to mix, can improve resisting carbonization of concrete effectively, reduce carbonization to shrink.(8)Is it reduce water is it split slow coagulation time proper concrete under pharmaceutical to defend, on the basis of preventing the fast water of cement from sending out heat effectively to mix, prevent the plasticity shrink that brings because the cement is not congealed for a long time from increasing.(9)Mix admixture concrete and getting easy and kind, surface easy to feel flat, form little membrane, reduce the moisture to evaporate, reduce drily and shrink. A lot of admixtures all have the functions of slow coagulation, increasing and apt, improvement plasticity, the experiment that we should carry on in this respect more in the project practice is compared with and studied, than lean against not improving terms more simple, may getting simple and more direct, economy.Early maintenance of 4 concretePractice has proved, the common crack of concrete , most is the surface crack of different depth, main reason its whether temperature gradient cause cold temperature of area lower too easy to form crack suddenly. So say the warm-keeping of the concrete is especially important to preventing the early crack of surface.From the viewpoint of temperature stress, should reach and require keeping warm following:1)Prevent concrete internal and external temperature poor and concrete surface gradient from, prevent the surface crack.2)Prevent concrete from to be ultra and cold , should is it is it make the minimum temperature is not lower than the steady temperature of concrete service time construction time in concrete to try to try one's best.3)Prevent the old concrete subcooling, in order to reduce the restraint among the old and new concrete.The early maintenance of the concrete, the main purpose lies in keeping the suitable warm and humid condition, in order to get the result of two respects, on the other hand make the concrete avoid the invasion and attack of the unfavorable and warm, humidity out of shape, the ones that prevent from harmfully are cold to contract and do to contract. On one hand make cement water function go on smoothly, is in the hope of reaching the intensity designed and resisting the ability of splitting.The suitable warm damp condition is interrelated. Mix warm-keeping measure paid to congeal often protects wet results too. Analyse, water concrete include moisture can meet demand, cement of water have enough and to spare newly theoretically. But because the reason of evaporating etc. often causes losses of the moisture, thus postpone or hinder water of the cement from, the surface concrete receives this kind of adverse effect easiestly and directly. Key period when maintained in initial a few days after so the concrete is built should pay attention to conscientiously in constructing.2. Quality control of waterproof concrete constructionCombined with experience, from formwork design, fabrication and installation, assembling reinforcement, pouring and curing of concrete and other aspects construction technology of fair-faced concrete is introduced as well as quality control measures and standards in order to reduce engineering cost to acquire satisfied economic and social benefits.The factors of influencing waterproof-concrete quality are very many. Any links does not pay attention to the water-proof concrete of field loss hinders the water function without exception jointly with degree. Engineering construction in the basement adopts secondary form board fabrication and installation, reinforced bar fabrication and bind, concrete stirring and mixing system and transport, concrete covibration beat with a stick, construction joint practice, concrete curing and dismantle model and being ready for backfill and so on aspects. These are very critical to quality method to ensure that water-proof concrete self water-proof, and the way of practicehas wan out.Method being under construction2.1 Fabrication and InstallationAccording to the concert of closely knit, demand of reason why to form board since the water-proof also concrete have made and have assembled corresponding rise is special, be to require that not leaving out thick fluid, firm closely knit block of wood deformation, water absorption Character should be small and ought to give priority to select and using bamboo slab rubber form board or the steel form.. Strict control form board room gap size, necessary exceeding 2 mms uses foam rubber or plastic to squeeze a crack in, porous form board nonutility without exception to board face Be ready for wall post at the same time rotting the prevention and cure job adopt the cement mortar pouring same, indicia in before the root segment sticking the foam rubber or plastic strip, the bottom puts on a cement mortar, concrete a concrete, first 5cm~10cm. Since water-proof, concrete structure wall thickness is mostly more infertile. Be to ensure that component geometry dimension, Chang adopt the inside and outside bolt to pull the measure meeting attention to, responds to on play receive bolt centre interpose stop water iron plate, to prevent water from forming pilotage passage along bolt leakage.2.2 Assembling reinforcementWater-proof concrete structure has demanding as follows to the reinforced bar:1)Reinforced bar should adopt twisted steel as far as possible, increases by hold wrap a force composing in reply a water ability2)Reinforced bars connect should try one's best to adopt to solder connection, stop using and being needless to bind connection to the full3)When binding a reinforced bar, the iron wire head responds to inner bending.4)Strict control reinforced bars protective layer thickness.Minimal thickness of water-proof concrete reinforced bar protective layer is not smaller than 25mms, the protective layer welcoming water surface especially inadmissibility to disappoint error. The iron wire and reinforced bar that application buries in advance within mortar piece while using mortar heel block as protective layer, are bound solid. When the cavalry puts up the fixed reinforced bar if adopt a reinforced bar, also need to increase solders water iron plate or fixation just goes ahead, to strengthen water-proof effect in the heel block. This project uses new materials nylon to have fixed there is an effect's had guarded against reinforced bar protective layer deviation piece big mass common failings.2.3 The concrete stirring and mixing makes and transportsSince the water-proof concrete requires that higher closely knit, reason why stir and mix system also need to have the fairly good homogeneity, should be ready for burning as follows almost for this purpose:1)Ensures that mixing time, mixing at every time are secondary jump intoa expect the general ejection of compact block of wood less than 2mins.2)Should use the apposition agent, the solution queen who should manufacture certain thickness from apposition agent adds the mixer inner, the dried powder or high concentration solution will add an agent extra not to adds the mixer inner directly, prevent from mixing is uneven but part concentrates, both lose the apposition agent effect, and affect concrete mass.3)Responds to the assured source of life degree having a spot test on the admeasurement concrete at the regular intervals collapsing in the process being under construction, construction is middle if Yu rains or other cause, respond to the ratio determining whose water ratio, and adjusting the composition being under construction in time when change happened in sandstone moisture content.4)Project uses the commodity concrete, has boundary have raised a concrete stirring mass and of all kinds effect apposition agent adulterating falls when amounts, the water ash having controlled a concrete strictly collapsing.5)Concretes adopt a pump to have given handicraft, effective avoiding a concrete producing the phenomenon isolating bleeding and leaving out thick fluid in the process of transportation.2.4 Matters needing attention in being under construction1)Construction school assignment soft and floury is divided. Water-proof concreting should stratify strictly being in progress, and a continuous construction is completed The front and back and high and low connect between the tier should subjugate within the cement initial setting time, For this purpose, with handling a worker dividing into several, at the same time each other, school assignment group faces or it is all right for each other, carry on the back.2)Achieve strictly fixed point determines the amounts of the components of a substance material down According to the vehicle capacities stratifying concrete altitude and the means of transport, the quantify carrying out fixed point strictly is able to go down one important ring expecting that this is to improve water-proof concreting mass.3)Concretes vibrating beat one important ring being to ensure that the concrete is closely knit, defend against to seep with a stick. Also, should adopt fixed point vibrating, handle meticulously on basis expecting that under determining the amounts of the components of a substance homogeneously in fixed point. Pay attention to high and low tier of linking up. Now that needing to prevent from miss and vibrating, not vibrating enough, being going to prevent a fault from vibrating again, Need to forbid using prying the method coming to aid to vibrate moving a reinforced bar or shaking a reinforced bar especially, such separates to making the front already concrete the reinforced bar and concrete shaking the reality part, causes serious consequences.4)Being ready for the assured source of life degree taking over thick fluid measure, and adjusting in time to collapse seriously. Average water-proof concrete structure construction, the construction joint being under construction respectively, composing namely on erecting wall sells be bottom board and vertical wall at reduced prices. Should irrigate thick a layer of 5cm~10cms surname indicia cement mortars in seam place first linking up closely knitting tier, in order to ensuring that the seam place vibrates when concrete vertical wall. Simultaneous, improve step by step with concrete an altitude, should fall off step by step with the water yield, diminish collapsing to fall degree prevent from concrete insist to be short but the cement paste is partial to much phenomenon to aggregate appearing on upper part.2.5 Dismantling model and curing of concreteThe water-proof concreting queen maintains goodness and badness working, not only affecting the intensity arriving at a concrete, moreover the impervious function affecting to the concrete. Evidence, water-proof concrete early phase dehydration or curing process lack for water, will reduce whose impervious function by a wide margin. Water-proof concrete curing responds to the block of wood less than 14ds. The water-proof concrete dismantles a model demanding to be unable to compare high, dismantle model time unsuitable untimely, respond to when dismantling a model handle meticulously, prevent an iron rod from using to pry stiffly, that the sledgehammer is knocked suddenly and forcibly pries, uses a concrete meet with destroy.2.6 Do good well at backfillWater-proof architectural backfill is a final working procedure, it be sometimes ignored, this is a very big faults in fact under the ground. When the water-proof structure job is over queen responds to the construction carrying out backfill immediately. Most important, we should take backfill seriously self mass; Secondly, backfill varia and ponding should clear up the pit bottom in the front, respond to densification with layers when backfill. Water-proof structure vicinity layer pounds true backfill, self is a reliable and economical as well water proofing drapery under the ground. In project basement engineering construction Shanghai, since organizing water proofing down to earth strictly with all above seven passes, the concrete is under construction, effect is comparatively ideal. The percolating water phenomenon does not appear.ConclusionsConstruction temperature and relation of crack in concrete the above carry on preliminary discussion of theory and practice, though the academia has different theories to origin cause of formation and computing technology of the concrete crack, but to concrete prevention and improving the measure suggestion to relatively unify, application in practice result fine too at the same time, concrete to is it observe, compare more by us to want in constructing, analyse more, summarize more after going wrong, combine many kinds of prevention and deal with the measure, the crack of the concrete can be avoided.一、翻译浅谈混凝土的施工过程中温度与裂缝控制摘要为了防止业主对混凝土工程的索要赔偿,我们就必须做好过程中的温度与裂缝控制。