【正文】 段降溫時混凝土的累計拉應(yīng)力小于該齡期混凝土允許的抗拉強度，以控制裂縫出現(xiàn)。 徐變裂縫的控制 適當加大端頭截面高度，配置承受水平力鋼筋、放射式配筋或彎起構(gòu)造筋（彎起方向平等于主拉應(yīng)力）。 6 結(jié)論 建筑工程中混凝土裂縫種類較多，而且是普遍存在的一種現(xiàn)象，它的出現(xiàn)不僅會影響建筑物的外觀，還會影響建筑物的使用功能和耐久性，嚴重者將會威脅到人們的生命和財產(chǎn)安全，因此要根據(jù)不同的部位、形態(tài)以及嚴重程度對混凝土裂縫進行認真分析，采用合理的方法進行處理，并在施工中采取各種有效的預(yù)防措施來預(yù)防裂縫的出現(xiàn)和 發(fā)展 ，保證建筑物和構(gòu)件安全、穩(wěn)定的工作。 processing 1. Foreword Building construction, concrete structures, cracks, it will affect the stiffness of the concrete structures and the overall resistance of the structure of the building, even if the cracks do not lead to the destruction of concrete structures or building collapse will affect the exterior of the buildingwhen the crack width exceeds a certain limit, can also cause corrosion, durability of structural elements. This article describes several mon cracks in the concrete construction of prevention measures, control methods and cracks on the concrete construction has a certain reference value. 2. Common cracks Category Concrete cracks are many reasons, the situation is more plicated, more a bination of factors. For some cracks, it is difficult to give an accurate and clear analysis. Engineering practice shows that the main reasons for crack formation from three aspects: deformation, load, and uneven settlement. Generally by the temperature difference, shrinkage, differential settlement cracks caused by the deformation in favor of about 80% load caused about 20%, of course, also need to consider the prehensive reason. Based on these main factors, often concrete cracks summarized shrinkage cracks, temperature cracks, settlement cracks, creep cracks, stress cracks and construction cracks in several categories. 3. Common fracture analysis and prevention Plastic shrinkage cracks and prevention Plastic shrinkage of concrete in the condensation of preSurface due to excessive water loss and shrinkage. General more mon in the dry and hot and windy weather cracks, the shape of the wide in the middle, both ends of the thin, noncoherent and of varying lengths, long cracks up to 2m3m, width up to , seriously affect the resistance of concrete permeability and durability. The main preventive measures: First, make use of the shrinkage value is smaller, higher early strength portland or portland cement. Second, strict control of the watercement ratio, to minimize the amount of water to ensure the concrete construction of the required slump and workability under the premise, if necessary, mixed with superplasticizer. Third, prior to pouring concrete, grassroots and templates uniform watering wet. Timely coverage of the grip material film or wet straw mats, hemp films and so on, to keep the concrete setting the front surface moist, or sprayed on the concrete surface with the conservation agent for conservation. Subsidence cracks and prevention Subsidence cracks in the main is due to the flooding of the structure foundation, soil is uneven or not pacting the backfill caused uneven settlement due. In addition, Concrete hardening process due to the stiffness is insufficient or does not firmly support the bottom of the template will cause subsidence cracks. The main preventive measures: First, the structure of the preconstruction, to ensure the quality of ground treatment. The original foundation soil must be dense, uniform, carrying capacity and to achieve the design requirements。 prestressed reinforcement in the ponent. Grouting, caulking block method Grouting method applies to the structural integrity of the influential or the repair of concrete cracks in the impermeable requirements, it is the use of pressure equipment will cementing material pressure concrete cracks cementing material hardened with concrete to form a whole, and thus play blocking the purpose of reinforcement. Commonly used in the cementing material grout, epoxy, methacrylate, polyurethane and other chemical caulking is the most monly used crack block, it usually gouges along the cracks, filling them with plastic or rigid sealing material in the slot. In order to achieve the purpose of closed cracks. Commonly used plastic material PVC clay, plastic ointment, butyl rubber, etc.。 in concrete mixed with fly ash or superplasticizer。 summer to avoid exposure, winter insulation cover. Take a long time conservation, and provide for reasonable removal time, and give full play to the concrete stress relaxation effect 。 set the required temperature reinforcement in the base。 concrete pouring should be based on the measured temperature and temperature lift curves to calculate each stage of cooling when the concrete tensile stress accumulated when its greater than the age of the concrete tensile ultimate strength heat conservation measures should be taken so that the accumulated tensile stress of concrete in various stages of cooling is less than allowed by the age of concrete tensile strength, to control the crack appears. More plex reasons concrete cracks, depending on the circumstances and conditions, to take one or several of the measures. settlement crack control Settlement cracks in the concrete surface along the long direction of horizontal reinforced through broad distribution of surface, usually in the form