【正文】 ors. 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。 in concrete mixed with fly ash or superplasticizer。 set the required temperature reinforcement in the base。 construction reinforced the protection layer thickness should be strictly controlled. Pouring concrete should be strict control vibrators, vibrators fully, and should not be too long layered interval. Creep crack control Appropriate to increase the height of the end cross section, and configured to withstand the horizontal forces reinforced radial reinforcement or bent construct tendons (bent parallel to the direction equal to the principal tensile stress). Bent angle depress the prestressing tendons, reduce nonpreloading。 transport between the ponents set skids fastened with each other, to prevent shaking large ponent of the collision。 lifting roof trusses, and lateral stiffness ponent, application scaffolding transverse reinforcement, set up and pulling the rope to prevent the lifting process shaking, collision。 ERECTION should have a more long time, the stacking crane girder last fixed as much as possible (Creep 3 months up to 60% the basic stability of four months later, six months creep to be pleted by 70% 80%), the creep deformation in the lifting (or fixed before) most of the concrete has a longer age period, the intensity is also higher。 early reinforced concrete conservation, improve early tensile strength and elastic modulus. 6, to avoid cooling and shrinkage joint action of the stress caused by superposition。 cooling pipes embedded in the base, pass into the circulation of cold water, and will export the heat of hydration。 First, before pouring concrete, strict inspection of reinforced protective layer to ensure that its thickness to meet design requirements, while ensuring a solid steel banding, and accurate position, to avoid the reinforced vibrated concrete shift and exposed tendons. Second, using the class with a good gravel aggregate concrete prepared. Vibration pacting concrete pouring. Timely processing of the concrete after form removal slag, cellular, and Ma surface phenomenon. 4 Common cracks approach Surface repair method Surface repair method is a simple, mon repair method is mainly applied to the processing of stability and no effect on the structure carrying capacity of surface cracks and deep into the cracks. The usual treatment measures in the cracks in the surface of smear grout, epoxy mortar or concrete surface brushing paint, asphalt and other anticorrosion materials, continue to crack in order to prevent the concrete role in protection while using crack surface paste of glass fiber cloth, when the concrete surface cracks in larger quantities, the distribution of the surface of a wider, often used to add a layer of cement mortar or fine aggregate concrete method of the overall surface treatment, while the overall surface should configure twoway steel mesh. Concrete replacemen