How to improve the deformation effect crack of cast-in-place concrete (2)
3 concrete self-shrinking cracks.High strength concrete in early stage has higher strength and elastic modulus, resulting in greater tensile stress after shrinkage and deformation than ordinary concrete, which is easy to crack.
Main prevention measures: 1, the use of high-performance concrete, the appropriate choice of concrete composition materials.2. Use low-alkali cement. The fineness of cement should not be too fine to avoid excessive strength in the early stage.3, the aggregate should be clean, good gradation, reduce the aggregate pores, reduce the sand rate.4. Be careful about the use of superfine mineral admixtures such as ground slag and silica powder.
4 temperature crack.Temperature cracks include two categories: internal and external temperature difference caused by hydration heat of cement, cracks caused by tensile stress and oversized components, and cracks caused by thermal expansion and cold contraction.
Main prevention measures: 1, improve the design structure.,2, the use of "jumping warehouse method" and other special construction technology.3. During the construction of mass concrete, do a good job in internal cooling and surface insulation, control the temperature difference between inside and outside within 25℃, and do a good job in temperature measurement.4. Adopt effective maintenance methods.
5 Deformation cracks caused by strong constraints.Due to the complexity of the restraint of concrete members, cracking is often caused when the restraint is large.
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