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混凝土裂缝大致分为变形裂缝,收缩裂缝,温度裂缝和沉降裂缝等。变形裂缝产生于荷载不均匀,缺乏空间刚度,外伤及结构不合理所造成。收缩裂缝主要产生水泥质量,水灰比,集料的粗度及集料的流动性,加附加剂、配合比、搅拌时间、搅拌方法、捣固时间、养护方法等。收缩裂缝首先在最大拉应力处发生,也可以与温度应力一块起作用产生其它类型的收缩裂缝。收缩裂缝随时间变化而变化。温度裂缝主要由温度变形引起的。当混凝土表面与外界气温差异很大,或冬季施工措施不当,或混凝土自由约束条件受限制等,都将导致混凝土产生压应力与拉应力。如果拉应力大于混凝土抗拉强度时,混凝土表面便出现裂缝。
Concrete cracks are roughly divided into deformation cracks, shrinkage cracks, temperature cracks and settlement cracks. Deformation cracks are caused by uneven load, lack of space stiffness, and trauma and structural irrationality. Shrinkage cracks mainly produce cement quality, water-cement ratio, aggregate coarseness and aggregate flowability, addition of additives, mix ratio, mixing time, stirring method, tamping time, and maintenance methods. Shrinkage cracks occur first at the maximum tensile stress and can also work with temperature stress to produce other types of shrinkage cracks. Shrinkage cracks change over time. Temperature cracks are mainly caused by temperature deformation. When the concrete surface is very different from the outside air temperature, or improper winter construction measures, or restrictions on the concrete free restraint conditions, etc., will cause the concrete to produce compressive stress and tensile stress. If the tensile stress is greater than the concrete’s tensile strength, cracks appear on the concrete surface.