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预制楼板地面纵向裂缝的原因之一是收缩,包括灌缝细石混凝土的收缩、面层水泥砂浆或细石混凝土的收缩。灌缝细石混凝土收缩减弱了其和板侧面的结合,减小了该结合面上的抗剪强度。当外荷载作用在某一块板上时,这块板就会向下弯曲。当外荷载在板侧面产生的剪应力超过灌缝混凝土的抗剪强度时,外荷载就不能传递到相邻的板上去,两相邻板的挠度差使地面产生了纵向裂缝。水泥砂浆或细石混凝土面层在硬化过程中也会产生收缩。这个收缩因受楼板的约束而在面层中产生拉应力,当其超过地面的抗
One of the causes of longitudinal cracks in prefabricated floor slabs is shrinkage, including the shrinkage of fine-clay concrete, shrinkage of surface cement mortar or fine stone concrete. The contraction of the fine-grained concrete with grouted seams weakens its combination with the side of the slab and reduces the shear strength at the joint surface. When an external load acts on a board, the board will bend downwards. When the shear stress generated by the external load on the side of the slab exceeds the shear strength of the concrete, the external load cannot be transmitted to the adjacent slab. The difference in the deflection of the two adjacent slabs causes longitudinal cracks in the ground. Cement mortar or fine stone concrete surface also shrinks during hardening. This shrinkage creates tensile stress in the surface layer due to the constraints of the floor when it exceeds the resistance of the ground.