水泥基材料塑性收缩抗裂判据研究

Research on the Judge Criterion of Plastic Shrinkage Cracking for Cement Based Materials

采用自行设计的塑性抗拉强度、塑性收缩开裂应力测定装置测试了水泥砂浆、混凝土塑性抗拉强度和塑性收缩开裂应力.出现塑性收缩开裂时,试件表面实际的塑性收缩开裂应力应大于或至少等于其塑性抗拉强度,据此提出了以试件的毛细管收缩开裂应力临界作用深度来计算其他试件的名义开裂应力,再以此计算它们的塑性收缩开裂抗裂指数,从而得出水泥基材料塑性收缩开裂抗裂判据的思路.实验发现:当抗裂指数≤1.360时,水泥砂浆、混凝土出现塑性收缩开裂;当抗裂指数>1.360时,水泥砂浆、混凝土不出现塑性收缩开裂.

The judge criterion of plastic shrinkage cracking for cement based material was studied through the testing of plastic tensile strength and plastic shrinkage capillary stress of cement mortar and concrete. The so-called critical capillary depth was built up on the assumption that the plastic shrinkage capillary stress of cement mortar and concrete must be bigger than or equal to the plastic tensile strength. The research results indicate that if the plastic shrinkage cracking index is less than or equal to 1. 360, the fresh cement mortar or concrete would crack at water-losing condition, while if the plastic shrinkage cracking index is more than 1. 360, the fresh cement mortar or concrete would not crack.