混凝土基体材料断裂特性试验研究

Experimental study of fracture properties of concrete matrix materials

以水泥净浆和水泥砂浆两种最为基础的混凝土基体材料为研究对象研究了它们的断裂特性.采用三点弯曲梁试件按强度和尺寸系列分别设计了3组断裂试件,获得了P-CMOD全曲线,并测得了起裂荷载.试验结果表明,即使在基体中加入粒径很小的骨料也会大大改善基体的断裂性能.水泥净浆并不是理想的脆性材料,它在断裂过程中也呈现出一定程度的非线性断裂行为,即在失稳破坏前存在着稳定的裂缝扩展过程,且这个过程随着抗压强度的提高而变短.试件尺寸越大起裂越早,裂缝稳定扩展阶段也越长.由此,根据水工混凝土断裂试验规程计算了水泥净浆和砂浆双K断裂参数,并对结果进行了分析讨论.

The fracture properties of cement paste and mortar which are two most basal matrix materials of concrete were studied using three groups of three-point bending beams with different sizes and strengths.A complete P-CMOD curve was directly obtained,and the initial cracking load was determined.The experimental results show that the resistance to crack propagation in matrix is enhanced due to sand aggregate in the matrix,even though the grain size used is very small.Cement paste is not an ideal brittle material,an apparent stable crack propagation before unstable failure is observed in cement paste,and this stable stage is shortened with the compressive strength increasing.The larger the size is,the earlier the crack initiation is,and the longer the stable crack propagation stage becomes.Therefore,based on the hydraulic engineering concrete fracture testing specification,the double-K fracture parameters were calculated for cement paste and mortar.The discussion on the obtained results was made.