Effects of loading history on fracture properties of concrete

A static fracture process zone (FPZ) model, which describes the nonlinear relationship between the crack-closure stress and the coexisting crack-opening displacement, was used to predict the effects of sustained and cyclic loading on crack propagation and fracture for concrete in tension. This study found that when plain concrete was subjected to an incremental tensile displacement loading, microcracks continued to grow for more than 1 hr after that increment was first applied. Such a process of slow damage accumulation is the cause of increases in deformation and crack length for concrete in the tensile zone of specimens subject to cyclic or sustained loadings. This conclusion is consistent with the results for previous studies on concrete fracture under compressive loading