Experimental determination of fracture parameters for crack propagation in hardening cement paste and mortar

Abstract

For all cement-based composite materials, hardening cement paste and mortar are the matrix materials. Their fracture properties are the basis for studying the fracture characteristic of cement-based composite materials. Therefore, three-point bending beams with three different sizes and three different strengths were tested to study the basic fracture properties of hardening cement paste and mortar. Corresponding values of load (P), crack mouth opening displacement (CMOD), and loading point displacement (δ) were simultaneously recorded. The initial cracking load P ini was determined by using resistance strain gauges making up a full-bridge circuit, and the crack propagation process was observed during the test. It was found that the fracture behavior of both hardening cement paste and mortar are not brittle fracture and show a steady crack propagation process before the peak load was reached. This means that the fracture behaviors of all cementitious composites are nonlinear, even hardening cement paste and mortar. Therefore, corresponding fracture parameters of the hardening cement paste and mortar were determined using the double-K fracture model. The results indicate that this model is applicable to hardening cement paste and mortar. In addition, according to the principle of work of fracture, fracture energy values of the tested hardening cement paste and mortar were calculated after taking into account the contribution of the tail of the P–δ curve on fracture energy.