A Crack Approaching the Edge of the Aggregate

Abstract

In this work, the influence of a crack approaching the edge of the amphibolite inclusion on fracture behaviour of cement composite is investigated. Specimens of the nominal dimensions 40 × 40 × 160 mm with polygonal amphibolite inclusion of 8 × 8 × 40 mm were provided with an initial central edge notch with a depth 12 mm, which was made by diamond blade saw. To determine the influence of polygonal cavity on fracture behaviour, fracture tests were conducted via three-point bending. The aim of this work is to analyse the behaviour of such specimen by means of finite element method (FEM) principles in Ansys, Inc. software. For this reason, a simplified 2D model was created for plane strain conditions. The crack propagation assessment was based on generalized fracture mechanics approaches using a criterion of an average value of tangential stress determined in dependence on the polar angle coordinate θ. The results of numerical analysis indicate that the debonding in the close vicinity of the bottom edge of the inclusion occurred. In other words, imperfect compaction of the fresh mixture and a smooth surface of the aggregate leaded to the formation of poor interface with lower mechanical-fracture parameters. Further, cutting of the initial notch by a diamond saw blade results in a precrack length greater than expected.