The effect of the bond between the matrix and the aggregates on the cracking mechanism and fracture parameters of concrete

Abstract

The aggregate–matrix interface plays a leading role in the fracture mechanisms and in the fracture response of concrete. In this work, the influence of the interface on the macroscopic fracture parameters of concrete is investigated. Eleven concrete batches were cast with the same matrix. Different—crushed or rounded—aggregates from the same quarry were used, and several surface treatments were applied to improve or degrade the bond between the matrix and the particles. Fracture tests (three-point bending tests and Brazilian splitting tests) were carried out to determine the fracture energy and other relevant fracture parameters of the concrete batches. The modulus of elasticity and the compressive strength were obtained from uniaxial compression tests. The macroscopic fracture behaviour was modeled by the cohesive crack model with a bilinear softening curve. The results show that concretes with the same matrix and aggregates, and similar behaviour under uniaxial compression, can give very different fracture responses. The work shows how fracture behaviour is governed by the interfacial properties that are also behind the cracking mechanism.