Strength and Fracture Properties of Aggregates

Abstract

This paper presents a study of the mechanical and fracture properties of various types of aggregates used in asphalt mixtures. Three types of rocks namely, greywacke, granite and limestone, were evaluated. Compressive and tensile characteristics of the rocks were determined by means of uniaxial compressive and indirect tensile tests, respectively. Resistance to fracture was determined by means of semi-circular bending tests. Results showed that the greywacke had the highest strength both in compression and in tension. The granite, on the other hand, had high compressive strength but the tensile strength was relatively low. Compressive tests also showed that the response of rock specimens under loading was linear elastic. It was found that the compressive elastic modulus of the limestone was the highest followed by the greywacke and the granite. Similarly, indirect tensile tests indicated that the response of the greywacke and the limestone rocks was linear elastic whereas that of the granite was non-linear. Furthermore, tensile elastic modulus values of the greywacke and the limestone were similar and about five times higher than that of the granite. As regards fracture, load-deflection curves for semi-circular bending tests indicated linear elastic behaviour of the three types of rocks. Thus, linear elastic fracture mechanics theory was applied to determine fracture toughness. Results showed that the greywacke had the highest resistance to fracture.