Mechanism of Fracture of Concrete

Abstract

H. J. COWAN'S¹ hypotheses for the fracture of concrete are very similar to those already proposed by Prof. M. Roš². Such hypotheses usually rely mainly on the observations of failing loads of specimens for their justification, and proceed from the assumption that concrete may be regarded as a homogeneous isotropic material. In the Division of Building Research of the Commonwealth Scientific and Industrial Research Organization, an extensive experimental study has been made of the strain distribution in various types of concrete specimen, using one concrete mix throughout. The results suggest that in all specimens the first failures occur when the tensile strain is about 10⁻⁴. In compression tests of cylinders, this strain occurs when the load is about fifty per cent of the ultimate, tand in unreinforced flexural specimens at about ninety per cent of the ultimate. The measurements made here also show how widely the concrete strains may vary in a region in which they are theoretically uniform.