Does Calcium Leaching Increase Ductility of Cementitious Materials? Evidence from Direct Tensile Tests

Abstract

There is an ongoing debate in the chemomechanics community over whether calcium leaching leads to an increase in brittleness or ductility of cementitious materials. While other research teams have addressed this question by size-effect studies of the fracture process of partially degraded mortar beams, we address this question, in this paper, through original results from direct tensile tests on unleached and asymptotically leached cement pastes and mortars. The test device is described first, followed by the presentation and a discussion of deformation and strength results. It is shown that: (1) the tensile strength of pastes degrades much less than that of mortars; (2) the strength degradation in tension is much lower than the compressive strength degradation; and (3) the deformation at failure increases substantially due to chemical softening for both paste and mortar. Finally, by employing different ductility definitions, ranging from deformation to fracture properties, it is concluded that cement-based materials become more ductile in the course of chemical softening by calcium leaching. This finding is substantiated by an analysis of the micromechanical sources of the material failure mechanisms in cement-based materials.