Strength reduction and length changes in concrete and mortar on water and methanol sorption

Abstract

The reduction in strength of concrete and mortar caused by sorption has been related to the lowering of the surface energy. Measurements of surface energy are obtained from dimensional changes on sorption and the use of Griffith's equation. However, previous work has been based on compressive strength which is not in accordance with the original concepts of Griffith's equation. In this paper, both tensile and compressive strength are used to determine surface energy values on sorption with water and methanol. It is proposed that values of surface energy determined on the basis of water sorption and compressive strength reduction are an upper bound to the “true value”. Methanol sorption because it produces no interlayer rehydration, provides a better estimate. Finally, it is shown that the reduction in the tensile strength of concrete on water sorption is due to a significant change in the surface energy.