Chemical and mechanical damage in concrete due to swelling of alkali-silica gel.

In the present work, concrete affected by alkali-silica reaction (ASR) is represented as a two-phase material made of a solid skeleton and an expanding gel, which exerts a pressure capable of severely damaging concrete. As suggested by the experimental results, degradation due to ASR is considered to be localized around the reactive sites and it is described through an isotropic chemical damage variable. Another internal variable is introduced to describe the mechanical damage induced by the external loads. The chemical damage evolution depends on the reaction extent and it is calibrated using the value of the gel pressure, estimated by applying the electrical double-layer theory to the experimental values of the surface charge density obtained from ASR gel specimens. The model is then employed to simulate compression and flexure tests results reported in the literature.