A linear elastic fracture mechanics-based study of the influence of aggregate size and gel mechanical properties during alkali-silica reaction

Abstract : We present a fracture mechanics model for Alkali-Silica Reaction for concretes made up of dense aggregates. Chemistry and diffusion (ions and gel) are not modelled. The focus is put on the mechanical consequences of the replacement of the outer layer of the aggregate by a less dense gel. A schematic cracking pattern is assumed: a ring-shaped crack appears in the cement paste surrounding the spherical aggregate depending on the pressure build-up. The onset of cracking is determined using an incremental energy criterion. The stored elastic energy and deformation of a given configuration are determined (using FEA) assuming that each aggregate behaves as if it was embedded in an infinite cement paste matrix. We note a very different behaviour of aggregates of different sizes. The macroscopic deformation is estimated by adding the aggregate's individual contributions. A rate of attack is identified that leads to recover the usual sigmoid ASR expansion curve.