Lattice discrete particle modeling of alkali-silica-reaction effects to concrete structures

A large number of structures especially in high humidity environments are endangered by Alkali-Silica Reaction (ASR). ASR is characterized by two processes: the first is gel formation resulting from contact between alkali and reactive silica in aggregate particles; the second is water imbibition into the formed basic gel which leads to progressive swelling behavior. In turn, swelling causes deterioration of concrete internal structure inducing strength and stiffness loss. Many research efforts were directed towards the evaluation, modeling and treatment of these phenomena but a comprehensive computational model is still lacking. In this paper, the ASR effect is implemented within the framework of a mesoscale formulation, such as the one of the Lattice Discrete Particle Model (LDPM), which simulates concrete heterogeneous character. The proposed formulation allows a precise and unique modeling of ASR effect including non-uniform expansions, expansion transfer and heterogeneous cracking. The model can replicate ASR cracking behavior even in free expansion tests. This is a capability that cannot be obtained within classical homogeneous and isotropic continuum based models. In addition, it reproduces reactive aggregate size and distribution effects on the ASR expansion considering temperature and stress state effects. The present model was validated based on the simulation of experiments for free and laterally passively restrained specimens under free expansion. The results showed good agreement with the experimental data.