A DISCRETE MODEL FOR ALKALI-SILICA-REACTION IN CONCRETE

The safety and durability of 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 the formation of gel which happens when water transmitted alkali come in contact with reactive silica in aggregates; the second is the imbibition of water into this formed basic gel and the consequent swelling, which, in turn, causes deterioration of concrete internal structure by a diffuse cracking. In this paper, the ASR effect on concrete deterioration is implemented within the framework of a mesoscale formulation, the Lattice Discrete Particle Model (LDPM), that simulates the heterogeneity of the concrete internal structure as well as the thermo-chemo-mechanical characteristics of the ASR reaction. 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 in free and confined expansion tests. This paper presents calibration and validation of the present model on the basis of experiments for unrestrained specimens under various axial loadings undergoing ASR expansion. The results show good agreement with the experimental data