A Framework for Assessing Alkali-Silica Reaction Risk in Aged Concrete Structures with Dissolving Aggregates

Assessing the risk of alkali-silica reaction (ASR) in large-scale concrete structures remains a critical challenge, particularly due to the scarcity of field-based data and the long timescales involved. This study proposes a methodology to evaluate ASR risk in concrete containing slowly dissolving aggregates. The approach consists of three steps: (i) identifying material properties such as the dissolution rate and chemical composition of the dissolved phases; (ii) determining the critical reaction degree at which amorphous silica forms, using equilibrium calculations based on GEMS thermodynamic simulations; and (iii) estimating the time required to reach this threshold by solving coupled equations for moisture transport and aggregate dissolution under real structural conditions. The methodology is demonstrated using in-situ data from the aged concrete walls of the Hamaoka nuclear power plant. Key factors that mitigate ASR risk are identified, including low dissolution rates, water depletion over time, and the presence of stabilizing species such as Al2O3 and MgO in the dissolved phase. While developed for a specific case, the proposed approach provides an adaptable framework for rational ASR risk evaluation in existing and future concrete structures.