Data-integrated numerical modeling of Alkali–Aggregate reaction and mechanical degradation in concrete gravity dams

The long-term performance of concrete gravity dams can be significantly affected by Alkali–Aggregate Reaction (AAR), a progressive deterioration mechanism associated with expansion, microcracking and degradation of material properties. Although AAR has been extensively investigated at the material scale, approaches capable of representing its spatial and temporal development over an entire dam remain limited. This study presents a sequentially coupled computational framework for evaluating AAR progression and the associated mechanical degradation in concrete gravity dams. Implemented in FEniCSx, the framework integrates transient thermal and hygric analyses, mechanical stress fields, AAR reaction kinetics and degradation of elastic modulus and tensile strength. The numerical implementation was supported by verification and mesh-convergence studies. The framework was applied to a representative gravity-dam section from January 1986 to December 1996 using time-varying environmental and reservoir-operating conditions. The results show that AAR develops progressively but non-uniformly, with greater progression generally occurring in the upper and interior regions and comparatively lower values near the foundation and exposed downstream boundary. The processed, history-dependent AAR variable increased in area-weighted mean from approximately 0.002 to 0.290 over the analysis period. Correspondingly, the mean elastic modulus decreased from about 20.99 to 17.36 GPa, while the mean tensile strength decreased from approximately 2.50 to 2.00 MPa, representing reductions of about 17% and 20%, respectively. The framework therefore provides a spatially resolved means of examining how coupled environmental and mechanical conditions influence AAR progression and material degradation, with potential application to monitoring, inspection planning and long-term dam assessment.