A chemo-transport-mechanical model for concrete deterioration under sulfate attack and calcium leaching in saturated conditions

Calcium leaching is widely recognized as a key factor in the deterioration of concrete exposed to external sulfate attack under saturated conditions. However, its precise role in governing the coupled processes of transport, reaction, and damage has not been fully captured in current modeling approaches. To address this gap, we developed a chemo-transport-mechanical model that integrates calcium leaching, multi-ion transport, reaction kinetics, evolving diffusion properties, and the coupled chemical and mechanical damage within a unified framework. The model is validated against multiple experimental datasets and accurately reproduces observed ion concentration profiles, calcium consumption, and the spatial morphology of sulfate-induced damage. The results show that calcium leaching significantly affects sulfate-induced deterioration by increasing near-surface transport capacity and local deformability, thereby affecting damage initiation and local failure morphology. The model also captures the mitigating effect of ongoing hydration and the contribution of ion interaction to the development of late-stage damage. In addition, a parameter analysis is performed to evaluate the effects of boundary sulfate concentration, initial diffusion coefficient, and buffer factor on transport, reaction, and damage responses. The proposed model provides a mechanistic framework for analyzing the coupled processes that govern sulfate attack and for quantifying the role of calcium leaching in sulfate-induced damage.