Fully coupled physicochemical-mechanical modeling of sulfate attack-induced expansion in cement-based materials

Sulfate attack-induced expansion in cementitious materials is a complex physicochemical-mechanical phenomenon influenced by numerous factors. To deepen our understanding of this deterioration process, multiphysics modeling and simulations that can consider various material, structural, environmental conditions are invaluable. This study presents a fully coupled physicochemical-mechanical model to simulate sulfate attack-induced expansion in cement-based materials. The proposed model integrates multiscale models of cement hydration, pore structure formation, moisture and ion transport within the cement matrix, and the geochemical code PHREEQC to compute chemical equilibrium in pore solutions. The model assumes that secondary formation of both ettringite and gypsum contributes to expansion. The mechanical response is simulated using elasto-plastic and damaging constitutive models for compression, tension, and shear in cement-based materials. In cases of cracking, the reactive transport model adjusts the mass-transfer properties of the material accordingly. Model validation against experimental data demonstrated that the proposed model reasonably predicts expansion trends under various conditions. Furthermore, the simulations suggested that sulfate attack-induced expansion is primarily driven by secondary ettringite formation, but also quantitatively showed the significant contribution of secondary gypsum under high sulfate ion concentrations. Sensitivity analysis also revealed the significant impact of mineral compositions of cement, particularly tricalcium aluminate (C₃A) and tricalcium silicate (C₃S) contents and the initial amount of gypsum in cement. This study provides a baseline for further investigations aimed to link sulfate attack-induced material deterioration with structural degradation, facilitating the assessment of structural integrity and remaining service life of deteriorated concrete structures.