Reactive transport modeling of acetic acid-induced degradation in portland cement paste

A reactive transport model was employed to investigate the influence of multiple hydrate phases during acetic acid attack on Portland cement paste. The simulation accounted for the dissolution of primary cement hydrates like Ettringite, Portlandite and C-S-H, along with the formation of silica gel products impacting diffusivity. The simulations primarily utilized independent material parameters, though the effective specific surface area of C-S-H phases required adjustment, indicating that only a small fraction is active in bulk paste compared to experimental values obtained from powders. Experiments involved exposing hardened cement paste samples to acetic acid (pH = 3) for durations ranging from 35 to 84 days. The model predicted changes in mineral assemblages, porosity, and pore solution chemistry versus degradation depth and time. Comparison of calculated Ca and Si-contents with experimentally obtained values from $\mu$XRF analysis demonstrated good agreement of within 6% error, highlighting the importance of considering multiple minerals.