Analytical Study of Microstructural Effects on the Degradation of Elastic Properties in Cement Paste

This study presents an analytical and multiscale investigation of the degradation of elastic properties in ordinary Portland cement (OPC) paste subjected to calcium leaching. Eight representative microstructures and three homogenization schemes (Mori–Tanaka, Hashin–Shtrikman, and Voigt) were evaluated to determine the most suitable configuration for predicting stiffness evolution. Model validation against benchmark experimental data at 14 and 56 days demonstrated good agreement, with prediction errors within 10%. Simulation results reveal that progressive decalcification leads to significant reductions in both bulk and shear moduli, with the calcium hydroxide (CH) phase being the most sensitive, followed by low-density (LD) and high-density (HD) calcium silicate hydrate (CSH). The overall stiffness loss increases with the water-to-cement ratio (w/c), exceeding 90% at w/c=0.5 under complete decalcification. A sensitivity analysis further shows that the rate of modulus degradation decreases with increasing w/c, reflecting a mechanical normalization effect rather than improved chemical stability. These findings highlight the dominant role of calcium preservation in maintaining mechanical integrity and provide a robust theoretical framework for predicting the chemo-mechanical degradation and long-term durability of cement-based materials in aggressive environments.