Reduction of drying shrinkage via C-S-H densification: The role of early-age thermal history

This study investigated the influence of curing temperature on the drying shrinkage behavior of cement paste by analyzing calcium silicate hydrate (C-S-H) microstructural changes. Ordinary Portland cement specimens were cured at 20, 60, and 80 °C and exposed to varying relative humidity conditions (11–95% RH). The microstructural evolution of C-S-H was quantitatively assessed using 1 H NMR relaxometry and X-ray diffraction/Rietveld analysis. Through evaluation of C-S-H density and specific surface area, we established that the densification mechanism induced by high-temperature curing mirrors the C-S-H stacking process during drying. This was supported by a consistent linear correlation between specific surface area and bulk density across all curing temperatures, indicating that high-temperature-cured specimens had already undergone partial shrinkage during curing. These findings provide a mechanistic explanation for the reduced drying shrinkage susceptibility of cement-based materials cured at elevated temperatures.