Variation in the Composition of C‐S‐H Gel in Portland Cement Pastes Cured at Various Temperatures

Variation in the composition of C‐S‐H gel, the main hydration product of portland cement, cured at various temperatures, was studied using scanning electron microscopy with energy dispersive X‐ray spectroscopy. Samples of two cement pastes were cured isothermally under water at 10°, 30°, and 60°C for one year. For the inner‐product C‐S‐H gel of both cement pastes, increased curing temperature decreased the Ca/Si and Al/Ca ratios, but increased the S/Ca ratio. The Al/S and (Al + Fe)/S ratios decreased with increased curing temperature. Sulfur, probably in the form of sulfate ions, could be sorbed by the C‐S‐H gel at higher temperatures.