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 po rtland cement, cured at various temperatures, was studied using scanning el ectron microscopy with energy dispersive X-ray spectroscopy. Samples of two cement pastes were cured isothermally under water at 10 degrees, 30 degree s, and 60 degrees C for one year. For the inner-product C-S-H gel of both c ement pastes, increased curing temperature decreased the Ca/Si and Al/Ca ra tios, but increased the S/Ca ratio. The Al/S and (Al + Fe)/S ratios decreas ed with increased curing temperature. Sulfur, probably in the form of sulfa te ions, could be sorbed by the C-S-H gel at higher temperatures.