Hydration Products of Cement-silica Fume-quartz Powder Mixture under Different Curing Regimes

Composition, morphology, and structure of hydration products in hardened pastes of three kinds of blended cement (cement-silica fume, cement-quartz powder and cement-silica fume-quartz powder) hydrated under different curing regimes (standard curing, 90 degrees C steam curing, 200 degrees C and 250 degrees C autoclave curing) were investigated by X-ray diffraction and field emission scanning electron microscope equipped with EDAX system. Results showed that the main hydration products in three kinds of hardened pastes under standard curing condition are all C-S-H gels, CH, and AFt. Under 90 degrees C steam curing condition, the main hydration products of cement-silica fume and cement-silica fume-quartz powder are C-S-H gels, whereas those of cement- quartz powder are C-S-H and CH. Under 200 or 250 degrees C autoclave curing condition, no obvious crystallized CH phase is found in hardened pastes of three kinds of blended cement, and C-S-H gels are transformed into one or more crystalline phases such as tobermorite, jennite, and xonotlite. The chemical composition and morphology of these crystalline phases depend on the composition of mixture and autoclave temperature.