Accelerating effects of colloidal nano-silica for beneficial calcium–silicate–hydrate formation in cement

The hydration process of Ca3SiO5 (C3S) cement is investigated, and accelerating effects of adding colloidal silica (CS) are established. CS accelerates dissolution of the C3S phase, and renders a more rapid formation of the calcium–silicate–hydrate (C–S–H) binding phase. The role of water is demonstrated. Water evaporation correlates with the appearance of a sharp IR band at 3650 cm−1 signifying non-hydrogen bonded OH groups. Incomplete hydration results in Ca(OH)2 precipitation. Suppression of water evaporation causes the 3650 cm−1 band to vanish. The Ca2+ ions become incorporated in the C–S–H network, the formation of which is accelerated by CS.