Ceramics-Silikáty 34, (2) 131 - 141 (1990)

Condensed silica fume, used as concrete and cement additive material, reacts with Ca(OH), liberated in the course of Portland cement hydration, forming supplementary calcium silicate hydrates. Infrared spectroscopy, X-ray diffraction, thermal analysis and scanning electron microscopy were used to study the kinetics of pozzolanic reaction in silica fume-modified cement pastes cured under normal conditions. A characteristic absorption band at 1120 cm⁻¹ was observed in the IR spectrum of silica fume, which was composed mainly of SiO₃. Infrared spectroscopy as the only of the methods tested enables to follow the role of silica fume in the process of Portland cement hydration not only through the binding of Ca(OH)₂ , but also directly, i.e. from the consumption of silica from added silica fume at some stage of the reaction. A high pozzolanic activity of silica fume from ferrosilicon production was proved by all the methods used.