Comparative study of the use of a quartz poor sand and a pure quartz sand for lime silica bricks and the kinetics of the hydrothermal hardening mechanism

Abstract

A series of test specimens were manufactured with a pure quartz sand (98% quartz) and quartz poor sand (50% quartz) under different autoclaving conditions. The amount of dissolved quartz is the same for both sand types and it is not the determining factor for the formation of calcium-silicate hydrates (CSH). Semicrystalline CSH-phases with a high Ca/Si-ratio are formed contemporaneously with 11 Å tobermorite during the initial stages of autoclaving. After all Ca(OH) 2 has been consumed the amount of 11 Å tobermorite increases, but the amount of the semicrystalline CSH-phases remains constant although the Ca/Si-ratio decreases. Under autoclaving conditions the hydrated silica species move toward the calcium source.