Study of hydration process of ternesite clinker

Abstract

Currently ternesite, Ca5(SiO4)2SO4, is used in the cement production, is one of two key phases of calcium sulfoaluminate cement. Some investigators claim that this phase is nearly inert or very low reactive and it hydrates only after later age of hydration. In order to improve knowledge in this field, process of hydration of neat ternesite clinker under specific conditions of exposure was observed in this study. Ternesite was prepared by firing of raw meal consisting of high calcium limestone, microsilica and calcium sulfate hydrate. The resulting ternesite clinker was subsequently hydrated in four storage environments. Kinetics of hydration process was monitored in water and in environment of saturated carbonic acid, at two different temperatures of 5 and 40 °C. Mineralogical composition of hydrated samples was analyzed by X-Ray diffraction analysis (XRD) and by differential thermal analysis (DTA) in particular ages of hydration. Based on the results, it can be claimed that rate of decomposition of ternesite was related to conditions of storage. The rate of decomposition was significantly accelerated by the environment of carbonic acid and also by the elevated temperature. Presence of calcium carbonates in mineralogical forms of calcite, vaterite and aragonite, coupled with gypsum and thaumasite was identified.Currently ternesite, Ca5(SiO4)2SO4, is used in the cement production, is one of two key phases of calcium sulfoaluminate cement. Some investigators claim that this phase is nearly inert or very low reactive and it hydrates only after later age of hydration. In order to improve knowledge in this field, process of hydration of neat ternesite clinker under specific conditions of exposure was observed in this study. Ternesite was prepared by firing of raw meal consisting of high calcium limestone, microsilica and calcium sulfate hydrate. The resulting ternesite clinker was subsequently hydrated in four storage environments. Kinetics of hydration process was monitored in water and in environment of saturated carbonic acid, at two different temperatures of 5 and 40 °C. Mineralogical composition of hydrated samples was analyzed by X-Ray diffraction analysis (XRD) and by differential thermal analysis (DTA) in particular ages of hydration. Based on the results, it can be claimed that rate of decomposition of ternesite was related to conditions of storage. The rate of decomposition was significantly accelerated by the environment of carbonic acid and also by the elevated temperature. Presence of calcium carbonates in mineralogical forms of calcite, vaterite and aragonite, coupled with gypsum and thaumasite was identified.