Effect of different calcination temperatures on clinker and hydration properties of solid waste-based calcium sulfoaluminate cement

Abstract

Calcium sulfoaluminate (CSA) cement is a promising alternative to Portland cement for reducing CO2 emissions in the cement industry. In this study, solid-waste-based calcium sulfoaluminate cement (SWCSA) was synthesized from steel slag, phosphogypsum, carbide slag, and bauxite. The effects of calcination temperature (1190–1310 °C) on the properties of the SWCSA clinker before and after hydration were studied, and the hydration process was simulated. The main mineral phases of the clinker were C4A3S̅, C2S, and C4AF. During calcination, Fe³⁺ could replace Al3+ in C4A3S̅ to generate C4A3S̅-c. As the calcination temperature increased, the extent of Fe3+ substitution increased, resulting in more C4A3S̅-c, and the amount of C4AF decreased. The element distribution diagram shows the distribution of minor elements in different phases (such as Ti, Mg and K). In terms of physical properties, the SWCSA setting time was prolonged upon increasing the calcination temperature. Furthermore, SWCSA with the best 28 d compressive strength (89.7 MPa) was obtained at a low calcination temperature (1190 °C). During hydration, the initial SWCSA hydration rate was fast, a large amount of ettringite was generated, and the cumulative hydration heat was low. The ratio of the amount of ye'elimite consumed to the initial amount was positively correlated with the compressive strength. In addition, a relationship was observed between AFt/AH3 and the compressive strength. Overall, SWCSA could be prepared at a lower calcination temperature than conventional CSA, offering a new avenue for recycling industrial solid waste via a less-energy-intensive process to obtain high-performance cementitious materials.