Ternesite-calcium sulfoaluminate cement: Preparation and hydration

Abstract

Ternesite-calcium sulfoaluminate (TCSA) cement exhibits excellent properties. However, it is hard for sulfoaluminate (C4A3$) and ternesite (C5S2$) to coexist in the clinker. In this study, phosphogypsum (PG) was used for producing TCSA cement clinker. The joint effects of P2O5 and F in PG as well as the CaSO4 content in raw meals on the coexistence of C4A3$ and C5S2$ were investigated. The grindability and morphology of TCSA cement clinker were characterized. By the comparison with belite-calcium sulfoaluminate (BCSA) cement, the hydration and properties of TCSA cement were investigated. Results shows that the coexistence of C4A3$ and C5S2$ is achieved under the joint effects of P2O5, F and a sufficient amount of CaSO4. TCSA cement clinker could be prepared at 1125–1200 °C for 15–30 min and the clinker exhibits a good grindability. Ternesite in TCSA cement clinker presents a rodlike or granular shape Compared with BCSA cement, due to higher hydration rate of C4A3$, the setting time of TCSA cement is shorter and early compressive strength is higher. Due to the hydration of C5S2$, TCSA cement exhibits a higher late age compressive strength.