High-Strength Low-Carbon Cementitious Materials: CaO-CaSO4-CaCl2–Activated Slag at Ambient Temperature

The manufacturing process of portland cement (OPC) necessitates considerable natural resource consumption and emits a substantial amount of carbon dioxide, thereby exerting severe negative impacts on the environment. CaO-activated slag (CAS) binder, recognized as a low-carbon cementitious material, emerges as a promising substitute for OPC. However, the slow strength development of CAS hinders its widespread application in engineering practice. Therefore, this study aims to develop a high-strength, low-carbon cementitious material by adding chemical activators CaSO4 and CaCl2 to CAS and systematically investigate the effects of each component in the CaO─CaSO4─CaCl2 system on the compressive strength and microstructure of CAS. Results indicate that with a fixed CaO content of 7.5%, the optimal content of CaSO4 and CaCl2 stands at 7.5% and 5%, respectively. This optimization results in a notable enhancement, increasing the 28-day compressive strength by 170% to 74.1 MPa compared to the control sample. Furthermore, a direct correlation exists between the C─ S─ H gel content and the compressive strength, and the total content of ettringite and hydrocalumite demonstrates a linear relationship with compressive strength. This study highlights the potential of CAS as a viable alternative to OPC, providing valuable insights into the development of high-strength, low-carbon cementitious materials.