Effect of different mineral admixtures on the performance of OPC-SAC composite cement and analysis of the microscopic mechanism

Abstract

Ordinary Portland Cement-Sulfoaluminate Cement (OPC-SAC) composite cement combines the advantages of rapid hardening, early strength, and late-age strength stability, making it highly valuable for applications such as rapid repair and low-temperature construction. However, the binary composite system faces challenges including difficulties in controlling setting time, concentrated hydration heat, and uncoordinated late-age strength development [1, 3]. This paper systematically investigates the effects of two typical mineral admixtures, slag and silica fume, on the setting time, mechanical properties, and microstructure of OPC-SAC composite cement. The results show that slag prolongs setting time and reduces early strength, but its late-age pozzolanic reaction significantly improves durability; silica fume (at a dosage of 5%–8%) achieves the best strengthening effect through ultra-fine filling and high pozzolanic activity; the combined addition of slag and silica fume further optimizes pore structure and hydration product distribution, resulting in better overall performance than either single admixture [5, 9]. The mechanisms of mineral admixtures are unified into three levels: physical filling, chemical activity, and synergistic hydration. This paper provides a theoretical basis for the material design and engineering application of high-performance OPC-SAC composite cement.