Effect of Ferrite Phase Content on Hydration Reaction, Mechanical Properties, and Chloride-Binding Behavior of Ordinary Portland Cement

Ferrite phase (C4AF) minerals have a high resistance to chloride erosion, to gain a comprehensive understanding of the effect of C4AF mineral content on the hydration, mechanical properties, and chloride erosion resistance of ordinary portland cement (OPC). In this paper, pure C4AF minerals were prepared by the sintering method and added to the reference cement. The effects of different C4AF mineral admixtures (0%, 5%, 10%, 15%, and 20%) on the hydration, mechanical properties, chloride-binding properties, phase composition, pore structure, and microstructure of OPC were investigated by the isothermal calorimetry, X-ray diffraction (XRD), thermogravimetric differential thermogravimetric (TG/DTG), nitrogen adsorption, and scanning electron microscope (SEM-EDS). The results showed that with increasing C4AF mineral content, the early hydration of the reference cement was delayed, C-10% had the highest compressive strength at 28 and 56 days, and the chemical binding chloride ion ability increased by 86.8%, 46.1%, 105.1%, and 67.8%, respectively (Compared with C-0%). Friedel's salts could fill the voids and optimize the pore size distribution. This work elucidates the effect of C4AF content on the resistance of OPC to chloride salt erosion.