Investigation of the Bonding Performance and Microstructure of MOC Binders for SiO2 as Rock-like Composites

The heterogeneity of natural rocks complicates the study of carbon sequestration within these materials and raises concerns about the reproducibility of experimental results. Consequently, identifying appropriate rock-like materials has become critical. This research examined the impact of various factors—humidity, binder content, curing period, and cold pressure—on the bond strength of magnesium oxychloride cement (MOC) through orthogonal testing. The tests utilized a molar ratio of MgO to MgCl2-6H2O to H2O of 7:1:18. Both X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to analyze the hydration reactions of MOC and to explore the correlation between the microstructure of the SiO2-MgO-MgCl2 system and its bonding characteristics. The findings indicated that a 5% relative humidity enhances the 7-day bond strength of MOC. Moreover, increasing the curing humidity to 60% relative humidity supports the ongoing hydration of the strength-contributing phases. A binder content ranging from 15% to 25% proved optimal, yielding samples with superior strength and stiffness. While cold pressing initially enhances the bonding properties of MOC, solution loss during the process adversely affects its long-term bonding characteristics. From a mechanical standpoint, the silica-magnesium oxide-magnesium chloride system demonstrates exceptional early strength and resilience, positioning it as a promising rock-like material system.