Enhancement of mechanical and microstructural characteristics of magnesium oxychloride cement with metasteatite

Magnesium oxychloride cement (MOC) has recently garnered considerable research attention as an environmentally sustainable building material. Nevertheless, the mechanical characteristics of MOC have effectively hindered its extensive implementation in engineering structures owing to their inefficient water resistance. In this regard, this study investigates the novel application of steatite to MOC to augment the water resistance of paste. First, steatite was thermally processed to improve the reactivity of the particle and was introduced as a metasteatite with rich magnesium silicate. Furthermore, metasteatite is substituted for MgO in the MOC paste by varying the replacement level from 0 % to 25 % with an interval of 5 %. Thus, metasteatite's effect on MOC paste water resistance is investigated in terms of compressive strength, strength retention under water exposure, and microstructural characterization. Compressive strength results revealed that the influence of metasteatite deteriorated the strength of the matrix with an increased dosage of metasteatite. Moreover, the compressive strength of MOC paste susceptible to water enhanced the strength retention coefficient to 42.9% for MS10 compared to control specimens. FE-SEM analysis exhibits the formation of M-S-H gel that leads to dense microstructure and contributes to water resistance. In addition, the porosity of the paste is decreased owing to the reaction of Phase 5 with SiO2. The EDS analysis and mapping showed the occurrence of hydration products and the binding affinity between Mg and Si, which improved the continuity of microstructure and water resistance of MOC paste. Therefore, the optimum enhancement is observed for the MOC paste with 10% metasteatite, demonstrating its efficacy in bolstering water resistance. Finally, this investigation elucidates the feasibility of using metasteatite as a supplementary material for MgO in MOC for developing water resistant MOC.