Early-age performance and mechanism of magnesium oxychloride cement mortar mixed with highland barley straw ash

Current approaches for improving the water resistance of magnesium oxychloride cement (MOC) weaken its mechanical behaviour or pore structure. Herein, we enhanced the water resistance of MOC mortar (MOCM) without compromising its other performances by incorporating highland barley straw ash (HBSA). The early-age performance, microstructure, and pore characteristics of the HBSA-modified MOCM were analysed and the performance mechanism was determined. The softening coefficient of MOCM with 10% HBSA was higher than that of unmodified MOCM. The flexural and compressive strengths increased, and the physical and working performances improved. These improvements can be attributed to magnesium silicate hydrate gel formation, which blocked dangerous pores, stabilised the main mechanical phase, and optimised the pore distribution of MOCM.