Effect of ethylene vinyl acetate redispersible polymer powder on the mechanical properties and water resistance of magnesium potassium phosphate cement

Magnesium phosphate cement, which is widely used as a rapid repair cementitious material, has limitations in terms of water resistance. Extensive studies have confirmed that adding redispersible polymer powder (RPP) to ordinary Portland cement enhances its water resistance. This study thus investigates the effect of ethylene vinyl acetate-based RPP on the mechanical properties and water stability of magnesium potassium phosphate cement (MKPC). The findings indicate that incorporating 0.5% RPP in MKPC achieves the highest flexural and compressive strengths compared to samples without RPP. The addition of 0.5% RPP also results in the greatest water stability and lowest water absorption. Thermogravimetric and X-ray diffraction analysis reveal that 0.5% RPP promotes the formation of hydration products. As shown in scanning electron microscopy results, MKPC with 0.5% RPP exhibits larger, smoother and more fully formed hydration products. The RPP adsorbs on the magnesium oxide surface, reducing flowability and delaying the hydration process. In later stages, the film-forming effect of RPP establishes a spatial network structure with hydration products, thereby enhancing the water resistance of MKPC.