Experimental analysis of Nano-SiO2 modified waterborne epoxy resin on the properties and microstructure of cement-based grouting materials

To improve the delayed effect of waterborne epoxy resin (WEP) on cement hydration and improve the early compressive strength of the composite paste. Nano-SiO2 (NS) modified WEP was prepared by in-situ polymerization and mixed into cement injection materials. The characteristics and microstructure of composite grouting materials were tested and analyzed, as well as the microscopic synergistic mechanism of each slurry component. The results demonstrated that increasing the NS concentration in WEP shortens the setting time of the composite slurry, and enhances slurry stability. When the content of NS in WEP was 4%, the compressive strength of specimens at 3 and 28 days increased by 33.71% and 39.03%, respectively. The stress-strain curve showed obvious stress step, besides, the stiffness and toughness were enhanced. The macroscopic failure form demonstrates the fine-grained rock's properties. The composite of NS with WEP promotes the production of C–S–H and C-A-S-H in cement and facilitates the fine crystallization of hydration products. The hydration crystals grow on the NS on the surface of WEP, thus, bridging the resin film and cement particles. In addition, the adsorption of Ca2+ by NS reduces the concentration of Ca2+ between interfaces and promotes the conversion of cementitious materials to hydration products.