Improving the interfacial strength of cement-polyacrylate grout and Ordovician limestone by graphene oxide

In coal mining on a high-pressure Ordovician limestone aquifer, grouting materials should have sufficient mechanical properties, particularly strong interfacial bonding performance to address stress concentration at the grout-limestone interface induced by rock stress disturbances during mining. In this study, graphene oxide (GO) was integrated into cement-polyacrylate composite grout to improve its interfacial bonding. First, four-point bending tests were conducted, and the Monte Carlo method combined with the simplex search algorithm was employed to determine the variations in shear cohesion and static friction parameters. The results reveal that GO can significantly increase both the tensile and shear cohesion of the grout-limestone interface, but minimally affects the interfacial friction coefficient. Second, nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) tests were performed. The results indicate that GO nanosheets result in a squamaceous microstructure of the grout consolidation mass, increasing the adhesion of the grout-limestone interface. Moreover, spiny Aft (ettringite) clusters can be induced in limestone fracture surfaces by GO, which could serve as anchors for limestone and grout consolidation mass.