Effects of Polymer–Curing Agent Ratio on Rheological, Mechanical Properties and Chemical Characterization of Epoxy-Modified Cement Composite Grouting Materials

This study designs and uses water-borne epoxy resin (WBER) and curing agent (CA) to modify traditional cement-based grouting for tunnels. The purpose of this paper is to analyze the rheological and mechanical properties of composite grouting with different ratios of WBER and CA and analyze the modification mechanism by means of chemical characterization to explore the feasibility of WBER as a high-performance modifier for tunnel construction. The composite grouting is prepared by mixing cement paste with polymer emulsion. A series of experiments was carried out to investigate the effects of WBER and CA, including the slump test, viscosity, rheological curve, setting time, bleeding rate, grain size distribution, zeta potential, compressive and splitting tensile strength, X-ray diffraction(XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), on the composite grout. The results show that WBER improves grout fluidity, which decreases in combination with CA, while also reducing the average particle size of the composite grout for a more rational size distribution. Optimal uniaxial (38.9%) and splitting tensile strength (48.7%) of the grout are achieved with a WBER to CA mass ratio of 2:1. WBER accelerates cement hydration, with the modification centered on the reaction between free Ca²⁺ and polymer-OH, significantly enhancing the strength, fluidity, and stability of the polymer-modified composite grout compared to traditional cement-based grouting.