Optimised repairment properties of waterborne epoxy resin-cement composite material: An experimental and simulation study

The demand for high-performance repair materials has significantly increased owing to continuous infrastructure construction. However, current research on epoxy resin-cement mortar composites lacks a theoretical investigation of the proportion of epoxy resin and hardener necessary to prepare a composite material with optimal performance. Composite material preparation often relies on the results of empirical studies. To address this issue, this study used E44 (waterborne epoxy resin, WER) and D230 (hardener) as raw materials to theoretically determine the optimal ratio for preparing a composite material. The optimal ratio and content were validated considering various test parameters, such as workability, mechanical properties, self-developed shear bond strength, and impermeability performance. The results indicated that the epoxy resin-to-hardener ratio of the composite material should be 4:1, with a 30% content. In addition, the microstructure of the composite material was analysed using various test methods, including scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and mercury intrusion porosimetry (MIP), to investigate its influence on the interfacial transition zone (ITZ), composition, and pore structure. Furthermore, molecular dynamics simulations were performed to analyse the mechanical properties, adsorption energy, mean square displacement (MSD), and radius dispersion function (RDF) of the calcium silicate hydrate (C-S-H) and epoxy resin molecule (cross-linked structure) composite, explaining the effect of water molecules on the composite material from an atomic-scale perspective. By combining experimentation and simulation, this study proposes a computational ratio design method that could provide new insights into the research and development of WER-cement composites while creating a simple shear bond strength test method for repair materials.