Study on micro-mechanical properties of EVA modified rubber-cementitious materials based on molecular dynamics simulation

As a green concrete material, rubber granules have the potential to significantly reduce the environmental pollution caused by discarded tires. However, the compatibility between cementitious surfaces and rubber particles is limited, leading to a reduction in the mechanical properties of concrete. The purpose of this study is to enhance the mechanical characteristics of rubber concrete mortar by using the ethylene-vinyl acetate copolymer (EVA). The results show that the compressive and flexural strengths of cement mortar are reduced when EVA is added to macro-mechanical studies. However, increasing the amount of EVA will gradually lead to an improvement in the flexural strength, shear strength, and toughness index of the cement mortar. Microscopic experiments, such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), demonstrate that the addition of EVA retards the hydration process of cement. Furthermore, as the amount of EVA increases, a membrane-like structure is formed on the surface of the cementitious matrix, enhancing the overall bond strength of the concrete. Molecular dynamics simulation results indicate that EVA primarily diminishes the interfacial effect by augmenting the inter-interfacial binding capacity through Ca-O ionic bonding and hydrogen bonding.