Study on the Mechanical Properties, Tensile Performance, Hydration Heat, and Microstructure of VAE-Modified Rubber Mortar

This study builds on the practice of using waste rubber to improve the ductility of cement mortar and further explores the potential of vinyl acetate-ethylene (VAE) in enhancing the ductility of rubber cement mortar (RM). It systematically analyzes the effects of VAE on the workability, mechanical properties, crack resistance, and microstructure of RM. Additionally, isothermal calorimetry was employed to investigate the mechanism of VAE’s influence on cement hydration heat. The results show that VAE significantly improves the flexural strength, tensile strength, and ultimate tensile strain of RM, while reducing its compressive strength and tensile elastic modulus, thereby markedly enhancing its flexibility and ductility. At a VAE content of 4%, the fluidity, 28-day flexural strength, tensile strength, and ultimate tensile strain of RM reached 240 mm, 4.83 MPa, 1.92 MPa, and 233 × 10⁻⁶, respectively, representing increases of 16%, 18.97%, 11.63%, and 62.94% compared to ordinary RM. However, when the VAE content exceeded 4%, both flexural strength and tensile strength began to decrease. Furthermore, the incorporation of VAE induced the formation of flexible polymer films within the RM matrix but also increased the porosity of the cement matrix, extended the induction period of cement hydration, and reduced the rate and degree of hydration. These findings provide valuable data to support the development of high-ductility and high-crack-resistance concrete repair materials.