Sustainable resource utilization of surface-modified waste rubber powder and fly ash in cement-based materials for enhancing mechanical and durability performance

Although the incorporation of recycled rubber particles (RP) into cement-based materials offers substantial environmental significance, its adverse impact on material strength restricts its widespread application in practical engineering. To address this limitation, this study focuses on developing a sustainable cement-based materials with superior mechanical and durability properties. A green and efficient surface modification of recycled rubber powder using tannic acid (TA) and Fe(Ⅲ) was employed to produce modified rubber powder (RTF). The RTF demonstrated good hydrophilicity and surface activity, forming numerous active sites on its surface that significantly enhanced the interfacial bond between the rubber particles and the cement matrix. Further investigations revealed that incorporation the RTF into cement-based materials and partially substituting cement with fly ash (FA) effectively mitigated the detrimental effects of rubber particles on mechanical properties. When FA replacement was maintained at 20 %, it optimized the material’s microstructure while markedly enhancing the mechanical strength and durability of the rubber-cement composites through its filling and pozzolanic effects. Additionally, the heavy metal components in the FA were effectively immobilized and encapsulated within the matrix. DFT calculations indicate that RTF possesses outstanding adsorption capacity for heavy metal ions, and its incorporation into cement-based materials significantly enhances the immobilization of heavy metal ions within the matrix. Thus, the development of this rubber-cement composites effectively facilitates the recycling of waste tires and fly ash from coal fired power plant, contributing to the promotion of economically viable and low-carbon green buildings.