A review on durability of nano-SiO2 and basalt fiber modified recycled aggregate concrete

To deal with the poor mechanical and durability of Recycled aggregate concrete (RAC), the effects of the addition of Nano-SiO2 (NS), Basalt fiber (BF), and composite addition of NS and BF are put forward. The addition of BF reduces the generation and development of early primary microcracks in RAC and prevents the generation and propagation of microcracks in the mortar. The addition of NS fills the microcracks in the concrete, which reduces the porosity, and facilitates the densification of the structure on the microscopic scale. By mixing NS and BF in experiments, NS can promote the adhesion between the fiber and matrix through the coupling effect, and effectively improve the fiber reinforcement effect. This review focuses on the effects of modified materials such as NS and BF on the interface structure, mechanical properties, carbonization resistance, freeze–thaw cycle resistance, salt erosion resistance, and high-temperature resistance of recycled concrete. The classical constitutive model, carbonization model and chloride ion diffusion model of concrete and recycled concrete are summarized. The application of current recycled concrete models is summarized, and feasible research directions are analyzed. This work also aims to understand the possible applications of nanomaterial, fiber, and fiber-nanomaterial modified recycled concrete in today's construction industry, so as to lay a theoretical foundation for the future application of recycled concrete in actual buildings and the durability evaluation of recycled concrete structures.