Pore structure and chloride diffusivity of recycled aggregate concrete with nano-SiO2 and nano-TiO2

Nano-SiO2 and nano-TiO2 particles were mixed into recycled aggregate concrete (RAC) to enhance its properties. Mercury intrusion porosimetry was used to test the pore structure of the mortar in RAC, and the rapid chloride migration instrument was selected to investigate the diffusivity of RAC. It is found that the addition of nanoparticle refines the pore structure of RAC and enhances the resistance to chloride diffusivity of RAC. Furthermore, a three-phase composite sphere model for the matrix in RAC was proposed by considering the new mortar, old attached mortar and original aggregate as continuous phases. The three-phase model considering the microstructure of RAC was verified by experiment results, which can be applied to predict the chloride diffusivity of RAC with nanoparticles.