Chloride diffusion in green mortars blended with recycled brick powder

This study focuses on green mortars blended with recycled brick powder (RBP). The effects of RBP dosage and water-to-binder (w/b) ratio on the chloride diffusion in green mortars have been investigated by testing free and total chloride content, chloride migration characteristics, water absorption performance, pore structure, hydration products, and phase distributions. Key findings demonstrate that incorporating 30 % RBP increases the maximum free chloride content by 10.7 % and chloride diffusion coefficient by 14.8 % at 360-d exposure, while w/b ratio optimization proves effective in counteracting RBP's adverse impacts on chloride diffusion. Furthermore, water absorption analysis confirms the significant role of capillary pores in chloride diffusion process. The addition of RBP elevates total porosity by 25.2–52.2 % relative to the control mortar B0. Notably, the chloride diffusion coefficient demonstrates a stronger linear relationship with transitional pore porosity (R² = 0.964) than with capillary pore porosity (R² = 0.853). Microstructural analysis reveals that RBP incorporation weakens interfacial transition zone (ITZ) integrity and results in more defects and pores. However, w/b ratio reduction enables microstructural densification, thereby effectively slowing down chloride diffusion in RBP-blended mortars. These findings provide critical insights for RBP utilization in sustainable building materials for chloride-rich environments.