Abstract: TiO₂ modified steel slag-based permeable concrete (TSSPC) was prepared with nano-TiO₂ incorporated as photocatalyst, steel slag and slag powder as binder, and large steel slag particle as aggregate. The effects of TiO₂ content on the compressive strength, water permeability and NO_x degradation performance of TSSPC were studied. In addition, combined with microscopic test and analysis methods such as XRD and SEM-EDX, the effect mechanism of TiO₂ on the mechanical properties, water permeability and photocatalytic performance of TSSPC was investigated, laying the foundation for the application of TiO₂ in permeable concrete. The results show that when the TiO₂ content is low, the “nucleation effect” of TiO₂ particles promotes the early hydration of binder materials. However, when TiO₂ content is high, TiO₂ particles tend to agglomerate, which is harmful to the mechanical properties of TSSPC. In addition, as the TiO₂ content increases, the connected porosity and water permeability coefficient of permeable concrete increase. Compared with the blank control group, the connected porosity and water permeability coefficient of TSSPC with a TiO₂ content of 5% (mass fraction, the same below) increase by 4.5 percentage points and 1.34 mm·s^-1, respectively. The NO_x degradation efficiency of TSSPC increases as the TiO₂ content (0%～5%) increases. However, due to the agglomeration phenomenon, when the TiO₂ content exceeds 3%, the effect of increasing the TiO₂ content on NO_x degradation efficiency decreases significantly.

Key words: steel slag, permeable concrete, TiO₂, mechanical property, NO_x degradation