Environmentally-optimized photocatalytic NOX degradation in cement mortars utilizing recycled red brick and waste glass for sustainable management.

The rapid development of industrialization and urbanization generates huge amounts of solid waste and causes serious air pollution. Utilizing photocatalytic cementitious materials integrated with solid wastes presents an effective strategy for addressing urban air pollution and mitigating environmental impact. This study investigated the use of recycled red brick (RRB) and waste glass (WG) as aggregates in various proportions to replace conventional river sand, while employing nano-TiO2 as a photocatalytic agent at varying dosages to prepare photocatalytic cement mortar. The study evaluated the performance of the prepared samples in terms of compressive strength, hydration heat, water absorption, and NOx degradation. Advanced characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric (TG), and mercury intrusion porosimetry (MIP), were employed to analyze the microstructure of samples. The results indicated that the incorporation of 3 wt% TiO2 significantly accelerated cement hydration, resulting in the lowest water absorption rate (9.98%) and porosity (20.09%) as determined by MIP. SEM analysis revealed the incorporation of TiO2 within RRB matrix. Consequently, an increase in RRB content enhanced NOx degradation, achieving a peak reduction of 9% at an RRB: WG ratio of 75: 25. However, this ratio also led to a decrease in compressive strength (30.2 MPa) due to the increased porosity of RRB. The development of photocatalytic mortar combining effective NOx removal with satisfactory mechanical properties highlights a resource-efficient method to recycle waste red bricks and glass, addressing both environmental pollution and sustainable waste management, which will provide guidance for government and industry to support timely decision-making on sustainable environmental policies.