Multi-level assessment of TiO 2 /graphene-modified molybdenum slag/bauxite-based alkali-activated composites mechanical, microstructural, and self-cleaning performances

The objectives of this study were to understand the mechanical, microstructure, and self-cleaning performance of alkali-activated composites (AACs) based on molybdenum (Mo)-slag/bauxite (Ba)-powder containing 1.5% and 3% TiO 2 and TiO 2 coated with graphene oxide (GO) nanoparticles. Mechanical properties were assessed through compressive and flexural strength tests. The MIP to check porosity, XRD, FTIR, TGA/DTG to detect new and remnant phases, FESEM/EDS to check morphology and composition of the matrix and the self-cleaning performance was evaluated using methylene blue (MB) dye degradation and surface wettability assessments. Results showed that AACs with 15% bauxite performed best mechanically, while 35% bauxite composites were weaker. Nano-TiO2 marginally improved 7-day strength, whereas nano-TiO 2 -GO significantly increased strength at both 7 and 28 days. FESEM images revealed a distinctive wrinkled morphology in TiO 2 -GO composites, illustrating interlocking interactions between nano-TiO 2 -GO and the gel binding matrix. In the BET test results, the specific surface area of synthesized TiO 2 -GO was about 25% higher than TiO 2. Also, MIP results demonstrated a significant refinement in AACs containing TiO 2 -GO, indicating increased polymerization products. According to TGA/DTG results, the highest weight loss in the first interval between 25–200 °C is related to the mixture containing 15% Ba-powder and 3% TiO 2 -GO. Additionally, the composition comprising 35% Ba and 3% TiO 2 -GO exhibited the highest level of MB dye degradation, reduced water contact angle following UV exposure, and superior self-cleaning performance. Finally, based on SHapley Additive exPlanation (SHAP) and P-value analyses, the specimen age, the nano-TiO 2 -GO dosage, and the Ba replacement ratio were recognized as the most crucial parameters affecting the mechanical performance of the synthesized AACs, respectively.