Effects of TiO₂-Modified RGO Composites on the Mechanical and Durability Properties of Ordinary Portland Cement Mortars

Various applications of graphene-based materials in construction are an alternative to improve the properties of ordinary Portland cement (OPC)-based binders. This paper used a titanium dioxide in situ intercalation method to enhance the dispersibility of reduced graphene oxide (RGO) and then explored the effects of the incorporation of the obtained TiO2–RGO composite and RGO on the mechanical and durability-related properties of the OPC-based binders. Experimental results showed that TiO2 was successfully intercalated into the RGO layers and could improve the dispersion of RGO in water or synthesized OPC pore solution significantly, probably due to the greater spacing between each RGO layer. Besides, a proper amount of TiO2-modified RGO composite (0.03 wt % in this study) could elevate the mechanical strengths of OPC mortars, evidenced by a large increment of 24.78% and up to 34.94% in the compressive strength and flexural strength, respectively. The TiO2–RGO composite led to higher flexural-to-compressive strength ratios with the given dosages (0.01–0.05 wt %), implying a higher fractural toughness. Moreover, the resistance of the enhanced OPC-based mortars toward chloride attacks and freeze–thaw cycles was significantly improved. Based on the microstructural analyses including scanning electron microscopy and X-ray diffraction results, it is found that the modified RGO could to some extent promote the hydration of OPC and densify the overall microstructure of bulk specimens, leading to enhanced mechanical and durability properties. Compared to normal RGO, the TiO2–RGO composite was more effective in enhancing the properties of OPC mortars, due in large part to its better dispersion state.