Thermoelectric and electrothermal cementitious composites enabled by chemically bonded graphene–nanoTiO2 composites

With the growing demand for smart infrastructure and intelligent concrete materials, imparting cementitious composites with self-powering and active heating capabilities has attracted increasing attention. In this study, a graphene-doped titanium dioxide (G–TiO 2 ) composite was incorporated into cementitious composites to develop continuous conductive networks, thereby enhancing both thermoelectric and electrothermal performance while maintaining satisfactory workability and mechanical strength. The results show that increasing the conductive nanofiller content and prolonging the dispersion time led to a moderate reduction in paste flowability; however, the flow diameter remained within 200–230 mm, indicating a good workability. When the conductive nanofiller content was 1.0% and well dispersed, the compressive strength increases from 45.7 MPa to 48.2 MPa. At higher nanofiller contents of 3% and 5%, the compressive strength became lower than that of the control specimen. In terms of thermoelectric performance, the cementitious composite generated a stable voltage of approximately 90 mV under a temperature difference of 43 °C. Even 20 min after the temperature gradient disappeared, a residual voltage of approximately 50 mV could still be observed. Regarding electrothermal performance, under humid conditions and an applied voltage of 48 V, the surface temperatures of the cementitious composite could be stably maintained at approximately 49.8 °C, with an energy conversion efficiency of 78.8%. The graphene sheets provided a continuous conductive backbone, while TiO 2 nanoparticles reinforced interlayer connections and reduced the overall electrical resistance. Meanwhile, the heterogeneous interfaces formed between graphene and TiO 2 exerted a selective effect on charge-carrier transport, increasing the average carrier energy and enhancing the thermoelectric response of the cementitious composites. Through the dual regulation of nanofiller content and dispersion state, the distribution of the G–TiO 2 within the cementitious matrix was further optimized, enabling simultaneous enhancement of thermoelectric power generation and electrothermal heating. The findings provide an insight into innovative applications such as de-icing in pavements and early fire-warning systems in buildings.