Thermochromic coatings for self-sensing seawater-mixed cementitious sensors: towards multifunctional applications in concrete pavements

This work explores the integration of thermochromic materials and self-sensing cementitious sensors to advance the development of multifunctional pavement systems. By employing seawater as the mixing medium, the pore solution chemistry is deliberately modified through elevated ionic concentrations, thereby enabling new pathways for performance enhancement and sustainability in coastal infrastructure. The temperature regulation capability of three different thermochromic (TC) coatings was experimentally verified, achieving a maximum temperature reduction of approximately 20.5 °C. With the TC coating, the rate of water loss of pore solutions was measured in this study. To demonstrate the solar radiation reflection, transmittance, and intensity of light, UV–Vis Spectroscopy (UV), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy (RS) methodologies have been applied in this research. Due to the high absorbance of visible light and near-infrared (NIR) radiation, more energy can be absorbed by the cement surface, causing the temperature of pure cementitious specimens to rise rapidly. With a suitable range of water saturation in cementitious mixtures (95–100 %), the ion conduction of self-sensing cementitious sensors has been improved. An elevated ion concentration within the self-sensing sensors stabilises their piezoresistive response, yielding a more consistent relationship between cyclic pressure variations and corresponding resistance changes. In addition, the incorporation of thermochromic coatings enables effective temperature regulation of the composites under solar irradiation. The compressive strength of the samples was enhanced by the 65 °C heating. After 72 h of heating, the strength improved due to the acceleration of the hydration of cement particles. The combination of TC materials and self-sensing function improved the mechanical and piezoresistivity properties of the cementitious matrix. It proved the application potential of multifunctional cementitious mixtures in pavement.