## 5 Application of Self-Sensing Materials for
### Energy Harvesting  
In everyday life, energy is often wasted in various forms, which contradicts global sustainability goals. To mitigate this energy wastage, it is crucial to harness it either by converting it into electricity or by storing it for future use. Consequently, energy harvesting from road pavement emerges as a critical endeavor aimed at reducing the reliance on traditional energy sources such as oil and coal, while promoting sustainable energy practices through energy recycling. This approach leads to a reduction in carbon dioxide emissions and helps protect the environment by minimizing the footprint associated with cement usage. In this context, electricity harvested from road pavement through EH by converting other forms of energy, including thermal, mechanical, and solar energy, can serve as a power source for various applications such as traffic lights, signs, and charging devices like sensors installed along transportation infrastructures. This contributes significantly to addressing sustainability issues. Various energy harvester systems have been employed to generate electrical energy by harvesting and converting different types of energy available in the environment, as depicted in Figure 26.  
Figure 26 illustrates the utilization of various systems for harvesting ambient energies and converting them into electrical energy. For example, piezoelectric ceramic can be integrated into pavement layers to transform the cyclic loading induced by vehicles into electrical energy through positive piezoelectric effects, or piezoelectricity [284]. In a separate study, a self-powered electromagnetic energy harvester was successfully developed to capture mechanical energy generated by human footsteps in railway environments, generating electrical energy suitable for powering small electronic devices and sensors [285]. However, implementing external energy harvester systems by embedding them into cementitious composites can compromise the integrity of pavement layers, leading to a reduced service life span. To address this challenge, intrinsic EH can be achieved by incorporating conductive fillers into cementitious composites to convert mechanical energy into electrical energy based on the concept of piezoelectricity. Piezoelectricity refers to the ability of multifunctional cementitious composites containing conductive fillers to convert mechanical energy into electrical energy. [PERSON] et al. [286] introduced an innovative smart pavement for WIM applications, combining vibration-based energy harvesting with self-sensing cementitious composites. This smart pavement operates in two modes: charging mode,  
Figure 26: Energy harvesting systems for electrical power generation. utilizing traffic-induced vibrations for energy generation, and monitoring mode, activated during the passage of vehicles, as depicted in Figure 27.  
Thermal energy holds potential for storage and conversion into electrical energy. To harness thermal energy, three types of thermoelectric harvesting systems are available: liquid heat dissipation system, solid heat dissipation system, and thermoelectric cementitious composites, as depicted in Figure 26. Among these systems, the thermoelectric cementitious composite, operating on the principle of thermoelectricity, emerges as the most feasible option due to its high thermoelectric properties, ease of preparation, low cost, and high strength and durability [287]. The conversion of thermal energy to electrical energy is achieved through the Seebeck effects or pyroelectric effects of thermoelectric and pyroelectric cementitious composites, respectively. Thermoelectric cement-based materials are employed to convert thermal energy into electrical energy based on the temperature differences or gradients between the pavement surface and the underground.