Piezoelectricity of Portland cement hydrates cured under the influence of electric field

Improvements on functions of construction materials through modifications of material properties from the nano-scale are major concerns in modern civil buildings and infrastructures nowadays. Portland cement (PC) hydrates are the massively applied construction materials, whose new usages have caught the continuously growing interests of current researchers. Though mechanically very robust with feasibility for massive application, PC hydrates have relatively lower piezoelectricity, meaning that constructional mechanical characteristics, such as vibrations and crack locations, cannot be easily detected by the associated piezoelectric signals. The limited piezoelectricity and the difficulty of embedding sensor networks over the entire civil structures induce great technical hurdles for the functional building material applications. Here, we report a novel technique for improving the piezoelectricity of PC hydrates, by applying the polarization process throughout curing of hydrated PC under the influence of an electric field. This technique is based on regulating displacements and reorientations of molecules under the nano-scale interactions between different charged elements consisted in PC hydrates. Results from AFM investigation show the polarized PC hydrates have the relatively more aligned morphology orientation at nano-scale. PC hydrates cured under an electric field has shown with an improved sensitivity of the generated electrical potential under mechanical loading. Our results indicate that the polarized PC hydrates shows improved piezoelectric properties, enabling potential civil applications of the polarized PC hydrates such as structural health monitoring and mechanical energy recycling.