Effect of SiO2 coated leuco-dye based thermochromic pigment on the properties of Portland cement pastes

Abstract

This study investigates the influence of silica-coated leuco dye-based thermochromic pigment (STC) on the properties of white Portland cement pastes. The surficial-SiO2 coating around thermochromic pigment was generated using the Stober method, followed by assessing the properties of cement pastes prepared using coated thermochromic pigment. The properties such as standard consistency, setting time, temperature change due to hydration reaction, compressive strength, and color stability of cement pastes were assessed. Besides, analytical characterizations such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), and Energy dispersive X-ray (EDX) analyses were also performed to evaluate the degree of hydration in cement pastes. Analytical characterizations indicate that STC pigment promotes the degree of hydration of cement pastes and accelerates the setting process, which in turn leads to higher compressive strength. SEM analysis revealed the presence of well-intact STC pigment microcapsules, indicating the protective effect of SiO2 coating against a harsh cementitious environment. The colorimetric study results indicate that STC pigment retains its thermochromic response; it can withstand the alkaline cementitious environment, thereby protecting the leuco-dye mixtures from unwanted reactions when exposed to water and high temperature.