Utilization of bio-waste eggshell powder as a potential filler material for cement: Analyses of zeta potential, hydration and sustainability

This study demonstrated the feasibility of utilizing bio-waste eggshell powder (ESP) as a potential filler material for cement. The collected eggshells were cleaned, membrane-removed, dried and ground into powder with Blaine fineness of 5650 cm(2)/g. To investigate the filler effect of ESP, different ESP amounts (0, 5%, 10% and 15% by weight) were adopted to replace cement in this study. Multiple experimental methods involving zeta potential test, isothermal calorimetry, compressive strength test, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to analyze the effect of ESP on cement paste. Results showed that zeta potential of ESP is controlled by the concentration-dependent adsorption of Ca2+, and is less affected by pH of the alkaline solution. Due to ESP's affinity to Ca2+, heterogeneous nucleation effect was facilitated and more hydrates were found to form and grow on the surface of ESP. Hence, cement hydration is increased. This founding was also supported by the decoupled cumulative hydration heat curves and the microscopic observations. Through XRD and FTIR analysis, it can be inferred that calcium carbonate in the ESP can react with the aluminum phase in the cement to produce monocarboaluminate. Eventually, sustainable assessment was conducted to analyze the carbon dioxide emission. It was concluded that in this study an ESP replacement level of around 5% provides the best performance and reduces environmental pollution.