Characterization of eggshell as limestone replacement and its influence on properties of modified cement

Food industry is known to produce, as a side product, huge amounts of eggshell. "Green chemistry" is searching for efficient ways of recycling antropogenic waste materials including also eggshell which is composed mainly from calcium carbonate and small amount of protein membrane. It is challenging to apply powdered chicken eggshell in cement industry and replace natural limestone. The impact of organic component of eggshell on modified cement was not studied yet. In the current report experimental studies were performed on the impact of the added powdered chicken eggshell instead of limestone on cement properties. 10, 20, and 30% of powdered eggshell (by weight) was added to Portland cement (CEM I 42.5 R) and the phase composition of limestone and eggshell was determined using an XRD technique and IR/Raman spectroscopy. Among the physical parameters analyzed were setting time, water demand of cement with mineral and bioinorganic admixtures and strength of mortar. The delayed hydration of cement paste and slightly lower strength parameters of mortar were observed in the presence of eggshell admixtures. This effect was explained by the presence of shell membrane in the admixture, composed from organic substances, including proteins. The results of our research can be useful in the field of materials science for creating ecologically improved building materials