Feasibility study of enhancing enzyme-induced carbonate precipitation with eggshell waste for sand solidification

Utilizing Enzyme-Induced Calcium Carbonate Precipitation (EICP) reinforcement technology has emerged as an innovative approach for soil improvement. In this study, kitchen waste eggshell powder was used as an additive material for EICP. The high external surface area and affinity for calcium ions of eggshell powder, which render it a suitable nucleation site for calcium carbonate precipitation. Experimental results demonstrate that the incorporation of eggshell powder, by increasing the number of nucleation sites and promoting calcium carbonate precipitation, reduces the inhibition of enzyme products, modulates the precipitation pattern of calcium carbonate, improves particle size distribution, and consequently significantly enhances the unconfined compressive strength of the samples. Furthermore, a neutral pH is achieved within the reaction system without the addition of any acid, thus preventing significant ammonia emissions. This underscores the potential of kitchen waste eggshells for recycling in biocement applications.