An Experimental Study of Oyster Shell as Calcium Source for Microbial Solidification

Microbial-induced calcium carbonate precipitation (MICP) is an emerging environmentally friendly foundation reinforcement technology that requires the consumption of a large number of chemical analysis-grade reagents, such as urea, calcium salts, etc., which have certain adverse effects on the environment. Based on the idea of utilizing waste resources, oyster shells from kitchen waste were selected as calcium sources of MICP solidified sandy soil and compared with chemical calcium sources such as calcium nitrate and calcium chloride. Through unconfined compressive strength test, permeability test, calcium carbonate content test, dry density test and scanning electron microscopy (SEM), the feasibility of oyster shells as calcium source of MICP solidified sand was discussed. The experimental results show that the MICP solidified sand column with raw clam shells as the calcium source has the largest average pore size, but the lowest apparent porosity, and the physical strength indexes such as unconfined compressive strength, permeability coefficient, calcium carbonate content and dry density are all higher than chemical calcium. SEM test results show that different calcium source solidified sand column sand particles have calcium carbonate precipitation on the surface, and the calcium carbonate precipitated crystal obtained from the raw clam shell calcium source has a relatively fine surface with a small pore shape; and nitric acid obtained from calcium carbonate precipitate is in a cluster of polygonal angles between the spherical and prismatic bodies; and calcium chloride obtained from calcium carbonate precipitate exhibits clusters in which the particles are interlaced with each other.