Application of waste eggshell as a source of calcium in bacterial bio-cementation to enhance the engineering characteristics of sand.

A technique to produce bio-cementation in sandy soil using the microbially induced calcium carbonate precipitation (MICP) process and calcium ions generated from eggshell is presented in this research. This research also focused on the application of S. pasteurii bacteria and L. fusiformis bacteria along with eggshell and calcium chloride cementing chemicals on the strength properties of sand. The experimental variables maintained in this research are bacteria type (S. pasteurii and L. fusiformis), cementing chemical type (eggshell and calcium chloride) and molarity of the cementing chemical (0.25, 0.50, 0.75 and 1.0). The engineering behaviour of bacteria treated sand was estimated by executing the unconfined compression test and permeability test in the laboratory. From the experimental findings, it is identified that the unconfined compressive strength of sand is enhanced and the value is in the range of 650 kPa. In addition to that, the permeability of sand is minimized in the order of two from 6.3 × E to 3.2 × E cm/s. The best improvement of Young's modulus and calcium carbonate content estimated in this research are 28.9 MPa and 17.9% when the sand is treated with S. pasteurii along 0.50 molarity of eggshell cementing chemical. The experimental findings are validated with the help of microstructural studies of scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX). This research showed that bio-cementation technology in the form of S. pasteurii and eggshell can be effectively adopted to enhance the engineering characteristics of sand.