Influences of Calcium Sources and Type of Sand on Microbial Induced Carbonate Precipitation

Microbial Induced Calcite Precipitation (MICP) is commonly carried out by injecting chemical solutions (e.g., urea and calcium source) and bacteria (e.g., Sporosarcina pasteurii, B. megaterium) to the soil where treatment is required. This research aims to explore a new source of calcium chloride. The new source was the egg shells. It has been exploring the feasibility of using a new source of calcium in improving the engineering properties of two different types of fine sand (river and silica sands). Also, explore the impact of the sand type on the results of MICP. Set of laboratory tests were conducted, including calcium carbonate content, unconfined compressive strength, soil permeability and microscopy Investigation (SEM). The results indicate that use calcium chloride produced of egg shells has the same effectiveness of that of pure calcium chloride (analytical grade) in the cementation solution. This was demonstrated clearly by measure the Precipitated Calcium Carbonate content, where the same amount of Calcium Carbonate of both calcium sources was precipitated. But it was slightly higher in the river sand. In both cases (river and silica sands samples) the use of cementation solution contained calcium chloride made of egg shells has a significant effect on the permeability, but the effect was greater in the silica sand samples. Also, the effect of using cementation solution contained calcium chloride made of egg shells was exactly the same effect of using cementation solution contained analytical grade of calcium chloride. Finally, from SEM images, the calcium carbonate type in all cases was the calcite and the crystals sizes were relatively same. But the crystals type of calcite was changed according to the type of sand.