Experimental Study of Bacillus Megaterium and Bacillus Cereus on Strength Characteristics of Sand and Soil Mixture
Soil bacteria such as Bacillus cereus, Bacillus megaterium, Bacillus subtilis and Sporosarcina pasteurii can hydrolyze urea by urease enzyme to produce ammonia as well as carbonate ions. In the presence of calcium ions it will precipitate calcium carbonate which is also known as natural cement. This Microbial induced calcite precipitation (MICP) technique is environmental friendly and has a wide range of applications. In this study two strains of bacteria i.e. Bacillus megaterium and Bacillus cereus are used. Locally available soil is mixed with natural sand in different percentages by volume (0%, 25%, 50%, 75%). These are casted in mould of 10cm x 5cm x 5cm and are treated with bacteria in nutrient broth with 2% urea in it. Later it is again treated with solidifying solution (urea-calcium chloride 1.5mol/L). This cycle is repeated for 7days. Then unconfined compressive strength & SEM are conducted. The strength of the sample containing Bacillus megaterium is higher than that of sample containing Bacillus cereus. As the percentage of soil increases the compressive strength also increases. This is due to the increase in particle to particle interaction. SEM shows the deposition of calcite in the sample.
Keywords - Bacillus Megaterium, Bacillus Cereus, Bio-brick, Compression Strength, Scanning Electron Microscopy.