عنوان مقاله [English]
The mechanical properties of soils often do not fulfill human needs and expectations due to world population growth. Preventing damage to buildings and infrastructures requires basic measures or ongoing maintenance. Due to this issue, the construction of any structure needs to be on a good soil bed with favorable strength parameters. So far, some improvement methods have been studied and applied. In geotechnical engineering, finding a low-cost and environmentally friendly method is the most improvement challenging problem. Microbial geo-technology is a new branch of geotechnical engineering that deals with the applications of microbiological. Microbial sedimentation method (MICP) is a new and emerging method that uses microorganisms in the soil and chemical processes and thus the production of calcite sediment, has increased shear strength, hardness, reduced permeability. In this research, we focus on microbial catalysis of urea hydrolysis, which led to the deposition of calcium carbonate in sand using Bacillus Pasteurii. However, recent researches have not been addressed the effects of some parameters such as temperature and material concentration and various bacterial concentrations simultaneously. In this study, under different temperature conditions, different material concentrations and different bacterial concentrations (different ODs), the reaction completion time is obtained. Importantly experimental results show that OD changes have little effect on the result. Also, it demonstrates by increasing temperature, the amount of calcium carbonate deposits has also increased. Moreover, the higher the concentration of the material raises, the more amount of the calcium carbonate deposits and makes its formation faster. Also, samples with higher concentrations need more time to complete their reaction. High-temperature samples have a higher reaction rate from the earliest hours, but low-temperature samples require more time to precipitate calcium carbonate. Also, with the help of electron scanning, the effect of material concentration on the way of connection bonding and bonding between particles has been investigated.