Researchers from the Indian Institute of Technology (IIT) Mandy developed sustainable methods of soil stabilization using harmless bacteria called S. Pasteurii.
Bacteria hydrolyze urea to precipitate calcite, and the process does not involve hazardous chemicals, and natural resources can be used sustainably.
“Our research will be useful in developing microbial methods to improve soil shear strength on a field scale, to protect soil from erosion in hilly areas and during geocatastrophes,” said Dr. KV Udai, an associate professor at the School of Engineering. IIT.
“We are also working on the production of building materials from quarry waste using microbes,” he added.
The findings were published in the Journal of Geotechnical and Geo-environmental Engineering of the American Society of Civil Engineers (ASCE).
Soil stabilization is the process of giving the soil long-term strength artificially. Used when construction work is to be carried out on unstable soils or to protect the soil from erosion.
Traditionally, mechanical processes such as compression and chemical processes such as injection of chemical solutions into the soil are used to stabilize the soil.
In recent decades, environmentally friendly and sustainable soil stabilization techniques have been studied around the world – microbial-induced calcite precipitation (MICP). In this method, bacteria are used to produce calcium carbonate (calcite) in the pores of the soil, which cements the individual grains together, thereby increasing the strength of the soil / soil.
“Although there are studies around the world to develop MICP methods to stabilize the soil, the factors that affect the effectiveness of the process are still not fully understood,” said Uday.
The experimental setup of the team consisted of a column of sand, through which a mixture of bacteria and a cementitious solution containing urea, calcium chloride, nutrient broth, etc.
They used a method that involved using orthogonal arrays to organize the parameters that affect any process and the levels at which they should vary.
The researchers found that the amount of calcite formed is not as important as the size and location of the calcite grains that form in the pores during the process. Higher concentrations of cementitious mortar led to higher strength. Similarly, the increase in strength is influenced by the flow rate and the feed rate of the cementitious mortar. For these parameters, there was an optimal value that ensured maximum calcite deposition and thus a better increase in strength.
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