Augmenting Pozzolanic Stabilization Using Novel Microbial Carbonate Precipitation in a Soft Soil

Rao, SM and Sukumar, R (2022) Augmenting Pozzolanic Stabilization Using Novel Microbial Carbonate Precipitation in a Soft Soil. In: Journal of Hazardous, Toxic, and Radioactive Waste, 26 (2).

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Abstract

To reduce carbon dioxide (CO2) emissions from the use of cement and lime in civil engineering applications, microbially induced calcite precipitation (MICP) is one of the sustainable technologies being explored. MICP utilizes the metabolic activities of bacterial species to produce chemical environments that are conducive for calcite formation, which either plugs the pore spaces and/or bonds the soil particles together to reduce permeability and increase the strength and stiffness of soils. This study examined the reduction in use of chemical stabilizers by employing microbially induced carbonate cementation (MICC) along with magnesium oxide (MgO) stabilization. A soft soil unconfined compressive strength (UCS) = 20 kPa was prepared in the laboratory by mixing equal-weight proportions of kaolinite (50%) and sand (50%) at a high (21%) water content. Simultaneous pozzolanic and microbial activity was induced in the soft soil by the addition of MgO and cattle manure (CM). Degradation of the CM by native microbes produced CO2, which dissolved in the water to form bicarbonate ions (HCO 3 -). The alkaline pH generated by the addition of MgO transformed the HCO 3 - ions to carbonate ions, and these precipitated as calcium and magnesium carbonates. The alkaline pH (11.73 to 8.89) facilitated by the addition of MgO also induced pozzolanic reactions. The deposition of carbonate precipitates and pozzolanic reaction products at aggregate contacts transformed the soft soil into a hard (UCS > 400 kPa) soil. For every tonne of chemical required in the field for ground improvement, augmenting pozzolanic stabilization using the proposed MICC method has the potential to reduce CO2 emissions by 0.78 t. © 2021 American Society of Civil Engineers.

Item Type:	Journal Article
Publication:	Journal of Hazardous, Toxic, and Radioactive Waste
Publisher:	American Society of Civil Engineers (ASCE)
Additional Information:	The copyright for this article belongs to American Society of Civil Engineers (ASCE)
Keywords:	Alkalinity; Calcite; Calcium carbonate; Carbon dioxide; Carbonation; Cementing (shafts); Compressive strength; Fertilizers; Ions; Kaolinite; Lime; Magnesite; Manures; Mineralogy; Slags; Soils; Stabilization, Alkaline pH; Calcite precipitation; Carbonate cementation; Cattle manures; Microbial cementation; Pozzolanic; Pozzolanic reaction; Pozzolanic stabilization; Soft soils; Unconfined compressive strength, Magnesia
Department/Centre:	Division of Mechanical Sciences > Civil Engineering
Date Deposited:	07 Jan 2022 06:08
Last Modified:	07 Jan 2022 06:08
URI:	http://eprints.iisc.ac.in/id/eprint/70909

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