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Sci Rep. 2018 Feb 7;8(1):2565. doi: 10.1038/s41598-018-20921-0.

Fly ash incorporated with biocement to improve strength of expansive soil.

Author information

1
Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration (SHUES), School of Ecological and Environmental Sciences, East China Normal University, Shanghai, 200241, China.
2
Faculty of Engineering, Hokkaido University, Sapporo, 0608628, Japan.
3
Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration (SHUES), School of Ecological and Environmental Sciences, East China Normal University, Shanghai, 200241, China. varenyam@re.ecnu.edu.cn.
4
Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China. varenyam@re.ecnu.edu.cn.

Abstract

Microbially induced calcium carbonate precipitation (MICP) results in the formation of biocement (BC). This process, also known as biocementation, is recently widely used to improve the strength and durability of building materials including soils. In the present study, effectiveness of biocement as admixture with fly ash (FA) was investigated as first few studies to improve geotechnical properties of expansive soils. Biocement precipitated by Bacillus megaterium was blend with four formulations of fly ash at concentrations of 0, 10, 25 and 50%, namely 0% FABC, 10% FABC, 25% FABC, and 50% FABC, respectively. These formulations were separately added to expansive soils. Specimens with 25% FABC resulted in significant improvement in unconfined compressive strength of expansive soil that was more than two-times higher than control. Further, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analyses characterized microstructures of soil specimens, and depicted the process of MICP in improving strength of expansive soils. This research indicates that incorporation of biocement in fly ash is an effective means of increasing the strength of expansive soils.

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