ORIGINAL RESEARCH
Effect of Calcium Carbonate Deposition Induced
by Microorganisms and Plant Urease
on Sand Reinforcement
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1
School of Architecture and Planning, Yunnan University, Kunming 650500, China
2
Kunming Junlong Geotechnical Engineering CO., LTD, Kunming 650500, China
Submission date: 2023-07-30
Final revision date: 2023-08-22
Acceptance date: 2023-10-02
Online publication date: 2024-02-06
Publication date: 2024-03-18
Corresponding author
Yin-Lei Sun
School of Architecture and Planning, Yunnan University, China
Pol. J. Environ. Stud. 2024;33(3):2877-2889
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ABSTRACT
Soil solidification based on microbial mineralization is an environmentally friendly and sustainable
technology. This study utilized microbial induced calcium carbonate precipitation (MICP) and
urease-induced calcium carbonate precipitation (EICP) to solidify standard sand and silty sand. The
physical and mechanical properties of the soil samples before and after solidification were tested, and
the mechanisms of Sporosarcina pasteurii and urease-induced calcium carbonate solidification were
analyzed. The results showed that the compressive strength of standard sand after MICP and EICP
treatment was higher than that of silty sand. MICP treatment resulted in significantly higher compressive
strength compared to EICP treatment. MICP formed a "skeleton" with calcium carbonate, enhancing
shear strength and compressive strength but reducing permeability. EICP sealed the pores with calcium
carbonate crystals, improving impermeability. The mechanical properties of solidified silty sand were
worse due to particle shape and size, but it had better impermeability. During solidification, Sporosarcina
pasteurii mainly stayed at the contact points between sand particles, with extracellular polymeric
substances (EPS) containing negative ion groups. This enabled stronger adsorption capacity for calcium
ions and facilitated the formation of "nucleation sites". Larger-sized, higher-strength calcium carbonate
crystals were produced by MICP, aggregating at particle contact points. MICP treatment resulted in
a sand microstructure resembling a "skeleton", enhancing shear strength, compressive strength, and
permeability. In contrast, EICP directly used smaller-sized urease enzymes, which were more likely
to be free in the pores. This caused the catalytically precipitated calcium carbonate to deposit between
the pores, closing some of them and improving permeability. However, EICP often produced calcium
carbonate in a disordered aggregate form with smaller size and brittle texture. The solidified samples
were more brittle and prone to brittle failure. The research findings have certain guiding significance for
sand soil solidification engineering.