Improvement of strength behaviour of residual soil via enzymatically induced calcite precipitation

Zango, Muttaqa Uba and Kassim, Khairul Anuar and Ahmad, Kamarudin and Muhammed, Abubakar Sadiq (2021) Improvement of strength behaviour of residual soil via enzymatically induced calcite precipitation. International Journal of Geosynthetics and Ground Engineering, 7 (78). ISSN 2199-9260

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Enzymatic induced calcium carbonate precipitation (EICP) is a biomediated soil improvement technique that utilizes free enzyme to produce a biocement material. This research investigated by performing test tube test the effect of varying urea-CaCl2 concentrations from 0.25 to 1.25 M on the mass and efficiency of calcium carbonate precipitation formed via EICP technique. The study also evaluated, by conducting UCS test, the strengths of EICP-treated residual soil prepared at various concentrations of cementation solution and different moulding water contents (– 2% to + 4% OMC). The test tube test results showed that the mass of calcium carbonate precipitation increased with an increment in the urea-CaCl2 concentrations from 0.25 to 1.00 M. Maximum mass of calcium carbonate precipitation of 1.577 g, 1.603 g and 1.603 g were obtained due to 1.00 M urea-CaCl2 at 3, 7 and 14 days, respectively. The effect of curing period beyond 3 days were found to be insignificant on the amount of CaCO3 precipitations. The strength of the EICP-treated soil increased with increasing concentrations of urea-CaCl2 and decreased with an increment in moulding water content. The maximum strengths values at all moulding water contents were obtained at 1.00 M urea-CaCl2. The highest shear strength of 728.5 kPa was determined at -2% OMC when 1.00 M was used as urea-CaCl2 and 4.33% calcium carbonate content was yielded. It was determined that there is a strong linear relationship (R2 = 0.8696) between UCS and calcium carbonate content in the treated soil. The amount of calcium carbonate content formed was found to decrease with an increase in mixing water content from 2% dry to 4% wet of optimum moisture content. Finally, the results from the field emission scanning electron microscope (FESEM) and energy dispersive X-ray (EDX) analyses confirmed the formation of calcite crystals in the EICP treated soil.

Item Type:Article
Uncontrolled Keywords:calcium carbonate precipitation, enzymatically-induced calcite precipitation (EICP), residual soil
Subjects:T Technology > TA Engineering (General). Civil engineering (General)
Divisions:Civil Engineering
ID Code:95841
Deposited By: Yanti Mohd Shah
Deposited On:20 Jun 2022 11:22
Last Modified:20 Jun 2022 11:22

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