When the natural soil cannot satisfy engineering requirements, soil improvement is regarded as a substitute. One of the most common methods for improving the soil in the past was to add cement or lime. There are numerous customised soil improvement methods accessible today. While some treatments are difficult to apply, others are not ecologically friendly. The development of alternatives to mechanical and chemical stabilisation for soil has led to the emergence of bio-stabilization approaches. Enzymes are frequently involved in the bio-stabilization process, which promotes ureolysis and causes calcite to precipitate in the soil mass. Recent studies on sustainable ground improvement techniques suggest that Enzyme Induced Calcite Precipitation (EICP) is a good choice for soil development.Soil sample was silty clay with liquid limit 69%, plastic limit 28.3%, and plasticity index of 40.7%. Soil has an undrained shear strength of 25.4 kPa. By using 2.5 g/l urease enzyme concentration, the liquid limit and plasticity index of the sample decreased by 20.3% and 51.4% respectively and plastic limit of the sample increased by 24.4% after 7 days of curing.By using 5 g/l urease enzyme concentration, the liquid limit and plasticity index of the sample decreased by 21.7% and 62.2% respectively and plastic limit of the sample increased by 36.4% after 7 days of curing.
Introduction
Soil stabilization is vital for constructing stable infrastructure, especially in constrained or sensitive areas. Traditional methods include mechanical techniques (compacting soil by removing air and moisture) and chemical methods (using binders like cement, lime, fly ash). Recently, biological approaches have emerged, such as Microbial-Induced Calcite Precipitation (MICP), which uses bacteria to strengthen soil by precipitating calcium carbonate, though it has drawbacks like uneven distribution.
A novel, eco-friendly alternative is Enzyme-Induced Calcite Precipitation (EICP), which uses free urease enzymes (instead of bacteria) to catalyze urea hydrolysis, producing calcium carbonate that binds soil particles. EICP offers benefits including sustainability, lower carbon emissions, and better suitability for harsh environments without requiring sterile conditions for bacteria.
In laboratory tests using soil samples treated with urease enzymes derived from jack bean meal and a urea-calcium chloride solution, EICP significantly improved soil properties. Results showed decreased liquid limit and plasticity index and increased plastic limit over curing periods (3 to 7 days), indicating enhanced soil strength and reduced deformability.
Overall, EICP represents a promising, sustainable soil stabilization technique with broad geotechnical applications like slope stabilization, erosion control, and seismic resilience.
Conclusion
1) By using 2.5 g/l urease enzyme concentration, the liquid limit and plasticity index of the sample decreased by 20.3% and 51.4% respectively and plastic limit of the sample increased by 24.4%.
2) By using 5 g/l urease enzyme concentration, the liquid limit and plasticity index of the sample decreased by 21.7% and 62.2% respectively and plastic limit of the sample increased by 36.4%.
3) The increasing concentration of urease enzyme had a positive effect on improvement of plasticity properties of the soil.
4) EICP can be used as an excellent method for the improvement of plasticity characteristic of fine-grained soils.
References
[1] Ahenkorah, I., Rahman, M.M., Karim, M.R., Beecham, S. (2021). Enzyme induced calcium carbonate precipitation and its engineering application: a systematic review and meta-analysis.Construct. Build Mater. 308, 125000
[2] Almajed, A.; Khodadadi Tirkolaei, H.; Kavazanjian, E. (2018). Baseline Investigation on Enzyme Induced Calcium Carbonate Precipitation. J. Geotech. Geoenviron. Eng., 144.
[3] Anie, G. and K, Kannan (2020). “Investigation on the Geotechnical Properties of Nanoclay Treated Clayey Soil”, International Journal of Research in Engineering, Science and Management, 03(02), pp. 453-455.
[4] Baiq, H., Yasuhara, H., Kinoshita, N., Putra, H., Johan, E. (2020). “Examination of calcite precipitation using plant derived urease enzyme for soil improvement”, International Journal of GEOMATE, 19(72), pp. 231-237.
[5] Calik, U., andSadoglu, E. (2014). Engineering Properties of Expansive Clayey Soil Stabilized with Lime and Perlite. Geomech. Eng., 6,403–418.
[6] Changizi, F.; Haddad, A. Effect of Nano-SiO2 on the Geotechnical Properties of Cohesive Soil.Geotech. Geol. Eng. 2016, 34, 725–733.
[7] Choi, S.G., Chang, I., Lee, M., Lee, J.H., Han, J.T., Kwon, T.H. (2020). “Review on geotechnical engineering properties of sands treated by microbially induced calcium carbonate precipitation (MICP) biopolymers”. Construct. Build Mater. 246, 118415
[8] Dilrukshi, R., Nakashima, K., Kawasaki, S. (2018). “Soil improvement using plantderived urease-induced calcium carbonate precipitation”, Soils and Foundations, 58, pp. 894-910.
[9] Gao, Y., He, J., Tang, X., Chu, J. (2019). “Calcium carbonate precipitation catalyzed by soybean urease as an improvement method for fine-grained soil”, Soils and foundations, 59(05), pp. 1631-1637.
[10] Gitanjali, A., Jhuo, Y.S., Yeh, F.H., Ge, L. (2024). “ Bio-cementation of sand using enzyme-induced calcite precipitation: Mechanical behavior and microstructural analysis”, Construction and Building MaterialsVolume 417, 135360.
[11] Han, L., Li, J., Xue, Q., Chen, Z., Zhou, Y., Poon, C.S. (2020). Bacterial-Induced Mineralization (BIM) for Soil Solidification and Heavy Metal Stabilization: A Critical Review. Sci. Total Environ.,746, 140967.
[12] Javadi, N., Krishnan, V., Hamdan, N., Kavazanjian, E. (2018). “EICP Treatment of Soil by Using Urease Enzyme Extracted from Watermelon Seeds”,Proceedings of International Foundations Conference and Equipment Expo, Orlando, Florida, 296, pp. 115-124.
[13] Kavazanjian, E.; Almajed, A.; Hamdan, N. (2017). Bio-Inspired Soil Improvement Using EICP Soil Columns and Soil Nails. Grouting, 13–22.
[14] Kavazanjian, E.; Hamdan, N. (March, 2015). “Enzyme Induced Carbonate Precipitation (EICP) Columns for Ground Improvement”, IFCEE. https://www.researchgate.net/publication/280445959.
[15] Oliveira, P. J. V., L. D. Freitas, and J. P. Carmona. (2016). “Effect of soil type on the enzymatic calcium carbonate precipitation process used for soil improvement.” Journal of Materials in Civil Engineering, 29(04), pp. 01-07.
[16] Park, S.S., Choi, S.G. and Nam, I.H. (2014). “Effect of plant-induced calcite precipitation on the strength of sand”, Journal of Materials in Civil Engineering 26(08), pp. 01-05.
[17] Putra, H., Yasuhara, H., Erizal,Sutoyo, andFauzan, M. (2020).“Review of EnzymeInduced Calcite Precipitation as a Ground-Improvement Technique”, Infrastructures, 5, 66.
[18] Rahman, M.M., Hora, R.N., Ahenkorah, I., Beecham, S., Karim, M.R., and Iqbal, A. (2020). State-of-the Art Review of Microbial-Induced Calcite Precipitation and Its Sustainability in Engineering Applications. Sustainability, 12, 6281.
[19] Renjith, R.; Robert, D.J.; Gunasekara, C.; Setunge, S.; O’Donnell, B. Optimization of Enzyme Based Soil Stabilization. J. Mater. Civ. Eng. 2020, 32.
[20] Roksanaa, K., Hewagea, S.A., Lomboyb, M.M., Tangc, C., Xued, W., Zhua, C. (2023). “Desiccation cracking remediation through enzyme induced calcite precipitation in fine-grained soils under wetting drying cycles”,Biogeotechnics, 100049.
[21] Shu, S., Yan, B.,Meng, H., Bian, X. (2022).“Comparative study of EICP treatment methods on themechanical properties of sandy soil”,Soils and FoundationsVolume 62, Issue 6, 101246.
[22] Tingle, J.S., and Santoni, R.L. (2003). Stabilization of Clay Soils with Nontraditional Additives. Transp. Res. Rec., 1819, 72–84.
[23] Tirkolaei, H., Javadi, N., Krishnan, V., Hamdan, N., Kavazanjian, E. (2020). “Crude Urease Extract for Biocementation”, Journal of Materials in Civil Engineering, 32(12), pp. 01-12.
[24] Whiffin, V.S., Van Paassen, L.A., Harkes, M.P. (2007). Microbial carbonate precipitation as a soil improvement technique. Geomicrobiol J. 24 (5), 417–423.
[25] Yousefi, R., Amooei, A.A., Sakhi, M.A., Karimi, A. (2021). “Experimental Study on Influence of Using Urease Enzyme on Stabilized Sandy Soil’s Engineering Property by Zeolite and Sawdust”. IJMT Vol.15/ Winter (17-27).
[26] Yuan, H., Liu, K., Zhang, C., Zhao, Z. (2021).“Mechanical properties of Namontmorillonite-modified EICP-treated silty sand”, Environmental Science and Pollution Research, Volume 29, pages 10332–10344.
[27] Yuan, H., Ren, G., Liu, K., Zheng, W., Zhao, Z. (2020). “Experimental Study of EICP Combined with Organic Materials for Silt Improvement in the Yellow River Flood Area”, Applied Science, pp. 01-19.