Soil stabilization via carbonate precipitation by plant-derived urease: comparison between soybeans fine powder and crude extract juice

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4. Soil stabilization via carbonate precipitation by plant-derived urease: comparison between soybeans fine powder and crude extract juice

Enzymatic Induced Calcite Precipitation (EICP) is an emerging alternative stabilization technique that can improve the geotechnical properties of problematic soils without the use of hazardous or costly chemical binders. In EICP, the urease enzyme catalyzes the hydrolysis of urea, which produces carbonate ions reacting with the calcium ions dissolved in the pore water, resulting in the precipitation of calcium carbonate. The precipitated calcium carbonate fills the soil voids and binds soil particles together thus reducing the water permeability and enhancing the material strength. The urease enzyme can be sourced from bacterial metabolic activity or many common plants and seeds. For a simple and low-cost procedure, this study considers harnessing the urease enzyme found in soybeans, either added to the soil in the form of fine powder or crude extract juice. The aim is to provide new insights into the advantages and disadvantages of the two different stabilization techniques on the mechanical properties of stabilized soils, especially where previous results seemed to benefit the first technique. The authors consider the influence of the temperature on the activity of the urease enzyme and calcium carbonate precipitation and the effect of the degree of saturation on the mechanical performance of the stabilized soils. The results show that increasing the curing temperature from 25°C to 60°C decreases the calcium carbonate precipitation and thus mechanical performance and that partial saturation affects the strength and stiffness of both unstabilized and stabilized samples, with lower humidity levels yielding better mechanical properties. These research findings represent a step forward in understanding the micro/macro mechanisms governing EICP stabilization, particularly in cases involving organic matter (such as soybean shells).

2025 International Conference on Bio-mediated and Bio-inspired Geotechnics (ICBBG2025)

General session: Bio-mediated methods for infrastructure construction