article · SOILS AND FOUNDATIONS
Expansive soils pose significant structural challenges due to their swelling behaviour and weak geotechnical properties. This research examines an environmentally friendly soil stabilisation approach combining enzyme induced calcium carbonate precipitation (EICP) with eggshell powder, an agricultural waste material. Using an optimal mixture of 0.75 mol/L EICP concentration and 14 percent eggshell powder across varying curing durations, the combined treatment markedly improved the engineering characteristics of the soil composite. Eggshell powder served both as a particulate filler between soil voids and as a nucleation site to promote calcium carbonate formation. Laboratory evaluations confirmed substantial mineralogical changes, with enhanced calcite formation reinforcing the soil matrix. Overall, the dual treatment decreased swelling pressure twenty-five-fold while substantially boosting compressive strength, cohesion, internal friction, and California Bearing Ratio values compared to untreated soil or single-additive methods.
Expansive soils often cause severe structural damage to roads and foundations because they shift and weaken when exposed to moisture. Using eggshell waste in combination with biological mineral precipitation provides a sustainable alternative to traditional chemical stabilisers. This method strengthens problematic ground for civil infrastructure while simultaneously reducing environmental impacts by repurposing large volumes of agricultural waste.
This method is relevant to civil engineering contractors, ground engineering firms, and transport infrastructure developers working on expansive soils. It could provide an environmentally conscious alternative to cement or chemical grouts while utilising agro-waste streams. Based on the experimental laboratory testing and microstructural analyses reported in the abstract, the technology sits at an early stage of research and will require field-scale validation before practical deployment on construction sites.
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• A feasible solution for using agro-waste eggshell powder to alleviate the geotechnical problems is determined. • Enzyme induced calcium carbonate precipitation (EICP) is a sustainable method of problematic soil. • A novel technique of using EICP in conjunction with ESP is adopted to enhance the geotechnical characteristics of expansive soil. • The stabilizing process was investigated in terms of changes in mineralogical and microstructural properties. Enzyme induced carbonate precipitation (EICP) is gaining more and more recognition that can be utilized on-site to enhance the quality of the weak soil. In this experimental study, a novel approach that combines EICP and eggshell powder (ESP) to strengthen the engineering characteristics of natural expansive soil has been implemented. The engineering properties of expansive soil were examined using the environmentally friendly method EICP with an optimal 0.75 mol/L concentration and 14% ESP optimal content, with varying curing durations. ESP serves as a filler between particles and also a nucleation site to promote the precipitation of calcium carbonate. A thorough examination of the soil’s microstructure development after treatment was additionally executed through scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The findings demonstrated that combining EICP and ESP decreases the swelling pressure about 25 times, compared with the individual treatment that yielded 5 and 1.5 times reduction for EICP and ESP, respectively. Additionally, the combined treatment led to an increase in the unconfined compressive strength, cohesion, internal friction angle, unsoaked CBR, and soaked CBR by 3, 1.6, 1.8, 8.0, and 9.5 times, respectively, indicating better enhancements than the individual treatments of EICP and ESP. Moreover, at the microstructural level, SEM imagery demonstrated a highly reinforced soil composite. The XRD analysis unveils distinct mineralogical changes, predominantly characterized by enhanced calcite formation and a refined microstructural composition. This study highlights the synergistic potential of combining EICP and ESP as stabilizing additives to enhance the engineering properties of expansive soil. Beyond soil enhancement, this innovative blend offers a sustainable solution by repurposing agrowaste. The mutual incorporation of EICP and ESP emerges as a promising strategy for advancing sustainable civil infrastructure development.
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DOI: 10.1016/j.sandf.2025.101567
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