Leaching Durability of EICP-Treated Collapsible Gypseous Soil

Samer J. Abdullah, Department of Highways and Geotechnical Engineering, College of Civil Engineering, University of Technology-Iraq, Alsina'a Street, 10066 Baghdad, IraqFollow
Mohammed Y. Fattah, Department of Highways and Geotechnical Engineering, College of Civil Engineering, University of Technology-Iraq, Alsina'a Street, 10066 Baghdad, IraqFollow
Aqeel Al-Adili, Department of Highways and Geotechnical Engineering, College of Civil Engineering, University of Technology-Iraq, Alsina'a Street, 10066 Baghdad, IraqFollow

Keywords

Gypseous soil, Enzyme-induced carbonate precipitation (EICP), Leaching durability, Hydraulic conductivity, Effluent chemistry, Carbonate retention, Seepage-induced deformation

Document Type

Article

Abstract

Gypsum dissolution and salt leaching make gypseous soils highly sensitive to seepage by weakening interparticle bonds and promoting fabric rearrangement. This study evaluated the seven day leaching durability of enzyme induced carbonate precipitation (EICP) treatment in a sand rich gypseous soil containing 29 wt.% gypsum. Specimens prepared at maximum dry density and optimum water content were used to evaluate nine formulations (A-H and J). Leaching tests were carried out in a modified Rowe cell for seven days under a vertical stress of 200 kPa and an upward hydraulic gradient of i = 20. Settlement, leaching strain, drainage volume, pH, electrical conductivity (EC), total dissolved solids (TDS), salt content and permeability were monitored on a daily basis. Net CaCO₃ was measured before and after leaching by Jackson pressure calcimeter method to quantify the amount of carbonate loss and retention. The best treatment formulations resulted in day-7 settlement reduction of up to 42.1% and permeability of up to 65.7% in comparison to untreated soil. The best control of settlement was achieved by mixtures D and J and the lowest final permeability was observed in mixture A. Net CaCO₃ after leaching was 0.612–2.68% and carbonate retention ratios were 55.6–85.6%. Overall, mixture D seems to be the best balanced performer. This is an indication that durable improvement is governed by retained carbonate that remains effective under seepage.

Recommended Citation

Abdullah, Samer J.; Fattah, Mohammed Y.; and Al-Adili, Aqeel (2026) "Leaching Durability of EICP-Treated Collapsible Gypseous Soil," Engineering and Technology Journal: Vol. 44: Iss. 11, Article 4.
DOI: https://doi.org/10.30684/2412-0758.1583

DOI

10.30684/2412-0758.1583

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