Carbon sequestration potential of electrokinetically treated fine-grained expansive soils

This study investigates the carbon sequestration potential of fine-grained expansive soils treated using electrokinetic (EK) stabilisation. It identifies the physicochemical conditions that promote gravimetrically inferred calcium carbonate [Formula: see text] precipitation, based on stoichiometric and gravimetric evidence, as a mechanism for laboratory-scale [Formula: see text] immobilization potential. EK tests were conducted using a five-factor face-centered central composite design with 48 experimental runs, and routine measurements of pH, salinity (Sal), total dissolved solids (TDS), electrical resistivity ([Formula: see text]), and electrical conductivity (σ) were recorded to quantify their relationship with gravimetrically inferred [Formula: see text] formation. A quadratic Response Surface Methodology (RSM) model incorporating linear, interaction, and quadratic terms was developed to predict [Formula: see text] sequestration potential. Experimental data from calcium chloride and sodium carbonate [Formula: see text] electrolytes applied to EK-treated soil blocks were analyzed with multivariate regression and ANOVA to identify governing parameters. The model demonstrated near-perfect statistical agreement within the validated experimental design space ([Formula: see text] = 1.000; adjusted [Formula: see text] = 1.000; predicted [Formula: see text] = 0.9997; p < 0.001). ANOVA confirmed the statistical significance of all model terms (p < 0.0001), with TDS, ρ, and σ as significant main effects. Interaction analysis further revealed significant contributions from Sal × σ, ρ × σ, pH × Sal, TDS × ρ, and Sal × TDS. An empirical calibration constant, [Formula: see text] = [Formula: see text]g [Formula: see text]g⁻¹·(S·m⁻¹)⁻¹ was derived by regressing gravimetrically measured [Formula: see text] contents against measured σ values and applying stoichiometric conversion. Optimal EK conditions for maximum model-predicted [Formula: see text]sequestration potential were achieved at pH ≈ 9.2, TDS ≈ 7.0 kg·m⁻³, Sal ≈ 4.0 g·kg⁻¹, ρ < 0.1 Ω·m, and σ > 7.9 S·m⁻¹. The model predicts an in-domain [Formula: see text] sequestration potential of approximately 2.0 g [Formula: see text] [Formula: see text] of EK-treated soil under optimal laboratory conditions. Within the validated experimental design space and EK-treated soil-electrolyte system, these findings provide a data-driven framework linking routine EK measurements to model-predicted [Formula: see text] immobilisation potential. The model is intended for laboratory optimisation and future pilot-scale validation rather than immediate field application.