Assessment of geopolymer and cement stabilizers on geotechnical properties of heavy metal-contaminated clay.

Heavy metal contamination (e.g., Pb, Ni) in clay soils poses significant environmental and geotechnical challenges. This study evaluates the efficacy of geopolymer (blast furnace slag-based) versus Portland cement in stabilizing contaminated clay. Soil samples CH classification were artificially contaminated with 5000 ppm Pb (NO), Ni (NO), and their 1:1 mixture, then stabilized with 5-15% cement/geopolymer. To examine the influence of stabilizers on soil that has been contaminated, a series of tests including particle size distribution, hydrometer, Atterberg limit, standard compaction, specific gravity (Gs), unconfined compressive strength (UCS), and consolidation tests aimed at ascertaining soil strength and compressibility parameters, alongside pH analyses to elucidate chemical characteristics and the mechanisms underlying pollutant retention in the soil, were executed. The results show that the Heavy metals reduced soil plasticity and unconfined compressive strength, also decrease its compressibility. In other words, with the insertion of heavy metal, the soil's texture changes from clay to silt and cohesive to granular behavior. Geopolymer outperformed cement, increasing UCS by 120% (vs. 80%) at a 15% dosage and elevating pH to 11.5 (vs. 10.2), enhancing Pb retention by 13%. Consolidation tests revealed geopolymer reduced compressibility by 30% more than cement. Geopolymer's superior performance, coupled with its lower CO emissions (~ 300 kg/ton vs. cement's 900 kg/ton), positions it as a sustainable alternative for contaminated soil remediation.