The effectiveness of quicklime-based stabilization/solidification (S/S) on lead (Pb) contaminated soils

Quicklime-based stabilization/solidification (S/S) technology was investigated with two types of laboratory-prepared soil spiked with lead (7,000 mg Pb/kg). Slurry tests with quicklime were also performed to evaluate the specific reaction products. Mechanical strength was tested by measuring the Unconfined Compressive Strength (UCS). The UCS results showed that all of the treated samples had a significant increase in strength to values higher than the USEPA requirement for landfill disposal of 3.51 kg/cm². The effectiveness of the quicklime-based S/S treatment was assessed by applying the Toxicity Characteristic Leaching Procedure (TCLP) test. The effect of curing time (28 days and 6 months) was investigated. Regardless of curing, all of the montmorillonite-sand samples treated with quicklime yielded TCLP Pb concentrations below the USEPA regulatory level of 5 mg/L. XRPD analysis of the slurry sample that was aged for 7 days showed that Pb immobilization was closely associated with the formation of calcium hydrogen silicate (CaH₄Si₂O₇), riversideite (Ca₅Si₆Oi₆(OH)₂) and lead silicate (Pb₅SiO₇). Overall, it can be concluded that the quicklime treatment was effective at significantly reducing Pb leachability.