Stability of solidified/stabilized heavy metal-contaminated clay under outdoor natural exposure and indoor standard curing

A comparative study on the strength and leaching properties of a nickel- and copper-contaminated soil hydroxyapatite-solidified/stabilized by a novel based binder is introduced under natural exposure and indoor curing. After a 360-d monitoring, the soil specimens are subjected to unconfined compression strength (UCS), leachability and soil pH tests. The results demonstrate that the UCS and pH of the contaminated soil remarkably increase with the addition of SPC, but the leaching concentrations of nickel and copper significantly decrease. With 5% binder addatin the leaching concentrations of nickel and copper are below their remediation goals after 7 d. The comparison shows that the strength and pH of the soil specimens under natural exposure is lower than that under indoor curing. Meanwhile, the leached concentrations of heavy metals of the treated soil under the two conditions is opposite. At 600 d, the slightly increased leachability of the treated soil still meets the remediation goal. The UCS of the treated soil decreased by 2.6%, and the pH value of the treated soil decreased by 0.3 units.