A review of the mechanical and leaching performance of stabilized/solidified contaminated soils

Stabilization/solidification (S/S) technology, which basically involves chemical fixation and immobilization of contaminants (primarily metals) in the matrix of cementitious binders, is widely used for treatment of contaminated soils. This paper presents a critical review of the performance of commonly used blended binder systems in S/S technology. The binders considered are Portland cement and blends of cement-fly ash, cement-slag, lime-slag, and lime-fly ash. This work compares and evaluates the performance of contaminated soils treated by the binders in terms of commonly used mechanical and leaching properties, including unconfined compressive strength (UCS), bulk density, hydraulic conductivity, and leachability. The long-term performance of S/S-treated soils is also reviewed. It was observed that the inclusion of slag in a binder blend gave superior performance compared to fly ash. Generally, the leachability of common contaminants in soil can be reduced to acceptable levels with approximately 20%-35% dosage of the different binders. The UCS was observed to be optimum around the optimum water content for compaction. The hydraulic conductivity was approximately 10(-9) m/s over time. Long-term performance of treated soils showed consistent effectiveness over a period of 5-14 years with fluctuations in mechanical and leaching behaviour caused by the complex nature and variability of S/S-treated soils.