Effect of Compaction Degree on Solidification Characteristics of Pb-Contaminated Soil Treated by Cement

摘要

Compaction is a necessary step after the solidification/stabilization of contaminated soil. This study analyzed the effect of compaction degree on the solidification characteristics of Pb-contaminated soil. Batch tests were conducted to measure the permeability coefficient, unconfined compressive strength, Pb leaching concentration, and micromorphology of the solidified bodies compacted at different degrees (from 0.90 to 1.00 at an interval of 0.02). The permeability coefficient of the solidified bodies decreased with the increase in penetration time and compaction degree (from 1.80 × 10−6 to 1.19 × 10−7 cm/s). With an increase in compaction degree, the unconfined compressive strength of the solidified bodies increased from 2.20 to 4.90 MPa. In addition, failure strain decreased first and then increased before and after the compaction degree reached approximately 0.95. Pb in soil was effectively stabilized by cement because the leaching concentration of Pb in all the samples was <2.5 mg/L. The leaching concentration of Pb increased first and then decreased before and after the compaction degree reached approximately 0.96, but pH values of lixivium decreased first and then increased. Compaction degree and the hydration products jointly determined the pore distribution and microscopic morphology of the solidified bodies, which comprised intra-particle, inter-particle, and intra-aggregate pores. The hydration products in the solidified bodies mainly consisted of ettringite and C–S–H. Low compaction degree was found to be beneficial for the formation of hydration products, the content and distribution of which jointly determined the leaching concentration of Pb.