Leaching and mechanical properties of cement-calcium superphosphate treated lead contaminated soils
ZHAO Sanqing;College of Civil Engineering,Wuchang Institute of Technology;
Ordinary portland cement(OPC) stabilization was one of practical approaches to remediate soil contaminated with high levels of lead(Pb),however,the OPC had less effective on high levels Pb-contaminated soil. Calcium superphosphate was commonly used for the remediation of high levels Pb-contaminated soils mostly due to its lower leachability,relatively effective and high environmental safety. Cement-calcium superphosphate composite material was used to stabilize/solidify lead-contaminated soils. Leaching test,unconfined compressive strength test and permeability test were conducted to investigate effects of cement and calcium superphosphate dosages on mechanical and leaching properties of cement-calcium superphosphate composite material treated Pb-contaminated soils. Results showed that cement had an inefficient effect on highly concentrated contaminated soil,and the unconfined compressive strength and hydraulic conductivity were improved significantly with the increase in cement dosage. The unconfined compressive strength increased from 0.56 MPa to 4.78 MPa and the hydraulic conductivity decreased from 8.2× 10-7 cm/s to 2.2×10-8 cm/s,while the leaching concentration decreased from 56.3 mg/L to 19.8 mg/L when the cement dosage increased from 5% to 30%. The leaching concentration was above the identification standards for hazardous wastes in China. Cement-calcium superphosphate composite material had an efficient effect on highly concentrated contaminated soil,and leaching concentration decreased significantly with the increase in calcium superphosphate dosage. However,calcium superphosphate could lowered mechanical properties of solidified soil. The unconfined compressive strength decreased from 1.17 MPa to 0.42 MPa,and the hydraulic conductivity increased from 3.0×10-7 cm/sto 1.3×10-6 cm/s when the calcium superphosphate dosage was increased from 0% to 5%. Therefore,the effects of calcium superphosphate on mechanical properties of solidified soil should be completely considered when stabilizing the Pb-contaminated soil using calcium superphosphate.
【CateGory Index】： X53
【CateGory Index】： X53