Enhancing road performance of lead-contaminated soil through biochar-cement solidification: An experimental study

The effectiveness of cement-based solidification for remediating heavy metal-contaminated soil diminishes at high levels of contamination. To overcome this limitation, the potential of a biochar-cement composite curing agent to enhance the properties of Pb ²⁺ contaminated soil was investigated in this study. The permeability, unconfined compressive strength (UCS), and leaching characteristics of the biochar-cement composite material were assessed under varying biochar contents. The results revealed that the addition of 1-5 wt% biochar in cement significantly improved the UCS of the solidified soil. However, excessive biochar contents had a detrimental effect on the strength of samples. Additionally, the incorporation of 3.0% biochar reduced the hydraulic conductivity and porosity to 7.75 × 10^-9 cm/s and 43.12%, respectively. Moreover, the biochar-cement composite material exhibited remarkable efficiency in treating highly concentrated Pb²⁺ contaminated soil, with leaching concentration decreasing significantly with increasing biochar content, falling below the Chinese hazardous waste identification standard. Overall, the utilization of a biochar-cement composite curing agent in the solidification of heavy metal-contaminated soil could be considered a promising subgrade filler technique.