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

Area of Science:

• Environmental Engineering
• Geotechnical Engineering
• Materials Science

Background:

• Cement-based solidification is effective for heavy metal remediation but struggles with high contamination levels.
• Lead (Pb²⁺) contamination poses significant environmental and health risks.
• Developing enhanced solidification agents is crucial for effective soil remediation.

Purpose of the Study:

• To investigate the efficacy of a biochar-cement composite as a curing agent for Pb²⁺ contaminated soil.
• To evaluate the impact of varying biochar content on the physical and chemical properties of the solidified soil.
• To assess the potential of this composite as a subgrade filler material.

Main Methods:

• Prepared biochar-cement composite samples with varying biochar percentages (1-5 wt%).
• Assessed material properties including permeability, unconfined compressive strength (UCS), and leaching characteristics.
• Analyzed the reduction in Pb²⁺ leaching concentration against Chinese hazardous waste standards.

Main Results:

• 1-5 wt% biochar significantly improved the UCS of solidified soil, with optimal performance observed within this range.
• Incorporating 3.0% biochar reduced hydraulic conductivity to 7.75 × 10^-9 cm/s and porosity to 43.12%.
• Biochar addition substantially decreased Pb²⁺ leaching, meeting hazardous waste standards.

Conclusions:

• Biochar-cement composites enhance the solidification of highly Pb²⁺ contaminated soils.
• The composite material demonstrates improved strength, reduced permeability, and effective heavy metal immobilization.
• This technique presents a viable and promising approach for utilizing contaminated soil as a subgrade filler.