Safe Re-Use of Coal Tar Contaminated Road Plannings Using SMR ReBind

Coal tar–contaminated road planings are typically classified as hazardous waste due to elevated polycyclic aromatic hydrocarbon (PAH) content. Under UK waste and environmental protection policy, reuse is only permissible where materials can be demonstrated to be stable, non-leachable, and suitable for use in a controlled engineering environment.

Project Objectives

To determine whether coal tar–contaminated road planings treated with SMR ReBind:

• Meet recognised leachability compliance criteria
• Exhibit stable long-term environmental behaviour
• Are suitable for reuse within bound pavement and engineering applications

Material Treatment

The treatment produces a monolithic hydraulically bound material (HBM) rather than an unbound or lightly stabilised waste.

Source material: Coal tar–contaminated road planings

Treatment: Hydraulic binding using 3% SMR ReBind Mix composition:

• 70% planings
• 30% fines

Testing and Standards

Independent laboratory testing was undertaken in accordance with:

• BS EN 13286-51 –Manufacture of hydraulically bound mixtures
• EA NEN 7375 – Monolithic tank leaching test for long- term environmental performance

Samples were cured for 28 days prior to 64-day tank leaching assessment, representing long-term, in-service conditions rather than short-term batch leaching.

Key Findings

Environmental Performance

• The SMR ReBind–treated material complied with EA NEN 7375 solubility criteria
• Overall contaminant emissions were low and diffusion-controlled
• Long-term leaching behaviour demonstrated chemical stability and encapsulation

PAHs

• Treated material released 2.7 mg/m² total 16 PAHs over 64 days
• Release rates were low, near analytical detection limits, and not progressive
• Separate unbound leaching tests on untreated planings produced ~100× higher PAH concentrations

Phenols

• Phenol concentrations were generally at or below detection limits aligned with UK Drinking Water Standards
• One isolated exceedance was recorded but was not sustained or indicative of ongoing mobilisation

pH Behaviour

• Elevated pH(≈ 9.8–11) was observed, consistent with hydraulically boundmaterials
• pH regulation was diffusion-controlled, indicating long-term stability rather than ongoing reactivity

Regulatory and Highways Relevance

The testing demonstrates that SMR ReBind:

• Converts coal tar planings froma leachable waste into a stable monolithic construction material
• Supports reuse under a source–pathway–receptor risk assessment framework
• Is compatible with Dilution Attenuation Factor (DAF) approaches commonly applied in pavement design (typically 10³–10⁶)
• Aligns with highways practice for bound pavement layers and engineered sub-bases, subject to appropriate design controls

The results provide robust technical evidence to support:

• Waste exemption or end-of-waste arguments
• Regulatory compliance discussions
• Reuse approvals in highways and infrastructure projects

Executive Conclusion

Independent testing confirms that coaltar–contaminated roadplanings treated with 3% SMR ReBind:

• Exhibit low, stable, diffusion-controlled contaminant release
• Perform significantly better than untreated planings
• Meet recognised environmental compliance criteria
• Can be safely reused in controlled highway and engineering applications

SMR ReBind provides a policy-aligned, regulator-ready solution that enables the safe reuse of coal tar–contaminated materials, reducing landfill dependency, lowering carbon impact, and supporting circular economy objectives.