Environmental Impacts and Life Cycle Assessment of Recycled Plastic Bricks

This study evaluated the mechanical performance, contaminant release, and life-cycle impacts of recycled plastic blocks manufactured from beach-collected and facility-sourced plastic waste. Four formulations combining polyethylene terephthalate, high-density polyethylene, low-density polyethylene, sand, and glass were evaluated. Unweathered blocks had compressive strengths between 20.6-24.3 N/mm², suitable for paving applications; however, higher plastic fractions led to lower strength and higher porosity. UV weathering reduced strength by 6-12% and increased metal leaching by up to ∼400%. Per- and polyfluorinated concentrations peaked at 13.8 ng/L; concentrations decreased slightly after weathering due to polymer photo-oxidation and embrittlement that enhanced sorption capacity and retention. Formulations with lower plastic content (∼33%) had higher strength and lower leaching. Life-cycle assessment identified extrusion and waste-plastic processing as dominant contributors to climate change (0.12 kg CO₂-eq/kg block) and particulate matter (0.42 x 10^-3 kg PM₁₀-eq/kg block), driven by fossil-based energy use and process emissions. Blocks with higher plastic ratios exhibited greater environmental burdens, matching leaching trends. These findings revealed that incorporating waste plastics into construction materials can support waste management and infrastructure, but durability, contaminant release, and processing emissions are sensitive to the formulation. Optimizing plastic-to-aggregate ratios and improving processing efficiency can improve durability while reducing environmental and health risks.