Utilization of plastic waste in hot mix asphalt using dry mixing processes: Laboratory assessment of airborne microplastics

• The ACP's airborne MCPs were successfully validated, reassuring that environmental concerns and health issues are addressed during operational processes. • Based on Thailand's conditions, the mixed plastic waste was used as a partial asphalt binder in the dry mixing process of ACP mix. • The Micro-FTIR test confirmed that the ACP shows no sign of airborne MCPs, providing a reassuring comparison to the conventional AC mix. • The ACP provided acceptable PM2.5, VOC, and heavy metal concentrations in mixing, laying, and in-service conditions. This study investigates airborne microplastic particles (MCPs) and pollutant emissions generated from the dry-mixing process of asphalt concrete incorporating recycled plastic (ACP). Airborne MCPs in construction environments raise potential health concerns, as prolonged exposure to fine particulate matter has been associated with respiratory inflammation and other adverse health effects. The dry-mixing method, which involves blending plastic waste with heated aggregates before adding the asphalt binder, was analyzed under controlled laboratory conditions across mixing, laying, and in-service phases. Pollutant emissions and airborne particulates were collected and analyzed, focusing on identifying MCPs through visual and spectrometric techniques. The results indicate that ACP mixing emitted more fine particles (0.30–1.00 µm) than conventional asphalt concrete (AC), significantly increasing during laying. However, in-service emissions were comparable between ACP and AC, suggesting no long-term MCP contamination. Additionally, plastic waste inclusion reduced PM2.5 concentrations by 51 % during mixing, potentially mitigating worker exposure to fine particulates, but increased PM2.5 levels by 74 % during laying, necessitating protective measures for occupational safety. Microstructural analysis confirmed no detectable airborne MCP contamination, as spectral matching remained below 80 %. While ACP exhibited a slight increase in VOC emissions, all levels remained within occupational health limits, with no significant rise in hazardous compounds. Heavy metal analysis further confirmed that ACP incorporation did not introduce statistically significant toxic elements. These findings contribute to a more comprehensive understanding of emissions from ACP production, supporting its potential application with appropriate safety considerations.