Report explores dry process plastics in asphalt mix
Evaluation of Post-Consumer Recycled Plastics in Asphalt Mixtures via the Dry Process
A new report from the Transportation Research Board (TRB) and the National Cooperative Highway Research Program (NCHRP) evaluates the use of recycled plastics added to asphalt mixes via the dry method.
This report presents findings from NCHRP 9-66, which evaluates postconsumer recycled (PCR) plastics in asphalt mixtures via the dry process, complementing FHWA’s wet process research. It examines performance and constructability based on plastic characteristics and production conditions, aiming to develop guidelines addressing performance, costs, safety, environmental, and recyclability concerns. The study involved five experiments: characterizing PCR plastics, comparing plant-produced recycled-plastics-modified (RPM) and control mixtures, surveying contractors, simulating production, and evaluating lab-prepared RPM mixtures.
Findings indicate that PCR plastics improve stiffness, rutting, and aging resistance but reduce workability and intermediate-temperature cracking resistance. Melt Flow Index (MFI) emerged as a key indicator, correlating with increased stiffness and reduced workability. However, laboratory-prepared mixtures could not fully replicate plant-produced performance, and binder analysis was inconclusive due to PCR plastics’ limited solubility.
Future research should address long-term performance monitoring, microplastic release, improved binder extraction methods, advanced imaging for PCR dispersion, compatibility with other additives, and the use of high-melting-point plastics as aggregate replacement.
Contributors to the report include Randy West; Fan Yin; Maede Mottaghi; Chen Chen; Raquel Moraes; Nam Tran; Yogesh Kumbargeri; Jean-Pascal Planche; Jeramie Adams; Joseph Rovani; C.J. DuBois; Gayle King
