The Paving Green Roads study is a research and development collaboration with various universities and research institutes to investigate the mechanical performance, health, safety, and environmental impact of incorporating plastic waste into asphalt roads. This not only presents an important market opportunity for difficult-to-recycle plastic waste but is also vital in fully understanding the implications of integrating such materials into road surfaces.

A comprehensive suite of test methods were utilised to understand the impact of incorporating plastic waste into road construction. This includes assessing the mechanical performance to comply with road authorities’ requirements, the potential health and environmental impacts, including the release of microplastics and particulates into the air, and the potential pollutants in water run-off.

Since the project’s launch in 2020, the Alliance’s partners at the National University of Singapore (NUS), Chiang Mai University (CMU), and the Federation of Thai Industries have studied the optimal material mix for incorporating plastic waste into asphalt application and the impact on mechanical and environmental performances for the selected road conditions. In the first quarter of 2023, the NUS team established sections of road with asphalt containing plastic waste, along with control sections for comparison. These included both urban arterial road and expressway so they could compare the performance of the roads subject to different conditions. In Thailand, the CMU team did the same for sections of rural road in the Chiang Mai area.

The results for the construction phases in both Singapore and Thailand suggest that there are no significant differences in the concentration of airborne particulates (PM2.5 and PM10) at the test and control sites as the road surface was being laid. In-field data collection and analysis were completed over a period of nine months in Singapore and six months in Thailand. The results demonstrate that there is no significant difference between the control and road sections that incorporated plastic waste from the field testing, from the perspectives of both mechanical performance and health and environmental impact.

Field trials will get under way in 2024 in a separate workstream of the project in India. This will be managed by the Central Roads Research Institute (CRRI) of India, with the trial location based in Raebareli, Uttar Pradesh in northern India. The chosen location will provide a robust test of the plastic waste incorporated road, with temperatures ranging from 2C in winter to as high as 46C in summer to verify the mechanical performance across seasonal temperature fluctuations. CRRI has obtained approval for the trial from the National Highways Authority of India and the construction was completed in June 2024.