The performance and durability of polyethylene terephthalate and crumb rubber–modified road pavement surfaces

Abstract

This research investigates the influence of waste polymeric polyethylene terephthalate (PET) materials obtained from waste plastic bottles and crumb rubber (CR) obtained from used automobile tyres on the performance (Marshall stability, flow and compression) and durability (weathering) characteristics of road-paving material made from Trinidad Petroleum Bitumen and the world-renowned Trinidad Lake Asphalt. Apart from possibly serving as additives to improve performance, incorporating waste PET and CR in asphaltic road-paving materials also offers a viable means of alleviating health and environmental problems associated with the waste disposal of PET and CR. The results of the Marshall testing found that the optimum dosage for polymer modification was 1.0% and 5.0% for PET and CR polymers, respectively. In comparison with a Marshall stability value for the unmodified asphalt sample of 10.2 kN with a corresponding flow value of 3.1 mm, the 5% PET modified sample had a Marshall stability value of 10.2 kN with a flow value of 3.2 mm, while the CR modified sample recorded the highest Marshall stability value of 10.7 kN at corresponding flow value of 2.8 mm. An undesirable trend of the gradual increasing of the voids in mineral aggregate (VMA) with incremental increases in the % of added PET and CR was observed; however, for all the modified specimens with the exception of the 5% PET modified sample, the VMA fell within the acceptable range of between 14% and 20%. The results of accelerated weathering and compression testing demonstrated that both the 1% PET and the 5% CR-modified samples had higher durability and compressive strength characteristics than the unmodified samples. Compressive stress values for the polymer-modified specimens were in excess of 45% compared to the unmodified ones. The relevance of the values obtained in this study cannot be ignored as it provides practical and essential data, especially of the optimal dosages of PET and CR required for the enhancement of the mechanical and durability properties of the Trinidad road-paving materials while simultaneously providing an environmentally desirable and sustainable method for reusing these waste polymers. Commercial application of the optimum formulation can be immediately implemented.