Evaluation of the Durability of a Waste Plastic–Enhanced Asphalt Road Pavement in Extreme Future London Weather Conditions

Climate change is increasing the frequency and intensity of extreme weather events, posing challenges to the durability of asphalt road pavement systems. Incorporating waste plastics, such as polyethylene terephthalate (PET), into asphalt mixtures has been proposed as a potential approach to reduce bitumen demand and modify mechanical performance; however, the response of such mixtures to future extreme climatic conditions remains insufficiently understood. This study examines the durability of PET‐modified asphalt under predicted future extreme winter, summer and seasonal weather conditions. A real‐time ageing method, defined as mimicking the daily fluctuation of extreme London weather, was employed. It consists of ten time‐varying temperature cycles representing freeze–thaw, freeze–heat and extreme heat conditions. These cycles were implemented in an environmental chamber and parameterised using ARIMA‐based projections and controlled laboratory simulations with thermal cycling calibrated against projected future London weather scenarios. Asphalt mixtures containing PET were compared with a control mixture without PET under identical conditioning protocols. Performance was evaluated using the Marshall asphalt mix method, with stability, flow, density, air voids and volumetric properties (VFA and VMA) assessed. The results indicate that, after ten freeze–thaw cycles, the PET‐modified mixture exhibited approximately 15% higher Marshall stability and up to 50% higher flow values relative to the corresponding aged control mixture, with absolute stability values remaining within acceptable specification limits. These findings suggest that PET modification can influence the mechanical response of asphalt under short‐term simulated extreme weather exposure. Overall, the study provides preliminary laboratory‐scale evidence that PET‐modified asphalt may exhibit altered durability characteristics under projected future climatic conditions. While the results are limited by the sample size and ageing duration, they offer initial insights into the potential role of waste PET in asphalt mixtures and highlight the need for longer‐term ageing studies and field validation before broader conclusions can be drawn regarding long‐term performance or waste‐management impacts.