Effect of long-term ageing on the rheological properties of rejuvenated asphalt binder

Abstract

Recycled asphalt products are increasingly being used in asphalt concrete pavements to improve pavement sustainability. Asphalt recycling, while it is undoubtedly an environmentally sustainable practice, includes asphalt binder that is already oxidised. Aged binder is highly brittle and becomes a driving factor for cracking related distresses. As a result, use of recycled materials can have a significant negative impact on pavement performance, specifically when used in increased amounts and cold climatic conditions. In order to improve the performance of asphalt concrete mixtures with recycled materials, rheological properties are changed by adding rejuvenators. In asphalt industry, rejuvenators are either used at an initial virgin state of the binder to reduce mix ageing or blended at a later stage in recycled materials to improve the properties of aged mix. The current study focuses on evaluating the performance of asphalt mixes prepared by blending rejuvenators in already aged binders. Virgin PG 64-22 binder was aged using RTFO and PAV and further mixed with three different kinds of rejuvenators namely Hydrolene 90T, Kendex@ME, and Hydrogreen S at 3%, 6% and 9% by weight of the total binder. To study the behaviour of rejuvenated asphalt binder samples over a long period of time, mixed asphalt samples were then aged for 5, 10, 15, 20, 40 and 60 h in the PAV. Frequency sweep tests were conducted to characterise binder rheology, and parameters such as Glower-Rowe, crossover frequency, and Superpave rutting parameter were calculated. A comparative analysis was carried out to determine the impact of increased ageing and rejuvenator addition in varying amounts on the performance of asphalt mixes. A significant correlation was found out between the types of rejuvenator used in different dosages and the level of ageing in the asphalt binder.