Influence of soft binder and rejuvenator on the mechanical and chemical properties of bituminous binders

Abstract At the end of their service life, asphalt pavements exhibit distresses such as cracking and ravelling due to the aged bituminous binder. The recycling process of reclaimed asphalt should compensate for the deteriorated binder properties. The main objective of this binder study is to compare two common recycling strategies: the use of a softer binder and a rejuvenator. Three recycling percentages, 0%, 40% and 70% of reclaimed asphalt binder were evaluated. All binder blends were prepared with similar penetration and softening point values. In order to simulate binder performance during service life, ageing protocols by means of rolling thin film oven test and pressure ageing vessel were performed. The investigation included both mechanical and chemical tests. A dynamic shear rheometer was used to assess different rheological parameters over an extensive temperature range. Linear amplitude sweep tests were performed to estimate the fatigue resistance at intermediate temperatures. Resistance to permanent deformation was assessed with a multiple stress creep recovery test. Fourier-transform infrared spectroscopy was used to assess the formation of bonds that indicate oxidative ageing after the ageing protocols. Moreover, an optimised method was introduced to calculate the carbonyl index for rejuvenated binders, which also allows to detect the presence of a rejuvenator in a bituminous binder. The results show that the inclusion of rejuvenator results in similar rheological behaviour compared to the application of a soft binder. Furthermore, the rejuvenator improves binder fatigue life without reducing the performance at elevated temperatures.