Introducing a soybean oil-derived material as a potential rejuvenator of asphalt through rheology, mix characterisation and Fourier Transform Infrared analysis

Abstract

The interest in rejuvenators has been growing rapidly in the past few years due to their ability to restore aged binders to their unaged state and the availability of aged recycled materials. The introduction of rejuvenators has made it possible to produce asphalt mixes with high recycled asphalt pavement (RAP) content. Typically rejuvenators need to be added to the RAP bitumen in high dosages, more than 10%, to achieve the desired effect. In this work a new soybean-derived additive is introduced as a rejuvenator, at 0.75% by weight of the bitumen. The effect of adding the soybean-derived rejuvenator on the rheological properties of both a performance grade (PG) 64-28 and a PG 58-28 bitumen is assessed using a dynamic shear rheometer, a bending beam rheometer and a rotational viscometer. Dynamic modulus specimens for both the control and modified blends were prepared using a mixing and compaction temperature of 120°C, as well as a temperature of 140°C, and master curves were constructed using test results. The dynamic modulus data were further analysed using a complex statistical technique which utilises a split-plot repeated measure concept. It was noted that, at such a low dosage, the rejuvenator greatly improved the fatigue and low-temperature properties of the tested asphalt binders. The dynamic modulus results revealed that the rejuvenator was successful in reducing asphalt binder stiffness, and that the extent of such a reduction depended largely on the asphalt grade. Additionally, the mixing and compaction temperature of 120°C had the effect of the mix performing better at lower test temperatures than the specimens produced using a mixing and compaction temperature of 140°C. The ageing characteristics of the rejuvenated binders were assessed using Fourier Transform Infrared-Attenuated Total Reflection, which revealed similar ageing behaviour of both the control and modified asphalt binders, as indicated by the evolution of the carbonyl and sulfoxide indices.