Abstract
The addition of recycled tyre rubber as a modifier to enhance the mechanical properties of bitumen has proven to provide asphalt mixtures with better mechanical performance. However the rubberised bitumen presents the limitation of requiring higher manufacturing and compaction temperatures. This could be solved by subjecting the tyre rubber to sort of pre-treatments such as: Adding warm-mix additives and/or using partial devulcanisation. These solutions have the potential of lowering the overall environmental impact of the asphalt pavement, however it is still not clear whether these can be detrimental for the rubberized asphalt binder mechanical properties. This paper investigates the effect on fatigue and healing properties of rubberized bitumen blended with pre-treated crumb rubber. An innovative combined fatigue and healing analysis will be presented and used to compare the several rubberised binders with a neat bitumen. The analysis consists in conducting time sweep tests by means of dynamic shear rheometer, by applying repeated cycles of stress or strain loading at selected temperatures and loading frequency. The healing potential of binders was evaluated by introducing short rest periods after a certain number of load pulses. At last, the unique energy parameter obtained using the Ratio of Dissipated Energy Change approach, was applied to obtain a unique index that could provide combined information for both fatigue binder damage and healing phenomenon. The results showed that the analysed rubberised bitumens show having better fatigue and healing performance when compared to the straight-run bitumen.
Highlights
The addition of recycled tyre rubber to the conventional bituminous materials has shown improved fatigue and rutting characteristics and, the road surface is expected to have longer service life and needs lower maintenance/repair costs [1,2,3,4]
It is well known that fatigue resistance of hot-mix asphalt (HMA) mixtures is significantly related to the properties of their bituminous binders and cracking usually starts and propagates within the binder
Many studies have suggested that the Strategic Highway Research Program (SHRP) fatigue parameter (G*·sinδ) does not reflect the true binder performance related to asphalt mixture or pavement performance [5,6,7,8,9,10]
Summary
The addition of recycled tyre rubber to the conventional bituminous materials has shown improved fatigue and rutting characteristics and, the road surface is expected to have longer service life and needs lower maintenance/repair costs [1,2,3,4]. It is well known that fatigue resistance of hot-mix asphalt (HMA) mixtures is significantly related to the properties of their bituminous binders and cracking usually starts and propagates within the binder. It is important to modify the base bitumen and evaluate the modifier effect on the fundamental and functional properties. The characterization of binders should be based on test methods and parameters that can reliably rate the binder contribution to fatigue damage resistance. Many studies have suggested that the Strategic Highway Research Program (SHRP) fatigue parameter (G*·sinδ) does not reflect the true binder performance related to asphalt mixture or pavement performance [5,6,7,8,9,10].
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