Laboratory study on asphalt mixture modified by polyacronitrile fibres and reclaimed asphalt planings

n this laboratory study, combined effects of polyacronitrile fibres and reclaimed asphalt planings on performance properties of asphalt mixtures were investigated. Performance properties of six asphalt mixtures in total were comparatively analyzed, always considering a standard mix design concept for asphalt binder courses. Three asphalt mixtures were prepared with fresh materials only: two asphalt mixtures were produced without incorporating fibres, one using unmodified plain binder of the type 50/70 Pen Grade (in the following used as reference mixture and therefore identified as Ref.), the other one using polymer modified binder of the type 40/100-65 Pen Grade (identified as PmB). The third one was a fibre reinforced asphalt mixture (FRAM), composed of 50/70 Pen Grade binder, and 0.15% by total weight of the asphalt mixture of polyacronitrile fibres added directly in the drum to the aggregates. In addition, three more asphalt mixtures were prepared similarly, but 50% of the total mass was replaced by recycled material originating from reclaimed asphalt planings (RAP). These three mixtures containing RAP were identified as Ref.+RAP, PmB+RAP, and FRAM+RAP. All six asphalt mixtures were subjected to performance tests: wheel tracking tests were conducted in the high temperature range to study permanent deformation resistance, indirect tensile tests were conducted at intermediate temperatures to study fatigue resistance, and thermal stress restrained specimen tests were conducted at low temperatures to study resistance to thermal cracking. Test results indicate that asphalt mixture modification by polyacronitrile fibres and reclaimed asphalt planings results in acceptable performance properties, and potentially improves high and intermediate temperature properties.