Improving the performance and rheological properties of RAP binders using gilsonite/nanoclay and softer binder

Abstract

One of the ways to improve the performance of asphalt containing RAP is the use of a modified softer binder, which can enhance the rheological and performance characteristics. In this study, to improve the rutting and fatigue properties of reclaimed asphalt binder (RAB), a softer binder containing vacuum tower bottom (VTB) and Gilsonite/Nanoclay (Gil/Nc) composite were used. In this regard, the behavior of modified RAP binders has been controlled and analyzed using physical, rheological, and performance criteria from a laboratory test and ANOVA statistical method. The three scenarios designed in this research included a neat binder, RAB containing a soft binder, and RAB containing Gilsonite and different percentages of Nanoclay. The results showed that the modified softer binders (MSB) due to the presence of a high percentage of asphaltene in Gilsonite cause a quasi-solid behavior with a lower decay rate against plastic strains and improve rutting resistance at high PG temperature. The results of the BBR test showed that despite the negative effect of the Gil/Nc combination on the low-temperature behavior, the presence of VTB containing significant aromatic compounds compensated this problem to a large extent. The simultaneous results of DSR and BBR tests showed that RAB25_Gil/Nc6, RAB50_Gil/Nc6, and RAB50_Gil/Nc3 binders with useful temperature ranges of 97.5 °C, 97.1 °C, and 94.2 °C have the best performance. The outcomes of the LAS test showed that MSB increases fatigue life and reduces the probability of cracking of RAB. MSB containing Nc6 performs better due to the formation of an elastic network due to the strong interaction between nanoparticles and functional groups of the binder. The statistical analysis based on the laboratory results showed that the changes in dosage of the Nc and RAB have a significant impact on the performance characteristics. According to technical and functional considerations, MSB_Gil/Nc6 combination was proposed for modification of the binder containing RAB50.