Investigating the effectiveness of Vacuum Tower Bottoms for Asphalt Rubber Binder based on performance properties and statistical analysis

Abstract

Numerous studies reported crumb rubber modifier (CRM) as an environmentally friendly additive that is able to improve asphalt performance and helps reduce environment pollutions. However, addition of CRM leads to the viscosity increase and, consequently, increase in the asphalt mixture production temperature and the greenhouse gas emissions in the atmosphere. The objective of this study is to evaluate the effectiveness of Vacuum Tower Bottoms (VTB) in the laboratory performance of Asphalt Rubber Binder (ARB). In order to study mechanical and rheological properties of ARB containing VTB, rotational viscosity (RV), dynamic shear rheometer (DSR), bending beam rheometer (BBR) and Multiple Stress Creep and Recovery (MSCR) tests were performed. The results of viscosity test showed that adding 50% and 70% of the VTB into ARB decreases viscosity 32% and 45.6% averagely, respectively. Furthermore, the results of PG tests indicated that the VTB decreases HT continuous grade and increases LT continuous grade of ARB. The VTB was also found to be able to enhance the performance at intermediate temperatures, i.e. fatigue resistance of ARB. MSCR test results shows that addition of CRM leads to an increase of rutting resistance and elastic response, however, VTB lead to an increase of Jnr values of ARB. The results of ANOVA showed that, at the confidence level of 95%, the VTB and CRM have significant effect on HT, LT and PG temperature span of ARB. Finally, Tukey test results indicated that there is significant difference between the means of PG temperature spans at both CRM dosages (15 and 20%) while it is not significant for VTB dosages (50 and 70%).