Impact of Integrating Crumb Rubber with an Isocyanate-Based Additive on the Conventional and Rheological Characteristics of Bitumen

Abstract

The predominant approach to enhancing the performance of bituminous mixtures involves the modification of bitumen using styrene-butadiene-styrene (SBS). Nevertheless, the application of SBS is constrained by its high cost, susceptibility to phase separation, and inadequate aging resistance. An alternative solution to mitigate some of these challenges, particularly the financial aspect, is the incorporation of crumb rubber (CR) derived from discarded vehicle tires, in conjunction with other polymers for bitumen modification. This research examines the influence of an isocyanate-based reactive additive (B2last) on both the conventional and rheological characteristics of bitumen, as well as its effectiveness when combined with CR. The performance of this hybrid binder is then evaluated in comparison to that of SBS-modified bitumen. Softening point, rotational viscosity, dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), and bending beam rheometer (BBR) tests were performed on original and aged binders. In conclusion it was determined that the combination of B2Last and CR showed a synergistic improvement in performance and made bitumen suitable for extremely high traffic conditions at high temperatures. The incorporation of 6-8% CR modification alongside 2%B2last demonstrated enhanced performance at elevated temperatures and superior resistance to rutting when compared to the 4% SBS modification. Although the use of SBS and B2last alone in bitumen modification slightly worsens the low temperature behavior. The combination of B2last and CR provided a satisfactory low temperature performance. This research contributes to the ongoing search for new additives and combinations to improve asphalt binders.