Rheological Evaluation of Modified Bitumen by EVA and Crumb Rubber Using RSM Optimization

Mohamad H Dehnad,Hossein Z Farahani,Behrouz Damyar,Youhong Tang

doi:10.1155/2021/9825541

Abstract

In the present study, ethylene-vinyl acetate (EVA) and crumb rubber (CR) were used as bitumen modifiers. The experiment was designed by response surface methodology (RSM) at different levels of modifier additives based on the central composite design (CCD). Next, the Superpave protocol was followed to evaluate the modified bitumen performance at different temperatures compared with the unmodified bitumen. In this regard, to evaluate at high temperatures, a dynamic shear rheometer (DSR) test was performed, and G ∗ /sinδ index was examined on bitumen samples after aging. Besides, the bending beam rheometer (BBR) test was performed to evaluate the low-temperature behaviour of the modified bitumen according to the SHRP standard based on the creep stiffness and creep rate. The optimal combination of additives was evaluated using RSM and analysis of statistical values to improve the performance properties of bitumen at high and low temperatures. Moreover, based on the DSR and BBR test results, 5.6% of EVA and 3.9% of CR were selected as the optimal values for the modified bitumen behaviour at the high and low temperatures of the mixture.

Highlights

Various studies have shown that mixing polymer additives and crumb rubber to bitumen has significantly changed the properties and rheology of bitumen and asphalt concrete
The bending beam rheometer (BBR) test was performed by measuring the creep stiffness and creep rate indices following Superpave instructions to evaluate the behaviour of bitumen modified at low temperatures
Pure bitumen has a limited cohesion despite its good adhesion and has a temperature limit between the breaking point and the softening point. e usage of these polymers expands the tolerable temperature range to more than twice that of unmodified bitumen while improving cohesion, which in turn enhances the resistance to flow, softening point, and higher viscosity under service conditions and reduces thermal sensitivity

Summary

Introduction

Various studies have shown that mixing polymer additives and crumb rubber to bitumen has significantly changed the properties and rheology of bitumen and asphalt concrete. Asphalt mixtures containing modified polymer bitumen are resistant to many deformations and stresses applied to the pavement. Crumb rubbermodified bitumen has shown several advantages, including lower temperature sensitivity, higher viscosity at higher temperatures, and more flexibility at lower temperatures. It has been found that asphalt mixtures produced with this type of bitumen have good resistance against rutting, permanent deformations, and fatigue cracking. These mixtures have higher resistance against reflective cracks [1,2,3,4]

Methods

Results

Conclusion