Recyclability of Rubberized Asphalt

Abstract

Bitumen is a black to dark brown sticky material obtained as a by-product of crude-oil distillation. It has been used in pavement engineering applications for more than two centuries. Over the years, the awareness about the environmental impacts of human activities brought the need to reduce the amount of waste material and promote recycling. This resulted in the usage of reclaimed asphalt pavement (RAP), aged hot mixed asphalt (HMA) obtained through milling the top layer, or full-depth removal of the pavement structure.

Furthermore, the idea of incorporating additional materials to enhance the performance of the HMA has grown popular in the last two decades. One of those materials used nowadays is crumb rubber (CR) obtained from end-of-life tires (ELTs). It was first introduced in 1979 in Alaska, and its usage has increased. However, pavement structures have a designed service life, and some CR-modified structures are reaching their final stage. Hence, there will soon be RAP from rubberized asphalt mixture to be used again in the field.

This study consists of two parts. The first is related to the microstructural analysis of bitumen mixed with crumb rubber, where we focus on the swelling phenomenon of CR inside the bitumen, which will be subjected to different aging temperatures. In the second part, crumb rubber-modified binders (CRMBs) will be aged and rejuvenated using three environmentally friendly agents, R1, R2, and R3. Following the rejuvenation process, the mechanical properties of these materials will be tested using various testing methods and compared to the reference material.

The results show that the conventional laboratory aging protocols are triggering an interaction between the rubber particles and the bitumen. The rubber particles will start swelling and will affect the final aging results. Thus, the pressure aging vessel (PAV) aging protocol was modified at 70˚C for eight days.

This was demonstrated through tests conducted on the rejuvenated material, which revealed that there was no specific dose of a rejuvenating agent that could restore the aged material to its original state. Therefore, it was concluded that R1, R2, and R3 function as softening agents.

Date of Award	Apr 2023
Original language	American English
Supervisor	MUTASEM El Fadel (Supervisor)