Activated Crumb Rubber Modified Binder as a Sustainable Paving Material: Pavement Performance Consideration

Abstract

Rubber modified Asphalt Concrete utilizes Crumb Rubber (CR) that is acquired by shredding and grinding waste rubber tires. It is considered as a superior paving material that can cut down the required construction material and eventually save current depleting resources and CO2 emissions associated with the material transportation, construction, and production. Implementation of CR in AC mixtures however, requires modification in the asphalt mix plant by including a specific agitating tank required to blend the CR with the asphalt binder at high mixing temperature for 45 to 60 minutes. Unfortunately, local asphalt mix plants do not have this kind of agitating tanks which is the biggest obstacle to producing such superior AC mixes locally in UAE. Pre-treated crumb rubber is an emerging technology that offers a new method to produce rubber-modified AC mixtures in the field using traditional asphalt mix plants without any required modifications. A new crumb rubber modifier that is industrially recognized as Reacted and Activated Rubber (RAR) is an upcoming crumb rubber product whose purpose is to be used in a dry mixing process. RAR can be directly mixed with the hot aggregates without the need to be blended with the asphalt binders to simplify the mixing process with no additional modifications to asphalt mix plants. The main objective of this research is to study and assess the properties of asphalt binders modified with RAR compared to the traditional asphalt binders that are used in the UAE. Two RAR binders were produced at 20% and 30% RAR by weight of asphalt binder. The laboratory test work included: penetration, softening point, and rotational viscosity tests to assess the viscosity of the three different asphalt binders at multiple temperature levels. The test results showed some very interesting results where the RAR-modified binders exhibited higher viscosity at higher temperature and lower viscosity at lower temperature compared to the traditional asphalt binder. To assess the impact of this positive modification on the pavement performance, the state-of-the-art AASHTOWare pavement ME design software is utilized. The pavement performance simulations showed that the 20% RAR modified binder is the most promising one to yield the best performing pavement with the least amount of fatigue cracking and rutting. This also offers a cost effective solution by extending the pavement service life by an average of 8 years with minimal maintenance and rehabilitations activities.