Abstract
Building more sustainable pavements for the future requires knowledge of alternative and innovative materials for utilization in future road construction and maintenance activities. Being mindful of this need, the present study investigates a Reacted and Activated Rubber (RAR) compound modifier with the aim of defining an optimal RAR percentage in Asphalt Concrete (AC) mixes. It is acknowledged that when this type of modifier is incorporated within an AC mix as an alternative for the bituminous binder material, the associated economic, environmental and social benefits are significant. Simply put, the use of RAR modifiers provides the potential to utilize a waste product (rubber tires) as a more sustainable alternative to bitumen within AC mixtures. However, it seems that the information about the overall performance of AC mixes modified with RAR is currently limited. On these grounds, the present study focuses on the surface course layer and evaluates (a) achieved physical characteristics (compaction degree/voids), (b) mechanical characterization results (stiffness moduli) and (c) friction-based properties of tested mixtures incorporating varying RAR levels and different test temperatures. From the evaluation, it is concluded that for the case of the surface course mixture under investigation, the optimal percentage by weight of bitumen for inclusion of the RAR modifier is 10%.
Highlights
All Reacted and Activated Rubber (RAR) mixture average modulus values are 12–13% greater than the corresponding reference asphalt mixture. This increase is true for all test temperatures and provides evidence that RAR modifiers have a positive effect on average modulus values based on indirect tensile stiffness modulus (ITSM) testing protocol
In regards to the bulk densities and air void percentages, the best results in comparison to the reference material were produced by the mixture containing 10% RAR-based materials
While as the rate of RAR materials increased above 20%, both values were below those of the reference material
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. It was stated that a significant percentage of waste tires end up in the landfill This offers the pavement engineering community an opportunity to turn these waste products into innovative and sustainable materials for pavement construction projects, provided that information is available regarding their influence on asphalt mixtures. Ma et al [31], for example, investigated the combination of transpolyoctenamer rubber (TOR), crumb rubber, and other additives to establish a new type of crumb rubber (CRT) to determine its effect on performance Beyond this technique, and with the positive outcomes regarding potential advantages of rubber-based material inclusion within AC mixes, a newer technique has emerged that included the end-of-life rubber material within AC mixes. The objective of the research is an investigation into achieved physical characteristics (compaction degree/voids) and mechanical characterization results (stiffness modulus) for various test temperatures with mixtures incorporating varying RAR levels for a course asphalt surface layer. It is worthwhile mentioning that until now, limited research has been available concerning the viability of RAR within course surface layers, and the present research aims to provide more information on the subject
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