Comparing the effectiveness of using SBS and Crumb rubber as asphalt mixture modifiers with different modification processes

Description

Comparing the effectiveness of using SBS and Crumb rubber as asphalt mixture modifiers with different modification processes

Hamidreza Sahebzamani, Seyed Rasool Fazeli, Nader Mahmoodinia

ABSTRACT. Pavement distresses are the major concern in the asphalt pavements industry. During the decades, researches were performed to postpone these distresses and their inescapable effect on road surface smoothness. Improving the characteristics of flexible pavements by adding appropriate additives to the asphalt mixture is one of the main solutions for this purpose. This led to higher durability against heavy traffic loads and decreased maintenance costs. Additives such as Styrene-Butadiene–Styrene (SBS) and waste tire crumb rubbers are used for this enhancement in asphalt mixtures. It has been proven that using Styrene-Butadiene–Styrene (SBS) in asphalt mixtures can significantly improve the mixture’s characteristics and reduce the effectiveness of those destructive factors. Using waste materials such as crumb rubber (CR) can also improve asphalt mixtures and asphalt binder characteristics and be cost-effective and environmentally friendly.

One of the main issues of using additives is adding them to the asphalt binder using a polymer-modified asphalt binder plant. Recently, the industry has tried to produce polymer modified asphalt mixtures using dry process which means adding additives directly to the pugmill of the asphalt plant.

This research tried to evaluate the effect of using two different additives (SBS and Crumb rubber) on the performance of asphalt mixtures. Furthermore, different modification processes (dry and wet) were investigated for both of the abovementioned additives.

Conventional dense-graded, Reacted, and Activated Rubber (RAR) modified asphalt mix (dry process), asphalt mix produced with crumb rubber modified binder (wet process), asphalt mixture produced with SBS modified asphalt binder (wet process), and asphalt mixture produced with SBS polymerized pellets (dry process) were compared.

Beam fatigue, Uniaxial Cyclic Compression, Hamburg Wheel-Tracking, and Illinois flexibility index tests were conducted in the laboratory. Both polymer-modified and rubberized asphalt mixtures showed significant enhancement compared to conventional mix. The findings show that using crumb rubbers from waste tires has great prosperity for asphalt pavements besides environmental and cost-effective advantages. Modifying asphalt mixtures using a dry process can be as good as using polymer modified binders, a performance point of view.

KEYWORDS: Rubberized asphalt, Polymer modified asphalt, Asphalt mixture, Crumb rubber, Styrene–butadiene–styrene, Reacted and activated rubber, Dry process, Wet process.