Date of Award

5-2014

Document Type

Thesis

Degree Name

Master of Engineering (ME)

Legacy Department

Civil Engineering

Advisor

Putman, Bradley J

Committee Member

Rangaraju , Prasad R

Committee Member

Ogle , Jennifer H

Abstract

Porous asphalt is a type of pavement in which surface water can permeate down into the subbase below. Open graded friction course (OGFC) is a type of porous asphalt often used as a surface course on top of dense graded pavements on high speed roadways. Due to an increase in waste tires, rubber modified asphalt has become an increasingly popular material around the world, including the US. The rubber modified asphalt is created by utilizing processed rubber particles blended into the mixture. This research investigated the effects of rubber modified binder on the performance of porous asphalt by evaluating the porosity, permeability, long term draindown, abrasion resistance, fatigue resistance and dynamic modulus. The variables of this research included tire type (passenger and truck tire), crumb rubber processing method (ambient and cryogenic processing) as well as rubber modified blending method (low shear and high shear blending) for a total of eight experimental mixes that were compared to mixtures prepared with typical styrene-butadiene-styrene (SBS) modified binders. To ensure that the rubber modified binders were of similar quality to the control SBS binder (PG 76-22), DSR testing was performed on varying rubber contents of each binder to find the true failure temperature and G*/sin(ä). The results were then compared to the control binder. The rubber contents selected matched the PG 76-22 true failure temperature and G*/sin(ä) values The optimum binder content was also considered to create comparable mixes. All rubber modified mixtures were mixed using 7.0% binder by weight of the batch. The control mix of PG 76-22 was mixed with 5.5% binder while PG 76-22 with fibers used 7.5% asphalt binder. This variability in the control mixes were necessary due to optimum binder and draindown test standards. This investigation found that mixtures made with truck tire rubber generally performed better in porosity, initial permeability and provided stable long-term draindown results when compared to passenger car tire rubber. Ambient rubber yielded more desirable results in initial permeability than cryogenic rubber. Overall, high shear and low shear blending gave similar results. With the use of these results, different rubber modified binders can be selected to meet desired performance properties. These results also showed that rubber can be used to replace cellulose fibers in porous asphalt.

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