Evaluation of Epoxy Asphalt Binders for Open-Graded Friction Course (OGFC) Application

Epoxy asphalt (EA) binder is an asphaltic material modified with thermosetting polymer. Compared to binders containing thermoplastic elastomers, EA binder has better thermal stability, rigidity, and resistance to deformation. The real breakthrough of EA binder is its superior resistance to aging and embrittlement, which are two major contributors to raveling of open-graded friction course (OGFC) mixtures. Therefore, EA has a potential to improve durability of OGFC mixtures and extend their service lives. Despite advantages, EA binder has limitations, most notably its high cost compared to styrene-butadiene-styrene (SBS) modified and rubberized asphalt binders. A cost-effective solution to reduce material expense is to dilute EA with unmodified asphalt binders, which in turn reduces the epoxy dosage rate in the resultant binder. The objective of the study was to evaluate curing behavior and rheological properties of EA binders produced with epoxy resins from two sources, based on their performance grade, multiple stress creep recovery, linear amplitude sweep, and Glover-Rowe parameter results. The following conclusions were made: Curing rate of EA binder is highly dependent on epoxy dosage rate and temperature; Superpave test methods are not suitable to EA binder with epoxy dosage rate of 40% due to the thermosetting polymer nature of epoxy resin; Diluted EA binders showed improvement in resistance to rutting, fatigue, and aging in comparison to neat binder but did not outperform SBS-modified binder; An epoxy dosage rate above 8% is needed for diluted EA binders to have comparable or better performance than SBS-modified binder.