Investigation of the Reactivity in Epoxy-Modified Asphalt as an Alternative Paving Material for Durable Open-Graded Friction Course

Several highway agencies in various countries are interested in utilizing open-graded friction courses (OGFC) as surface layers for various safety and environmental benefits. Oxidative aging in surface layers contributes to the loss of adhesion between binder and large aggregates, which leads to raveling as the predominant distress in OGFC. The epoxy-modified asphalt (EMA) technology offers an alternative paving material that provides an opportunity to enhance the durability of OGFC. Although the use of epoxy-modified OGFC in New Zealand and the Netherlands has shown superior resistance to raveling, one of the major challenges for wider implementation is the lack of comprehensive understanding of the reactivity between epoxy components and the reactive compounds in base binders. This study investigates the base-binder dependency of epoxy reactivity, effectiveness, and performance of reactive polymer-modified asphalts. To this end, four base-binder sources, carefully selected to represent different chemistry and potential reactivity with epoxy modifiers, were modified with various dosages of the epoxy package (i.e., 0% to 25% by weight), and tested using bending-beam rheometer, the dynamic shear rheometer’s concentric-cylinders geometry, asphalt-binder quality test, and Fourier-transform infrared spectroscopy. The proposed framework showed effectiveness in characterizing EMA reactivity and optimizing epoxy dosages. Results highlighted the limitations of some standard test methods and proposed specification limits when evaluating EMA. This study is part of a larger effort to advance the knowledge and state of practice of EMA technology for successful implementation in the U.S.