Design and Performance of Open-Graded Friction Course Mixtures Containing Epoxy Asphalt

Abstract

Open-Graded Friction Course (OGFC) is a type of pavement primarily composed of coarse aggregates and high asphalt content. Higher permeability, better friction resistance, improved visibility, reduced pavement noise, and reduced hydroplaning are some of the benefits associated with the uniform aggregate structuring with an extensive, interconnected air void system. However, a severe limitation of OGFC to date is surface raveling leading to reduced service life. This thesis aims to determine the viability of using epoxy-modified asphalt (EMA) to improve the long-term durability and life span of OGFC mixtures. To that end, a comprehensive literature review and experimental laboratory plan were conducted. The chemical compatibility of EMA binders was evaluated using fluorescence microscopy and image analysis. EMA OGFC mixtures were prepared at different epoxy dosage rates (EDR) with epoxy materials from domestic (U) and foreign sources (J), and 30% EDR was determined as optimum with respect to mixture performance and cost estimation. The EMA mixtures showed improved raveling resistance and durability as EDR increased between 15% and 40%. After extended long-term aging, the EMA mixtures at 30% EDR and high polymer (HP) mixtures showed significantly better raveling resistance and durability than the polymer-modified asphalt (PMA) mixtures. All OGFC mixtures had acceptable Tensile Strength Ratio results regardless of the type of asphalt binder used. Two EMA mixtures prepared with the domestic epoxy materials exhibited high severity stripping failures in the Hamburg Wheel Tracking Test (HWTT), possibly due to the lack of cohesive strength of the not fully cured EMA binder. Additional HWTT testing conducted on U-EMA mixtures cured for one to four weeks at room temperature indicated that the performance of the mixture improved with time as the EMA binder cured.