Cracking Characterization of Recycled Plastic, Ground Tire Rubber, and Aramid Fiber Modified Asphalt Mixtures: A Laboratory-Based Study

Abstract

Through the years, efforts have been made to incorporate a range of additives and modifiers to enhance the performance, durability, and sustainability of asphalt mixtures. This thesis investigates the cracking resistance of asphalt mixtures modified with three additives, ground tire rubber (GTR), recycled waste plastics, and aramid fibers. The laboratory experimental program evaluated 10 asphalt mixtures from the MnROAD Additive Group (AG) study, which complements the National Center for Asphalt Technology (NCAT) Test Track AG experiment, designed to assess the impact of these additives on mixture cracking resistance. Laboratory testing included the Indirect Tensile Asphalt Cracking Test (IDEAL-CT), the Disk-shaped Compact Tension (DCT) test, and the Texas Overlay Test (OT) following two mixture aging conditions: short-term reheating and critical aging. Mixtures containing GTR and recycled plastics included two methods of introducing the additive to the plant-produced mixtures, referred to as the wet-process and the dry process. The laboratory results showed that additive modified mixtures had enhanced cracking resistance compared to control mixtures, with dry process recycled plastic and rubber mixtures showing more significant improvements. The dry process mixtures with GTR and recycled plastics had improved fracture energy and cracking tolerance compared to the corresponding wet-process mixtures. Furthermore, the mixture with aramid fibers- demonstrated notably better durability and cracking resistance for reheated mixture samples. Additionally, the results show that the aging process impacts the mixtures differently, with critically aged samples having a reduction in cracking resistance, but the magnitude of the change varies based on the additive type.