Improvement of Asphalt Mixture Design for Cold Climatic Region

Abstract

Asphalt material is widely used for roadways in the United States, underscoring its crucial role in the country's transportation infrastructure. In cold climatic regions such as Minnesota, the asphalt pavement undergoes significantly low-temperature cycles in winter resulting in shrinkage of the asphalt, which leads to thermal cracking, and subsequently potholes. The present study explores the behavior of asphalt mixes with an emphasis on improving the resistance of the mixes against low-temperature thermal cracking. The study included high and low-density mixes and considered the impact of polymer-modified asphalt binders. In the first phase of the study, seven asphalt mixes were designed and tested, with three using the conventional Superpave (Superpave-4) mix design method, three utilizing the Superpave-5 mix design method for high-density asphalt mixes and one using regressed air-void method for a reference. In the second phase, eight asphalt mixes were tested, with four using polymer-modified binder and four using non-polymer-modified binder. The Disc-Shaped Compact Tension (DCT) test, Indirect Tensile Strength (ITS), and Dynamic Modulus (DM) tests were conducted to study the performance of the mixtures. From the test results, it was found that the Superpave-5 mix design samples containing polymer-modified binders exhibited better fracture properties or higher resistance to low-temperature thermal cracking compared to the Superpave-4 mixes, with non-polymer modified binder. The study further explores other relevant behaviors of Superpave-4 and Superpave-5 mixes to recommend needed modifications of the asphalt mixes that will experience less environmentally driven distresses when used in cold climatic regions.