Twenty-Five Years of Rubber Tire Wheel Tracking of Asphalt Pavements in a Laboratory

Abstract

This paper assesses the state-of-the-art for rubber tire wheel tracking of asphalt mixtures in a laboratory setting with emphasis on differentiating moisture damage from rutting. This assessment made use of a comprehensive literature review and roughly 300 experiments conducted over several years with the second generation of the Purdue Laboratory Wheel Tracker (PURWheel). The literature review revealed that direct separation of rutting from moisture damage with physical measurements taken with a rubber tire under otherwise identical conditions is not common practice. Collective analysis of these roughly 300 experiments revealed that second-generation PURWheel protocols offer two specific contributions to the asphalt mixture testing community: (1) a pneumatic rubber tire is used, which is most representative of vehicle traffic; and (2) the effects of moisture damage can be decoupled from rutting by testing under both wet and dry conditions where all other parameters are constant. The analysis was performed on data collected for other purposes, but the data did provide seven manners to evaluate moisture damage and three manners to evaluate variability in the context of standardizing protocols. These 10 evaluations clearly demonstrated the potential of rubber tire wheel tracking to improve characterization of asphalt mixtures beyond what has occurred to date. This paper works toward standardization of protocols for rubber tire wheel tracking in wet and dry conditions, and some discussion is provided on the status and needed advancements toward this eventual goal.