Practical Specimen Preparation and Testing Protocol for Evaluation of Friction Performance of Asphalt Pavement Aggregates with Three-Wheel Polishing Device

AASHTO has provisionally endorsed the use of a three-wheel polishing device (TWPD) for polishing and the dynamic friction tester (DFT) for measuring the friction of the coarse aggregates used in hot mix asphalt (HMA). Despite ample studies showing the feasibility of such a system for HMA specimens, research efforts related to quantifying the coarse aggregates that are used in those mixes have been less common. The results of a study to accelerate the test and to decrease the tedium of specimen preparation for aggregates are reported here. Three identical TWPD devices that complied with the AASHTO provisional specification were fabricated. A new specimen preparation method was introduced to reduce the associated time and cost. Several operational parameters that can impact the repeatability and reproducibility of the process, such as tire type and tread condition, specimen preparation, and DFT rubber pad thickness, were investigated. This study verified that the TWPD/DFT test method can delineate the polishing/friction performance of different aggregates with acceptable repeatability and reproducibility. The TWPD/DFT test time and cost can potentially be decreased considerably by using the proposed practical and analysis modifications.