Evaluation of AIMS-II and Micro-Deval for Friction Characteristics of Aggregates

Abstract

There is a need for a rapid quantitative way to evaluate the quality of aggregate friction properties for use in an asphalt surface (wearing) course. Aggregates that are resistant to polishing and capable of retaining their shape characteristics are desirable in the asphalt wearing course. The wearing course should be capable of maintaining an adequate amount of friction when subjected to polishing due to heavy traffic in order to ensure the safety of the roadway. Current laboratory procedures used to evaluate the friction properties of aggregates are said to be time consuming and subjective. The purpose of this research study was to evaluate the correlation between aggregate performance in a laboratory test consisting of the second generation Aggregate Imaging Measurement System (AIMS-II) and Micro-Deval to field friction performance. The AIMS-II device was used to quantify aggregate shape characteristics (angularity, texture, and form) before conditioning (polishing) and after conditioning in the Micro-Deval at different increments of time. The aggregates used for testing were selected based on their friction performance in surface courses at the National Center for Asphalt Technology (NCAT) Pavement Test Track. Field friction performance data for the selected test sections was obtained using the locked-wheel skid trailer. Aggregate shape indexes, more specifically, angularity and texture, were compared with the results obtained from the skid trailer in the field to see if a correlation could be established. The results showed the AIMS-II device was capable of detecting changes in aggregate shape characteristics when subjected to conditioning in the Micro-Deval. However, the analysis showed a good correlation between the AIMS-II indexes and the field friction data could not be established with the procedure that was used in this research study. This research study was a useful step in working towards developing a test method that may use the AIMS-II in conjunction with the Micro-Deval to predict the skid resistance of an asphalt wearing course mixture in the field. Future research is needed to enhance the test method used in this research study and take other factors into consideration that affect field friction performance.