Permeability, and Friction Performance Trends for Asphalt Pavement Surface Types: First- and Second-Year Results

This report summarizes a detailed report presenting the first and second year of field and laboratory measurements and statistical analyses and performance estimates for tire/pavement noise, permeability, ride quality, distress development, and friction properties of four types of asphalt pavement surface types used by the California Department of Transportation: open-graded asphalt concrete (OGAC), rubberized open-graded asphalt concrete (RAC-O), rubberized gap-graded asphalt concrete (RAC-G) and dense-graded asphalt concrete (DGAC). Tire/pavement noise was measured using the on-board sound intensity method (OBSI). A factorial experiment was developed and executed that considered these surface types, rainfall, traffic and age, with sections selected in the following age groups: less than one year old, one to four years old, and four to eight years old. A partial factorial was included for another type of open-graded mix, called F-mix. In addition, special sections placed by various Caltrans pilot and research projects were also included in the plan for field monitoring and laboratory testing. The report summarizes the measured performance and presents summary statistics for the results. Statistical analyses were performed, including single-variate regression to identify significant variables, multivariate regression, survival analysis, and principal components regression, depending on the type of data, in order to estimate performance. The performance models were used to estimate the life of the various surface types for the conditions in the experiment. The median noise reduction across the population included in the experiment is approximately 2 dB(A) for OGAC and approximately 3 dB(A) for RAC-O mixes compared to the DGAC mixes for the Standard Reference Test Tire (SRTT), with values converted from the Aquatred tire measurements used in the project. The Aquatred results are slightly different prior to conversion to the SRTT values, indicating slightly less noise benefit from open-graded mixes and less difference between OGAC and RAC-O.