Development of a Performance-Based Mix Design for Porous Friction Course

Abstract

The development of a performance-based mix design procedure for Porous Friction Course (PFC) will help to mitigate some of the life cycle issues encountered with PFC pavements. PFC pavements are prone to raveling and cracking which lead to short service lives. A PFC is typically more expensive than a dense-graded mix due to required high quality aggregate materials, modified asphalt binder and higher asphalt binder contents. The use of PFC provides numerous safety benefits and also improves the noise quality of surrounding areas. Many agencies once used PFC for these reasons but have since halted its use due to performance issues. This study used laboratory performance tests to evaluate three PFC pavements that had good field performance (up to 18 years) and three PFC pavements that had poor performing field performance (less than 8 years). This research study was composed of four parts. The first was to evaluate the six designs and determine if there was a distinguishable difference in performance results between the good and poor designs. The second part evaluated the use of increased P-200 content to provide more durable designs. The third section used asphalt binder modifiers to determine if mixture performance was affected. These designs had the stabilizing additive (fiber) removed from the design to evaluate if the binder modifiers could eliminate the need of the fiber as a stabilizing agent. The fourth and final part evaluated the strength of varying nominal maximum aggregate size (NMAS) mix designs at three different lift thicknesses to determine if the typical lift thickness (1.0 inch) of PFC pavements was adversely effecting performance of the designs. A balanced mix design approach was selected for designing PFC pavements. Criteria and performance tests for durability, cracking and cohesiveness were selected. An increased P-200 content had a positive effect on almost all of the results, and it is recommended that the current P-200 gradation band be expanded. The binder modifications did not show total improvement but did provide some alternative design options. The NMAS to lift thickness ratio does not affect the durability of the mix.