| An open graded friction course (OGFC) is a type of porous pavement that has been used to improve safety, mainly in wet conditions. However, this mix also has exhibited poor durability and strength which limits its use in some pavement applications. This research investigated the effect of aggregate gradation on the performance of OGFCs. Ten OGFC gradations which are used by twenty different states were compared. One asphalt binder was used throughout the research (PG76-22) and hydrated lime and cellulose fibers were also added to all of the mixes.;Several tests, using various standardized testing procedures, were used in this study to evaluate laboratory performance of the different OGFC mixes. These included draindown, Cantabro abrasion loss, rutting resistance, permeability, and moisture susceptibility.;The results of the study indicated that the addition of fiber stabilizers significantly reduced the potential for draindown and significantly improved the durability of the mixtures. All of the mixes unconditioned and conditioned had an abrasion loss well below the limit criteria. The results also indicate that an increase in dry rodded unit weight of the aggregate gradation contribute to significant reduction in porosity and permeability of the OGFC mixture. Consequently, strengths decreased as air voids increased, porosity increased with air voids, and permeability increased as air voids increased. There was no significant difference between unaged and aged sample abrasion resistance results except for two mixes. The ten mixes showed good moisture resistance characteristics and most of the mixes had no significant difference in tensile strength after the moisture-conditioning procedure. Furthermore, the effects of rutting did not correlate with dry rodded unit weights or air void content.;Finally, it was found that the aggregate gradation does influence the performance of OGFC mixtures; an increase in the dry rodded unit weight (reduction in void ratio) of the gradation reduces the permeability and increases the strength. Therefore, an aggregate gradation for an OGFC mixture can be optimized depending upon the performance requirements (permeability or strength) based on the void ratio of the gradation. |
