Laboratory Performance Testing of Open-Graded Friction Course Mixtures

Several lab tests were used in this study to evaluate mixture properties. A draindown test, Cantabro stone loss test, a permeability test, and a modified version of AASHTO T-283 were used to evaluate laboratory performance of open-graded friction course (OGFC) mixes. Some of the more pertinent conclusions were as follows. The CoreLok procedure appears to be a more accurate method of determining bulk specific gravity of compacted specimens than the dimensional method. The minimum air voids content for new-generation OGFC mixtures should be 18% on the basis of the dimensional method and 16% on the basis of the CoreLok method. The addition of fiber stabilizers significantly reduced the potential for draindown. Superpaver; gyratory compactor (SGC)-compacted samples can be used for the Cantabro stone loss procedure. Unconditioned SGC samples should have stone loss of no more than 20%. If an aging process is used, the maximum amount of stone loss should be limited to 24%. Because there is not a significant difference between unaged and aged sample results, the aging procedure is not necessary. Results from this study show no significant difference in tensile strength when one, three, and five freeze-thaw cycles are used in the moisture-conditioning procedure. Therefore, only one freeze-thaw cycle is needed.