Comparison of open graded friction course mix design methods currently used in the United States.

摘要

This research compares the open graded friction course (OGFC) mix design methods which are currently being used in the United States. OGFCs are a type of porous pavement that have been used in the United States since 1944, but has provided inconsistent and highly variable performance results. The design procedures for several agencies were obtained, and then compared for similarities. All of the design methods were then conducted to determine the optimum binder content. The optimum binder content (OBC) of a single aggregate gradation for each method was tested for properties and performance characteristics.;The design methods which are currently used all fall into three categories. The first is a property and performance specification where samples of various binder contents are tested for certain characteristics and samples prepared of the OBC have to meet a set of criteria. The second is an oil absorption method where the oil absorption of the aggregate is used in a series of empirical calculations to determine the optimum binder content. The final method is a visual determination where binder draindown is visually analyzed to determine the optimum binder content.;Although most of the trends in testing data follow that of a dense graded pavement, a few characteristics did not. The air voids, VFA, porosity, permeability, and abrasion data trends were all seen as expected. The BSG and VMA results did not show the trend, but can be attributed to the high air void content of OGFCs.;The design methods produced optimum binder contents which had high variability. The oil absorption and visual determination methods all produced a single optimum binder content which varied over 0.5%. The property and performance specification results showed a range of results which were only capped by the binder content range used in research.