Comparison of Mix Design Methods for Porous Asphalt Mixtures

Abstract

Porous asphalt mixtures have been used for more than 60 years, but it was not until 1974 that the first formalized procedure was created by the Federal Highway Administration to design mixtures for open-graded friction courses (OGFC). Since that time, there have been several other mix design procedures developed and adapted, mainly for OGFCs on high-volume roadways. In the past decade, porous asphalt pavements have been gaining popularity as a storm water best management practice and utilize similar mixtures as those used for OGFCs. However, for any porous mixtures to perform as intended, they must be designed and constructed properly. Across the United States, there are currently more than 20 different methods used to design these mixtures. The objective of this research was to compare the different mix design procedures currently used in the United States. The results indicated that some of the procedures result in a range of design binder contents instead of a single value. This does not provide much guidance to inexperienced designers, which could result in pavement performance issues that could deter the future use of porous asphalt mixtures.