Structural contribution of open-graded friction course mixes in mechanistic-empirical pavement design

Open-graded friction course (OGFC) is often believed to have no contribution to the structural capacity of flexible pavement. In this study, five types of OGFC mixtures were prepared and tested for rutting potentials, and three of them were tested for dynamic moduli, which were further used to analyse pavement's response and performance based on the procedures in the mechanistic-empirical pavement design guide (MEPDG). It was found that the tensile strain at the bottom of asphalt concrete layers and the compressive strain at the top of sub-grade layer are sensitive to the availability of OGFC, regardless of mixture type. The fatigue and permanent deformation damages of a flexible pavement can be effectively reduced after adding the OGFC layer, due to the alteration of loading frequency, thermal gradient and modulus ratio. Trial designs using MEPDG software in two different climates verify the above observations.