Investigation of Short- and Long-Term Variations of Pavement Surface Characteristics at the Virginia Smart Road

Analysis of the frictional properties of the tire-pavement interface provides useful information to minimize wet-weather accidents and aid state agencies in making better pavement management decisions. In this paper, the surface friction and texture properties of 12 asphalt pavement sections placed at the Virginia Smart Road pavement facility were studied over a 6-year time period. The surfaces investigated include five SuperPaveTM mixes, an Open-Grade Friction Course (OGFC) and a Stone Matrix Asphalt (SMA) mix. The levels of friction and macrotexture of these pavement sections were compared and analyzed. Short-term (seasonal) and long-term (multi-year) variations of the surface characteristics were investigated in order to learn how the properties vary with temperature and time, which can be used to support asphalt mixture selection, determine the need for friction correction factors, and assess their suitability for use on the network pavement monitoring. The investigation confirmed that the environmental factors have a significant effect on the seasonal variation of friction. For all mixture types investigated, the friction measurements experienced variation within a year (short-term) and throughout several years (long-term). Both the friction number at zero speed [FN(0)] and percent normalized gradient (PNG) decrease in the summer and thus friction varies differently at low and high speeds. In the long term, the low-speed friction increases first due to weathering of the asphalt film from the aggregate, and then starts to decrease, probably due to polishing and weathering. Macrotexture variations are almost unnoticeable within a year and small across 5 years. The measured texture depth initially decreases a little, and then starts a modest ascending trend. This is probably due to the loss of fines through weathering and/or washing by the rainfall.