High Friction Surface Treatment Deterioration Analysis and Characteristics Study

High friction surface treatment (HFST) is used to improve friction on curved roadways, especially on curves that have a history of wet pavement crashes. Observations on the long-term performance monitoring of HFST sections at the National Center for Asphalt Technology (NCAT) Test Track showed friction (skid number, SN) dropped significantly at the end of service life of HFST, creating unsafe driving conditions. There is no clear, observed friction deterioration trend to predict the friction drop when using friction performance measures like SN. Therefore, there is an urgent need to explore and develop supplementary HFST safety performance measures (such as aggregate loss) that can correlate to friction deterioration and provide predictable, cost-effective, and easily measurable results. The objectives of this paper are to (i) analyze the correlation between HFST aggregate loss percentage area and friction value using a dynamic friction tester (DFT), and (ii) study the characteristics of HFST deterioration associated with aggregate loss, at the NCAT Test Track and at selected HFST curve sites in Georgia (using 2D imaging and high-resolution 3D laser scanning). Results show a strong correlation between HFST aggregate loss percentage area and DFT friction coefficient. Where friction measurement is used as the primary safety performance measure, it is recommended that HFST aggregate loss be used as a supplementary performance measure for monitoring the HFST safety performance deterioration. Aggregate loss can be easily identified by characteristics such as color and texture change. Preliminary texture analyses of 3D HFST surface profiles show lower mean profile depth (MPD) and ridge-to-valley depth (RVD) texture indicators can also identify loss of aggregate spots on HFST surface.