Laboratory and Field Evaluation of Single Layer and Double Layer High Friction Surface Treatments

Abstract

High friction surface treatment (HFST) has been proactively used as a solution to extreme friction demands at locations such as horizontal curves, ramps, bridge decks, and intersections. Considerable efforts have been made to evaluate the use of HFST across the United States (U.S.) The American Association of State Highway and Transportation Officials (AASHTO) has issued a provisional specification, i.e., AASHTO PP 79-14, to help state Departments of Transportation (DOTs) to successfully apply HFST. This paper presents a further effort made by the authors to evaluate and compare the friction performance and durability of single and double layer HFTS systems with calcined bauxite aggregate. The laboratory accelerated polishing was conducted to evaluate the effects of aggregate candidate gradations on the friction performance, such as friction coefficient and macrotexture mean profile depth (MPD), and to determine the aggregate gradation for field evaluation. Field evaluation was conducted on both single and double layer HFST systems using test strips under actual traffic polishing over a time period of nine months that covered an entire snow season. It was found that larger aggregate size tends to yield larger MPD, but larger MPD does not necessarily imply larger friction. The double layer HFST did not outperform the single layer HFST with respect to friction and durability. If the properties of calcined bauxite aggregate are precisely defined, either surface friction or MPD can solely be utilized as the frictional metric for quality assurance (QA) of HFST.