Evaluation of Trapezoidal Shaped Grooves
EXECUTIVE SUMMARY The Federal Aviation Administration (FAA) Airport Technology Research and Development Team initiated research to evaluate a new trapezoidal-shaped pavement groove configuration. The purpose of this evaluation was to determine if a new trapezoidal-shaped pavement groove configuration offered any benefits over the current FAA standard, square-shaped groove configuration, specifically in the areas of water evacuation, rubber contamination, integrity, longevity, and friction values. The new trapezoidal-shaped groove configuration is 1/4 in. deep, 1/2 in. wide at the top, and 1/4 in. wide at the bottom, spaced 2 1/4 in. apart. The current FAA standard groove configuration is 1/4 in. deep, 1/4 in. wide, spaced 1 1/2 in. apart. The FAA standard groove configuration for saw-cut grooves on runway surfaces is based on comprehensive research conducted in the past that evaluated several groove configurations based on square-cut grooves. The FAA standard groove configuration has performed successfully for both rigid (Portland cement concrete) and flexible (hot mix asphalt) pavements. Saw-cut grooves deteriorate over time from repeated rubber deposit removal, brooming, and snowplowing operations. Past research considered these sources of deterioration but did not consider trapezoidal-shaped groove configurations partly due to practical limitations in saw blade manufacturing and design technology. A proposal from a recognized industry grooving and grinding enterprise suggested that different geometries for saw blades are feasible. The sloped sides of the proposed groove geometry may have a positive influence on the groove integrity and longevity. Test sections of the new trapezoidal-shaped pavement grooves, along with sections of the FAA standard grooves, were installed at the FAA National Airport Pavement Test Facility, the Atlantic City International Airport, Marine Corps Air Facility Quantico, and Chicago O’Hare International Airport. Researchers conducted water evacuation measurements, analysis of rubber contamination, width measurements, and surface friction tests on the trapezoidal-shaped pavement groove test sections under a variety of different conditions and compared the results directly to those of the current FAA standard grooves. The results showed that the trapezoidal-shaped pavement groove configuration offered several benefits over the current FAA standard groove configuration, including improved water evacuation capability, greater resistance to rubber contamination, better integrity, and improved longevity. The friction values for the trapezoidal grooves were comparable to the FAA standard grooves. Analysis of the data collected during this evaluation indicates that the new trapezoidal- shaped pavement groove should be considered an acceptable alternative for pavement grooving on airports.
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