Evaluation of Trapezoidal Shaped Grooves

Leading-edge buildup

Figure 32. Rubber Contamination at MCAF Quantico—Trapezoidal-Shaped Groove Researchers concluded that the difference in the rubber buildup on the leading edge of the grooves was due to the angular differences in the groove design. The standard groove has edges that are 90°, which would be more likely to shave or cut into the aircrafts rubber tire as it passes over it, while the trapezoidal-shaped groove has a slightly flatter angle of 117°. The difference in the sharpness of these edges very likely determines how much rubber is caught on those edges. Researchers observed evidence of this phenomenon at several locations on the runway at MCAF Quantico but decided to wait several more months before making a final determination. In June of 2009, researchers returned to MCAF Quantico to conduct further evaluation of the grooves resistance to wear and durability. Upon arrival at MCAF Quantico, researchers were disappointed to learn that the airport had recently conducted rubber removal operations on the entire runway. As a result, the rubber buildup that had occurred since the grooves were first installed had been removed. The airport manager explained that they were very pleased with the performance of the trapezoidal-shaped grooves in regards to their resistance to rubber contamination, as they were able to delay the rubber removal process for almost 9 months longer than they have historically been able to do with the standard grooves. This information was valuable to researchers, as it showed that the airport made its own assessment of the trapezoidal- shaped grooves improved wear and durability and was able to appreciate a noticeable difference in their performance. Over the life of the pavement, the airport manager explained that the airport would save a lot of money due to the lesser frequency of rubber removal expenses. During their visit, researchers conducted their inspection of the grooved surfaces with the understanding that they had been exposed to a recent rubber removal operation. Upon inspection, researchers were still able to see evidence that the standard grooves had collected

33