Volume 32, Issue 1 (January 2004)
Evaluation of Hot Mix Asphalt Macro- and Microtexture
Pavement macrotexture is considered the primary factor in skid resistance at speeds over 65 km/h (40 mph). A total of 18 projects (9 Superpave and 9 Marshall mix designs) were evaluated to determine if the macrotexture of the pavement surface was influenced by gradation changes associated with the move to Superpave mix designs. The Federal Highway Administration ROSAN high-frequency laser system was used to measure macrotexture. Changes in microtexture, also a factor in skid resistance, were evaluated using a British Pendulum (BP) tester to determine the BP numbers of laboratory-compacted samples. Results indicated that the macrotexture did not change as a result of changes in mix design practices. The nominal maximum size of aggregate seemed to be the key factor in change in pavement surface macrotexture. Mixes, either Superpave or Marshall, with a nominal maximum size 9.5 mm or 12.5 mm have macrotextures of less than 0.5 mm. Based on information in the literature, the skid resistance for these Alabama pavements was estimated at 40 or higher.