A Comparison of the Frictional Properties of 4.75 and 12.5 mm HMA Surface Mixes

摘要

The use of 4.75 mm Nominal Maximum Aggregate Size (NMAS) asphalt mixtures is gaining popularity as an efficient paving alternative. These mixes are placed in thin lifts, thereby reducing the quantity and cost of materials, as well as construction time. While 4.75 mm mixes possess many advantages, the nature of these mixes could pose safety concerns relating to skid resistance. A field study was performed to compare the frictional properties of 4.75 and 12.5mm mixtures, both newly constructed and after 15 months in service. A number of test methods were used to determine the frictional characteristics of the pavement sections, including the British Pendulum test, the volumetric method for texture depth, the Dynamic Friction Tester, the Circular Track Meter, a full-scale skid trailer, and the Automatic Road Analyzer (ARAN). The International Friction Index (IFI) was also considered. The results of the study indicated that the 4.75 mm mixtures have performed well and maintained their frictional properties over time, whereas the 12.5 mm mixtures have exhibited a decrease in both microtexture and macrotexture after 15 months of service. Overall, it was concluded that the frictional properties of the 4.75 mm mixtures appear adequate for routine use as a cost-effective surfacing alternative.