Site Assessment of Surface Texture and Skid Resistance by Varying the Grit Parameters of an SMA

For the safe operation of vehicles, pavement should provide adequate skid resistance, which can be achieved by using high polishing–resistant aggregate in wearing courses. However, supplying high-quality aggregate is not always feasible due to high transportation costs. For this reason, a method called gritting was adapted to meet the Highway Technical Specification (HTS) of Turkey in 2013. According to the method, for certain parts of the country, the wearing course can be constructed with local aggregates that have minimum polished stone value (PSV) of 40 ($\mathrm{PSV}\ge 40$), but, in this case, the surface must be covered with a high polishing–resistant aggregate ($\mathrm{PSV}\ge 50$), after the rollers’ first pass. The objective of this study was to improve the present gritting method by investigating the effect of grit parameters on pavement performance under real traffic conditions. In this regard, during its construction, the wearing course of O-51 Highway was gritted with different aggregate types (slags and natural), sizes (1–3; 1–5 mm), spreading amount (1.5; 2; $2.5\mathrm{kg}/{\mathrm{m}}^2$), and spreading time (before and after the first pass of a roller) on eight test sections. Then, the macrotexture and skid resistance performance of these sections were evaluated under real traffic and environmental conditions for longer than 4 years. Changes in surface texture and skid resistance with respect to traffic were determined for each section. The results showed that higher skid resistance values were obtained at the sections gritted with metallurgical slags. Additionally, the sections gritted with 1–5 mm aggregates had better skid resistance than those gritted with 1–3 mm, while the change in mean texture depths were not very significant.