Assessment of the Darmstadt scuffing device for ravelling resistance in porous asphalt used in Italian motorways

Porous asphalt (PA), widely used in wearing courses of Italian motorways, continues to gain attention for its ability to enhance rainwater drainage and improve road friction under adverse weather conditions. However, PA is susceptible to ravelling, a degradation process primarily caused by tire/pavement interaction during vehicle manoeuvres. This study investigates the ravelling resistance of PA under both dry and wet conditions using the conventional Cantabro test and the innovative Darmstadt Scuffing Device (DSD) which simulates the tire movements during steering, acceleration, and braking. PA mixtures from ten different asphalt plants, produced according to Italian technical specifications for motorways, were tested. Results show that the DSD is effective in measuring ravelling resistance. Comparison of the DSD and Cantabro test results revealed poor correlation, likely due to differences in testing temperatures and the DSD’s more realistic loading conditions. Two limits for the DSD test results were established to assess the PA ravelling performance. Finally, the repeatability of the DSD test was preliminarily assessed.