This paper details the first assessment of asphalt mixes used in Ireland using the Wehner Schulze test equipment. The mixes assessed were 10mm SMA, 14mm SMA and hot rolled asphalt (HRA) made with PSV 62 greywacke aggregate. The Wehner Schulze was developed about 30 years ago in Germany and is currently being considered as a European Standard test method. The equipment used was located at IFSTTAR in Nantes, France. Asphalt test specimens (305mm x 305mm x 50mm) were prepared using a Cooper roller compactor. 225mm diameter cores were then extracted from the slabs for testing on the WS machine. The results found the 10mm and 14mm to have higher friction coefficient values compared to the hot rolled asphalt. Analysis of the data suggests that this is probably due to differing types of contact between the asphalt surface and the Wehner Schulze polishing rollers and rubber pads used for friction measurement. The investigation suggests that the tire / asphalt surface interface needs further research to help explain both the laboratory and on-site measurement of friction.
