Comparison of the Wehner-Schulze and PSV test for estimating the polishing resistance of New Zealand chip seal aggregates Presented by : Dr Haran Arampamoorthy Principal research Engineer OPUS Central Laboratories 3rd International Road Surface Friction Conference , Gold Coast, Queensland, 15 – 18 May 2011
Key topics • Introduction • Purpose of the research • The two tests • Previous test results • Data collection • Results • Conclusion
Purpose of the research • Majority of New Zealand roads are chip seal surfaced • British Polish Stone Value test adopted in NZ in the 1990s to select aggregate • Prediction of aggregate performance by the PSV test is extremely variable. • Purpose to determine the ability of Wehner- Schulze test to predict or rank the on road skid resistance of New Zealand aggregate
British Polish Stone Value test • Developed in Britain and commonly used in New Zealand and Australia • Test was adopted in New Zealand in 1990’s • Surfacing aggregate is currently selected according to the NZTA T/10 specification (Skid Resistance Deficiency Investigation and Treatment Selection) • PSV test relies on an operator hand placing stones.
Previous Central Laboratories Research • NZTA project looking relationship between quarry source, PSV and the SCRIM value • SCRIM relationship to PSV is not a robust relationship • SCRIM data with Aggregate source estimator gives a better relationship
Wehner- Schulze test aggregate polishing test • Developed in Germany in 1960’s • Ability to test samples taken from the road • Potential to measure aggregate polishing when aggregate orientation is typical of a normal road surface
Specimen preparation for WS test • WS tests were conducted at the Technical University Dresden, Germany • Chip seal core from road can’t be tested using their standard test method • Too high stress on their equipment if tested using chip seal core (equipment cost $200,000) • Their standard procedure: hand place chips specimen
Asphalt surface test results SCRIM Vs PSV (Alan et.al. (2008) Results shows SCRIM influenced by factors other than PSV
WS test results against PSV results (three points A, B and C from Woodbridge et. al. (2006))
Discussion • British materials have similar results to the New Zealand data which confirms that the testing performed has been consistent. • One significant outlier - British limestone, ( point C) has a low PSV and WS value. • Slag (No 6) not a natural aggregate shows similar relationship to WS values as the natural aggregates • Both figures show tests are not good predictors of on road performance • Good correlation between the WS value and PSV
Conclusion • Results do not confirm that the WS is better than PSV test in predicting the field performance of chip sealing • The WS test have potential to evaluate bituminous mixes • Chip seal can’t be tested using WS test • The test in its present form can not be used in New Zealand.
Contact details: Ph No.: 0064 4 5870651 E-mail: Haran.Arampamoorthy@opus.co.nz