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COMPARISON OF THE WEHNER-SCHULZE AND PSV TEST FOR ESTIMATING THE POLISHING RESISTANCE OF NEW ZEALAND CHIP SEAL AGGREGATES

Presented by : Dr Haran ArampamoorthyPrincipal research Engineer

OPUS Central Laboratories

3rd International Road Surface Friction Conference , Gold Coast, Queensland, 15 – 18 May 2011

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Key topicsIntroduction

Purpose of the researchThe two testsPrevious test results

Data collectionResultsConclusion

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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

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British Polish Stone Value test

Developed in Britain and commonly used in New Zealand and Australia

Test was adopted in New Zealand in 1990’sSurfacing 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.

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Polisher for the British pendulum tester equipment

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British pendulum tester

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PSV specimens

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Previous Central Laboratories Research NZTA project looking relationship between

quarry source, PSV and the SCRIM valueSCRIM relationship to PSV is not a robust

relationshipSCRIM data with Aggregate source estimator gives

a better relationship

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Data selection

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Wehner- Schulze test aggregate polishing test Developed in Germany in 1960’sAbility to test samples taken from the roadPotential to measure aggregate polishing when

aggregate orientation is typical of a normal road surface

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Wehner - Schulze (WS) test instrument

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Accelerated polishing part

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Main skid resistance tester

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Specimen preparation for WS testWS tests were conducted at the Technical

University Dresden, GermanyChip seal core from road can’t be tested using

their standard test methodToo high stress on their equipment if tested

using chip seal core (equipment cost $200,000)Their standard procedure: hand place chips

specimen

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Specimen for Wehner - Schulze

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Asphalt surface test results SCRIM Vs PSV (Alan et.al. (2008)

Results shows SCRIM influenced by factors other than PSV

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Data selection

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Selected quarry samples and the expected PSV

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Test results

Quarry No. Pavement Source District

Test results

PSV Wehner Schulze

1 Waiotahi Gisborne 60 0.41

2 Waotu_Quarry Hamilton 51 0.31

3 Balclutha Dunedin 61 0.42

4 Gore_Gravel Invercargill 54 0.37

5 Whitestone Christchurch 55 0.36

6 Slag material Napier 46 0.33

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Relationship between WS and aggregate source estimate

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WS test results against PSV results (three points A, B and C from Woodbridge et. al. (2006))

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DiscussionBritish 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

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ConclusionResults 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.

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Thank You

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Contact details:

Ph No.: 0064 4 5870651

E-mail: Haran.Arampamoorthy@opus.co.nz