Laboratory test method for the prediction of the evolution of road skidresistance with traffic

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Laboratory test method for the predictionof the
evolution of road skid-resistance with traffic

• Minh-Tan Do
• LCPC
• Research engineer
• E-mail minh-tan.do_at_lcpc.fr

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Scope

• Need to predict skid-resistance evolution
• Existing empirical tools
• LCPC polishing tests
• From laboratory simulation to road prediction
• Conclusions

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Need to predict skid-resistance evolution

• Road skid-resistance evolves with time
• due to mechanical actions (traffic)
• due to climate effects
• Prediction of skid-resistance evolution is
  needed
• to forecast road maintenance
• to ensure long-term performance
• to optimize material choice

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Existing empirical tools

• Experimental sites tracked over time
• drawbacks costs ?, time ?

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LCPC polishing tests Objectives

• Quick laboratory tests
• Able to test concrete-asphalt mixes and
  aggregates
• Comparable results with road data
• Means to predict skid-resistance evolution

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LCPC polishing tests Test machine
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LCPC polishing tests Wehner/Schulze machine
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LCPC polishing tests Specimens

• Concrete asphalt
• Cores taken from pavements or laboratory-made
  slabs
• Aggregates
• Mosaic discs (fraction 7.2/10 mm)

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LCPC polishing tests Test procedure

• Friction-time plot
• Friction measurement every 1000 passes ? µmax is
  reached
• Next stops 3-5-9.104 passes
• End 180,000 passes

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LCPC polishing tests Laboratory results (1/2)

• Aggregates vs asphalt mixes

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LCPC polishing tests Laboratory results (2/2)

• Wehner/Schulze vs PSV

µWS 1.06(PSV/100) 0.20
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From laboratory to road

• Core sampling on new roads tracked over time

Wheel paths
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From laboratory to road

• Core sampling on circulated roads

Wheel paths
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From laboratory to road

• Relationship polishing duration traffic

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From laboratory to road

• Simulation vs actual evolution

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From laboratory to road

• Towards a prediction of skid-resistance
  evolution
• Problem statement

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From laboratory to road

• Towards a prediction of skid-resistance
  evolution
• Approach

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From laboratory to road

• Towards a prediction of skid-resistance
  evolution
• Relationship µWS LFC/SFC (source from Huschek,
  2004)

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From laboratory to road

• Towards a prediction of skid-resistance
  evolution
• Comparison prediction/measurement

actual LFC-T plot
µWS-N plot converted into equivalent LFC-T plot
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Conclusions Where are we / objectives?

• Quick laboratory tests
• ½ day to plot a full friction-time curve, could
  be ? depending (N 0.024T) on anticipated
  traffic
• Able to test concrete-asphalt mixes and
  aggregates
• Yes, except very aggressive surfaces
• Comparable results with road data
• Yes, first tendencies to be supported by other
  experiments
• Means to predict skid-resistance evolution
• Promising first results

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Conclusions Next step

• Investigate the relationship polishing duration
  ? traffic
• k (N kT) should be constant ?
• Relationship µWS ? LFC/SFC
• Relative influences light vehicles/trucks
• Prediction model, taking into account other
  mechanisms (seasonal variations, ageing)