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

This article discusses the need to predict the evolution of road skid-resistance over time and presents a laboratory test method using the Wehner/Schulze machine. The results are compared with road data to ensure long-term performance and optimize material choice. The article also explores the relationship between skid-resistance and traffic count, as well as the influence of other factors such as aging and seasonal variations.

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

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  1. 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@lcpc.fr

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

  3. 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

  4. Aggregate testing (i.e. PSV) • drawback: transposition aggregates  mixes? Existing empirical tools • Experimental sites tracked over time • drawbacks: costs , time 

  5. 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

  6. Wehner/Schulze machine • Origin: University of Berlin (70’s) • Functions: polishing & friction measurement • Specimens: cores Ø 22.5 cm • Tested materials: concrete asphalt, aggregates, sand LCPC polishing tests – Test machine

  7. “Polishing” function • Principle: rolling rubber cones with (water + abrasive) mix • Cone contact pressure: 0.4 N.mm-2 • Rotation speed: 500 rpm • “Friction measurement” function • Principle: sliding rubber pads with water • full « braking » curve (µ-time) from 100 km/h to complete stopping LCPC polishing tests – Wehner/Schulze machine

  8. 22,5 cm 22,5 cm LCPC polishing tests – Specimens • Concrete asphalt • Cores taken from pavements or laboratory-made slabs • Aggregates • Mosaic discs (fraction 7.2/10 mm)

  9. µmax • Microtexture measurements (polished part) • Initial state (0 pass) • At µmax • 90,000 and 180,000 passes 15 profiles, spaced every 0.5 mm L = 76 mm, x = 0.01 mm 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

  10. LCPC polishing tests – Laboratory results (1/2) • Aggregates vs asphalt mixes

  11. LCPC polishing tests – Laboratory results (2/2) • Wehner/Schulze vs PSV µWS = 1.06(PSV/100) – 0.20

  12. Polishing tests (just after road construction) Ageing effect (every 6 months) Traffic count Skid-resistance evolution (every 6 months) simulation vs actual evolution From laboratory to road • Core sampling on new roads tracked over time Wheel paths

  13. Polishing tests Traffic count Friction measurements (Wehner/Schulze machine) polishing duration  traffic From laboratory to road • Core sampling on circulated roads Wheel paths

  14. N = k.T N: number of passes T: cumulated truck number (source from Tang PhD thesis, 2007) k = constant = 0.024 Calibrated from 13 sites From laboratory to road • Relationship polishing duration – traffic

  15. From laboratory to road • Simulation vs actual evolution

  16. ? Simulation from Wehner/Schulze machine Measurement by means of ADHERA device (blank PIARC tyre, locked wheel) From laboratory to road • Towards a prediction of skid-resistance evolution • Problem statement

  17. ? N = 0.024 T From laboratory to road • Towards a prediction of skid-resistance evolution • Approach

  18. LFC (80 km/h) = 1.04 µWS– 0.01 LFC from Stuttgart Friction Tester, ribbed tyres SFC (80 km/h) = 0.96 µWS + 0.06 SFC from SCRIM From laboratory to road • Towards a prediction of skid-resistance evolution • Relationship µWS – LFC/SFC (source from Huschek, 2004)

  19. Overestimation 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

  20. 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

  21. 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)

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