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Pavement skid resistance
This document discusses various methods and standards for measuring pavement surface characteristics like skid resistance and texture. It covers topics like factors that influence skid resistance, methods for measuring micro-texture and macro-texture, standards for measuring polished stone value, and devices for measuring skid resistance at different speeds. The summary provides an overview of the key methods and standards discussed in the document.
Pavement skid resistance
- 1. KUNSAN NATIONAL UNIVERSITY Prof.Park Dae-Wook Vo Viet Hai
- 3. Skid resistanceis the friction developed to prevent a tire from sliding along the pavement surface. Lower when affected by water due to the phenomenon of hydroplaning and contaminated by mud or loose detritus resulting from the day to day usage. Important safety factor - Inadequate skid resistance will lead to higher rick of accidents.
- 4. Vehicle speed Surface texture (macro-texture) Surface condition Tire characteristics Weather Road geometry Aggregates (micro-texture)
- 6. According toBS 812 The Polished Stone Value of aggregate gives a measure of resistance to the polishing action of vehicle tires under conditions similar to those occurring on the surface of a road. The samples are first polished by the Accelerated Polishing Machine. Then the British Pendulum tester is use to measure the PSV.
- 7. Specimens before andafter polished 14 chips of sample clamped around the periphery of the 'road wheel’ 2 phases of abrasion The first phase is of abrasion by a corn emery for three hours, and then 3 hours of polishing with an emery flour Road wheel
- 8. According toASTM E303-93 The specimen is clamped into the holder in the same direction it has been polished in the machine The specimen and the slider are thoroughly wetted before each reading The mean value is reported as PSV PSV over 50 is regarded as a High Skid Resistant Aggregate, PSV over 65 is needed for particularly high stressed sites, PSV over 70 for rick sites Slider traverses a length of 76±0.5 mm
- 9. Micro-texture British Pendulum tester Featureon site measurement Static (spot measurement) skid resistance test equipment operated by hand Does not measure the impact that macro-texture has on skid resistance as vehicle speeds increase Not suitable for large scale investigating Cheap, portable and is suitable for site and incident investigation
- 10. According toASTM E1911 Measure pavement surface friction as a function of speed A disc that is made to rotate horizontally at a specified velocity before being lowered onto a wet pavement to measure friction The friction is measure by the resistance between the test surface and spring-loaded slider Spring-loaded slider
- 11. Device Features (Saitoet al. 1996) Measurement can be made in a very short time The device is designed to be compact and easy to handle Coefficient of friction is reported as a function of speed at a contact pressure similar to that of typical vehicles The slider can be easily replaced onsite, allowing the friction characteristics of different tire’s materials
- 12. According toASTM E274 To take a measurement, the vehicle (or trailer) is brought to the desired testing speed (typically 64 km/hr (40 mph)) Water is sprayed ahead of the test tire to create a wetted pavement surface The test tire braking system is then actuated to lock the test tire The result is reported as a Skid Number (SN).
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- 14. Skid Number Comments <30 Take measures to correct ≥ 30 Acceptable for low volume roads 31 - 34 Monitor pavement frequently ≥ 35 Acceptable for heavily traveled roads Advantage Most commonly use in U.S Reality Typical Skid Numbers (from Jayawickrama et al., 1996)
- 15. Popular choicefor the routine (proactive) monitoring of road networks The pavement is tested wet and the vehicles are fitted with large water tanks The test speed typically adopted is 50km/h (slip speed of 17km/h) Expensive compared to other types of test equipment
- 16. Compact andlightweight; easy to operate and to transport Braked wheel, fixed slip design with drag and load measured continuously Can be towed at any of the standard testing speeds up to 130 km/h; can also be used in pushing mode Simple on-site calibration takes only 10 minutes Rapid and simple data acquisition and presentation
- 17. Benefit Reliable - Low cost,robust and easy to maintain Durable - Excellent repeatability and reproducibility Accurate - Readings unaffected by road curvature Versatile - Suitable road and runway Easy To Transport - Can be towed by a wide variety of vehicles Efficient - 100 miles of testing with one tank of water Correlated Data - E274 Locked Wheel Tester, British Pendulum Tester and SCRIM Data Integration - Standard and custom data integration into any pavement management system (PMS) High Resolution - One reading every 32 inches
- 18. Measurement offriction and texture Wet or dry measurements Summer and winter measuring capability Reporting of the International Friction Index (IFI) Reporting of the peak friction Single test wheel can be mounted to any kind of host vehicle or trailer. Relatively expensive compared to portable tester and the grip tester
- 19. This methodologyoffers several advantages over current methods used in the practice The aggregates on the sample tray with marked grid points The images of each sample are automatically captured for the analysis of angularity and texture The results are showed on the computer (Masad, 2003) Sample tray
- 20. Advantages Analyze the shapeof a wide range of aggregate types and sizes Combining both the coarse and fine aggregate analysis into one system Distinct difference between angularity and texture; these properties have different effects on performance
- 21. Developed in2004-2006 Measurement of: ◦ Macro-texture in circular path ◦ Micro-texture in certain points of that path Structure: Rotating level Micro camera Adjustable mechanism Lens + Extension ring Converging cercal of two lasers Built-in macro sensor Optical precision bearer Micro laser emitter Translating level
- 24. According toASTM E965 Sand gradation follow by:
- 25. Surface texture depth Volumeof sand Diameter of sand spread
- 26. According toASTM E2380
- 27. Feature This approach ischosen when the texture depth probably too low (<0.3mm) The surface is pre-wetted in 1 minute The time required for water drop from upper reference line to lower reference line is recorded Very short outflow time is indicative of rough surface and vice versa 3 and 10 seconds are satisfactory for an asphalt pavement surface
- 28. The replacementfor sand path and outflow meter Larger quantity of valuable and less expensive Greatly reducing the safety and traffic control problems Report mean profiled depth (MPD)
- 29. According toASTM E 2157 CT Meter uses a laser to measure Record mean texture depth (MTD) and root mean squared (RMD) for each measurement Record date, temperature, concrete surface moisture, and concrete distress at test location
- 31. IFI isa harmonized value of Friction index to convert all skid and texture measurement to a common scale. Developed by PIARC According to ASTM E1960 IFI consists of two parameters: ◦ F60 – the coefficient of Friction at slip speed at 60km/h (Skid) ◦ Sp - the speed constant related to the surface texture depth (Texture)
- 32. F(s) isthe measurement of skid resistance made by any piece of equipment, operating with slip speed A and B are constants, the values of which were determined for each piece of skid resistance measuring equipment S = a slip speed 60 60 ( ) exp P S F A B F s S − = + × × ÷
- 33. Sp =the speed constant related to the texture depth, Tx PS a b Tx= + × a and b are constants relating to the texture depth measurement equipment.
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- 35. Design ◦Choose aggregate gradation(SMA or porous) ◦Reduce asphalt binder content Maintain ◦Small chip seal (with high PSV aggregate) ◦Grooving ◦Shot-blasting ◦High velocity water retexturing ◦Bush hammering ◦Rotating discs ◦New materials
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