DOUGIE MILLAR TRANSPORT SCOTLAND

Transcription

1 DOUGIE MILLAR TRANSPORT SCOTLAND

2 A Collaborative Approach to HIGHWAY MANAGEMENT The Journey from SMA to TS2010 Dougie Millar Consultant Materials Advisor Transport Scotland

3 Traditional surfacing Hot-rolled asphalt HRA Once widely used on major roads Many routes still have this type of surfacing Skid resistance provided by chippings pre-coated with bitumen Chippings spread and rolled while asphalt mat is hot

4 Thin surfacing systems Thin surfacing Developed in Germany/France Coarse and fine aggregate bound by mastic Bitumen may contain fibres and/or polymers Quicker to lay than traditional Reduced road/tyre noise & spray High rut resistance First trialled in the mid to late 90s

5 Performance of asphalt 2006 surfacing review Objectives Document the current performance of asphalt surfacing materials used on the Scottish trunk road network Identify and quantify the extent of any defects Recommend improvements

6 Observed defects loss of aggregates 4 months 8 months 1 year 3 years

7 Observed defects fatting up

8 Observed defects - workmanship

9 Transport Scotland Pavement Forum (TSPF) TSPF Objectives Chaired by Transport Scotland To review trunk road network surfacing issues, such as safety, durability, performance, cost effectiveness and workmanship To liaise with other Overseeing Organisations and stakeholders, including the materials supply sector To ensure best practice is being implemented.

10 Transport Scotland Pavement Forum In Collaboration with: TRL MPA RBA IAT Operating Companies Transport Scotland Scottish Road Works Commissioner SCOTS PAG And specialists when required

11 TSPF initiatives (2007) Enhance the performance of surfacing Trial of modified materials on M8 Annual surface inspections (SIP) raising the quality bar Team of cross-industry surfacing experts will report on quality and performance issues Dissemination training/education seminars Best practice guides, e.g. RN42: Philosophy of durability

12 SIP Results Comparison of average markings for SIP2008 to SIP2012 Type of defect recorded on SIP surveys Comparison of recorded defects for SIP surveys

13 M8 trial - 65,000 vehicles/day

14 Trial Layout Jt 5/ Shotts 1.2km (8 x 150m sections, G = gritted) S1.1 S1.2 S1.3 S1.4 S2.1 S2.2 S2.3 S2.4 0/14 0/10 0/8 0/6 0/6G 0/8G 0/10G 0/14G JT 6/ Airdrie M8 Newhouse to Duntilland

15 Gritting Close-up of 0/14mm before (left) and immediately after (right) gritting

16 Skid resistance measurements Phase 1 Early life Context Bitumen wears away Duration is traffic dependant Perceived accident risk!? Phase 2 Polishing Phase Normally 1yr+ Phase 3 Equilibrium Most of the life of the surfacing Varies cyclically through year; peaks in winter, lowest in mid-summer

17 Skid resistance measurements Low speed High speed SCRIMtex: Test wheel angled at 20 degrees, at a test speed of 50 km/h Also carries a laser sensor to measure SMTD GripTester: The gear ratio makes the test wheel rotate more slowly, induces around 15% at a test speed of 50 km/h Pavement Friction Tester (PFT): Measures locked-wheel friction number (Fn) up to 120km/h

18 Equilibrium phase Low Speed (wet) (After 21 months) (Wheel path) HD28 - IL After 21 months

19 TS2010: What are the main differences No Texture requirement PSV declared Skid resistance (GN) 4 weeks and 6 months verification with SCRIM Annually and re-classified TAIT required, 3 stages Air Voids range in the mat required Gritted mat for early life skid resistance

20 HE Approach IAN 154 (SHW Clauses 903,921 &942 ) Min and Max Texture requirement and Average set of 10 minimums Texture requirement changes for HIGH, LOWER speed roads and Roundabouts Stress level introduced IAN 156 (HD36) Reduce PSV requirement for Surface course aggregates Non event sites only 10mm advised for roundabouts

21 Latest Information

22 Latest Information

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24 TS 2010 update

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27 Emerging Experience Stone size Increasing aggregate size Increasing contact area

28 Maintenance : Reconstruction example Normal Construction Reconstruction Surface Course 40 mm Lasts 5 Years 25 mm TS 2009: Lasts 15 years? Binder Course Base Course 80 mm 95 mm Possibly cost neutral initially EME2 Therefore in 30 years 14mm Thin Surfacing would be removed and replaced 6 times! 6 mm TS2010 replaced Twice! You do the Maths!

29 The future? Innovation through Collaboration Client/Industry/research, TSPF and TS Research Board Crumb Rubber (reducing the bitumen content) Warm, Half Warm and Cold asphalt Learn from mistakes Build Maintenance in use of averaging beam for all paver laid material Educate and share knowledge Grab the interest of young Engineers The improvement will follow

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32 Thank you for your attention