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High PSV on Auckland Motorways

High PSV on Auckland Motorways. Bruce Chappell, AMA Glynn Holleran, AMA. Central Motorway area 200,000 vpd Areas of ramps and mainline require PSV >65 Mainline requires high texture surfacing for spray suppression and skid resistance - OGPA

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High PSV on Auckland Motorways

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  1. High PSV on Auckland Motorways Bruce Chappell, AMA Glynn Holleran, AMA

  2. Central Motorway area 200,000 vpd Areas of ramps and mainline require PSV >65 Mainline requires high texture surfacing for spray suppression and skid resistance - OGPA Default in the past has been to use PSV65 Motouhora aggregate Now AMA uses slag in OGPA on mainline Slag does not provide PSV to old or new T/10 The Problem

  3. For some ramp areas and low speed high volume SH mainline lanes, T/10 also requires PSV of high skid resistance surfacing (HSRS). But for long term performance HSRS’s rely on a compatible pavement underneath, i.e. structurally sound no cracking or differential thermal movement Many sites failed to provide long term value The Problem continued

  4. For mainline areas use slag in OGPA and monitor skid performance (SCRIM survey) For ramps and low speed areas check crash history to determine whether slag is an option Consider the pavement structure, is it suitable for HSRS? Compare whole of life costs for two options: HSRS surfacing with structural fix if required Slag aggregates in asphalt and replace more often The Solution

  5. Accept slag option fails T/10 PSV requirement Slag option is less than half calcined bauxite cost (without a structural pavement repair). Does HSRS give twice or better the life? Not without a compatible pavement (risk) Not if poorly constructed (risk) AMA proposes to implement best whole of life option that meets safety requirements. The Solution continued

  6. Slag Aggregates • More cubical • High PSV • Consistent • Cost effective • Recycled base material • High Surface friction

  7. Properties • Crushing resistance less than 10% at 230KN (NZ 4407 Test 3.10) • Weathering Quality Index: 98.2 (NZ 4407) • Cleanness Value: 95 (NZ 4407) • Quality Index: AA (NZ 4407) • LA Abrasion Test: 18% (NZ 4407) • Wet Dry strength variation: 3 max (NZ 4407)

  8. Development Trials Slag aggregate over 5 years similar performance to calcined bauxite

  9. Browns Road Trial • British Pendulum Skid (TNZ Test T/2) • Conventional: 84 -90 • Slag : 94-97 • Calcined Bauxite: 95-98 • PSV • Calcined bauxite: approx 70 • Slag : 63-65 •  Now 3 years old- no accidents due to surface- formerly black spot

  10. Grip Testing Browns Rd

  11. Hillsborough Road Asphalt Base Line

  12. Grip Tester Now 2 years old- no accidents due to surface- formerly black spot

  13. Courtesy New Zealand Steel

  14. Melter Slag In Service Performance:More Recent Sites – Hawkes Bay Courtesy New Zealand Steel

  15. State Hiway 22/Glenbrook Rd. Intersection Melter Slag In Service Performance:Early Trials Courtesy New Zealand Steel

  16. Slag makes good mixes • SMA used SH20,NGA AMA • OGPA used NGA and AMA

  17. SMA in practice • Kirkbride Road • Heavy traffic • Maintains scrim results • Is made with Slag SMA

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