New Zealand Performance Based Chip Seal Bitumen Specification Opus Research Austroads Workshop 4 December 2014

Outline  What is a performance based bitumen specification?  Need for a performance based specification  Plans for development of a performance based specification for NZ  Key points in a performance based specification  Chip seal bitumen specification – underlying physical principles  Draft outline specification  Next steps

Performance based bitumen specification  Current NZTA M/1 specification is an empirical specification  Checks batch to batch consistency  Bitumen is graded according to needle penetration at 25C  No clear mechanistic relationship to seal performance  Satisfactory ranges established through trial and error  Performance based specification principles  Test properties have direct relationship to key performance requirements  Properties are tested at temperatures relevant to field conditions not one standard temperature

Need for a Performance based Specification  Limitations with M/1  M/1 evolved during a period of long term stability and consistency in bitumen supply  Consistent crude slate  Consistent production route (Marsden Point Refinery)  Changes in the supply chain now mean that Bitumen must now be sourced from multiple suppliers and a wide range of crudes  All bitumens still meet M/1 but differences in properties that may affect performance are not being controlled

Plans for Development  Replace M/1 with a performance based specification  Separate specification for asphalt and chip seal bitumens planned  Recognises that many performance requirements are different between the two surfacing types.  Asphalt bitumen specification being developed by Contractor working group  Closely based on US research (AASHTO MP 19)  NZTA Conference paper (Queenstown November 2014)  Chip seal bitumen specification being developed by Opus Research

Key Points in an Ideal Specification  Properties tested are directly related to on-road performance  Surfacing performance also depends on factors un-related to the bitumen  Specification limits must presume a ‘properly’ constructed surfacing  Grades are climate based - binders are tested over the temperature range that they will experience in the field  >99% of the sealed network falls within of -7 to 55 ⁰ C  Aim is to have 1-3 sealing grades

Bitumen Performance Requirements  Aggregate retention  Resists aggregate loss under traffic stresses  Cumulative damage  Resists embedment and shearing in multilayer seals  Resists fatigue cracking  Durability  Not excessively prone to oxidation  Adhesion  Resists water induced stripping

Strain Conditions Between Chips  Mean element size 0.04 mm3  17 mm cube of bitumen

Strain Conditions Between Chips

Low Strain- High Strain Behaviour Similar moduli at low strains Different behaviour at high strains  Can’t accurately predict overall behaviour from measurement at a single strain

 Two main testing regimes are proposed  Aggregate retention  Use large (failure) strain conditions leading to film rupture (chip loss)  Cumulative damage  Use small strain conditions leading to incremental damage (permanent deformation higher temperatures, fatigue cracking at low temperatures) Bitumen Test Conditions

Large Strains-Aggregate Retention

Winter yield stress Summer yield stress Upper limit of traffic stress Large Strains-Aggregate Retention

Small Strains – Cumulative Damage Permanent deformation Vehicle loading time

 Four main test procedures proposed  High temperature stress-strain test  Yield stress  Yield strain  Low temperature stress-strain test  Yield stress  Yield strain  High temperature multiple creep-recovery test  Accumulated permanent deformation  Low / intermediate temperature fatigue test  Number of cycles to failure Aggregate Retention Cumulative Damage

 Satisfactory adhesion determined by  Physical properties- bitumen flow into micro-texture of the surface  Chemical interaction between the aggregate surface and the bitumen  Vialit type physical test involving bitumen and aggregate proposed  Advantages  Models chemical interactions with aggregate  Models wetting of aggregate  Models potential bitumen reaction with adhesion agents  Disadvantages  Requires standard aggregate Adhesion

 Safety- explosion risk  Handling – pumping and spraying  Adulteration – fillers, volatile modifiers Other Properties

Binder property to measureProperty to be ControlledTest method Flashpoint (min) Explosion hazardASTM D92 (Cleveland open cup) Viscosity at 135°C (min-max range) Spraying properties, pumpingASTM D2171 (kinematic viscosity by capillary viscometer) Solubility in Trichloroethylene (% min) Adulteration with fillersASTM D2042 (gravimetric method) Mass loss after RTFO (%max) Presence of ‘volatile’, non- permanent modifiers that would be lost during spraying ASTM D2872 (RTFO) Yield stress and strain at high temperature (min) Aggregate loss - ductile failure (‘roll over’) Amplitude sweep test AASHTO TP101 OR DSR at constant shear rate, parallel plate geometry (e.g. Proc. AAPT 2009 v78 p 597 OR Tensile test machine at constant loading rate Yield stress and strain at low temperature (min) Aggregate loss - brittle failure Direct tension test (AASHTO T314) OR Bending Beam Rheometer (AASHTO T313) OR Tensile test machine at constant loading rate Elastic recovery at high temperature (% recovery) Permanent deformation – chip embedment and seal shearing (contributing to flushing) DSR multiple stress creep recovery test (MSCR), (AASHTO TP-70). Fatigue cracking after accelerated oxidation (min cycles to failure)) Durability Pressure vessel oxidation: NZTA T/13 (60°C, 300psi, 80 hours). Fatigue life: DSR using the direct time sweep method (e.g. 5% strain, 10Hz) or the draft AASHTO method TP-101. Adhesion to aggregate (% aggregate retention) Resistance to water induced strippingVialit type test with aggregate

 Validation of property-performance relationships - full scale wheel tracking  Development of detailed draft specification and grades  Field validation- trials Next Steps Industry consultation

Thank You Acknowledgement This research was funded by: The New Zealand Ministry for Business Innovation and Employment The New Zealand Transport Agency Contact: