New Zealand Performance Based Chip Seal Bitumen Specification Opus Research Austroads Workshop 4...
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Transcript of New Zealand Performance Based Chip Seal Bitumen Specification Opus Research Austroads Workshop 4...
New ZealandPerformance BasedChip 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 betweenthe 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 C⁰ 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
Displacement (strain)
Fo
rce
(s
tre
ss
)
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
Displacement (strain)
Fo
rce
(s
tre
ss
)
Yield stress
Yield strain
Fast loading or low temperatures:Brittle failure
Slow loading or high temperatures:Ductile failure
Displacement (strain)
Fo
rce
(s
tre
ss
)
Winter yield stress
Summer yield stress
Upper limit of traffic stress
Upper limit of traffic stress
Upper limit of traffic stress
Large Strains-Aggregate Retention
Small Strains – Cumulative Damage
Time
Dis
pla
ce
me
nt
(str
ain
)
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 measure Property to be Controlled Test methodFlashpoint (min)
Explosion hazard ASTM D92 (Cleveland open cup)
Viscosity at 135°C(min-max range)
Spraying properties, pumping ASTM D2171 (kinematic viscosity by capillary viscometer)
Solubility in Trichloroethylene(% min)
Adulteration with fillers ASTM 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 TP101OR DSR at constant shear rate , parallel plate geometry (e.g. Proc. AAPT 2009 v78 p 597OR 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 stripping Vialit 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: [email protected]