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: Phil.Herrington@Opus.co.nz