Introducing High Modulus Asphalt(HiMA)

Prepared for presentation at the JD Roberts Award functionCSIR Pretoria, 27 September 2011 CSIR Pretoria, 27 September 2011

Erik Denneman

1

� The need for innovative asphalt technology,

� Background to the HiMA T2 project,

� Benefits of HiMA technology,

� Designing for performance,

� Implementation of the technology,

� Way forward,

Outline of presentation2-27

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� Way forward,

� Conclusions.

© CSIR 2011

The need for innovation3-27

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- Economic growth,Economic growth,

-- Higher traffic volumes,Higher traffic volumes,

-- Higher axle loads,Higher axle loads,

-- Higher tyre pressures,Higher tyre pressures,

-- Need for sustainable use of resources,Need for sustainable use of resources,

-- Design concepts from 1950s still suitable?Design concepts from 1950s still suitable?

Background: What is High Modulus Asphalt ?4-27

Origin: France early 90s

“Enrobés à Module Elevé” (EME)

Typical characteristics:

• High binder content ≈ 6% by mass of aggregate,

• Hard binder: Pen 10-25,

• Low air voids content,

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• Low air voids content,

• High Modulus > 14 GPa at 15°C, 10 Hz,

• High resistance against permanent deformation,

• Good fatigue resistance,

• Impermeable,

• Increased mixing temperature.

Background: The greater scheme of things5-27

SAPDM

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SA asphalt design manual

HiMAT2

Background: Structure of SABITA T2 project6-27

Phase IIPreliminary mix and structural design guidelines

Phase IFeasibility study

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Phase IVFinal guidelines and specifications

Phase IIIImplementation: APT,LTPP and lab study

Background: The properties of HiMA7-27

1000

10000

100000

Dy

na

mic

Mo

du

lus

(M

Pa

)

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1

10

100

0.00001 0.001 0.1 10 1000 100000

Dy

na

mic

Mo

du

lus

(M

Pa

)

Reduced frequency (Hz)

BTB Mix

Coarse/SBS

Medium/SBS

HiMA

Background: The properties of HiMA8-27

2.5%

3.0%

3.5%

4.0%

4.5%

5.0%

Pe

rma

ne

nt

stra

in [

%]

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0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

0 5 000 10 000 15 000 20 000 25 000 30 000

Pe

rma

ne

nt

stra

in [

%]

Load repetitions

BTB 1 55°C Coarse AE2 55°C Medium AE2 55°C

HiMA 55°C Medium 60/70 55°C BRASO 55°C

Rutting9-27

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Background: The properties of HiMA10-27

1000

10000

ST

RA

IN (M

icro

str

ain

)

Strain-fatigue relationship at test temperatures at 70% initial stiffness reduction

Mix 1 (BTB)

Mix 3

Mix 4 (HiMA)

All at 10 Degrees C

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10

100

1000 10000 100000 1000000 10000000 100000000

ST

RA

IN (M

icro

str

ain

)

Number of load cycles

Fatigue11-27

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The benefits of HiMA: Thickness reduction12-27

180mm BTB

450mm C3

50mm HMA

100mm HiMA

450mm C3

50mm HMA�

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450mm C3

Subgrade

� Average base layer thickness reduction of 30% �

450mm C3

Subgrade

The benefits of HiMA: Long life pavements13-27

180mm BTB

450mm C3

50mm HMA�

180mm HiMA

������

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450mm C3

Subgrade

� Less maintenance = less road user delays, less

emissions & less us of non-renewable materials �

Performance related mix design14-27

Select components

Formulate design grading

Select binder content

Compact gyratory specimens

Workability criteria met?

Yes

No

� First implementation of performance related mix design method in SA,

� Direct link between mix design and pavement performance,

� Requirements set for SA test methods:

� Workability,

Durability,

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Durability criteria met?

Dynamic modulus criteria met?

Compact slab

Rut resistance criteria met?

Fatigue criteria met?

Implement!

YesNo

Yes

Yes

Yes

Yes

No

No

No

� Durability,

� Stiffness,

� Rut resistance,

� Fatigue.

Implementation15-27

� Mix designs prepared for Cape Town international airport and OR Tambo

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� South coast road Durban

Implementation16-27

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Implementation17-27

� Road owned by eThekwini municipality,

� Major access road for DBN harbour,

� Frequent maintenance to pavements required (six months life span not uncommon),

� Road too busy to use concrete,

Estimated number of standard axels: 8000

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� Estimated number of standard axels: 8000 per lane per day (60 Million E80s in 20 years),

� CSIR tasked by SABITA to provide implementation advice.

Implementation18-27

� Mix Design:

� Interim design guide used to develop mix,

� Mix includes 20% Reclaimed Asphalt Pavement (RAP),

� 10-20 penetration grade binder,

Aggregate packing optimized,

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� Aggregate packing optimized,

� Several iterations to optimise design,

� Relatively low binder content to optimise permanent deformation resistance.

Implementation19-27

� Mix Design:

� Interim design guide used to develop mix,

� Mix includes 20% Reclaimed Asphalt Pavement (RAP),

� 10-20 penetration grade binder,

5.2% binder content selected to optimise

4.0%

5.0%

6.0%

7.0%

8.0%

Pe

rma

ne

nt

stra

in [

%]

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� 5.2% binder content selected to optimise permanent deformation resistance

0.0%

1.0%

2.0%

3.0%

0 1 000 2 000 3 000 4 000 5 000

Pe

rma

ne

nt

stra

in [

%]

Load repetitions

BTB 1 55°C Coarse AE2 55°C Medium AE2 55°C

HiMA reference Medium 60/70 55°C BRASO 55°C

Design 5.7 Design 5.2

Implementation20-27

� Innovations in the structural design process:

� CSIR Pavement temperature prediction software used,

� Use of new SAPDM models for rutting prediction,

� Use of new SAPDM approach to determine stiffness of HiMA at

Vertical plane parallel to Y-Z at X = 0

Shear Strain YZ

-0.000018

-0.000081

-0.000144

-0.000208

-0.000271

-0.000334

-0.000397

-0.000461

-0.000524

-0.000587

-0.000650

-0.000714

-0.000777

-0.000840

-0.000903

-0.000966

-0.001030

-0.001093

-0.001156

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determine stiffness of HiMA atcombination of loading speed and temperature,

� Preferred option: Two 80 mm HiMA layers, with 30 mm Stone Mastic Asphalt (SMA) surfacing,

� Predicted life of HiMA base layers >100 Million standard axels.

0

5000

10000

15000

20000

25000

30000

35000

-10 0 10 20 30 40 50 60

Mo

du

lus

(Mp

a)

Temperature (°C)

HiMA stiffness

-0.001156

Implementation21-27

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Implementation22-27

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Implementation23-27

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Implementation24-27

� Paving of HiMA layers South Coast road completed 6 September 2011,

� Many challenges overcome and lessons learned during construction,

� Performance of section over time to be monitored by CSIR.

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Way forward25-27

� HiMA mix designs developed for two major asphalt producers,

� The use of HiMA being investigated for various road construction projects,

� Laboratory trials with warm mixed HiMAunderway,

CSIR and Much Asphalt collaborate on

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� CSIR and Much Asphalt collaborate on innovative labour intensive HiMA application,

� The experience gained with performance related mix design will be used in the development of the South African Asphalt Mix Design Manual.

Conclusions

� HiMA technology successfully transferred,

� Performance related mix design guidelines available to industry,

� Benefits of HiMA:� Reduction in life cycle costs,� Improved durability,

� Reduction in road user delay costs,

Increased sustainability of pavement

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� Increased sustainability of pavement structure.

� Link between mix design and pavement performance made,

� HiMA set for large scale implementation,

� HiMA is a cost effective, innovative solution to help meet the increased demands placed on the SA road infrastructure.

Acknowledgements

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