High Modulus Asphalt T 2

Prepared for presentation to the AAPA study tourCSIR Pretoria, 7 September 2011

Erik Denneman

1

Slide 2 of 41

� Background on HiMA and the T2 project,

� Benefits of HiMA technology,

� Designing for performance,

� Implementation of the technology,

� Way forward,

� Conclusions.

Outline of presentation

© CSIR 2011

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Background: What is High Modulus Asphalt ?

© CSIR 2011

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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,

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

• High resistance against permanent deformation,

• Good fatigue resistance,

• Impermeable,

• High mixing temperature.

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Background: The greater scheme of things

© CSIR 2011

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Background: Structure of SABITA T 2 project

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Background: The properties of HiMA

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1

10

100

1000

10000

100000

0.00001 0.001 0.1 10 1000 100000

Dyn

amic

Mod

ulus

(MP

a)

Reduced frequency (Hz)

BTB Mix

Coarse/SBS

Medium/SBS

HiMA

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Background: The properties of HiMA

© CSIR 2011

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0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

3.0%

3.5%

4.0%

4.5%

5.0%

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

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Background: The properties of HiMA

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10

100

1000

10000

1000 10000 100000 1000000 10000000 100000000

ST

RA

IN (M

icro

stra

in)

Number of load cycles

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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The benefits of HiMA: Thickness reduction

© CSIR 2011

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180mm BTB, 5000 MPa

450mm C3, 1500 MPa

50mm HMA, 3500 MPa

Subgrade, 100 MPa

450mm C3, 1500 MPa

100mm HiMA, 9000 MPa

Subgrade, 100 MPa

� Average base layer thickness reduction of 30% �

20 mm UTFC

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The benefits of HiMA: Perpetual pavement

© CSIR 2011

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Monismith (2006)

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Performance related mix design

© CSIR 2011

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Select components

Formulate design grading

Select binder content

Compact gyratory specimens

Workability criteria met?

Durability criteria met?

Dynamic modulus criteria met?

Compact slab

Rut resistance criteria met?

Fatigue criteria met?

Implement!

YesNo

Yes

No

Yes

Yes

Yes

No

No

No

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

� Direct link between mix design and pavement design models,

� Requirements set for SA test methods:

� Workability,

� Durability,

� Stiffness,

� Rut resistance,

� Fatigue.

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Performance related mix design

© CSIR 2011

12-25Property Test Method Performance requirements

HiMA base

course

HiMA binder course

Class 1 Class 2 Class 1 Class 2 Class 3

Workability Gyratory

compactor, air

voids after 100

gyrations

ASTM

D6926

≤ 6.3% ≤ 3.8 % 3.2 to 6.3 % for D = 10,

2.5 to 5.7 % for D = 14

Moisture

sensitivity

Modified

Lottman

ASTM

D4867

Refer

Table

10

Refer

Table

10

Refer

Table

10

Refer

Table

10

Refer

Table

10

Permanent

deformation

RSST-CH,

55°C, 30 000

reps

AASHTO

320

≤ 1.7%

strain

≤ 1.7%

strain

≤ 2.3%

strain

≤ 1.7%

strain

≤ 1.1%

strain

Dynamic

modulus

Dynamic

modulus test at

10 Hz, 15°C

AASHTO

TP 62

≥ 14

GPa

≥ 14

GPa

≥ 9 GPa ≥ 14

GPa

≥ 14

GPa

Fatigue Beam fatigue

test at 10 Hz,

10°C, to 70%

stiffness

reduction

AASHTO

T 321

≥ 330

µε for

10 E6

reps

≥ 430

µε for

10 E6

reps

≥ 360

µε for

10 E6

reps

≥ 330

µε for

10 E6

reps

≥ 330

µε for

10 E6

reps

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Implementation

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� Warning! Do not try this at home

� Validation through APT pending...

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Implementation

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

� South coast road Durban

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Implementation

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Implementation

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� 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 per lane per day (60 Million E80s in 20 years),

� CSIR tasked by SABITA to provide implementation advice.

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Implementation

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� Mix Design:

� Interim design guide used to develop mix,

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

� 10-20 penetration grade binder,

� Aggregate packing optimized using Bailey method concepts,

� Various iterations to optimise design,

� 5.2% binder content selected to optimise permanent deformation resistance.

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Implementation

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� 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 permanent deformation resistance

0.0%

1.0%

2.0%

3.0%

4.0%

5.0%

6.0%

7.0%

8.0%

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

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Implementation

© CSIR 2011

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� Structural analysis:

� Pavement temperatures predicted using CSIR ThermalPADS,

� First use of SAPDM damage models,

� First use of master curve to determine stiffness of HiMA at combination of loading speed and temperature,

� Different structural options analysed,

� Final 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

10

20

30

40

50

60

70

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Tem

pera

ture

s (D

egre

es)

Hour of the day

Diurnal temperature profile for hottest recorded day (2 Feb 1960), DURBAN WO

Created with CSIR ThermalPADS

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

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Implementation

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Implementation

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Implementation

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

� Many challenges overcome and lessons learned during construction,

� SMA surfacing to be installed by 11 September,

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

� Workshop to be held at CAPSA on design using HiMA.

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Way forward

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� Two viable HiMA mix designs available, one in KZN and one in Gauteng, more to follow,

� The use of HiMA planned for various road rehabilitation projects,

� APT testing for fatigue pending,

� Laboratory trials with warm mixed HiMA underway,

� CSIR and Much Asphalt collaborate on the use of HiMA in innovative labour intensive road construction product,

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

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Conclusions

© CSIR 2011

� HiMA technology successfully transferred,

� Performance related mix design guidelines available to industry,

� HiMA has distinct benefits in terms of:� Reduction in life cycle costs,� Improved durability => Less maintenance

actions => less road user delays,� Increased sustainability of entire 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.

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Slide 25 of 41

Thank you!