ARRA Semi-Annual Meeting | Minneapolis, MN | October 16-19, 2017

ARRA Semi-Annual Meeting | Minneapolis, MN | October 16-19, 2017

"Balanced Mix Design of BSM

- A Recipe forSuccess"

Kim Jenkins

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Wechsel des Folienlayouts

What is around the next corner?? – Be prepared!!

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Years

20101990 2000

RealityIndex

Compaction

Testing Z

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C,f Mix design to PerformanceDesign BSM layers

h1

h2

h3

>200 project mix designs!

Stabilisation Mix Designs

EVOLUTION OF LAB TESTS FOR BSM

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Sampling

Sample preparation

Preliminary tests

SUITABLE?

Blend

Effect of active filler

Optimum bitumen addition

Yes

No

ITS

Specification

ITSdry

(kPa)ITSwet

(kPa)

>225 >100

BSM Stabilisation Mix Design Procedure

Phase 1: Material Selection + Binders (ITS)

:

Wechsel des Folienlayouts Emulsion

Foam

Processing RAP: Impact crusher with 20mm gap setting

Hot regions: Triaxial testing at representative temperature

Grading Requirements Update

FOAM EMULSION

Plasticity PI (%) <6 <6

Filler Content <75%RAP

P0.075 (%) 100% RAP

>4 >2

>2 >2

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Sampling asphalt layers

Obtain bulk sample

(full depth)

Normal operating speed of advance (± 8m/min)

Speed of advance (± 3m/min)

Use a recycler

Or, a milling machine

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Sampling asphalt – equipment and method

“GRINDING”

Pulverised

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Sampling asphalt layers

0

10

20

30

40

50

60

70

80

90

100

0.1 1 10

Percen

tag

e P

assin

g

Sieve Size (mm)

TYPICAL GRADING CURVES FOR MILLED ASPHALT

Pulverised Slow milling Fast milling

Crackedasphalt

Impact crusher

Down-milling

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(Stellenbosch University)

Compaction Apparatus and Method

Hammer

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Refusal Density

Comparison of refusal density for G2 and G4 material

Selection of Compaction Frame

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40°C curing temperature (time variable)Curing Procedure of BSM

ITS specimens – 72 hours + dry to constant mass

Soaking: 24 hours submerged

Curing of ITS Specimens

150mm dia

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13

Which active filler should be added for effective stabilisation ?

Active filler addition

1% lime 1% cem 0%

A series of test specimens are made, each with a different type of active filler and none

The specimens are then “cured” for 3 days (strength gain)

They are then tested to determine the Indirect Tensile Strength (ITS)

Mix Design - Selection of Active Filler

1% lime 1% cem 0%Wet condition (soak 24 hrs @ 250C)

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14

Why limit the active filler content?

0.5 1 1.5

1

3

5

Strain e (%)

Flexural

Stress s(MPa) BSM+1% cemStrength1%

BSM+2% cemStrength2% Dissipated Energy= Area under curve≡ Damage Resistance

Strength, Stiffness & Flexibility of BSM

A2

A1

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15

How much bitumen should be added for effective stabilisation ?

Bitumen addition

A series of test specimens is made, each with a different amount of bitumen added

(% by mass of the material being treated)

Specimens “cured” for 3 days (moisture loss)

They are all then tested to determine the Indirect Tensile Strength (ITS)

Half the specimens are then soaked under water for 24 hours

Mix Design - Selection of Bitumen Content

2% 2.2% 2.4%1.8%

2% 2.2% 2.4%1.8%

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50

100

150

200

250

300

1.8 1.9 2 2.1 2.2 2.3 2.4

ITS

(kP

a)

Bitumen Addition (%)

ITS dry ITS wet

ITSWET

ITSDRY

BSM specification

Select 2.1%

ITS results versus Spec

Variability

Binder Content Selection versus Specification

DRY

WET

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Phase 2: Triaxial Performance Properties

Sampling

Sample preparation

Preliminary tests

SUITABLE?

Blend

Effect of active filler

Optimum bitumen addition

Determine shear

properties

Yes

No

ITS

TRIAXIAL

Specification

C (kPa) f (0)

>250 >40

BSM Stabilisation Mix Design Procedure

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Inter-Layer Roughening Device (IRD)

5 layersTriaxial

Inventor: Wynand van Niekerk

Triaxial Specimen Preparation

IRD 145mm f (± 1mm) fitted with protruding teeth for roughening the upper horizon of a compacted layer

Each layer @ 100% Mod. Proctor density

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40°C curing temperature

Triaxial specimens – 24 hrs in mould+ 8hrs @ 400C

+ seal and 48 hrs @ 400C (equilibrium mc)

Soaking: 24 hours submerged

Curing of Triaxial Specimens

Curing Procedure of BSM

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Specimen Pairs Tested at 4 different confining pressures

0kPa 50kPa 100kPa 200kPa

100kPa

Soaked

100kPa

Soaked

Specimen Preparation for Triaxial Testing of Shear Properties

OutlierTest forDensity

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Triaxial Cell & Membrane

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Triaxial Test Setup

Test at 250C

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Benefit of Bitumen Stabilisation

t

s

Shear stress

Normal stress

Cohesion

f Friction angle

UNBOUND

BSM

σ1

σ3

σ1

σ3

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Determine the shear properties (C and φ)

t

s

Shear stress

Normal stress

Cohesion C

f Friction angle

s150 100 200

σ1

σ3

0

Mohr-Coulomb Analysis of BSMs

Specification BSM1

C (kPa) f (0)

>250 >40

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Retained Cohesion Spect

s

Shear

stress

Normal

stress

CBSM

Cohesion

f Friction

angle

Retained Cohesion CR = CR*100/CBSM

Effect of

MoistureCohesion Loss = 25% max

Triaxial Analysis of Moisture Damage

Specification BSM1

CR = Ret.C >75%

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Triaxial Analysis - Data Capture and Reporting

1270

1262

1436

1515

1821

1772

2255

2315y = 5.1834x + 1252

R² = 0.9911

1000

1200

1400

1600

1800

2000

2200

2400

0 50 100 150 200

Determine the relationship between σ1,f and the confining pressure (σ3)

This relationship is: Plot the combinations of σ1,f

and σ3

for all

unsoaked specimens. Perform a linear regression analysis (best-fit line) to determine the values of A (slope) and B (intercept):

EXAMPLE

σ3 σ1

0 1270 1262

50 1436 1515

100 1821 1772

200 2255 2315

A (slope) = 5.18 B (intercept) = 1252

σ 1,f A x σ3 +

Typical Example

B=

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Spin-offs from Vibratory Hammer Compaction and Triaxial Testing1

➢ Representative packing and density

➢ CT scans showing void distribution

➢ Interlayer bond

➢ Direct links between Mix Design and Pavement Design

➢ Moisture damage insights

➢ TSR = ITSWET/ITSDRY has higher COV

➢ Direct link of Cohesion Loss to Performance

(increase in deviator stress ratio)

27

S1A

-5

5

15

25

35

45

55

65

75

85

0 20 40 60 80 100

Volume in %

Sca

n s

lice

nu

mm

er

(bo

ork

ern

le

ng

te i

n m

m).

voids

Mortar

stone

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➢ Identifying true behaviour of recycled materials Spec result

➢ Bitumen-Rubber Asphalt RAP (M4 example)

➢ Soft bitumen in the RAP

Adjust mix to achieve desired shear properties

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➢ Repeatability and reproducibility

➢ Over application of cement = spike in Cohesion (above 400kPa)

➢ Dissipated energy

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Conclusions

Pavement investigation and sampling (new)

New Mix Design Procedure

New specimen compaction (Vib hammer)

New test methods (Triaxial)

Testing protocols standardized (TG2)

Benefits of Triaxial Tests

Reliable material evaluation (less variation)

Direct link to performance of BSM

Mix design feeds into Structural Design

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ARRA Semi-Annual Meeting | Minneapolis, MN | October 16-19, 2017 · Wechsel des Folienlayouts...

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Transcript of ARRA Semi-Annual Meeting | Minneapolis, MN | October 16-19, 2017 · Wechsel des Folienlayouts...