Bitumen StabilisedMaterials

MIX DESIGN OVERVIEW

Kim Jenkins

tellenbosch

Pre-Conference Course

ISAP 2012, Fortaleza30 Sep 2012

Hot

ColdIn Place In Plant

MOISTURE

TEMPERATURE

TRAFFIC

AGGREGATESSUPPORT

BINDERS

Factors influencing mix selection

Pavement Materials & Behaviour

Greater flexibility

Greater ru

t resistance

Bitumen binder 6%4%

Active F

illerBSM

flexural

brittle

HMA

Time, temp dependent

granular Vis

co-e

last

cemented

“Linear-elastic”

Lean Mix Concrete

Lightly cemented

UnboundCrushed stone / gravel / soil

Stress dependent

Less economical mixes

Primary Design Objectives

• Load spreading– Resilient Modulus (Mr)

• Rut resistance– Shear Strength

• Flexibility– Displacement at Ultimate Strength

• Durability– Moisture resistance

BINDERS

Aggregate

Chemical Additives Active Filler

Foamed Bitumen

Bitumen Emulsion

Recycling AdditivesGranular and RAP Materials

BSM Binder

FOAMED BITUMEN

Mill

Acid orCaustic Soda

Surfactants

Wat BitumenWater

5 microns

Water

Hot bitumen

Air

Expansion chamber

BITUMEN EMULSION

Colloidal Mill

Foaming in laboratory

Foamed bitumen characteristics

Half-life– time (seconds) for the foam to collapse to half of

its maximum volume

– measure of the stability of the foam

Expansion Ratio– maximum volume of foam relative to the

original volume of bitumen

– a measure of the viscosity of the foam

– indicates how the bitumen will disperse

FOAMING CHARACTERISTICS

Water addition (% by mass of bitumen)

1 2 3 4

Exp

ansi

on

Rat

io (

tim

es)

Hal

f-L

ife

(sec

on

ds)

20

15

10

5

40

30

20

10x

x

x

xx

x

x

x

Bitumen Temperature 175°C

8 MIN

6 MIN1.54.1

Optimum foaming water content

AGGREGATES

Microscopic Analysis

BSM-emulsion BSM-foam

Grading and PI requirements

0

20

40

60

80

100

0.08 0.15 0.3 0.6 1.18 2.36 4.75 6.7 9.5 13.2

Sieve size (mm)

Cumulat

ive

% p

assing

Foam

Emulsion

2%

Low %RAP 4%High %RAP 2%

PI<10%

PI<7%

Optimisation of grading curve

0

100

200

300

400

500

600

700

Emulsion

3.3% bitumen

Foam

3.5% bitumen

Ind

ire

ct

Ten

sile

Str

en

gth

(k

Pa

)

Without blending

With 10% fines blend

<30 RAP: Recovered pen >30

<5% RAP: Recovered BC(%) >5%

<2% Emulsion Residual BC >2%

No Rejuvenating Agent Yes

TG2/Wirtgen Mix Design Marshall/Superpave

Bitumen StabilisedNon-continuously

boundContinuously

bound

Asphaltic

BSM: RAP Influence

Classes of RAP

Pen : >30 30 20 15 <15

Active Inactive

Increasing Ageing

Bitumen State

ElasticVisco-elasticViscous

Adhesion Stickiness Some Stickiness Not Sticky

Wirtgen, 2010

Pen : >25 20 15 10 <5

Changes

Visco-elastic propertiesBeam tests on BSM-foam Tref = 20C

HMA

HWFatigue cracks

Rutting

HOT T or Slow Traffic

Equiv COLD T or Fast Traffic

Equiv

BSM

TEMPERATURE

BITUMEN DISPERSION

Particles < 0.075 mm (# 200 sieve)

± 100°C

Thin bitumen film around steam

± 20°C

Tiny bitumen “pieces”

Aggregate Temperature vs Particle coating (BSM-foam)

05

101520

2530

3540

35 45 65 85

Aggregate Mixing Temperature (degC)

Max

imu

m P

arti

cle

Siz

e (

mm

)

Practically no coating

Partial coating

Completecoating

Jenkins, 2000

Foam > 25ºC

Foam 15ºCEmulsion 10ºC

Foam <15ºCEmulsion<10ºC

Aggregate Mixing Temperature

√

OK

X

MOISTURE

Mr (field) versus cure

N7 PSPA Mr Analys is over 7 Months

0500

1000150020002500300035004000

0 50 100 150 200 250

Tim e (days)

Mr

(MP

a)

B1-B3 B4-B6 Poly. (B4-B6)

PSPA

Moisture

Mr

MOISTURE DAMAGE

HVS Cape Town on BSM

Water introduction into 2.3% foamed bitumen stabilised base

PERMEABILITY

MIX DESIGN

BSM Mix Design & Classification

Level 1

100mm

Aggregate blend

Compaction fluids

Act filler – type & cont

Level 3

150mm

300mmH

Strength & moisture resistance1

2 2=3

Shear properties & resilient modulus

Final mix selection

Reliable performance related properties

Flexibility?

Level 2

150mmBinder cont 0.2% inc

Binder type & content – Level 1

ITS

BSM Binder Content

ITSdry

ITSwet

BSM2Min ITSdry

Min ITSwet

Min BC

Level 1 and 2 Classification

Test Dia mm

BSM1 (kPa)

BSM2 (kPa)

BSM3 (kPa)

Comments

ITSdry 100 >225 175 to 225

125 to 175

Indicates OBC

ITSwet 100 >100 75 to 100

50 to 75

Indicates active filler type & amt

TSR 100 Not applicable Prob mat TSR < 50 % ITSdry > 400 kPa

ITSequil 150 >175 135 to 175

95 to 135

OBC refined

ITSsoaked 150 >100 75 to 100

50 to 75

Adjusted to ITSwet

Vibratory Compaction Hammer

Rear View of Frame

Kango Hammer

Mould

Zero Line

Sleeve

Base Plate

Steel Rod

Side of Mould

Vibratory Hammer

Wooden base

To prepare specimens

Kelfkens

Influence of Tamping Foot

Sleeve

Vibratory Hammer

Compaction time (vibratory)Phase Level 1 Level 2 Level 3

Test ITS ITS UCS Triaxial

Foot 100mm 150mm 150mm 150mm

Height 65mm 95mm 125mm 300mm

Layers 1 2 2 5

Surchg 5 kg 10 kg 10 kg 10 kg

Foam 10 sec 25 sec 25 sec 25 sec

Emuls 10 sec 15 sec 15 sec 15 sec

Co

mp

Tim

e

Bitumen Stabilised Material

Non-continuously bound

Continuously bound

Asphalt

DIFFERENT BEHAVIOUR PATTERNS

Testing the Material

Nature of BSM e.g. foam

Critical Material Properties• Tri-axial test to determine:

– Shear parameters ( C & )– Resilient modulus ( Mr )

– Permanent deformation behaviour1

t

1

tC

i

t

p

log t

Triaxial Testing

Shear properties (monotonic triaxial at 25°C)

Cohesion C

0

100

200

300

400

500

A-75C

-0

B-75C

-0

C-75C

-0

A-75C

-1

B-75C

-1

C-75C

-1

A-75M

-0

B-75M

-0

C-75M

-0

Co

hes

ion

[kP

a]

E E E E E E FFF20

25

30

35

40

45

50

A-75C

-0

B-75C

-0

C-75C

-0

A-75C

-1

B-75C

-1

C-75C

-1

A-75M

-0

B-75M

-0

C-75M

-0

Fri

ctio

n a

ng

le [

deg

rees

]

Friction Angle

E E E E E E FFF

Ebels

25% RAP 25% RAP75% RAP 75% RAP

New “Simple triaxial”

BSM Classification ito Shear Properties

Cohesion (kPa)

> 250

100 – 250

50 – 100

Angle of Internal Friction (º)

> 40

30 to 40

< 30

Equivalent BSM Class

BSM 1

BSM 2

BSM 3

0.01

0.10

1.00

10.00

10 100 1000 10000 100000 1000000

Number of load repetitions [-]

Per

man

ent

axia

l st

rain

[%

]

0.55

0.50

0.60

0.45

0.38

Deviatorstress ratio:

Permanent Deformation (Triaxial)

BSM-emulsion with 75% RAP (A-75M-0)

25% RAP

75% RAP

0.01

0.10

1.00

10.00

10 100 1000 10000 100000 1000000

Number of load repetitions [-]

Per

man

ent

axia

l st

rain

[%

]

0.85

0.45

0.60

0.75

0.85

Deviator stress ratio:

Permanent Deformation (Triaxial)

BSM-foam with 75% RAP (C-75M-0)

75% RAP

25% RAP

BSMs Mr change:Effective Long Term Stiffness

0

500

1000

1500

2000

0 1 2 3 4 5 6 7 8 9 10

Eq

uiv

alen

t S

tiff

nes

s (M

pa)

Years

1% cem CTSB

1% cem G5SB

BSM1 all

BSMs Mr change:Effective Long Term Stiffness

0

500

1000

1500

2000

0 1 2 3 4 5 6 7 8 9 10

Eq

uiv

alen

t S

tiff

nes

s (M

pa)

Years

1% cem CTSB

2% cem CTSB

1% cem G5SB

2% cem G5SB

cementTrafficBrittle (cem)Poor Support

BSM1 all

(Prelim) Effective Long Term Mr for BSM base

BSM Class C3 Subbase G5/G6 Subbase

BSM 1 (RAP + G1 or G2)

900 – 1750 700 – 1200

BSM 1(G1 or G2)

800 – 1200 600 – 900

BSM 2 400 – 750 300 – 500

BSM 3 Not in use Not in use

ELT Mr = f (aggregate type and quality, RAP %, bitumen %, support, traffic, climate)

FLEXIBILITY

Purpose of Active Filler• Improve adhesion

• Improve dispersion

• Modify plasticity

• Increase stiffness & strength

• Accelerate curing

Emulsion Foam

• Breaking time Dispersion!

• Improve workability

• Improve adhesion PRIMARY

• Improve dispersion REASONS

• Modify plasticity

• Increase stiffness & strength

• Accelerate curing

Emulsion Foam

• Breaking time Dispersion!

• Improve workability

Influence of Active Filler

Strength and flexibility

0

100

200

300

400

500

600

700

800

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3

Cement : Foamed Bitumen Ratio

Str

ain

-at-

bre

ak

0

500

1000

1500

2000

2500

3000

3500

4000

Un

con

fin

ed C

om

pre

ssiv

e S

tren

gth

(kP

a)

Foamed bitumen, StrainCement, Strain*Foamed bitumen, UCS Cement, UCS*

CSIR

b

BSM

Cement < 1%?

Can 1.5% cement work?

BSM-foam + 1.5% cemusing cracked CTB

2 years of traffic

0

200

400

600

800

1000

1200

1400

1600

1800

0 0.1 0.2 0.3 0.4 0.5 0.6

Strain

Str

ess

(kP

a)

Dissipated Energy

W = 0.5 A1A2

BSM+2%cem

BSM+1%cem

0

0,2

0,4

0,6

0,8

1

1,2

1,4

0 0,2 0,4 0,6 0,8 1 1,2

Ver

tica

l Dis

pla

cem

ent

at IT

Sm

ax (

mm

)

Active Filler Content (%)

ITS wet (All)

85% RA Emul

85% RA Foam

75% RA Foam

25% RA Emul

85% RA Emul

85% RA Emul

85% RA Foam

ITS displacement at max

(from Mix Design) Similar trend for triaxial

On Foam & Emulsion

Mixes

Triaxial data from Mix Design

Can refine by separating data based on 3

Conclusions

• Understanding of material behaviourof BSMs has increased significantly

• Flexibility is NB! Active filler versus bitumen content!!

• More advanced test evaluation (triaxial = shear properties)

• Mix Design is linked to Structural Design method for BSMs

Thank you

Roads & Enviro!

200

600

400

WHOLE OF LIFE ENERGY & COSTMJ / m²

40

120

80

US$ / m²

$

MJ

$ $

$

MJ

MJ

MJ

PATCH &

OVERLAY

MILL &

REPLACE

CEM STAB &

GRAN O’LAY

BSM STAB

Resilient Modulus of BSM

• Granular Type Behaviour: Foamed BC = 2%

150

350

550

750

950

1150

1350

0.0 200.0 400.0 600.0 800.0 1000.0

Sum of Principal Stresses q (kPa)

Re

silie

nt

Mo

du

lus

Mr

(MP

a

12kPa24kPa48kPa72kPa

s3