Introduction to Bitumen Stabilised Materials BSMs

Kim Jenkins

SARF Course on BSMsAssagai, Shongweni

14 and 15 July 2015

tellenbosch

Hot

ColdIn Place In Plant

What defines a BSM?

Bitumen

Cem

ent

Rut resistant

Strongly cemented

Lightly cemented

UnboundCrushed stone / gravel / soil

Stress dependent

Less economical

Fatigueresistant

1%

3%

2%

1% 2% 3% 4%

FBS(NZ)

FBS(Aus)

QuickLime

0%

HMA

BSM(RSA)

?

?

5%

1. BSM Binder Type

FOAMED BITUMEN

Mill

Acid orCaustic Soda

Surfactants

Wat BitumenWater

5 microns

Water

Hot bitumen

Air

Expansion chamber

BITUMEN EMULSION

Colloidal Mill

2. Bitumen Dispersion

BSM-emulsion BSM-foam

Microscopic Analysis

Type of Dispersion

BSM-emulsion BSM-foam

Painting Spot-welding

Nature of BSMs (cold)

0.5mm

Bitumen dispersion:Non-continuously bound

BSM-foam (sand)

BITUMEN DISPERSION

Particles < 0.075 mm (# 200 sieve)

± 100°C

Thin bitumen film around steam

± 20°C

Tiny bitumen “pieces”

Natural Gravel

CBR>25%

Crushed Gravel

CBR>45%

GradedCrushed

Stone

50% RAP+ GCS

100% RAP

3. Aggregate TypesRecycled Materials

4. Grading 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)

Cum

ulative

% p

ass

ing

Foam

Emulsion

Optimisation of grading curve

0

100

200

300

400

500

600

700

Emulsion

3.3% bitumen

Foam

3.5% bitumen

Indi

rect

Ten

sile

Str

engt

h (k

Pa)

Without blending

With 10% fines blend

Moisture: DurabilityEMULSION FOAMED BITUMEN

Poorly graded Well graded Well graded

5. Bitumen content

BSM Class Aggregate Bitumen (%)

BSM 1 >75% RAP + Crush agg 1.6 – 2.1

BSM 1 >25% RAP + Crush agg 1.8 – 2.5

BSM 1 <25% RAP + Crush agg 2.0 – 3.0

BSM2 Natural Gravel (CBR>45%) 2.2 – 3.5

BSM 3 Natural Gravel (CBR>25%) 2.5 – 4.0

(Wirtgen Recycling Manual, 2012)

Foam > 25ºC

Foam 15ºCEmulsion 10ºC

Foam <15ºCEmulsion<10ºC

Aggregate Mixing Temperature

√

OK

X

Aggregate Temperature vs Particle coating (BSM -foam)

05

101520

25303540

35 45 65 85

Aggregate Mixing Temperature (degC)

Max

imum

Par

ticle

Siz

e (

mm

)

Practically no coating

Partial coating

Completecoating

Jenkins , 2000

7. Moisture Regime (mix & compact)EMULSION

Bitumen coating (thin films)

Some partial coating

FOAMED BITUMEN

Bitumen dispersion selective

Partial coating

Optimum Fluids Content 70% to 90% of OMC

MOISTURE DURABILITY

HVS Cape Town on BSM

Water introduction into 2.3% foamed bitumen stabilised base

PERMEABILITY

Resilient Modulus of BSM -foam (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)

Res

ilien

t Mod

ulus

Mr

(MP

a)

12kPa24kPa48kPa72kPa

s3

8. Behaviour = Granular type

Stress dependency (triaxial)

Resilient moduli 75C -0 blend

100

1000

10000

100 1000 10000

Bulk stress [kPa]

Res

ilien

t mod

ulus

[MP

a]

A-75C-0

B-75C-0

C-75C-0

Mix:1% cem0% cem

Not main purpose

BSM-emulsionBSM-foam

Visco -elastic properties of BSM-foam

Tref = 20C

HMAHW

Fatigue cracks

Rutting

HOT T or Slow Traffic

Equiv COLD T or Fast Traffic

Equiv

BSM

Validation (100% RAP Foamed Mix)

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

0 200000 400000 600000 800000 1000000

Number of load repetitions [-]

Per

man

ent a

xial

strai

n [%

]

60C

40C

50C

σ1

σ2

Repeated Load

Triaxial

40ºC

50ºC60ºC

10. Active Filler: Purpose?• 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-b

reak

0

500

1000

1500

2000

2500

3000

3500

4000

Unc

onfin

ed C

ompr

essi

ve

Str

engt

h (k

Pa)

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

* CSIR

εb

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)Mix Design Testing

A1

Cemented

Bituminous

It’s undeniable: More cement = more strength!

CompressiveTensileShear

strength

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 σεA1A2

Cemented

Bituminous

It’s undeniable: More cement = more strength!

CompressiveTensileShear

strength

11. Time DependencyMr (field) versus cure

N7 PSPA Mr Analys is ove r 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

TG2 : 2nd EDITION

Published inSouth Africa

byAsphalt Academy

(CSIR / SABITA)

May 2009

BITUMEN STABILISED MATERIALS

Conclusions

• Many combinations of aggregates can be used (continuous grading)

• BSMs = asphalt• BSM is granular with higher

cohesion and shear strength• Flexibility is NB! Active filler content

needs to be restricted

/

Thank you

Roads & Enviro !