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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