Post on 18-Jan-2021
transcript
BSM Stabilisation (Mix) Design
Kim Jenkins
SARF Course on BSMs
KZN DoT13 and 14 August 2015
tellenbosch
Life is full of surprises…
Try to keep them to a minimum
Primary Design Objectives
• Load spreading
– Resilient Modulus (Mr)
• Rut resistance
– Shear Strength
• Flexibility
– Displacement at Ultimate Strength
• Durability
– Moisture resistance
Early South African pavements
CEMENT STABILISED BASE
40mm HMA SURFACING
Selected subgrade layer
REFLECTIVE CRACKING
Key pavement considerations
The South African “inverted” pavement
CEMENT STABILISED SUBBASE
40mm HMA SURFACING
CRUSHED STONE BASE
Selected subgrade layer
CRACK PREVENTION LAYER
The Concept
HIGHER COMPACTION HIGHER Mr WATER!!!!
The South African “upside-down” pavement
CEMENT STABILISED SUBBASE
40mm HMA SURFACING
Selected subgrade layer
The Upgrade
BITUMEN STABILISED BASE
Distress Mode?
UnboundPermanent deformation
(shear/ruts)
BoundFatigue
(cracking)
Durability??
MOISTURE
TEMPERATURE
TRAFFIC
AGGREGATESSUPPORT
BINDERS
Factors influencing mix selection
Traffic vs Classes of BSM
• BSM1
• BSM2
• BSM3
• > 6 MESA
• High shear strength
• Crushed stone or RAP
• 1 to 6 MESA
• Mod shear strength
• Graded nat gravel, RAP
• < 1 MESA
• Soil gravel or sand
AGGREGATES/COMPACTION
37.5
26.5
19.0
13.2
9.5
6.7
4.7
5
2.0
0
0.8
5
0.4
25
0.2
5
0.1
5
0.0
75
Sieve Size (mm)
0
10
20
30
40
50
60
70
80
90
100P
erc
en
t P
assin
g
Less suitable
Marginal
MarginalIdeal
37.5
26.5
19.0
13.2
9.5
6.7
4.7
5
2.0
0
0.8
5
0.4
25
0.2
5
0.1
5
0.0
75
Sieve Size (mm)
0
10
20
30
40
50
60
70
80
90
100P
erc
en
t P
assin
g
Less suitable
Marginal
MarginalIdeal
BSM Grading requirements (1)
Emulsion slightly coarser than foam
BSM Aggregate requirements (2)
Emulsion Foam
• PI < 7% PI < 10%
• P0.075> 2% P0.075> 4%
• Reclaimed asphalt RA + (15 to 25% Crusher dust)
• Triaxial tests at representative temperature (especially hot regions)
<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
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, U Stell
Influence of Tamping Foot
Sleeve
Vibratory Hammer
Compaction time (vibratory)
Phase Level 1 Level 2 Level 3
Test ITS ITS UCS Triaxial
Foot φ 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
BINDERS
Quality Assessment: Foamed bitumen
Emulsion Plant
Bitumen Emulsion
Emulsifiers, acid
Hot water
Bitumen
Heat
Oil in water emulsion (O/W)
Oil phase
Water phase
Bitumen Emulsion Types
BITUMEN EMULSION
Fatty Acids+ NaOH
-ve
Amines+ HCl+ve
No charge
Cationic Anionic Non-IonicType
Emulsifier
pH10 -12ALKALI
2 – 6ACID
7NEUTRAL
RSA BSMsGlobal BSMs
Factors influencing mix design
TEMPERATURE
MOISTURE
Curing Protocol TG22009
CURING METHOD
Preliminary Mix Design
All BSMs72 hours at
40 °C, unsealed
Level 2 & 3 Mix Design
BSM-foam20 hours at 30 °C unsealed
48 hours at 40 °C sealed
BSM-emulsion26 hours at 30 °C unsealed
48 hours at 40 °C sealed
Level 1 Mix Design
CURING METHOD
Preliminary Mix Design
All BSMs72 hours at
40 °C, unsealed
Level 2 & 3 Mix Design
BSM-foam20 hours at 30 °C unsealed
48 hours at 40 °C sealed
BSM-emulsion26 hours at 30 °C unsealed
48 hours at 40 °C sealed
BSM-foam20 hours at 30 °C unsealed
48 hours at 40 °C sealed
BSM-emulsion26 hours at 30 °C unsealed
48 hours at 40 °C sealed
Level 1 Mix Design
“dry”
“equilibrium”“equilibrium”
Curing Protocol (BSM lab)ConditionsSimulated
“dry”
Constant mass @ 40oC
“wet”
Soak 24hrs @ 25oC
60% of OMC @ 40oC, seal
“equilibrium”
CURING: FIELD VALIDATION
Mr (MPa)
EMC (%)
Time
?BASE
PROPERTY
PSPA
Mr (field) versus cure
N7 PSPA Mr Analys is over 7 Months
0
500
1000
1500
2000
2500
3000
3500
4000
0 50 100 150 200 250
Tim e (days)
Mr
(MP
a)
B1-B3 B4-B6 Poly. (B4-B6)
PSPA
Moisture
Mr
MIX DESIGN
Mix Design(TG2, 2009)
PRELIMINARY STEPS
•Aggregate selection and blending
•Aggregate classification
•Pre-treatment
LEVEL 1 Mix Design
•Using Selected Aggregate Blend
•Consider Climate & Early Traffic
Treatment Type Foamed BitumenBitumen Emulsion
Expansion Ratio
& Half-life
Acceptable?
Aggregate-EmulsionCompatibility
Acceptable?Compaction & CureVibratory or Marshall
φ=100mm specimens•ITS dry and soak
NO
•Select bitumen type and content
•Select filler type and content
•Results acceptable?
LEVEL 2 MIX DESIGN
Vibratory Compaction & Cure at Optimums
φ=150mm h=127mm• ITS equil and ITS soak
LEVEL 3 MIX DESIGN
NO
Vibratory Compaction & Cure at Optimums
φ=150mm h=300mm•Triaxial (monotonic)
• MIST (wet) triaxial
FINALISE MIX SELECTIONDETERMINE DEMAC AND CERTAINTY
YES
YES
NO
Done
NO
•Optimise bitumen content
•Check ITS results
•Results acceptable?
Design Traffic < 3 MESA
DoneDesign Traffic < 6 MESA
YES
YES
YES
NO
YES
NO
PRELIMINARY STEPS
•Aggregate selection and blending
•Aggregate classification
•Pre-treatment
LEVEL 1 Mix Design
•Using Selected Aggregate Blend
•Consider Climate & Early Traffic
Treatment Type Foamed BitumenBitumen Emulsion
Expansion Ratio
& Half-life
Acceptable?
Aggregate-EmulsionCompatibility
Acceptable?Compaction & CureVibratory or Marshall
φ=100mm specimens•ITS dry and soak
NO
•Select bitumen type and content
•Select filler type and content
•Results acceptable?
LEVEL 2 MIX DESIGN
Vibratory Compaction & Cure at Optimums
φ=150mm h=127mm• ITS equil and ITS soak
LEVEL 3 MIX DESIGN
NO
Vibratory Compaction & Cure at Optimums
φ=150mm h=300mm•Triaxial (monotonic)
• MIST (wet) triaxial
FINALISE MIX SELECTIONDETERMINE DEMAC AND CERTAINTY
YES
YES
NO
Done
NO
•Optimise bitumen content
•Check ITS results
•Results acceptable?
Design Traffic < 3 MESA
DoneDesign Traffic < 6 MESA
YES
YES
YES
NO
YES
NO
PRELIMINARY STEPS
•Aggregate selection and blending
•Aggregate classification
•Pre-treatment
LEVEL 1 Mix Design
•Using Selected Aggregate Blend
•Consider Climate & Early Traffic
Treatment Type Foamed BitumenBitumen Emulsion
Expansion Ratio
& Half-life
Acceptable?
Aggregate-EmulsionCompatibility
Acceptable?Compaction & CureVibratory or Marshall
φ=100mm specimens•ITS dry and soak
NO
•Select bitumen type and content
•Select filler type and content
•Results acceptable?
LEVEL 2 MIX DESIGN
Vibratory Compaction & Cure at Optimums
φ=150mm h=127mm• ITS equil and ITS soak
LEVEL 3 MIX DESIGN
NO
Vibratory Compaction & Cure at Optimums
φ=150mm h=300mm•Triaxial (monotonic)
• MIST (wet) triaxial
FINALISE MIX SELECTIONDETERMINE DEMAC AND CERTAINTY
YES
YES
NO
Done
NO
•Optimise bitumen content
•Check ITS results
•Results acceptable?
Design Traffic < 3 MESA
DoneDesign Traffic < 6 MESA
YES
YES
YES
NO
YES
NO
Mix Design(Wirtgen, 2012)
Bitumen Stabilised Material
Non-continuously bound
Continuously bound
Asphalt
DIFFERENT BEHAVIOUR PATTERNS
Testing the Material
BSM = non-continuously bound
0
50
100
150
200
250
300
350
400
450
0 500 1000 1500 2000 2500 3000 3500
UCS (kPa)
150m
m I
TSw
et (
kPa)
MR439 Zambia Greece
UCS versus ITS
Developing the Right Tools
Mix Design Approach(TG2, 2009)
• Preliminary tests
• Level 1
• Level 2
• Level 3
• Grading, MDD, OMC, Atterberg Limits (PI)
• 100mmφ Marshall ITS
• Binder, Active filler
• 150mmφ ITS for OBC
• > 3 MESA refine OBC
• 150mmφ 300H Triaxial
• >6 MESA reliability
2013 BSM Stabilisation Design1
Natural Material Charactr
Grading
Moisture density (Mod)
Atterberg Limits (PI)
ITS – select active filler
Step 1
150mmφdry
wet
Typical Bitumen %
0% 1%Lime 1%Cem
3 reps
Typical Bitumen % for BSM-foam
Typical Bitumen % BSM-emulsion
2013 BSM Stabilisation Design1
Natural Material Charactr
Grading
Moisture density (Mod)
Atterberg Limits (PI)
ITS – select active filler
Step 1
150mmφdry
wet
ITS – select bitumen %
Step 2
150mmφdry
wetequil
Typical Bitumen %
0% 1%Lime 1%Cem
3 reps
Selected active filler
-0.4% -0.2% 0% +0.2%
3 reps Bit %
Ref: (Wirtgen,
2012)
Binder type & content – Level 1
ITS
BSM Binder Content
ITSdry
ITSwet
BSM2
Min ITSdry
Min ITSwet
Min BC
2013 BSM Stabilisation Design3
Step 3
150mmφ
300mmH
σ1
σ2 σ2=σ3
Triaxial: Shear properties
Final mix selection
Reliable performance related properties
Flexibility?
C
ϕτ
σ0 50 100 200 kPa
4 σ3 x 2 reps = 8 specimens
Equilibrium
C
ϕτ
σ100 kPa
1 σ3 x 2 reps = 2 specimens
Wet
Level 1 and 2 Classification
Test Dia φmm
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
Critical Material Properties• Tri-axial test to determine:
– Shear parameters ( C & ϕ )– Resilient modulus ( Mr )
– Permanent deformation behaviour
σ1
t
σ1
tC
ϕτ
σ
εi
t
εp
log t
Triaxial Testing
Effect of using BSMτ
σ
Shear stress
Normal stress
C = Cohesion
φ Friction angle
Higher
Cohesion
Effect of Binder
Typical target binder contents
>75% RAP + Cr Dust
Granular GM > 2
Granular GM < 2
Typical Binder Cont. (%)
2% 2.5% 3%
Shear properties (monotonic triaxial at 25°C)
Cohesion C
0
100
200
300
400
500
A-7
5C
-0
B-7
5C
-0
C-7
5C
-0
A-7
5C
-1
B-7
5C
-1
C-7
5C
-1
A-7
5M
-0
B-7
5M
-0
C-7
5M
-0
Co
hesio
n [
kP
a]
E E E E E E FFF20
25
30
35
40
45
50
A-7
5C
-0
B-7
5C
-0
C-7
5C
-0
A-7
5C
-1
B-7
5C
-1
C-7
5C
-1
A-7
5M
-0
B-7
5M
-0
C-7
5M
-0
Fri
cti
on
an
gle
[d
eg
rees]
Friction Angle φ
E E E E E E FFF
Ebels
25% RAP 25% RAP75% RAP 75% RAP
Simple triaxial trials - with latex membrane as confining tube
(Mulusa)
New “Simple triaxial”
Research Triaxial Test RTT versus Simple Triaxial Test STT
0
200
400
600
800
1000
1200
1400
0.0 1.0 2.0 3.0 4.0 5.0
Strain [%]
Ap
pli
ed
Str
ess [
kP
a]
RTT
STT
0
200
400
600
800
1000
1200
0.0 1.0 2.0 3.0 4.0
Strain [%]
Ap
pli
ed
Str
ess [
kP
a]
RTT
STT
BSM Crushed Hornfels with 3.3% Emulsion
σ3 =50 kPa and 1% Cement σ3 = 200 kPa and 0% Cem
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
MOISTURE DAMAGE
Durability of BSMs: Improved Tests- Untreated Material Properties - Moisture sensitivity tests
Moisture Induction Sensitivity Test MIST
(Twagira)
50mmlayer
0.20
0.40
0.60
0.80
1.00
1.20
0 10 20 30 40 50
Foam +1%Lime
Foam +1%Cement
Pulsing time (sec)
De
gre
eo
fs
atu
rati
on
(%)
MIST saturation time
Effect of moistureτ
σ
Shear stress
Normal stress
C
Cohesion
φ Friction angle
Lower Cohesion
Effect of Moisture
Retained Cohesion (Twagira)
0
10
20
30
40
50
60
70
80
90
Q+ 0C -F
Q+ 1C -F
Q+ 1L -F
Q+ 1C-E
Q+ 1L -E
H+ 0C -E
H+ 1C -E
H+ 1L -E
BSM 1
BSM 2
BSM 3
Res
idua
l coh
esio
n [%
]
Tested BSMs
BSM Classification ito Moisture Resistance
Retained Cohesion (%)
> 75
60 – 75
50 – 60
< 50
Equivalent BSM Class
BSM 1
BSM 2
BSM 3
Unsuitable
SUPPORT
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
(k
Pa
)Dissipated Energy
W = 0.5 σεA1A2
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
Ve
rtic
al
Dis
pla
ce
me
nt
at
ITS
ma
x (
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 measures (from Mix Design)
Triaxial data from Mix Design
Can refine by separating data based on σ3
So we need quality from structural design
Conclusions
• Understanding of material behaviour of BSMs has increased significantly
• Active filler versus bitumen content is very important
• More advanced test methods (triaxial)
• Mix Design is linked to Structural Design method for BSMs
Thank you
Questions??