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Pavement Design using BSMs
Kim Jenkins
SARF Course on BSMsAssegai, Shongweni
14 and 15 July 2015
tellenbosch
Life is full of surprises…
Try to keep them to a minimum
Permanent Deformation
• UCS ITS (compressive and tensile strength)
• Triaxial (shear strength)
• Measure Load versus displacement
Flexibility• Effective long term stiffness
300 kN 300 kN 100 kN
1300 kPa
TRAFFIC Overloadingcement vs bitumen
Damage Factor
DF = P Std
n
n =7 cementedn = 3.5 granularn =4.5 BSM?
Key Question: What is Mr?
Available information?
250mm CIPR: 3% Foam 1% Cem
90mm Asphalt
12 24 36 480
Time after construction (months)
MR
CURENo classic fatigue
Rutmm
Time / Traffic
Permanent deformation20mm
15 years8 years
Design
N7 Cape Town2002 Rehab and HVS TRIALS
In-situ recycled crushed stone base material NB: 1% cement and 2.3% foamed bitumen SB: 1% cement and 3% bitumen emulsion
∆ Moisture during Curing N7 SB
Moloto, 2009
BSM-emulsion
BSM-emulsion Mr vs time
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)
Mr vs load repetitions (triaxial)
0.0
200.0
400.0
600.0
800.0
1000.0
1200.0
1400.0
1600.0
1800.0
2000.0
100 1 000 10 000 100 000 1 000 000
Res
ilien
t Mod
uli (
MP
a)
.
Load repetitions
SR=49%SR=57%SR=65%SR=67%
Jenkins et al, IJPE
BSM-foam (2%)
N7 Cape Town2002 Rehab and HVS TRIALS
In-situ recycled crushed stone base material NB: 1% cement and 2.3% foamed bitumen SB: 1% cement and 3% bitumen emulsion
Mr back -calc vs time (N7)
0
200
400
600
800
1000
1200
1400
1600
1800
1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012
Mr
Bac
k-ca
lcul
ated
(M
pa)
Year
90th Percentile
Rehab
Stellenbosch University
?
Mr versus Base Layer Index
0
200
400
600
800
1000
1200
1400
1600
1800
0 2 4 6 8
Mr
Bac
k-ca
lcul
ated
(M
pa)
1/BLI
N7 90th Percentile Mr
2010
2004
2000
1994
Stellenbosch University
N7 SAPDM: FWD Backanalysis
(Theyse)
P243: BSM-foam 1.8% bit 2% cem
(Theyse)
BSM Stiffness during service life
Time / traffic
Stiffness modulus
app. 1 year
curing phase
stiffness reduction phase
?
t = x
eq. traffic loading
stiffness
CIPR Brazil (Jenkins & Ebels, 2005)
Effective Mr of BSM for recycling?BSM vs HMA?
FatigueBSM 75%Crushed stone + 25%RAP
HMA Base 2000MPa
Back -calculated Stiffness ProfileSB Case Study R35 (Lynch, 2013)
200mm BSM (Emulsion) - 2% cement, 2.4% bitumen
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
0 50 100 150 200 250 300 350 400
Ba
ck-c
alc
ula
ted
Sif
fne
ss (
MP
a)
Days since Construction
Pri
me
Asp
ha
lt
Ca
pe
Se
al
Tra
ffic
Generalised Stiffness ProfileSB R35 BSMs (Lynch, 2013)
Time since Construction
Stif
fnes
s
360
Day
s
Traf
fic A
pplie
d @
90
Day
s
Disruption of stiffness development due to prime application
Stable Stiffness to 360 Days
Possible stiffness reduction due to traffic application
Back -calculated Stiffness ProfileNB Case Study R35 (Lynch, 2013)
200mm BSM (Foam) - 1% cement, 2.4% bitumen
0
200
400
600
800
1000
1200
1400
1600
0 20 40 60 80 100 120 140 160 180 200
Ba
ck-c
alc
ula
ted
Sif
fne
ss (
MP
a)
Days since Construction
95th
%ile
5th %ile
Average
Pri
me
Asp
ha
lt
Ca
pe
Se
al
Tra
ffic
BSMs Mr change:Effective Long Term Stiffness
0
500
1000
1500
2000
0 1 2 3 4 5 6 7 8 9 10
Equ
ival
ent S
tiffn
ess
(Mpa
)
Years
1% cem CTSB1% cem G5SB1% cem G7SB
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
Equ
ival
ent S
tiffn
ess
(Mpa
)
Years
1% cem CTSB2% cem CTSB1% cem G5SB2% cem G5SB1% cem G7SB2% cem G7SB
cementTrafficBrittle (cem )Poor Support
BSM1 all
BSMs Mr change:Effective Long Term Stiffness
0
500
1000
1500
2000
2500
3000
3500
4000
0 1 2 3 4 5 6 7 8 9 10
Equ
ival
ent S
tiffn
ess
(MP
a)
Years
AsphaltBSMCTSBGranular
MoistureAcceler’tdDistress
Mill & Replace Asphalt
(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)
Structural Design Methods
1. SN Method 2.TG2 Method (Pavement Number) 3. Mechanistic (Stress Ratio)4. SAPDM
1. SN design method
Drainage for SN
SN example for 8.5 mesa
Method 2: Pavement Number Knowledge Based Approach
• Gather all available field performance data• Utilise best elements of mechanistic analysis• Robust and easy to use• Validated!• Develop clear, strong links to field testing
(material classification) and specifications• Data Sets
– 20 field sites – 7 HVS Sites (22 test sections) – Construction, maintenance & performance
information
Subgrade Characterization• Starting point for design• Determine stiffness using Material Class
Design equivalent material class
Stiffness value (MPa)
DE-G6 or better 180
DE-G7 140
DE-G8 100
DE-G9 90
DE-G10 70
• Adjust for climate• Adjust for cover depth (stress -dependent)
118 MPa
6. Calculate Layer ELTS Values
118 MPa
4. Adjust for cover (118 MPa)
Example, Moderate Region
1. Material Classes
2. Determine subgrade stiffness (140 MPa)3. Adjust for climate (126 MPa)
CBR 7-15%
180 mm G6
200 mm C4
150 mm BSM2
150 mm G7
5. Assign modular ratio’s and Maximum Emods
MR = 1.8, EMax = 180
MR = 3, EMax = 400
MR = 2, EMax = 700
7. Layer PN = thickness * ELTS
8. PN = Σ layer PN
6. ELTS = min (E support *MR , Emax)
ELTS = 180
ELTS = 400
ELTS = 700
www.bitstab.roadrehab.com
Design Criteria
0
5
10
15
20
25
30
35
0 10 20 30 40 50
Pavement Number
Min
imum
Str
uctu
ral C
apac
ity
(ME
SA
)
Category ACategory B
Not a transfer function
Rather, design frontier
Cat BCat A
95% reliability90% reliability
Example 18
Calibration: LTPP Dataset (15 sections) + HVS
R2 = 0.95
0
5
10
15
20
25
30
35
40
0 5 10 15 20 25 30 35 40Pavement Number
Tra
ffic
Acc
omm
odat
ed (
mes
a)
Sound
Warning
Failed
Expon. (Warning)
A B C
Stress Ratioτ
σ
Shear stress
Normal stress
σ3 σ1
C
Cohesion
φ Friction angle
σ1,f
σd= σ1- σ3
σd,f= σ1,f- σ3
=σd/σd,f
( )( )φ
φσφσsin1
cos..2.sin1 3,1 −
++=
Cf
t
/t
σ2
σ3
σ1Method 3
Stress RatioPut simply
Deviator
Stress
σd
Strain ε
Low
Medium
High
a. BSM Performance Permanent Deformation vs Stress Ratio
Triaxial Testing
σd/σd,f = 40%
Vertical
Plastic
Strain εp vert
Time or Load Reps (N)
σd/σd,f = 50%
σd/σd,f = 60%εp = aNb
Ref: K JenkinsPhD Univ Stell
Mulusa, UnivStell 2009
0.01
0.10
1.00
10.00
10 100 1000 10000 100000 1000000
Number of load repetitions [-]
Per
man
ent a
xial
stra
in [%
]
0.40
0.60
0.50
0.30
Deviator stress ratio:
Permanent Deformation Triaxial(No cement)
BSM-foam with 25% RAP (C -75C-0)
0.01
0.10
1.00
10.00
10 100 1000 10000 100000 1000000
Number of load repetitions [-]
Per
man
ent a
xial
stra
in [%
]
0.40
0.40
0.60
0.50
0.45
Deviatorstress ratio:
BSM-emulsion with 25% RAP (A -75C-1)
Similar trends for BSM -foam with 1% cem
Permanent Deformation Triaxial(1% cement)
0.01
0.10
1.00
10.00
10 100 1000 10000 100000 1000000
Number of load repetitions [-]
Per
man
ent a
xial
stra
in [%
]
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 a
xial
stra
in [%
]
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
Load Reps vs Stress Ratio
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1.E+09
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2Stress ratio
Load
rep
etiti
ons
N7 0%BC 0%CN7 2.3%BC 0%CN7 1.50%BC 1%CN7 2.3%BC 1%CN7 3%BC 1%CN7 2.3%BC 2%CG1eer 1%BC 0%CG1eer 2%BC 0%CG1eer 2%BC 1%CG1eer 4%BC 0%CG1van 1.5%BC 2%C
4% Plastic strain
Zone of concern
Pavement Balance and Modular Ratio
Mr (MPa)
BSMDesign
Asp
BSM1
CTSB
SG
Asp
BSM1
CTSB
SG
3000
Sub-layering
Mr (MPa)
800 to 1200
1200
150
200
3000
1200
150
200
80010001200
Perpetual Pavement
Thin surfacing - low rutting
Foamed bitumen stabilised – flexible, reconsitutes, stress-dependent, rut resistant, load spreading, low permeability
Cement or lime stabilised –rigid anvil for compaction, lowers neutral axis
+
-
Documentation
Conclusions
• General BSM behaviour• Material Classification feeds into
Structural Design• Modular ratio• Effective Long Term Stiffness NB• Deviator Stress Ratio – good design
parameter
Thank you
Questions??
4. SAPDM (Godzilla)
• Elasto -plastic response model• Change in Mr versus time – further
analysis (R35 etc )• Include flexibility “strain -at-break”• Recursive analysis
– Rate of rutting– Rate of cracking
Strain -at-Break resultsεb
BSM
Strain -at-break vs Fatigue25%RA & 0%Cem
1E+00
1E+01
1E+02
1E+03
1E+04
1E+05
1E+06
1E+07
100 1,000 10,000
Num
ber o
f rep
etiti
ons
Strain [x 10-6]
emulsion A
emulsion B
foamed bitumen C
Strain at break
AB
C
4PB Fatigue
Stellenbosch University
Strain -at-break vs Fatigue 25%RA & 1%Cem
1E+00
1E+01
1E+02
1E+03
1E+04
1E+05
1E+06
1E+07
100 1,000 10,000
Num
ber o
f rep
etiti
ons
Strain [x 10-6]
emulsion A
emulsion B
foamed bitumen C
Strain at break A
C
B
4PB Fatigue
Stellenbosch University
R35 Analysis with SAPDM (Theyse) 1
Effective Fatigue Simulation (Theyse) 2
Survival Hitogram and design risk (Theyse) 3