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