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Hossain Extending Asphalt Pavement Life Using Thin...
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Extending Asphalt Pavement Life Using Thin Whitetopping Mustaque Hossain, Ph.D., P.E. Department of Civil Engineering Kansas State University
Transcript of Hossain Extending Asphalt Pavement Life Using Thin...
Extending Asphalt Pavement Life Using Thin Whitetopping
Mustaque Hossain, Ph.D., P.E. Department of Civil Engineering
Kansas State University
DisclaimerThe contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the information presented
herein. This document is disseminated under the sponsorship of the Department of Transportation
University Transportation Centers Program, in the interest of information exchange. The U.S.
Government assumes no liability for the contents or use thereof.
Slide design © 2009, Mid-America Transportation Center. All rights reserved.
Sharmin SultanaUniversity of Texas, Austin
Acknowledgements
OutlineBackgroundObjectiveModeling of Thin Whitetopping PavementResultsConclusions Recommendations
Background
Whitetopping is the process of rehabilitating asphalt concrete (AC) pavements using a concrete overlay
There are three types of whitetopping:Conventional: thickness > 8 in.Thin: thickness = 4-8 in.Ultra-thin: thickness < 4 in.
Thin Whitetopping Pavement(US 287, Lamar, Colorado)
Thin Whitetopping Construction (I-70, Salina, Kansas)
Thin Whitetopping Pavement(I-70, Salina, Kansas)
Background
Whitetopping Interface Bonding Condition:BondedUnbonded
(After Rasmussen and Rozycki 2004)COE1
Slide 9
COE1 I removed the comma. o/k. default, 2/10/2012
Background
Cases where whitetopping is feasible:
Existing AC pavements highly deteriorated (rutted and cracked)Adequate vertical clearanceNo AC layer settlement issues
Background
Existing design procedures for whitetopping:
AASHTO*Colorado*New JerseyPCA/ACPAModified ACPAIllinoisTexas*
* Thin whitetopping only
Objectives
To assess the behavior of thin whitetopping(TWT) with respect to:
Thin whitetopping thickness (5 in., 6 in., and 7.5 in.)Existing AC thickness (5 in., 7 in., and 9 in.)Interface bonding conditions (Bonded and Unbonded)Existing AC modulus (250 ksi and 350 ksi)Shoulder (Unpaved or Paved)Temperature gradient
To estimate the service life
Finite Element Modeling
Structure: Thin whitetopping (TWT) on existing AC pavement FE software: SolidWorksPavement model: A three-layer pavement system:
TWTExisting HMA/AC layerSubgrade layer
(After McGhee 1994)
Finite Element Modeling
Layer materials: Isotropic and linear elastic
Mesh: High quality
Symmetry: Both geometry and loading
Pavement segment : 3-ft. wide & 30-in. in depth
Joint spacing: 6 ft.
Finite Element Models
With Tied and Paved Shoulder No Tied or Paved Shoulder
Model Loading
• Loading: 20,000 lbs on a single axle with dual tires (legal load in Kansas)
• Loaded area: Rectangular, normal, uniform, and equal to the tire inflation pressure
• Self weight: Considered for all layers
Model Loading
No Paved Shoulder
Paved Shoulder (After Dumitru 2006)
Analysis Results• The critical response, maximum transverse
tensile stress, was found at the bottom of the thin whitetopping (TWT) layer
• It varied from 75 psi for bonded 7.5-in. TWT to as much as 442 psi for unbonded 5-in. TWT
Effect of Interface Condition
0
50
100
150
200
250
300
350
400
450
500
Bonded Unbonded
Interface Condition
PCC
Stre
ss (p
si)
5 in.TWT6 in. TWT7.5 in.TWT
Effect of Interface Condition
Unpaved Shoulder Paved Shoulder
0
50
100
150
200
250
300
350
400
450
Bonded 0.75 0.5 0.25 0
Frictional Coefficiant
PCC
Str
ess
(psi
)
AC Modulus250 ksiAC Modulus350 ksi
0
50
100
150
200
250
300
350
400
Bonded 0.75 0.5 0.25 0
Frictional CoefficiantPC
C S
tres
s (p
si)
AC Modulus250 ksiAC Modulus350 ksi
Effect of TWT Thickness
Bonded TWT with Paved Shoulder Unbonded TWT with No Shoulder
PCC Stress vs. Bonded Unpaved TWT Thickness(AC Modulus 250 ksi)
0
50
100
150
200
250
300
350
400
450
500
5 6 7.5
TWT Thickness (in.)
PCC
Stre
ss (p
si)
5 in.AC7 in. AC9 in.AC
PCC Stress vs. Unbonded Unpaved TWT Thickness(AC Modulus 250 ksi)
0
50
100
150
200
250
300
350
400
450
500
5 6 7.5
TWT Thickness (in.)PC
C St
ress
(psi
)
5 in.AC7 in. AC9 in.AC
Effect of AC Thickness
0
20
40
60
80
100
120
140
160
180
5 7 9
AC Thickness (in.)
PCC
Stre
ss (p
si)
5 in.TWT6 in. TWT7.5 in.TWT
Effect of Existing AC Modulus
0
20
40
60
80
100
120
140
160
180
250 350
AC Modulus (ksi)
PCC
Stre
ss (p
si)
5 in.AC7 in. AC9 in.AC
Effect of Paved Shoulder
0
20
40
60
80
100
120
140
160
180
Unpaved Paved
Shoulder Condition
PCC
Stre
ss (p
si)
5 in.AC7 in. AC9 in.AC
Effect of Temperature Gradient
0
50
100
150
200
250
5 6 7.5
TWT Thickness (in)
Curli
ng S
tress
(psi
)
BondedUnbonded
Computation of Service Life
• In PCA method, allowable load repetitions are calculated based on the stress ratio (= calculated tensile stress/modulus of rupture)
• If the stress ratio is less than 0.45, the pavement can take unlimited load repetitions
PCA model
• For S.R. > 0.55
• For 0.45 ≤ S.R. ≤ 0.55
• For SR < 0.45 N=Unlimited
S.R. = ration of flexural stress to modulus of raptureN = number of allowable load repetitions
0828.097187.0)(log10
SRN −=
268.3
43248.02577.4
⎟⎠⎞
⎜⎝⎛
−=
SRN
Service Life (full bonding)(for various ADTT level)
0
2
4
6
8
10
12
5 6 7.5
TWT Thickness (in.)
Serv
ice
Life
(yrs
)
≤200300400500
Service Life (unbonded TWT & 5” AC)
(250 ksi AC Modulus and Unpaved Shoulder)
0
2
4
6
8
10
12
5 6 7.5
TWT Thickness (in.)
Serv
ice
Life
(yrs
)
≤200300400500
(350 ksi AC Modulus and Unpaved Shoulder)
0
2
4
6
8
10
12
5 6 7.5
TWT Thickness (in.)
Serv
ice
Life
(yrs
)
≤200300400500
(AC, 250 ksi AC Modulus and Paved Shoulder)
0
2
4
6
8
10
12
5 6 7.5
TWT Thickness (in.)
Serv
ice
Life
(yrs
)
≤200300400500
(AC, 350 ksi AC Modulus and Paved Shoulder)
0
2
4
6
8
10
12
5 6 7.5
TWT Thickness (in.)
Serv
ice
Life
(yrs
)
≤200300400500
Service Life(unbonded TWT & 7” AC)
(250 ksi AC Modulus and Unpaved Shoulder)
0
2
4
6
8
10
12
5 6 7.5
TWT Thickness (in.)
Serv
ice
Life
(yrs
)
≤200300400500
(350 ksi AC Modulus and Unpaved Shoulder)
0
2
4
6
8
10
12
5 6 7.5
TWT Thickness (in.)
Serv
ice
Life
(yrs
)
≤200300400500
(250 ksi AC Modulus and Paved Shoulder)
0
2
4
6
8
10
12
5 6 7.5
TWT Thickness (in.)
Serv
ice
Life
(yrs
)
≤200300400500
(350 ksi AC Modulus and Paved Shoulder)
0
2
4
6
8
10
12
5 6 7.5
TWT Thickness (in.)
Serv
ice
Life
(yrs
)
≤200300400500
Service Life(unbonded TWT and 9” AC)
0
2
4
6
8
10
12
5 6 7.5
TWT Thickness (in.)
Serv
ice
Life
(yrs
)
≤200300400500
Conclusions• Interface bonding is the most important
factor that affects the longevity of thin whitetopping
• Bonding has a more pronounced effect on transverse tensile stress for the unpaved shoulder condition than that of the tied and paved shoulder condition
• Thin whitetopping thickness has a more pronounced effect for the unbondedinterface condition than the bonded condition
Conclusions (cont.)
• Tied, paved PCC shoulder decreases stresses in thin whitetopping
• Tied, paved PCC shoulder is particularly useful for unbonded thin whitetopping with low truck traffic
Recommendations
• Field experimentation to investigate actual behavior of thin whitetopping
• The effect of environment, subgrade soil types, and different joint spacing can be investigated
Recommendations (cont.)
• Pavement response under moving loads would give a better approximation of the actual scenario
• Partial bonding at the interface should be investigated as it is very difficult to achieve full bonding in the field
Thank You!
