Whitetopping Mustaque Hossain PhD PE Department of Civil Engineering Kansas State University Disclaimer The 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 dissemin ID: 598829
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Slide1
Extending Asphalt Pavement Life Using Thin Whitetopping
Mustaque Hossain, Ph.D., P.E. Department of Civil EngineeringKansas State UniversitySlide2
Disclaimer
The 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.Slide3
Slide design © 2009, Mid-America Transportation Center. All rights reserved.
Sharmin SultanaUniversity of Texas, Austin
AcknowledgementsSlide4
Outline
BackgroundObjectiveModeling of Thin Whitetopping PavementResultsConclusions RecommendationsSlide5
Background
Whitetopping is the process of rehabilitating asphalt concrete (AC) pavements using a concrete overlayThere are three types of whitetopping:
Conventional: thickness > 8 in.
Thin: thickness = 4-8 in.
Ultra-thin: thickness < 4 in
.Slide6
Thin Whitetopping Pavement
(US 287, Lamar, Colorado)Slide7
Thin Whitetopping Construction
(I-70, Salina, Kansas)Slide8
Thin Whitetopping Pavement
(I-70, Salina, Kansas)Slide9
Background
Whitetopping Interface Bonding Condition:BondedUnbonded
(After Rasmussen and
Rozycki
2004)Slide10
Background
Cases where whitetopping is feasible:Existing AC pavements highly deteriorated (rutted and cracked)
Adequate vertical clearance
No AC layer settlement issuesSlide11
Background
Existing design procedures for whitetopping:AASHTO*Colorado*
New Jersey
PCA/ACPA
Modified ACPA
Illinois
Texas*
*
Thin
whitetopping
only Slide12
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 lifeSlide13
Finite Element Modeling
Structure: Thin whitetopping (TWT) on existing AC pavement FE software: SolidWorksPavement model: A
three-layer
pavement system:
TWT
Existing
HMA/AC
layer
Subgrade layer
(After McGhee 1994)Slide14
Finite Element Modeling
Layer materials: Isotropic and linear elastic Mesh: High qualitySymmetry:
Both geometry and loading
Pavement segment :
3-ft.
wide & 30-in. in depth
Joint spacing:
6
ft.
Slide15
Finite Element Models
With Tied and Paved Shoulder
No Tied or Paved Shoulder Slide16
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 pressureSelf weight: Considered for all layers Slide17
Model Loading
F=10,000
lbs
No Paved Shoulder
Paved Shoulder
(After
Dumitru
2006)
Slide18
Analysis Results
The critical response, maximum transverse tensile stress, was found at the bottom of the thin whitetopping (TWT) layerIt varied from 75 psi for bonded 7.5-in. TWT to as much as 442 psi for unbonded 5-in. TWTSlide19
Effect of Interface ConditionSlide20
Effect of Interface Condition
Unpaved Shoulder
Paved Shoulder
Slide21
Effect of TWT Thickness
Bonded TWT with Paved Shoulder
Unbonded
TWT with No Shoulder
Slide22
Effect of AC ThicknessSlide23
Effect of Existing AC ModulusSlide24
Effect of Paved ShoulderSlide25
Effect of Temperature GradientSlide26
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 Slide27
PCA model
For S.R. > 0.55For 0.45 ≤ S.R. ≤ 0.55For SR < 0.45 N=UnlimitedS.R. = ration of flexural stress to modulus of raptureN = number of allowable load repetitionsSlide28
Service Life (full bonding)
(for various ADTT level)Slide29
Service Life
(unbonded TWT & 5” AC)Slide30
Service Life
(unbonded TWT & 7” AC)Slide31
Service Life
(unbonded TWT and 9” AC)Slide32
Conclusions
Interface bonding is the most important factor that affects the longevity of thin whitetoppingBonding has a more pronounced effect on transverse tensile stress for the unpaved shoulder condition than that of the tied and paved shoulder conditionThin whitetopping thickness has a more pronounced effect for the unbonded interface condition than the bonded conditionSlide33
Conclusions (cont.)
Tied, paved PCC shoulder decreases stresses in thin whitetoppingTied, paved PCC shoulder is particularly useful for unbonded thin whitetopping with low truck trafficSlide34
Recommendations
Field experimentation to investigate actual behavior of thin whitetoppingThe effect of environment, subgrade soil types, and different joint spacing can be investigatedSlide35
Recommendations (cont.)
Pavement response under moving loads would give a better approximation of the actual scenarioPartial bonding at the interface should be investigated as it is very difficult to achieve full bonding in the field Slide36
Thank You!