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Tommy E. Nantung PhD PE
Design and Construction of
LONG LIFE PAVEMENT
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Introduction to Pavement
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Roadmap to Presentation
• Definition of Long Life Pavement
• Why pavement failed
•
A little history of pavement• Type of pavement distresses
• AASHTO 1993/1998 Pavement Design
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Definition of Long Life Pavement
• A Long-Life Pavement is defined as apavement
– no significant deterioration will develop in the
foundations or the road base layers provided thatcorrect surface maintenance is carried out.
• This definition implies that
– all pavement layers, except the road surface layer
are considered as permanent pavement layers andcommon distress mechanisms should, in principle,be eliminated completely.
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Introduction to pavement structure
• A pavement is a structure composed of
structural elements, whose function is to
protect the natural subgrade and to carry the
traffic safety and economically.
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Introduction to pavement structure
• As a wheel passes:
– Elastic deformations occur
– Plastic deformations occur elastic deformations
may lead to fatigue
– Plastic deformation deformations may lead to
excessive rutting.
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Type of pavement based on structure
• Rigid Pavement
– A pavement structure of which the surface courseis made of Portland cement concrete
• Flexible Pavement – A pavement structure of which the surface course
is made of asphaltic concrete, that maintainsintimate contact with and distributes loads to the
subbase or subgrade and depends upon aggregateinterlock, particle friction, and cohesion forstability
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The difference between pavement structure
• The essential difference between Flexible
pavement and Rigid pavement is the manner
in which they distribute the load
– Flexible pavement is one which can adjust its
position to the shape of the underlying layers
without sustaining significant damage.
–Rigid pavement tend (work as slab) to distributethe load over a relatively wide area of soil. Why?
(High modulus of elasticity)
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Definitions
• Pavement Section
– A layered system designed to distribute
concentrated traffic loads to the subgrade.
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Factors Affecting Pavement Performance
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Traffic
Subgrade
Soil
Materials
Construction
Variability
Environment
Maintenance
and Rehabilitation
Design
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A Little History of Pavement Performance
Roman Roads
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Telford Road
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Macadam Road
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Macadam
Regardless of thethickness of thestructure many
of the roads in GreatBritain deteriorated
rapidly
when the subgradewas saturated.
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Three Keys to Long Term Performance
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Water Infiltration
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Subgrade
AC / PCC
Base / Subbase
Collector
Pipe
To Outlet
Shoulder
Permeable &
Filter Layer
Water Infiltration
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Source of Moisture
Brand New Pavement Drought in the Summer
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Variation of Resilient
Modulus with Moisture Content
3-1960 80100
0
2
4
6
8
10
12
14
16
% Saturation, S
Resilient Modulus MR, ksi 100% AASHTO - T99
95% AASHTO - T99
402010 30 50 70 90
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Another Key to Long Term Performance
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Influence of Soil Compaction
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Another Key to Long Term Performance
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Flexible Pavement
• Structure
– Surface course
– Base course
– Subbase course
– Subgrade
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Types of Flexible Pavement
Dense-graded
Open-graded Gap-graded
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Flexible Pavement – Construction
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Types of Rigid Pavement
• Jointed Plain Concrete Pavement (JPCP)
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Types of Rigid Pavement
• Continuously Reinforced Concrete
Pavement (CRCP)
Photo from the Concrete Reinforcing Steel Institute
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Pavement types based on traffic
• Low
– Un-surfaced
– Dust oil
– Penetration macadam – Surface treatment
• Intermediate
– Dense cold mix
–
Cold mix – Open cold mix
– Lime treated base - Soil cement
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Pavement types based on traffic
• High Type
– Asphalt concrete surfaced
– Portland cement concrete
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Definition of Stress
• Stress is defined as force per unit area. It has
the same units as pressure, and in fact
pressure is one special variety of stress.
However, stress is a much more complexquantity than pressure because it varies both
with direction and with the surface it acts on
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Definition of Stress
• Compression Stress that acts to shorten an object.
• Tension Stress that acts to lengthen an object.
• Normal Stress Stress that acts perpendicular to asurface. Can be either compressional or tensional.
• Shear Stress that acts parallel to a surface. It can causeone object to slide over another. It also tends todeform originally rectangular objects intoparallelograms. The most general definition is thatshear acts to change the angles in an object.
f f
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Definition of Strain
• Strain is defined as the amount of
deformation an object experiences compared
to its original size and shape. For example, if a
block 10 cm on a side is deformed so that itbecomes 9 cm long, the strain is (10-9)/10 or
0.1 (sometimes expressed in percent, in this
case 10 percent.) Note that strain isdimensionless.
f f
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Definition of Strain
• Longitudinal or Linear Strain Strain that changes
the length of a line without changing its direction.
Can be either compressional or tensional.
• Compression Longitudinal strain that shortens anobject.
• Tension Longitudinal strain that lengthens an
object.• Shear Strain that changes the angles of an object.
Shear causes lines to rotate.
fi i i f i
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Definition of Strain
H k’ L
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Hook’s Law
• Hook’s law is a quantitative relation betweenstress and strain – "Within elastic limit , strain produced in a body is
directly proportional to stress"
– i.e. Strain µ Stress – OR Strain =(Constant)(Stress)
– Where 1/K = constant of proportionality
– Strain =(1/K)(Stress)
– OR Stress / Strain = KORStress / Strain = K
Y ’ M d l
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Young’s Modulus
• "The ratio of stress to the longitudinal strain is
called Young's modulus."
– Young's Modulus = Stress / Longitudinal Strain
– OR Y = s /
– But s = F / A and = L / L
– Putting these values in equation
• Y or E =( F / A) / ( L / L)OR
Y or E = F L / A L
S S i D
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Stress-Strain Demo
• http://www.esm.psu.edu/courses/emch13d/d
esign/animation/Fnecking.html
• http://www.youtube.com/watch?v=mzb4Hpm
rub4
R l f P t S f
http://www.esm.psu.edu/courses/emch13d/design/animation/Fnecking.htmlhttp://www.esm.psu.edu/courses/emch13d/design/animation/Fnecking.htmlhttp://www.esm.psu.edu/courses/emch13d/design/animation/Fnecking.htmlhttp://www.esm.psu.edu/courses/emch13d/design/animation/Fnecking.htmlhttp://www.youtube.com/watch?v=mzb4Hpmrub4http://www.youtube.com/watch?v=mzb4Hpmrub4http://www.youtube.com/watch?v=mzb4Hpmrub4http://www.youtube.com/watch?v=mzb4Hpmrub4http://www.youtube.com/watch?v=mzb4Hpmrub4http://www.esm.psu.edu/courses/emch13d/design/animation/Fnecking.html
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Role of Pavement Surface
Surface (PCC or HMA)
Base Course
Subbase Course
Subgrade Soil
4 Roles:
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Smooth ride
Skid resistance
Moisture barrier
Distribute load
Ri id t
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Rigid pavement
• One which will bridge minorundulations in underlyinglayers without failing.
• Westergard theory or slab onelastic foundation.
• Portland cement + aggregate(+ steel)
• Types of failure
– Polishing
– Scaling
–Joint needs filling
– Fatigue
– Pumping
T ffi L di i Ri id P t
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Traffic Loading in Rigid Pavement
Ri id P t C iti l L di
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Rigid Pavement Critical Loading
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Subgrade Support
LOAD
Maximum Stress
Bottom of Slab
CRITICAL LOAD CONDITION ASSUMPTIONS
Maximum stress at pavement edge
25% Load Transfer to adjacent slab
Ri id P t C iti l L di
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Rigid Pavement Critical Loading
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LOAD
TOP DOWN CRACKING DUE TO EDGE OR CORNER LOADING NOT
INCLUDED IN DESIGN
Maximum stress due to corner or edge loading condition
Risk increases with large multi-wheel gear configurations
These conditions may need to be addressed in future procedures
Maximum Stress
Top of Slab
C li t
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Curling stress
Curling stress
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Curling stress
JPCP Bottom-Up Cracking –
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Base
Subgrade
Critical stress region at
bottom of slab
JPCP Bottom Up Cracking (Mid-slab Load + Positive Curl/Warp Condition)
JPCP Top Down Cracking
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Base
Subgrade
Critical stressregion at top of slab
JPCP Top Down Cracking(Joint Load + Negative Curl/Warp Condition)
JPCP Top down Cracking
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Top of slab(crack initiation)
JPCP Top-down Cracking
Flexible pavement
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Flexible pavement
• Can adjust its position to theshape of the underlying layerswithout damage.
• Based on layered systemconcept.
• Asphalt cement or liquidasphalts + aggregate
• Failure types
– Bleeding
– Polishing
–
Deformation (rutting) – Fatigue
Traffic Loading in Flexible Pavement
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Traffic Loading in Flexible Pavement
Stress and strain in flexible pavement
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Stress and strain in flexible pavement
Chapter 3 Section 2 Flexible Pavement Design
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Chapter 3 Section 2 – Flexible Pavement Design
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Subgrade Support
Wearing Surface
Subgrade
Subbase
Base Course
Approximate Line ofWheel-Load Distribution
Area of Tire Contact
Wheel LoadHorizontal Strain and Stressat the bottom of the asphalt
Vertical Subgrade Strain
Must also guardagainst potentialfailure in baselayers
Importance of stresses in pavement
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Importance of stresses in pavement
• To understand
– The mechanism of load distribution
– To use in improved design methods
– To evaluate the performance of materials.
Stress – strain analysis in pavement
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Stress – strain analysis in pavement
• Flexible Pavements:
– Layered elastic theory
– Finite element analysis
– Visco elastic analysis
• Rigid Pavements:
– Slab on elastic foundation (Westergard)
– Others (finite element).
Pavement loading
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Pavement loading
Pavement loading
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Pavement loading
• Wheel can be single or dual
• Axle can be single or Tandem
• Legal axle loads are (18 kip to 20 kip) for more
load add more axles
• Allowable is 32 kip with spacing of 40"-48".
Pavement loading – tire pressure
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Pavement loading tire pressure
• If tire is inflated correctly – The contact pressure between pavement and tire is
equal to the tire pressure.
• If tire has low pressure, then edge pressure ishigher than center.
• If tire has high pressure, then center pressure ishigher than edge pressure.
• For correct inflation, and assuming a uniformcontact pressure, the tire imprint may beassumed circular.
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PAVEMENTS ARE DESIGNEDTO FAIL
(IN A PREDICTABLE WAY)
Performance vs Design Life
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Performance vs Design Life
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AND WHY PAVEMENT FAILSPREMATURELY
(IN AN UNPREDICTABLE WAY)
Two Measures of Pavement Performance
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Two Measures of Pavement Performance
• Functional performance:
– present serviceability index, pavement surface
friction, and wet-weather safety index
• Structural performance: – pavement structural capacity to accommodate
future traffic
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Attributes of a Pavement in Good Condition
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Attributes of a Pavement in Good Condition
• High level of service (LOS)• Safe
• High customer satisfaction
•
Exceeds target performance indicators or haslimited deterioration; e.g., – IRI < 15 cm/km (95 in/mi)
– PCI > 70 or PCR ≥ 3.5• Surface Distress (cracks, faulting, etc.)
– Skid Number > 35
– Deflection < 305 microns (12 mils)
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Typical HMA Pavement Distresses
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Typical HMA Pavement Distresses
• Fatigue cracking• Bleeding
• Polishing
• Edge cracking
• Roughness• Longitudinal and transverse cracking
• Reflection cracking
• Raveling/weathering/oxidation
• Potholes
• Rutting (stable/unstable)
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Primary HMA Deterioration Load
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Primary HMA Deterioration Load
Plastic
Deformation
Rutting
Load
Fatigue
Cracking
Primary HMA Deterioration Traffic
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Primary HMA Deterioration Traffic
Friction Loss
Polishing
Surface
Wear
Traffic
Primary HMA Deterioration Environment/Aging
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Primary HMA Deterioration Environment/Aging
Block Cracking
Raveling/Weathering Asphalt
Hardening
or
Oxidation
Environment / Aging
Primary HMA Deterioration Material/Mix
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Primary HMA Deterioration Material/Mix
Material Problems
Friction Loss
Bleeding/Flushing
Secondary HMA Deterioration Moisture
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Secondary HMA Deterioration Moisture
Infiltration
Breakdown of
Existing Cracks
Deteriorated CracksCracks+
Moisture
Infiltration
Composite Pavement Deterioration
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Composite Pavement Deterioration
Horizontal
Movement
(environmental)+Vertical
Movement
(load)
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Reflection Cracking
Composite Pavement Deterioration
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p
Cracking
+
Moisture
Infiltration
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Delamination
Typical Rigid Pavement Distresses
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yp g
• Blow-ups
• Transverse cracking
• Longitudinal cracking
• Corner breaks
• Materials-related distress
•
Transverse joint faulting• Joint spalling
Joint seal damage
Loss of fines(pumping)
Polishing (loss offriction)
Map cracking andscaling
Roughness
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PCC Pavement Deterioration - Load
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Loads
Slab Fatigue
Transverse Cracking
PCC Pavement Deterioration - Traffic
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Traffic
Surface Wear
Friction Loss
Polishing
PCC Pavement Deterioration - Environment/Material
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Material
Joint
Problems
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Joint Seal Damage
Environmental/Materials
PCC Pavement Deterioration - Construction
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Joint and
SurfaceProblems
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ScalingPoorConstruction
Quality
PCC Pavement Deterioration - Construction
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Joint and
SurfaceProblems
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Map Cracking
PoorConstruction
Quality
PCC Pavement Deterioration - Construction
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Joint andSurface
Problems
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Longitudinal Cracking
PoorConstruction
Quality
PCC Pavement Deterioration - MoistureInfiltration
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Infiltration
Breakdown of
Existing Cracks
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Deteriorated Cracks
Cracks/Joints+
Moisture
Infiltration
PCC Pavement Deterioration - MoistureInfiltration
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Infiltration
Cracks/Joints+
Moisture
Infiltration
Subgrade
Softening
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Loss of Fines (Pumping)
PCC Pavement Deterioration - MoistureInfiltration
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Infiltration
Cracks/Joints+
Moisture
Infiltration
Subgrade
Softening
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Corner Breaks
PCC Pavement Deterioration - MoistureInfiltration
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Infiltration
Cracks/Joints+
Moisture
Infiltration
Subgrade
Softening
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Transverse Joint Faulting
PCC Pavement Deterioration - Incompressibles
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Cracks/Joints+
Incompressible
Material
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Blow-Ups
PCC Pavement Deterioration - Incompressibles
http://training.ce.washington.edu/PGI/Modules/09_pavement_evaluation/Images/rigid_distress/sr195_blowup2.JPGhttp://training.ce.washington.edu/PGI/Modules/09_pavement_evaluation/Images/rigid_distress/sr195_blowup2.JPG
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Cracks/Joints+
Incompressible
Material
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Joint Spalling
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Mystic Connecticut