Selected Topics in Construction
STR-665: Selected
Topics in Construction
Lecture 4: Pavement Asset Management
Dr. Hesham Osman
Assistant Professor, CEM
Faculty of Engineering, Cairo University
Reference
Shahin, M (2002). Pavement Management for Roads
Airports & Parking Lots, 2nd Edition
Select portions from chapters 1,2,3,7 & 8
1 Hesham Osman © 2010
Selected Topics in Construction
Pavement Management
Process & Network
Definition
Why bother with pavement
management?
Interesting quotes:
“The only time I have is spent fighting fires”
“We always use a 2 inch overlay”
“Just spray the pavement black at the end of the year”
“I can’t afford to do inspections; I’d rather spend the
money to fix the pavement”
2 Hesham Osman © 2010
Selected Topics in Construction
Why is preventative maintenance
important?
Network vs. Project Level Pavement
Management
Project Level
Global overview of entire network needs
Consideration of available budget and organizational objectives
Tradeoff between competing needs and limited budgets
3 Hesham Osman © 2010
Selected Topics in Construction
Network vs. Project Level Pavement
Management
Project Level
In depth pavement evaluation and design for individual
pavement sections
Selection of specific M&R types to be performed
Little or no consideration given to the resource requirements of
other pavement sections
Pavement Management Process
Inventory Definition
Pavement Inspection
Condition Assessment
Condition Prediction
Work Planning
4 Hesham Osman © 2010
Selected Topics in Construction
How do we organize our pavement
inventory
A logical grouping of Airports Runways,
Network Identification pavement for M&R Taxiways and Roads
Management
A readily identifiable City streets
Branch Identification portion of the network Individual street names
with a distinct use
Sections of a branch
City streets
having consistent
Homogenous
Section Identification characteristics (e.g.
portions of a street
traffic, pavement
type, soil).
What factors should we consider when
selecting pavement sections?
Road functional classification
Pavement structure
Construction History
Traffic
Condition
Section Size
5 Hesham Osman © 2010
Selected Topics in Construction
Examples of pavement sections: Road
Network
Examples of pavement sections:
Airports
6 Hesham Osman © 2010
Selected Topics in Construction
Examples of pavement sections:
Commercial Parking Lot
Pavement Condition
Surveys
7 Hesham Osman © 2010
Selected Topics in Construction
Pavement Condition Index (PCI)
Widely accepted as a universal index that indicates structural
distress of a pavement section
Initially developed by U.S. Army
Corps of Engineers, now
formally published as ASTM
standard.
Several adaptations proposed
by road agencies
Pavement Condition Index
PCI is a function of three distress variables:
Distress Type: The type of default occurring in the pavement.
Different distresses impact overall condition to various extents.
Distress Severity: A distress can be present in different levels of
severity. Generally speaking, the more severe a distress the
lower the PCI value
Distress Quantity: Defines the extent of the defect distribution
throughout the pavement section. Generally speaking the
quantity the lower the PCI value
8 Hesham Osman © 2010
Selected Topics in Construction
How do we conduct a pavement rating
survey?
Manual Distress Data Collection: Rating is done in the
field. Typical tools include a hand odometer, straight
edges.
Automated Distress Data Collection: Data collection is
done via a vehicle, rating is performed in the office
Conducting the pavement survey:
Sample Units
In order to properly assess
a pavement section, it is
sometime appropriate to
divide the section into
sample units.
For roads, typical sample
units should be sized
250m2 ± 100m2
9 Hesham Osman © 2010
Selected Topics in Construction
Dealing with sample units
During a pavement condition survey do we have to
assess all sample units?
Recommended
Sample Size
Systemic Random
Sampling
Common Pavement Distress: Alligator
Cracking
Description
Series of interconnected cracks
caused by fatigue failure of the HMA
surface (or stabilized base) under
repeated traffic loading. Cracking
initiates at the bottom of the HMA layer
where the tensile stress is the highest
then propagates to the surface as one
or more longitudinal cracks. After
repeat traffic loading the cracks
interconnect.
Problems
Allow moisture infiltration
10 Hesham Osman © 2010
Selected Topics in Construction
Common Pavement Distress: Bleeding
Description
A film of asphalt binder on the
pavement surface. It usually creates a
shiny, glass-like reflecting surface
Possible Cause
Bleeding occurs when asphalt binder
fills the aggregate voids during hot
weather and then expands onto the
pavement surface. Since bleeding is
not reversible during cold weather,
asphalt binder will accumulate on the
pavement surface over time
Common Pavement Distress: Block
Cracking
Description
Interconnected cracks that divide the
pavement up into rectangular
pieces. Blocks range in size from
approximately 0.1 m2 to 9 m2
Possible Cause
HMA shrinkage and daily temperature
cycling. Typically caused by an
inability of asphalt binder to expand
and contract with temperature cycles
Problems
Moisture infiltration and roughness
11 Hesham Osman © 2010
Selected Topics in Construction
Common Pavement Distress:
Longitudinal Cracking
Description
Cracks parallel to the pavement's
centerline or laydown
direction. Usually a type of fatigue
cracking.
Possible Cause
Poor joint construction or
location. Joints are generally the least
dense areas of a pavement.
A reflective crack from an underlying
layer
HMA fatigue (indicates the onset of
future alligator cracking)
Common Pavement Distress: Rutting
Description
Surface depression in the wheelpath
Possible Cause
Permanent deformation in any of a
pavement's layers or subgrade
Problems
Ruts filled with water can cause
vehicle hydroplaning, can be
hazardous because ruts tend to pull a
vehicle towards the rut path
12 Hesham Osman © 2010
Selected Topics in Construction
Calculating PCI: Completion of Survey
Pavement Condition
Prediction Models
13 Hesham Osman © 2010
Selected Topics in Construction
S-Shaped Curves
ρ
PCI = 100 −
(ln(α ) − ln( AGE ))1/ β
S-Shaped Curves
Effect of α parameter
α determines the age
at which the PCI is
projected to reach 0
14 Hesham Osman © 2010
Selected Topics in Construction
S-Shaped Curves
Effect of β parameter
β determines the rate
of deterioration
(overall slope of the
curve)
Polynomial Constrained Least Squares
P ( x) = a0 + a1 x + a2 x 2 + a3 x 3 + ... + an x n
P(x): PCI or roughness
Regression is constrained by ensuring the slope of the
function is always negative
15 Hesham Osman © 2010
Selected Topics in Construction
Constrained versus Unconstrained
Regression
Maintenance &
Rehabilitation Methods
16 Hesham Osman © 2010
Selected Topics in Construction
Types of Maintenance & Rehabilitation
Localized M&R: Applying a repair method to a small
localized area of a pavement. Usually suitable when
deterioration is only localized. Typically has a minimal
impact on extending the service life of the pavement
Global M&R: Application of a repair method to a large
portion of the pavement section. More suitable when
deterioration is more widespread. Provides a small
extension in pavement service life.
Major M&R: Considered a full rehabilitation of the
existing asphalt or base course. Provides a large
extension in pavement service life. Typically the most
costly type of intervention.
Localized M&R - Crack Sealing
Process of cleaning and sealing of
cracks in AC pavement.
Used to fill longitudinal and
transverse cracks.
Primary purpose is to prevent
surface water infiltration into
pavement foundation.
Considered a preventative
maintenance technique as it does
not extend pavement service life.
17 Hesham Osman © 2010
Selected Topics in Construction
Localized M&R – Full depth patching
Replacing the full depth of the AC
layer and may include replacing
base and sub base layers.
Used to repair structural and material
related distresses such as alligator
cracking and rutting
Global M&R – Fog Seal
Spraying a light coat of bituminous
material (0.12-0.2 l/m2) to surface of
existing pavement using a distributor
Used to prolong life of pavement by
helping to reduce raveling and
improve water proofing.
Suitable for low-volume roads
Low cost M&R technique but not
suitable if structural damage has
occurred
18 Hesham Osman © 2010
Selected Topics in Construction
Major M&R – AC overlay
Involves adding one or more AC
layers to existing pavement
Used to correct or improve structural
capacity or functional requirements
such as skid resistance
Most effective when pavements are
not fully deteriorated
If properly placed and pavement
structure is in good condition will
usually result in substantial
extension to service life
Major M&R – Reconstruction
Removal and replacement of the
entire pavement structure (sub-
base, base and pavement
wearing surface).
Used as a last resort when
pavement is badly deteriorated.
Most costly and time consuming
rehabilitation technique
19 Hesham Osman © 2010
Selected Topics in Construction
Crack Seal
Fog Seal Asphalt
Overlay
Asphalt
Reconstruction
Pavement Capital
Planning
20 Hesham Osman © 2010
Selected Topics in Construction
The capital planning process aims to
answer the following questions
Short-term planning
What projects should I implement in the short term (1-
3 years) given a set budget?
Long-term planning
Given a specific budget for repair and rehabilitation
over the next 10 years, what will be the expected
condition of my network?
If I want to achieve specific performance levels over
the next 10 years how much should spend?
Priority levels for intervention
21 Hesham Osman © 2010
Selected Topics in Construction
Conducting what-if-analysis
The complexity of the decision-making
problem
22 Hesham Osman © 2010
