Pavement could happen in any pavement design in

      Pavement Design CoursePavement Project     Name: Muhannad HaddadinID: 1410256Subject: Flexible
Pavement Distresses Table of ContentsLiterature review
3introduction
3Objective
3Types of distresses
14Cost Estimation………………………15Recommendation
19References
20         IntroductionDistress is something that is
important to consider in any pavement design as each expected failure should be
separately developed and to be taken care of for every distress that could
occur, mainly distresses happen due to deficiencies in more than an aspect that
could happen during construction, could be in materials used in construction
and also could be in the maintenance phase after the construction has been
done. An engineer should have a good knowledge about all types of distresses
that could happen in any pavement design in order to deny it from happening or
at least to know how to handle it if it occurs in his/her project. Objective We must know all types of distresses
that could occur in any pavement design process, their causes (reasons of
happening), how to prevent them from happening, and how to deal with them if
any of them happens during construction period or afterwards which is the
maintenance period. Literature
Review1The first literature review will
visually inspect & evaluate the failures of flexible pavements for
maintenance planning. It is quite important to identify and examine the causes that
led to the pavement to fail to select an option for treatment. From previous experiences, and what
is obtained through literature reviews, systematic guidelines for evaluation of
damaged pavement are there to provide information that are useful for maintenance
work. The study consisted of two tasks: 1)     
Visual
inspection of the existing pavement failures.2)     
 Investigating the actual causes of these
failures. As of this study, Obeid Khatim road
in Khartoum was the selected road for investigation. A field work was done on
the existing pavement condition of this road. It was found that most of the
damaged pavement sections suffered from severe cracking & rutting failures.
These failures might have been caused by fatigue failure on pavement structure
due to the movement of heavily loaded truck-trailers. The damage could also be
attributed to the inadequate design, poor water drainage and improper pavement
materials used.The experimental work program
consists of two tasks; field work and laboratory testing. Three trail pitholes
of two meter depth were excavated in the road, a pithole in each section.
Disturbed soil samples were collected from 1 to 2m depth to represent the
subgrade soil. The tests performed include sieve analysis, Atterberg limits, and
compaction and California Bearing Ratio (CBR) tests. The tests results are
given in Table 4.

From Table 4 it is cleared that the
subgrade soils in sections C and B compared to A have high values of liquid
limit and plasticity index and low CBR values. These soils of sections B and C
can be classified as expansive clay. While the subgrade soil in section A has
low liquid limit and plasticity index and relatively high CBR and classified as
nonexpansive soil. Thus the subgrade soils in sections B and C is considered as
weak subgrade. The Dynamic Cone Penetration (DCP) tests were carried out on the
pavement structure at three locations. The penetration depth measured up to 75
cm below the base course level. The data from DCP tests were proceeded to
determine the penetration resistance (mm/blow), which is simply the distance
that the cone penetrates with each drop of the hammer. The field CBR value was
determined using Transportation Research Laboratory (TRL) correlation as follows:Log (CBR) =
2.48 – 1.057 Log (DCP)

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The DCP test is used to evaluate the
strength of granular pavement materials; base and subbase. The results of DCP
tests are given in Table 5. For the road, the average CBR values of the base,
subbase and embankment materials are 67%, 37% and 18% respectively. The results
illustrated that the base materials is not comply with the specifications (i.e.
CBR ? 80%). While the subbase and embankment materials comply with the
specifications.This study has been undertaken to
investigate the pavement failures and propose a method for inspection and
evaluation of failed pavement. The results and the conclusions drawn as
follows: 1)     
 The method developed in this research has been
based on previous experiences. The focus is on establishing a systematic, and
yet simple and easy to understand guidelines that is flexible enough for use in
a variety of situations. 2)     
The
pavement failure investigation method developed in this research can serve as a
useful guide for the inspection and evaluation of pavement failures. The
method, combined with the experience of the highway engineer and adequate
materials investigation, will help to ensure that the cause of a pavement
failure can be reliably determined. 3)     
The
method developed for inspection and evaluation was trialed in pavement failures
of Obeid Khatim road, to evaluate the effectiveness of the method for real use.
It was found that the method was good as a general guide, particularly for
junior highway engineers. However, the experience of the engineer is also an
important factor in correctly diagnosing the pavement failures cause and
determining the best maintenance option.2This
paper summarizes the development of a method for predicting pavement
performance in terms of present serviceability index and four primary distress
types (area and severity) and application of the method to the design of
flexible pavements. The method is based upon an s-shaped performance curve.
These parameters have been found for 164 pavement test sections throughout the
State of Texas. The pavement test sections were categorized in three main
types: asphaltic concrete pavements on unbound base course, asphaltic concrete
pavements on bituminous base course, and asphaltic concrete overlays. The pavement
structure including the elastic modulus of each layer, the environment, and the
traffic data for these pavements were used to develop regression models for the
curve fit parameters. A sensitivity analysis was made of these models to
determine the effects of climate in four highway districts in Texas and the
results proved to be satisfactory performance curves. The regression models
along with the proposed performance equations and the stochastic form of these
equations have been incorporated into the Texas Flexible Pavement Systems (FPS)
design computer program. The modified version of FPS provides a listiny of the
optimal pavement designs selected on the basis of least total cost including
material and user costs, overlay costs, and salvage values. This version of FPS
lists all of the costs, the performance periods, the thickness of overlays that
were placed, and the ultimate pavement failure mode for ·each period. Typical
results of these analyses are given.The form of the performance equation
as developed from the AASHO Road Test is as follows:

Where:G = damage function ranging from 0
to 1N = the applied load (the
accumulated 18-kip equivalent single axle loads or total elapsed time)

 = a curve fit parameter which represents the
applied load when g reaches a value of 1

= a curve fit
parameter which defines the degree of curvature or the rate at which damage
increases.The primary concern in the use of
Equation arises from the following imposed boundary conditions:1)     
The
functional (structural) performance curve must have a maximum (minimum) value,
at the traffic level or time equal to zero, and must be strictly decreasing
(increasing) as the traffic level or time increases. 2)     
The
performance curve cannot predict negative values of serviceability index nor
can it predict a distressed area greater than 100 percent of the total area for
large values of traffic level or time. 3)     
The
performance curve should asymptotically approach the limiting values, as it is
physically unrealistic to predict complete pavement failure, i.e. PSI=0 or
distressed area=100 percent, at a specific traffic level or point in time.Studies are continuing to develop
new rules for selecting a desirable level of reliability but in the meantime,
even this result is encouraging for it indicates that the new FPS program,
revised as described in this paper, is more realistic than the former version,
more sensitive to the factors which cause pavement deterioration, and thus more
useful in the design of flexible pavements. 3Existing data is required when maintenance
of a pavement is needed; and also detail data of the current distresses is
required. Therefore, pavement has to be visually inspected prior to each
maintenance program to determine the type, severity and extent of each
distress. This process has a high cost and takes a lot of time. The main objective
of this paper is to develop distress prediction model for flexible pavements.
The model parameters that are in this paper cover the common types of pavement
distresses appear on Riyadh’s main and secondary streets. Pavement distress
density is used as the dependent variable for the developed model.

Pavement distress behavior is
expected to be affected by several parameters. Considering types of collected
data, distress behavior can be expressed as a function of: ? 1)     
Distress
type, (the common distresses in main and secondary streets); ?2)     
 Distress Severity, (three levels: low, medium,
high) ?3)     
 Percentage of distress density ? 4)     
Urban
Distress Index (UDI) ? 5)     
Time,
in years ? 6)     
Highway
class (two classes: main and secondary) ? 7)     
Traffic
Level, (either low or high)The
hypothesis is that distress severity, traffic level and time are directly
proportional to the distress density. The pavement condition (UDI) is expected
to decrees with increase in distress density. Based on the literature review
and engineering judgment, the following assumptions can give a general idea
about the expected shape and behavior of the distress density prediction model:
?1)       In general, distress density
starts its propagation process very slowly, but this propagation accelerates
more at a later stage. This can be represented in distress density model by the
power, exponential function, or polynomial function. ? 2)      Distress density propagation, on a new or recently overlaid
pavement section having poor UDI, will deteriorate faster than pavement section
having excellent UDI. ? 3)      Distress density behavior on pavement sections that are subjected
to high traffic will be damaged more than pavement sections that have low
traffic. ? 4)      Distress severity levels have an effect on behavior and propagation
of distress density. For example, high severity level will propagate faster
than low severity level.To
improve the fit and the ability to predicate the distress density, non-linear
transformation function was tried. The transformed function used has the
following form:

 In
this paper, model for predicting individual distress density on flexible
pavement was developed. The developed model was based on data collected from
the Pavement Maintenance Management System of Riyadh city. The models
constructed for the most common types of distress on main and secondary streets.
The model works in predicting the distress density over a period of time associated
with each level of severity, the condition of the pavement, and both traffic
level and highway class. A total of 61 and 28 cases were developed for main and
secondary streets, respectively. All the cases developed by the model were
found to be statistically significant in the prediction of the distress
density. Reserved data points where to validate the model used. The validation
process indicated that the model could adequately predict the distress density
with reasonable accuracy. Therefore, the developed model can be used to update
distress data prior to each maintenance program. This will minimize the need
for comprehensive visual inspection which proven to be costly and very time
consuming. 

         4Pavement condition survey normally
includes surface distresses, such as cracking, rutting, and other surface
defects. Broadly, pavement roughness is also included as a condition survey
item in some literature. This paper reviews past research efforts in this area
conducted at several institutions, including the automated survey system of
pavement surface cracking at the University of Arkansas. The paper also
proposes a new direction of technology development through the use of stereovision
technology for the comprehensive survey of pavement condition in its broad
definition. The goal is to develop a working system that is able to establish
three-dimensional (3D) surface model of pavements for the entire pavement
lane-width at 1 to 2-millimeter resolution so that comprehensive condition
information can be extracted from the 3D model.  With rapid advances in digital
camera and computing power of microcomputers, we believe that the time is right
to integrate such a system with commonly available devices and develop
efficient and accurate algorithms in software sub-systems to achieve the
following goals: 1)       High-resolution. The 3D
surface model will provide 1 to 2-millimeter resolution in all three coordinate
axis directions, X, Y, and Z. 2)      Comprehensive survey. The information obtained from the 3D surface
model includes cracking, roughness, rutting, potholes, and other surface
defects associated with both flexible and rigid pavements. 3)      Real-time at highway speed for both image acquisition and processing.
Based on the new real-time technology developed at the University of Arkansas
for pavement cracking with 2D images, the realization of this goal will provide
all condition results while images are being acquired at real-time.As a
part of a larger research effort to develop a digital highway data vehicle
started in the mid 1990s, the researchers at the University of Arkansas focused
on the development of a real-time automated system for distress survey. After
examining the feasibilities of using neural net and fuzzy sets, traditional
imaging algorithms and customized approaches have been developed to achieve the
goal of real-time processing at highway speed. Figure 2 shows the digital
highway vehicle at the university. Its basic features are: 1)      The vehicle is based on a full-digital design. 2)      The vehicle includes two sub-systems for pavement surface image
collection and automated distress analyzer to identify and classify pavement
cracks at real-time.3)       The vehicle collects
right-of-way video or still frame images and save them in digital format in
real-time. 4)      The vehicle acquires the location through the use of a GPS device
and a distance measuring instrument (DMI). 5)      Real-time relational database engine, inter-computer communication
techniques, and multi-computer and multi-CPU based parallel computing. 

A four-camera system to cover 5,000 kilometers of lane-mile at full
lane-width would require two computers and one-terabyte storage. It is expected
that 500 GB single drives will be available in less than two years. At the cost
of a high-end laser profiler vehicle, the new system, including four cameras,
two high-end microcomputers, and all necessary peripherals and circuits, will
be able to collect the vast majority of pavement condition and serviceability
data, produce comprehensive survey results, including roughness, cracking,
rutting, and other surface deficiencies, at the spatial resolution of 1 to
2-millimeter.

   Types of
distressesBleeding: bleeding is one of many types of distresses that take place on the
pavement surface that will cause it to appear shiny and will have some black
spot areas.

Causes: bleeding will occur when the asphalt binder fills the voids of the
aggregates that takes place during summer time that will make it expand onto the
pavement surface; the problem occurs when summer time is over and winter time
arrives as this effect is not reversible and thus will accumulate on the
surface of the pavement over a period of time. High amounts of asphalt binder
in the pavement while having low air void content causes it to happen. Leads to: bleeding leads to a reduction in the friction characteristics of
the pavement surface leading to lowering the skid resistance that increases the
crash rate of vehicles. Repair/maintenance: maintenance depends on the severity of bleeding as if it was
minor, coarse sand is enough when applied to the pavement surface that will
absorb the excess asphalt binder, but if the pavement was severely bleeding,
the surface of the pavement may need to be replaced with a new surface layer
with a better binder mixture for bleeding to not occur again anytime soon.   Cost Estimation

Work Description

Material Used

Cost 1m2 (JD)

Damaged  Pavement Removal

Loader

0.5

Removal of loose material (cleanining)

Labor s+ Compressor

0.4

Addition of MC

MC Material + Labor

0.32

Addition of Asphalt binder (HMA) + Compaction

Labor + Material + Machines

4

TOTAL

 

5.22

Note: Prices are estimated for a
thickness of 5cm.The price depends based on the area
required to repair (the larger the area the less the cost per 1m2)

   Patching: A patch has a clear visible area on the pavement surface that is
due to a replacement of surface that had a distress.

Causes: patches are meant to be a short term solution as a temporary
replacement for an area that had been damaged due to distresses. Leads to: patches that are well placed will minimize the quantity of water
that will enter the first layer; on the other hand a badly placed patch will
cause water to enter the surface layer that will lead into differential
settlement and weakness in the surface strength that will cause cracks. Repair/maintenance: well, a patch is by itself a repair method but it will look
defected even if it was well placed, but it must be to prevent water from
entering into the pavement.

Potholes/Debonding: potholes are voids found on the pavement surface that has a shape
of a bowl. Debonding happens when there is a separation between the surface
layer and its underlying asphalt layer.

Causes: potholes start to show in small areas due to inadequate bonding
between layers, segregation of binder and aggregates during placement, but will
expand with time with every repetition of vehicle load on it. Leads to: potholes causes’ water to enter the pavement that will cause
subgrade failure and could even lead to vehicle damage if a person passes over
a pothole at a high speed. Repair/maintenance: usually a patch is applied to eliminate the differential elevation
of the pothole, but it is preferable (best treatment) to make a rectangular cut
around the pothole and to remove the rectangular layer then for the cut to be
filled with new asphalt and to be compacted well in order to prevent water
intrusion.

Longitudinal
Cracking: it is usually
observed at the center of the road and its direction is known to be parallel to
the direction of flow of vehicles.

Causes: longitudinal cracking cause is related to poor joint construction,
besides other reasons that could be fatigue, especially when the cracks are
seen near the edge of the road.Leads to: the cracks will allow water to enter through the pavement that
will lead to a decrease in the pavement strength through damaging the
underlying support material. This distress is the beginning form of the other
distresses.Repair/maintenance: as this distress leads into other distresses, the longitudinal
cracking should be avoided in the first place, but if happened, early crack
sealing must be applied as soon as observed to minimize the spread of
deterioration.  Recommendation:Most of the failures due to
distresses in flexible pavement happen from materials used in construction that
are the binder mixture, aggregates and water ratio. It is recommended for each
mixture to be tested in a lab In order to meet the requirements and specifications
of the mixture and the ratio intended to be used in our pavement construction.                    References:1 Magdi M.E. Zumrawi – University
of Khartoum, Department of Civil Engineering, Khartoum, Sudan – Survey and
Evaluation of flexible Pavement Failures.2 M. Riggins, R. L. Lytton, and A.
Garcia-Diaz Texas Transportation Institute Texas A&M University System
College Station, Texas – Washington, D.C., January 1985 – Developing stochastic
flexible pavement distress and serviceability equations.3 Flexible pavement distress
prediction model for the city of Riadh, Saudi Arabia, A. Al-Mansour – (Received
December 2003 and accepted May 2004) – Emirates Journal for Engineering
Research, Vol. 9, No.1, 20044 Wang, Gong, submitted to 2002 Pavement Evaluation Conference,
21-25, 2002, Roanoke, Virginia – Automated Pavement Distress Survey: A Review
and A New Direction

http://sites.udel.edu/dct/files/2013/12/Tech-Topic-Streets-Pavement-Distresses-p5rptr.pdf

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