"Pavement failures and their Maintenance" Technical Seminar report

C T Akshay Kumar – 1BI15CV041 Seminar Report
Department of Civil Engineering, Bangalore Institute of Technology Page 1
Chapter 1
Introduction
1.1 Pavement
A pavement is the durable surface material laid down on an area intended to sustain vehicular
traffic, such as a road or walkway. A pavement is designed to support the wheel loads
imposed on it from traffic moving over it.
It should be strong enough to resist the stresses imposed on it and should have sufficient
thickness to distribute the stresses on the subgrade safely. Pavements should have the
following desirable characteristics –
1. It should be structurally strong and have sufficient thickness to withstand the stresses
imposed on it and distribute the loads safely to the subgrade. The pavement should have
long life and its maintenance cost is low.
2. Its surface should be hard to resist the abrasive action of wheels. It should provide safe
riding quality to the road users. It should develop low frictional resistance to reduce the
energy consumption. The surface of the pavement should have adequate roughness to
prevent he skidding of vehicles
3. The surface should be impervious so that water does not percolate into the lower layers
and subgrade and cause deterioration.
1.2 Pavement structure
The structural design of the pavement is done by considering the various factors like traffic,
soil type, drainage, climatic and environmental factors and the desirable design life.
The pavement structure consists of layers of selected superior pavement materials laid over a
prepared soil subgrade. Each layer is laid evenly and compacted over a well-compacted
subgrade to serve as a highway pavement. The compacted soil subgrade and the pavement
layers form the pavement structure.
Pavement structure consists of the following layers
1. Soil subgrade – is a layer of natural soil prepared to receive the loads from the the layers
of pavement materials.
2. Sub-base course – is constructed over the subgrade. It is made up of soils which are of
superior than subgrade soil (gravel, moorum, etc). Its function is to act as drainage layer
and support the base coarse to distribute the loads.

C T Akshay Kumar – 1BI15CV041
Department of Civil Engineering, Bangalore Institute of
3. Base course – is constructed over sub
It is the structural member of the pavement and helps in distributing the wheel
4. Surface course – is the topmost layer. It is made up of superior quality aggregates and
binder to resist abrasive action of traffic, prevent percolation of water into the pavement
and provide skid resistant, smooth and uniform driving surface.
1.3 Types of pavement
1. Flexible pavements – are those which have a low or negligible flexural strength and
flexible in their structural action of loads.
pavements.
2. Rigid pavements – are those which possess high flexural strength. They are also called as
Cement Concrete pavements.
Fig 1.2 Cross section of Flexible and Rigid Pavement
1BI15CV041 Seminar Report
Department of Civil Engineering, Bangalore Institute of Technology
is constructed over sub-base and is made up of crushed stones with binder.
It is the structural member of the pavement and helps in distributing the wheel
is the topmost layer. It is made up of superior quality aggregates and
and provide skid resistant, smooth and uniform driving surface.
Fig 1.1 – Pavement structure
are those which have a low or negligible flexural strength and
flexible in their structural action of loads. They are also called as Bituminous Concrete
are those which possess high flexural strength. They are also called as
Cement Concrete pavements.
Fig 1.2 Cross section of Flexible and Rigid Pavement
Seminar Report
Page 2
base and is made up of crushed stones with binder.
It is the structural member of the pavement and helps in distributing the wheel loads.
is the topmost layer. It is made up of superior quality aggregates and
are those which have a low or negligible flexural strength and
They are also called as Bituminous Concrete
are those which possess high flexural strength. They are also called as

Table 1.1 – Differences between Flexible and Rigid pavement
Sl.No. Flexible Pavement Rigid Pavement
1. A flexible pavement consists of a thin
wearing course built over a base course
and sub-base course resting upon o
compacted subgrade.
A rigid pavement consists of a cement
concrete slab (Pavement quality concrete
over Dry Lean Concrete) built over sub-
base course and subgrade.
2. It has negligible or low flexural
strength.
It has high flexural strength compared to
flexible pavement.
3. The load distribution is by grain to
grain contact.
The load distribution is by beam action.
4. Its stability depends upon aggregate
interlock, friction and cohesion.
Its stability is provided by pavement slab
by beam action.
5. Its design depends upon the strength of
subgrade.
Its design depends upon the flexural
strength of concrete.
6. Design life is 10 – 15 years. Design life is 30 – 40 years.
7. Initial cost of construction is less but
maintenance is regular and costly.
Initial cost of construction is high but
maintenance cost is less.
8. It is suited for staged construction. It
can be opened to traffic immediately
after construction.
It is not suited for staged construction. It
requires 28 days of curing before opening
to the traffic.
1.4 Types of pavement failures
1. Cracking
2. Potholes
3. Rutting
4. Shoving
5. Raveling
6. Bleeding

Chapter 2
Cracking
Cracking occurring in flexible pavements can be classified into three types, i.e. surface
cracks, fatigue cracks and others. Surfacing cracks are associated with the aging and
deterioration of the surface bituminous layer due to shrinking and hardening of the
bituminous binder with a loss of volatiles. These cracks are in general not load- related.
Fatigue cracks (commonly called alligator or crocodile cracks) are a series of interconnected
cracks in a chicken-wire pattern. The cracks are caused by traffic loading, occur only in
wheel-paths and are often associated with deformation. Early signs of fatigue cracks are fine
parallel longitudinal cracks in the wheel-path. Other types of cracks in flexible pavements are
longitudinal, edge, transverse, reflection and stabilization cracks.
2.1 Types of Cracking
1. Alligator cracking
2. Block cracking
3. Longitudinal cracking
4. Transverse cracking
5. Reflection cracking
2.2 Alligator cracking
Alligator cracks are also called as map cracking or crocodile cracking. This is a fatigue
failure caused in the asphalt concrete. A series of interconnected cracks are observed due to
such distress. Repeated loading and stress concentration will help the individual cracks to get
connected. This looks like a chicken wire or similar to the alligator skin. This cracking is load
associated structural failure. This cracking is observed in areas that have repeated traffic
loading. Alligator cracking is one of the major structural distress. This distress is later
accompanied by rutting. The failure can be due to weakness in the surface, base or sub grade;
a surface or base that is too thin; poor drainage or the combination of all three.

Fig 2.1 Alligator cracking
2.3 Block cracking
It is caused mainly due to the shrinkage of the asphalt pavement due to inability of the binder
to expand and contract with temperature changes. It is also called as thermal cracking. It is
not load associated, but loads can increase the severity of cracks. Block cracking has cracks
in well-defined rectangular shapes. Block cracks divide the asphalt surface into
approximately rectangular pieces. The blocks range in size from approximately 0.1 to 10m².
The occurrence of block cracking usually indicates that the asphalt has hardened
significantly. Block cracking normally occurs over a large portion of pavement area, but
sometimes will occur only in non-traffic areas.
Fig 2.2 Block cracking

2.3 Longitudinal and Transverse cracking
These are cracks are parallel to the pavement centerline. They are caused by shrinkage of
asphalt surface due to low temperature. These can be a result of pavement fatigue, reflective
cracking, or poor joint construction.
Fig 2.3 Longitudinal cracking Fig 2.4 Transverse cracking
2.4 Reflection cracking
It is caused by differential movement across the underlying crack or joint. These cracks are
found in flexible pavement overlay over a rigid pavement (i.e., asphalt over concrete). They
occur directly over the underlying rigid pavement joints.
Fig 2.5 Reflection cracking

2.6 Remedial measures for Cracking
1. A thin (150 to 300 mm) strip of geo-textile can be applied on the crack.
2. Cracking can be sealed by application of a membrane of Polymer modified bitumen
(PMB).
3. Less sever surface cracking can be addressed with the application of a rejuvenator to the
surface.
4. Extensive and severe surface cracking can be rectified by removal and replacement of the
defective portion of the layer. A tack coat and a new layer of bituminous concrete is
applied and well compacted.
Fig 2.6 Repairing cracks

Potholes are small, bowl-shaped depressions developed on the surface of the flexible
pavement. They generally have sharp edges and vertical sides near the top of the hole.
penetrate all the way through the asphalt layer down to the base course. Pothol
result of moisture infiltration, stagnation of water and usually the end result of untreated
alligator cracking. As alligator cracking becomes severe, the interconnected cracks create
small chunks of pavement, which can be dislodged as vehicles
remaining hole after the pavement chunk is dislodged is called a pothole.
fatigue is the main reason behind the formation of potholes. The occurrence of fatigue
cracking will interlock to form alligator cracking. These chu
the pavement will become loose and will be picked out under continuous loading and
stresses. This will leave a pothole on the pavement.
Fig 3.1 Formation of Pothole
In cold temperatures, the water trapped in the pothole
action that leads to additional stresses and crack propagation.
distress grows resulting in the continuous removal of pavement chunks. Water entrapped will
increase this rate of expansion of distress. The pothole can expand to several feet in width.
They don’t develop too much in depth. The vehicle tires
Chapter 3
Potholes
shaped depressions developed on the surface of the flexible
They generally have sharp edges and vertical sides near the top of the hole.
penetrate all the way through the asphalt layer down to the base course. Pothol
small chunks of pavement, which can be dislodged as vehicles drive over them. The
remaining hole after the pavement chunk is dislodged is called a pothole. The pavement
cracking will interlock to form alligator cracking. These chunks between the cracks formed in
stresses. This will leave a pothole on the pavement.
Fig 3.1 Formation of Pothole
In cold temperatures, the water trapped in the pothole will carry out the freezing and thawing
action that leads to additional stresses and crack propagation. Once the pothole is formed, the
ion of distress. The pothole can expand to several feet in width.
They don’t develop too much in depth. The vehicle tires get damaged due to large potholes.
Seminar Report
Page 8
shaped depressions developed on the surface of the flexible
They generally have sharp edges and vertical sides near the top of the hole. They
penetrate all the way through the asphalt layer down to the base course. Potholes are the
drive over them. The
The pavement
nks between the cracks formed in
will carry out the freezing and thawing
Once the pothole is formed, the
ion of distress. The pothole can expand to several feet in width.
damaged due to large potholes.

3.1 Causes
1. Severe and untreated alligator cracking leads to formation of potholes.
2. Water infiltration and water stagnation leads to potholes.
3. Water in the voids freezes in cold temperature and thawing action leads to formation of
cracks which finally leads to formation of potholes.
4. Segregation of bituminous mix during laying and lack of bond between surface sourse
and base course.
5. Insufficient bitumen content at some locations on the surface course.
Fig 3.1 Potholes

3.2 Remedial measures for Pot holes
1. Pot holes can be rectified by patching the entire depth of the pot hole. Bituminous
pavement adjoining the pothole also gets deteriorated and develops cracks.
2. The weak material around the pothole is removed before patch work. Rectangular area
adjoining the pot hole is cut to a maximum depth of pot hole.
3. Tack coat is sprayed over the area. Then the pot hole is filled with a mix of aggregates
and binder.
4. It is then compacted. A resurfacing course is also laid to provide smooth riding surface.
Fig 3.2 Filling a pothole

Chapter 4
Rutting
Rutting is the longitudinal deformation or depression of the pavement surface along the
wheel paths of heavy vehicles. Longitudinal ruts in asphalt pavements are channelized
depressions in the wheel-tracks. Longitudinal ruts are formed due to the repeated application
of heavy loads along the same wheel path resulting in permanent deformation of the
pavement layers and also subgrade. Shallow ruts are caused due to consolidation or
deformation of the surface coarse, insufficient pavement thickness, weak asphalt mixes, or
moisture infiltration.
Fig 4.1 Formation of Ruts
Rutting can occur on the surface as well as on the subgrade. If rutting is accompanied by
heaving along the pavement edges, it is a clear indication of weak pavement with respect to
present wheel loads and that shear failure has taken place in the pavement layers.
4.1 Causes
1. Rutting is caused due to inadequate stability of subgrade or sub-base or base course.
2. Inadequate compaction of subgrade or any of the pavement layers leads to rutting.
3. Channelized movement of heavy vehicles causes significant vertical strain on the
subgrade. This leads to formation of ruts.
4. Improper design of bituminous mix and inadequate thickness of flexible pavement leads
to rutting mechanism.

Fig 4.2 Rutting
4.2 Remedial measures for Rutting
1. The affected area is cleaned and tack coat is applied covering the rut.
2. Then the ruts are filled using dense graded or open graded pre–mix.
3. Finally a seal coat is applied and the surface. A thin bituminous resurfacing is provided to
achieve good riding quality.

Fig 4.3 Filling the ruts

Shoving is the formation of ripples or the longitudinal displacement of localized areas across
a pavement caused by shear forces induced by traffic loading. A form of plastic movement
that is seen in the form of the wave is called as shoving distress. Thes
perpendicular to the direction of the traffic. Shoving occurs at locations having severe
horizontal stresses, such as at intersections. It is caused by excess asphalt content, high
quantity of fine aggregate, presence of rounded aggregate, o
Fig 5.1 Formation of Shoving distress
5.1 Causes
1. An unstable (i.e. low stiffness) bituminous layer or high binder content
distress.
2. Shoving is caused by mix contamination, poor mix design and poor binder
manufacturing,
3. Excessive moisture in the subgrade or weak granular sub
4. Presence of rounded aggregates
Chapter 5
Shoving
that is seen in the form of the wave is called as shoving distress. These are observed
quantity of fine aggregate, presence of rounded aggregate, or a weak granular base.
Fig 5.1 Formation of Shoving distress
An unstable (i.e. low stiffness) bituminous layer or high binder content leads to shoving
aused by mix contamination, poor mix design and poor binder
Excessive moisture in the subgrade or weak granular sub-base.
Presence of rounded aggregates in the bituminous mix leads to shoving.
Seminar Report
Page 14
e are observed
r a weak granular base.
leads to shoving
aused by mix contamination, poor mix design and poor binder

Fig 5.2 Shoving
5.2 Remedial measures for Shoving
1. Shoving can be rectified by partial or full depth patch work.
2. The surface is first cleaned and then a tack coat is applied.
3. The affected area is then filled with aggregates and bituminous mix.
4. A seal coat is applied and a resurfacing course is applied.
Fig 5.3 Repairing Shoving Distress

Chapter 6
Raveling
Raveling (or aggregate loss) is the process where the aggregate particles are dislodged from
the pavement surface where the asphalt binder is removed. Raveling is caused by the abrasive
action of traffic, low binder content, and construction during wet weather, delayed rolling or
over heating of the bituminous mix.
Fig 6.1 Early stages of raveling – Loss of fine aggregate
In premixed bituminous surfacing, progressive disintegration of the surface may occur due to
bitumen binder failing to bind the aggregates. This results in the aggregates of the surface
getting gradually loosened from the surface due to moving traffic. Initially the fines are
removed from the matrix followed by coarse aggregates.
6.1 Causes
1. Raveling is caused due to construction during wet weather conditions leading to improper
coating of the aggregates by the bitumen binder or stripping of binder from the
aggregates.
2. Delayed rolling after the bituminous mix has cooled down resulting in porous surface due
to inadequate densification of the layer.
3. Insufficient binder content in the mix and improper gradation of the aggregates or
segregation of the mix during laying leads to raveling.

Fig 6.2 Raveling
6.2 Remedial measures for Raveling
1. If the raveling is in the initial stage, the surface is cleaned, the loose particles are removed
and a seal coat is applied.
2. For severe raveling conditions, first the surface is cleaned and a tack coat is applied. This
is followed by applying a resurfacing course of bituminous premix of required thickness.
Fig 6.3 Repairing raveling

Chapter 7
Bleeding
Bleeding is the condition where a film of bituminous binder is present on the surface which
creates a shiny, reflective surface which may be tacky in hot weather. It is caused by high
asphalt content, low air void content, using an asphalt cement with too low a viscosity (too
flow able), too heavy a prime or tack coat, or an improperly applied seal coat.
Bleeding reduces the skid resistance of the pavement with affects the safety of the road users.
The filling of asphalt binder into the aggregate voids during hot weather conditions and their
expansion in later situations will result in bleeding.
Bleeding occurs more often in hot weather when the asphalt cement is less viscous (more
flow able) and the traffic forces the asphalt to the surface. As the process of bleeding cannot
be reverted in cold temperatures, they remain on the top of the pavement as such.
The surface then develops low skid resistance and reduces the safety of vehicles moving over
them. The layer will have bubbles which are seen as blisters. The asphalt binder formed will
be sticky in nature.
7.1 Causes
1. Excessive asphalt binder in the mix or using binder with low viscosity leads to bleeding
of the pavement.
2. Excessive application of the binder during surface treatment (prime coat or tack coat)
causes bleeding.
3. Improper application of the seal coat cause bleeding of pavement.
4. Low air voids ratio or no adequate voids for the bitumen to penetrate causes bleeding.

Fig 7.1 Bleeding
7.2 Remedial measures for Bleeding
1. Minor bleeding can be corrected by applying coarse sand to blot up the excess asphalt
binder.
2. Major bleeding can be corrected by cutting off excess asphalt with a motor grader or
removing it with a heater planer. This is followed by a resurfacing.

References
1. S K Khanna, C E G Justo, A Veeraragavan “Highway Engineering” revised 10th
edition
2. Al-Mustansiryah University, Faculty of Engineering, Department of Highways and
Transportation Engineering, “Highway Maintenance Course” (2015-2016).
3. Zulufqar Bin Rashid, Dr. Rakesh Gupta “Study of defects in Flexible Pavement and its
Maintenance” Volume 15, Issue 2 (Ver. II) Mar. - Apr. 2018
4. Sharad.S.Adlinge, Prof.A.K.Gupta “Pavement Deterioration and its Causes”
5. Surajo Abubakar Wada “Bituminous Pavement Failures” Volume 6, Issue 2, (Part - 4)
February 2016

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