The document discusses the necessity and types of highway maintenance, highlighting the various causes of pavement failures such as material quality defects, construction issues, and environmental factors. It categorizes maintenance works into routine, periodic, and special repairs, and details specific types of failures in flexible and rigid pavements, including their causes and characteristics. Methods of pavement evaluation are also covered, emphasizing the importance of assessing structural integrity and surface conditions to maintain highway performance.

1. UNIT - V
HIGHWAY MAINTENANCE

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Need For Highway Maintenance
• The road maintenance is one of the main components of road system.
• The maintenance operation involves the assessment of road condition.
• Even if the highways are well designed & construction they may require effective
maintenance.
General causes of failure of pavement:
Some of the general causes of pavement failure leading maintenance measures,
I. Defects (Imperfections) in quality of material used
II. Defects in quality of construction & quality control during the constructions.
III. Inadequate surface & subsurface drainage in the locality.
IV. The settlement of the foundation of the embankment of the filled materials itself.
V. The environmental factors., such as intensity of rainfall, temperature variations,
soil erosion, high water table, snow, snowfall, frost action.,etc

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Classification of Maintenance works
In maintenance works it is generally classified as given below:
• Routine maintenance – patch repairs, maintenance of shoulders, to
maintain cross slope, the road side
drains.,etc
• Periodic maintenance – It include all renewals of surface pavement
& wearing course.
• Special repairs - Re-construction of pavement, overlay of
construction, widening of roads, repairs
damages caused by the flood, signals.,etc

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Failures in flexible Pavement Components
• The uneven settlement of any one component layer of the flexible pavement
structure could enough to cause pavement failure.
• This demands that each of the layers should be carefully designed & laid.
• The figure illustrate below the concept of pavement failure, ultimately there
is surface deformation when failure takes place either in subgrade or base
course.
Failure in subgrade:
One of the prime cause of flexible pavement failure is excessive
deformation in subgrade soil.
The failure of subgrade may be attributed due to two basic reasons:
1. Inadequate stability
2. Excessive stress application

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Failure in Flexible
pavement

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Cont.,
Failure in Sub-base or Base Course:
The following are the chief types of sub-base or base course failures:
1. Inadequate stability or strength
2. Loss of binding action
3. Loss of base course materials
4. Inadequate wearing course
5. Use of inferior (Lower) materials and crushing of base course materials
6. Lack of lateral confinement for the granular base course.

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Following are some of the typical flexible pavement failures:
1. Alligator (or) cracking
2. Consolidation of pavement layers
3. Shear failure
4. Longitudinal cracking
5. Frost heaving
6. Lack of binding to the lower course
7. Reflection cracking
8. Formation of waves and corrugation.
Characteristics (TYPICAL) of flexible Pavement Failures

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Alligator (or) cracking:
o This is the most common type of failure and occurs due to relative
(related) movement of pavement layer materials.
• This may be caused by the repeated application of heavy wheel
loads (In a particular point), resulting in fatigue failure (or due to
moisture variations resulting in swelling & shrinkage of subgrade).
Consolidation of pavement layer:
• Formation of ruts are mainly attributed to the consolidation of one
or more layers of pavement.
• Shallow ruts on the surface course can also be due to wearing along
the wheel path. Mostly it may estimated by depending upon the,
deformation has been caused in the subgrade or in subsequent
layers.
Cont.,

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Shear Failure & Cracking:
Shear failures are associated with the inherent (natural) weakness
of the pavement mixtures.
The shearing resistance being low due to inadequate stability or
excessively heavy loading.
The failure causes upheaval of pavement materials by forming a
fracture or cracking.
Cont.,

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Longitudinal Cracking:
• Due to frost action and differential volume changes in subgrade
longitudinal cracking is caused in pavement traversing (crossing)
through the full pavement thickness.
• Settlement (Compaction) Fill
• Sliding of side slopes
Frost Heaving:
In shear failure, the upheaval of portion of pavement is
followed with a depression. Then it is mostly caused by ground water
and climatic conditions.
Cont.,

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Lack of Binding with Lower Layer:
Slipping (or Sliding) occurs when the surface course is not
bound with the underlying (primary) base. This is also results in
forming of patches or pot holes.
Another one case, when the prime/tack coat b/w two layers is
lacking.
Cont.,

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Reflection Cracking:
• It is mostly caused by bituminous overlays provided over existing
cement concrete pavements.
• The structural action of the total pavement section is not much
influenced (Partial) by the presence of reflection cracks.
• To allow surface water to seep through and cause damage to the soil
subgrade or result in ‘mud pumping’.
FAILURES IN CEMENT CONCRETE PAVEMENTS
Failure of cement concrete pavement are recognized mainly by the
formation of structural cracking.
The failures are mainly due to two factors.
1. Deficiency (Lack or Shortage) of pavement materials
2. Structural inadequacy of the pavement system.
Cont.,

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1. Deficiency of pavement materials
Following are the chief causes would give rise to the different defects or
failure of cement concrete pavements:
I. Soft aggregates
II. Poor workmanship in joint construction
III. Poor joint filler
IV. Poor surface finish
V. Improper and insufficient curing
The various defects (Faults or imperfections) that creep in due to the above
are:
i. Disintegration (Breakdown) of cement concrete
ii. Formation of cracking
iii. Spalling (lack of alignment) of joints
iv. Poor riding surface
v. Slippery (greasy or oily) surface
vi. Formation of shrinkage cracks
vii. Ingress (Entrance) of surface water and further progressive failures.
Cont.,

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2. Structural inadequacy of the pavement system.
Inadequate subgrade support pavement thickness would be a
major cause of developing structural cracking in pavements.
Following are the causes and types of failure which develop:
i. Inadequate pavement thickness
ii. Inadequate subgrade support and poor subgrade soil
iii. Incorrect spacing of joints
Above would give rise to the failures of the following types:
1. Cracking of slab corners
2. Cracking of pavements longitudinally
3. Settlement of slabs
4. Widening of joints
5. Mud pumping (The Soil Slurry ejects in to the pavement Joints)
Cont.,

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Following are some typical and basic types of failures in rigid
pavements, which are dealt (distributed) here in details:
1. Scaling of cement concrete
2. Shrinkage cracks
3. Spalling of joints
4. Warping cracks
5. Mud pumping
6. Structural cracks
7. Scaling of cement concrete
The scaling (climbing) is mainly attributed due to the deficiency
in the mix or presence of some chemical impurities, which damage mix.
Excessive vibration given to mix – cement mortar comes to top.
So, it will create abraded (roughened) surface.
Characteristics (TYPICAL) of rigid Pavement Failures

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2. Shrinkage cracks:
The shrinkage cracks normally develop, i.e., immediately
after the construction of cement concrete pavement.
The placement of cracks are in longitudinal as well as in
transverse direction.
3. Spalling of joints:
The concreting is completed without noticing this faulty
alignment of the filler material (concrete filling or joints construction or
finishing works or reinforcement settings).
Thus this forms an overhang of a concrete layer on the top side
and the joint later on shows excessive cracking and subsidence.
4. Warping (Distorting or bending) cracks:
If the joints are not well designed to accommodate the warping
of slabs at edges, this results in development of excessive stresses due to
warping and the slab develops cracking at the edges in an irregular
pattern.
Cont.,

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5. Mud Pumping:
When the soil slurry ejects out through the joints and cracks of
cement concrete pavement caused during the downward movement of
slab under the heavy wheel loads.
Following factors are which cause the mud pumping:
i. Extent (Degree or Amount) of slab deflection
ii. Type of subgrade soil
iii. Amount of free water
Cont.,

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Pavement Evaluation
To examine the efficiency & effectiveness of the basic components of the pavement such
as,
– subgrade,
– base course,
– surface course,
– pavement thickness,
– loading & Environment.
The methods of pavement evaluation are,
 Structural evaluation of pavement
 Evaluation of pavement surface condition
(To evaluate the surface conditions of flexible pavement by the unevenness, ruts, patches, and
cracks)
(To evaluate the surface conditions of Rigid pavement may be assessed by the cracks
developed & Faulty joints affecting the Riding the Quality) – Profilograph, indicator,
profilometer or roughometer.
1. Structural evaluation of pavement
The structural evaluation of both flexible and rigid pavement may be carried out by ‘Plate
bearing test’.
The structural capacity of the pavement may be assessed by the load carried at a specified
deflection of the plate or by the amount of deflection at a specified load on the plate.

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• Field investigation and tests carried out in various countries have
shown that the performance of flexible pavement is closely related to
be elastic deflection under loads or its rebound deflection.
• In above all case, and based on that various equipment used.
• “Benkelman Beam” is most commonly used, as the measurements
are simple and easy.
Cont.,

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“Benkelman Beam” Method
Introduction:
This method was originally devised by ‘A. C. Benkelman’
in U.S.A .
Benkelman beam measurement are preceded by a rating
survey of the road.
So, as to the road was divide into homogenous section of
approximately similar serviceability.
Cont.,

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Cont.,

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• Components:
 Slender beam – 3.66 m
 Pivoted datum frame – 2.44 m from the probe end
Cont.,