Transportation pavement complete presentation

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2. Pavement
• A highway pavement is a structure consisting of superimposed
layers of processed materials above the natural soil sub-grade
to distribute the applied vehicle loads to the sub-grade safely.
• The ultimate aim is to ensure that the transmitted stresses
due to wheel load are sufficiently reduced, so that they will
not exceed bearing capacity of the sub-grade.
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3. Pavement Requirements
An ideal pavement should meet the following requirements:
• Sufficient thickness to distribute the wheel load stresses to a
safe value on the sub-grade soil,
• Structurally strong to withstand all types of stresses imposed
upon it,
• Adequate coefficient of friction to prevent skidding of
vehicles,
• Smooth surface to provide comfort to road users even at high
speed,
• Dust proof surface so that traffic safety is not impaired by
reducing visibility,
• Impervious surface, so that sub-grade soil is well protected
• Long design life with low maintenance cost.
• Low noise pollution
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4. Types of Pavement
There are two types of pavements on the basis
of structure.
• Flexible pavements
• Rigid pavements
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5. Flexible Pavements
Flexible Pavements are constructed from bituminous material
and the stress is transmitted to the Natural soil sub-grade
through the lateral distribution of the applied vehicle load with
depth via different intermediate soil layers (Aggregate Sub-base
Course & Aggregate Base Course).
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Natural Soil (Subgrade)
Aggregate Sub-base Course
Aggregate Base Course
Asphalt Concrete

6. • Bituminous materials are dark brown or black, semi-solid
or liquid, thermoplastic mixtures of hydrocarbons derived
from natural or synthetic processes in which hydrocarbon
mixtures have lost their volatile components leaving a denser
residue. Natural bitumens come from exposed and weathered
petroleum and rock deposits.
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7. Wheel Load Distribution in Flexible Pavement
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The wheel load acting on the pavement will be distributed to a wider
area, and the stress decreases with the depth.
In flexible pavements, wheel loads are transferred by grain-to-grain
contact of the aggregate through the granular structure.

8. Typical Layers of a Flexible Pavement
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Typically flexible pavement consists of following layers;
Seal coat, surface course, tack coat, binder course, prime coat,
base course, sub-base course and sub-grade.
Typical x-section of flexible pavement

9. Typical Layers of a Flexible Pavement
Seal Coat:
Seal coat is a thin surface treatment used to water-proof the surface and
to provide skid resistance.
Tack Coat:
Tack coat is a very light application of asphalt, usually asphalt emulsion
diluted with water.
It provides proper bonding between two layers of binder & surface course
and must be thin, uniformly cover the entire surface, and set very fast.
Prime Coat:
Prime coat is an application of low viscous cutback bitumen
(Liquid Bitumen) to an absorbent surface like granular bases on which
binder layer is placed. It provides bonding between two layers.
Note:
1) Emulsified asphalt is a mixture of asphalt cement, water, and emulsifying
agent (a type of soap)
2) Liquid asphalts or cutback asphalts are asphalt cements mixed with a
solvent (Naptha, Kerosene or light oil) to reduce their viscosity to make
them easier to use at ordinary temperatures
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10. 1. Prime Coat :
This is a single coat of low viscosity bituminous binder. This coat
is applied to existing untreated pervious layer like WBM. The
main purpose is to improve the adhesion between base and
bituminous surface.
Functions :
• The most important function is to imporve the adhesion
between existing pervious base and wearing surface.
• To bind the dust and loose particles together to form hard and
tough surface.
• It provides temporary seal to prevent the surface water from
penetrating through the surface.
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Typical Layers of a Flexible Pavement

11. 2. Tack Coat :
This is single coat of low viscosity bituminous binder applied to
the existing treated impervious layer such as bitumen or cement-
concrete base. This boat is applied between treated base and
bituminous surface.
Function :
• It is provided to improve the adequate bond between existing
impervious base and wearing surface.
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12. 3. Seal Coat :
Seal coat is the final coat of bituminous material that is applied on
the top of surface to prevent the entry of moisture through the
voids.
Function :
• To provide water tight surface.
• It improves the visibility at night and develops skid resistant
texture.
• To improve the wearing resistance of an existing road surface.
Note:
1) Emulsified asphalt is a mixture of asphalt cement, water, and
emulsifying agent (a type of soap)
2) Liquid asphalts or cutback asphalts are asphalt cements mixed
with a solvent (Naptha, Kerosene or light oil) to reduce their
viscosity to make them easier to use at ordinary temperatures
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Seal Coat
Prime Coat
Tack Coat

14. Typical Layers of a Flexible Pavement
Surface course
Surface course is the layer directly in contact with traffic loads and
generally contains superior quality materials. They are usually
constructed with dense graded asphalt concrete (AC). The functions
and requirements of this layer are:
– It provides drainage & will prevent the entrance of excessive
quantities of surface water into the underlying road layers.
– It must be tough to resist the distortion under traffic and
provide a smooth and skid- resistant riding surface,
Binder course
It's chief purpose is to distribute load to the base course. The binder
course generally consists of aggregates having less asphalt and
doesn't require quality as high as the surface course, so replacing a
part of the surface course by the binder course results in more
economical design.
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15. Typical Layers of a Flexible Pavement
Base course
The base course is the layer of material immediately beneath the
surface of binder course and it provides additional load distribution
and contributes to the sub-surface drainage it may be composed of
crushed stone and other untreated or stabilized materials.
Sub-Base course
The sub-base course is the layer of material beneath the base
course and the primary functions are to provide structural support,
improve drainage, and reduce the intrusion of fines from the sub-
grade in the pavement structure.
Note: A sub-base course is not always needed or used. For example,
a pavement constructed over a high quality, stiff sub-grade may not
need the additional features offered by a sub-base course.
Sub-grade
The sub-grade is a layer of natural soil prepared to receive the
stresses from the layers above. It should be compacted to the
desirable density, near the optimum moisture content.
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16. Water bound Macadam Road
• The Short form of Water Bound Macadam Road is
WBM which is the most commonly used
road construction procedure for more than 100 years.
The Water Bound Macadam is named based on the Scottish
engineer John Loudoun Macadam who
first introduced and construct the WBM road.
• It is a type of flexible pavement in which the base and surface
layer contains crushed stone or broken rock pieces.
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• Water-bound macadam road is a road in which the wearing
course consists of clean crushed aggregates which are
mechanically interlocked by rolling. These aggregates are
bound together with filler material and water laid on a well-
compacted base course.

18. Materials Required For the Construction of
WBM Road
There are mainly three types of construction materials
are required for the construction of WBM roads:
• Coarse Aggregate
• Screening
• Binding Material
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19. • Coarse Aggregate
Coarse Aggregate consists of a mixture of hard and durable
crushed aggregate and broken stones. The aggregate used
for every layer of the Water Bound Macadam Road construction
should be well graded.
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20. The below tables shows the gradation of the aggregates that
can be adopted.
The coarse aggregates used in the construction of the WBM
road should possess the following properties:
• It should be strong, hard, and durable.
• It should not have an excessive amount of elongated and
flaky particles.
• It should be in acceptable shape and size as shown in the
gradation table
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21. • Screening
• A screening is a construction material used in WBM road
construction work to fill the void or space left
between aggregate particles after compaction is done.
• Generally, construction materials used
for screening purposes have smaller sizes compared to coarse
aggregate.
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The following table shows the standard grading required for screening for the
construction of WBM Road. To reduce the overall cost of WBM
roads, IRC has recommended using non-plastic materials such as kankar,
murram, or gravel instead of screening.

23. Construction Procedure
• Preparation of Foundation for WBM Road :
The subgrade or base course is properly prepared for the required grade
and camber of WBM road. The potholes and the depressions on the
surface of the road are properly filled up and compacted.
• Providing Lateral Confinement :
The lateral reinforcement or confinement is constructed before
the laying of different layers of Water Bound Macadam materials.
Before laying of aggregates the shoulders have a thickness similar
to the WBM road properly compacted layers. It should
be constructed with proper quality of murram or earth.
But if the soil is unstable and the road is at a higher
elevation or required to be filled, then the retaining wall can be
constructed as lateral confinement.
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24. The main purpose of
providing
lateral confinement is
that the road surface to
be constructed is
retained in between
them and it becomes
easy for the
lay of coarse
aggregates.
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25. • Spreading of Course Aggregates :
The course aggregates are uniformly spread on
the prepared base after the construction of the
shoulders. Total number of layers and thickness
of WBM road depends upon the details of
design pavement.
In general for ordinary roads, single layer of
compacted thickness 75 mm may be sufficient.
For special roads, 2 layers of 150 mm each
compacted thickness may be provided.
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Then, the road profile is checked by placing templates across the road every 6 m.
the surface is checked from time to time to ensure the
proper camber and grade of the road.

27. • Rolling Operation :
Rolling operation is carried out for compacting the
course aggregates. Generally it is done with the help of 3-
wheeled power rollers weighing 6-10 tonnes or with the help of
vibratory rollers.
Skilled operators should be used for driving the rollers as the
fault rolling operations causes formation of corrugations,
unequal finish of road surface, wearing of road in few months of
construction.
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28. • Application of Screenings :
After the rolling operation is properly finished screenings is
applied to properly fill the voids remained after the compaction
of aggregates. The screening may be applied in 3 or more layers
as per the site conditions.
After uniformly spreading of screening compaction is carried out
with the help of dry rollers for each layer of screenings. After
compaction brooming of the each layer should be properly done
to remove the uncompacted screening material.
The quantity of screening is generally used to fill about 50% of
the total voids and the remaining 50% of voids are filled
with filler materials.
The process of spreading, booming, and rolling is carried
out simultaneously for each layer till the surface of coarse
aggregate seems firm and well compacted without any voids.
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29. • Sprinkling of Water and Grouting :
After completion of wet rolling with screening materials, the
layer is water sprinkled and then again rolled so that the water
erodes the surface finer and seeps and deposits it to the inner
voids.
Preparation of Shoulders :
• At the time of Curing of road, shoulders are constructed
alongside by filling earth to specified cross slope. They are
properly compacted.
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30. 10 ) Open for Traffic :
• After proper drying and without any
depressions, the road is then made upon for
traffic. For few days the traffic should be well
distributed over full width of road by placing
obstacles longitudinally in the form of drums,
barricade etc.
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31. Rigid Pavement
• A rigid pavement is constructed from cement concrete or reinforced
concrete slabs.
• The design of rigid pavement is based on providing a structural
cement concrete slab of sufficient strength to resists the loads from
traffic.
• The rigid pavement has rigidity and high modulus of elasticity to
distribute the load over a relatively wide area of soil.
• The layers of material between the concrete and the sub-grade are
called as base or sub-base course.
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32. Rigid Pavement
• Rigid pavements are placed either directly on the prepared
subgrade or on a single layer of granular or stabilized
materials (called base course or sub-base).
• Use of base course in rigid pavements:
– Control of pumping (ejection of soil slurry of subgrade soil
through joints, cracks, and along the edges).
– Improvement of drainage (raise pavement from water
table).
– Control of shrinkage and swell (work as waterproof and as
surcharge load).
– Expedition of construction (working platform).
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33. Types of Rigid Pavements
1. Jointed Plain Concrete Pavements (JPCP).
2. Jointed Reinforced Concrete Pavements (JRCP).
3. Continuous Reinforced Concrete pavements
(CRCP).
4. Prestressed Concrete Pavements (PCP).
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34. 1. Jointed Plain Concrete Pavements (JPCP)
• Constructed with closely spaced contraction joints.
• Dowels or aggregates interlock may be used for load transfer
across the Transverse joints.
• Joint spacing ( 15 to 30 ft)
• Tie bars are used for longitudinal joints.
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35. 2. Jointed Reinforced Concrete Pavements (JRCP)
• Steel reinforcement in the form of wire mesh or deformed
bars are installed.
• Allow the use of longer joint spacing.
• Joint spacing (30- 100 ft).
• Dowels are required for load transfer across the joints.
• The amount of distributed steel increases with the increase in
joint spacing and is designed to hold the slab together after
cracking.
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36. 3. Continuous Reinforced Concrete pavements (CRCP).
• It has no joints.
• Eliminating joints reduced thickness of pavement by 1 to 2”.
• Most frequent distress is punch-out at the pavement edge.
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38. 4. Prestressed Concrete Pavements (PCP).
• The pre application of a compressive stress to the concrete
greatly reduces the tensile stresses caused by traffic and thus
decrease the thickness of concrete required.
• Has less probability of cracking and fewer transverse joints
and therefore results in less maintenance and longer
pavement life.
• Used more frequently for airport pavements than for highway
pavements because the saving of thickness for airport
pavements is much greater than for highways.
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41. Composite Pavements
• Composed of both HMA & PCC.
• Using PCC bottom layer & HMA top layer results in an
ideal pavement with most desirable characteristics.
• PCC provide strong base
• HMA provides a smooth non-reflective surface.
• Very expensive and rarely used.
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Comparison of Flexible & Rigid Pavement

43. THANKS
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