Pavement Design of constructional aspect.pdf

Construction engineering

1. CONSTRUCTIONAL ASPECTS OF
PAVEMENTS

2. Pavement
◻Pavement is one type of hard surface made from durable surface material
laid down on an area that is intended to carry vehicular or foot traffic.
◻Its main function is to distribute the applied vehicle loads to the sub-grade
through different layers.
◻The road Pavement should provide sufficient skid resistance, proper riding
quality, favorable light reflecting characteristics, and low noise pollution.
◻Its goal is to reduce the vehicle transmitted load so that it will not exceed
the bearing capacity of the sub-grade.
◻The Road Pavements are playing a crucial role in the development of any
construction. There are mainly two types of road pavement used namely
flexible and rigid pavements road.

3. Ideal Road Pavement Requirement
◻it should have required thickness to distribute the wheel load stresses to a safe
value on the sub-grade soil.
◻It should be structurally strong to resist all types of stresses imposed upon it.
◻To prevent the skidding of vehicles, it should have a sufficient coefficient of
friction.
◻It should have a smooth level surface that offers comfort to road users even at high
speed.
◻Ensure less noise when the vehicle moving on it.
◻It should be dustproof so that there is no danger of traffic safety.
◻It must provide an impervious surface, so that sub-grade soil is well protected,
and
◻It should offer low maintenance with long life.

4. Types of Pavement
◻The following are two major pavement types used in road construction,
Flexible pavement
Rigid Pavement.
◻Flexible pavements, vehicular stress is transferred to subgrade through grain to grain
contact of the aggregate through the granular structure. These types of roads have less
flexural strength, act like a flexible sheet (e.g. bituminous road).
◻In the case of rigid pavement, vehicle loads are transferred to sub-grade soil by flexural
strength of the pavement and the pavement acts as a rigid plate (e.g. cement concrete
roads).
◻A combined pavement is also used which is known as semi-rigid pavement. In this, a rigid
pavement is provided with a thin layer of flexible pavement over it and is an ideal
pavement with the most desirable characteristics. However, these types of combinations of
pavements are rarely used in new construction because of the high cost and complex
analysis required.

5. Flexible Pavements
◻In Flexible Pavement, wheel loads are transferred to subgrade by grain-to-grain
transfer through the points of contact in the granular structure.
◻The wheel load stresses acting on the pavement are distributed to a larger area and
the stress decreases with the depth.
◻Considering this load distribution characteristic of flexible pavements, it has many
layers.
◻Hence, a flexible pavement design system uses the concept of a layered system.
◻By considering this the flexible pavement should have better quality to
sustain maximum compressive stress, in addition, to wear and tear.
◻Below layers are accepted to experience the magnitude of stress
and low-quality material can be used.

6. Scheme of a flexible pavement

7. Constructional Aspects
◻In the construction of flexible roads mainly bituminous materials are used.
◻Defects in the flexible road can be seen on the surface if there is
a settlement of the lower layer.
◻The design of flexible pavement is done by considering the overall
performance of the road, and the stresses produced should be kept well
below the allowable stresses of each road layer.
◻The following are major types of flexible pavement,
Conventional layered flexible pavement,
Full-depth asphalt pavement, and
Contained rock asphalt mat (CRAM).

8. Conventional Flexible Pavements
◻Conventional flexible pavement uses the layered system. In which
high–quality materials are placed at the top of the pavement layer to
resist maximum stress and low-quality cheap materials are placed in
lower layers.

9. Full-depth Asphalt Pavements
◻It is constructed by placing bituminous layers directly on the soil
sub-grade. These types of pavement are most suitable when there is
high traffic and local materials are not available.

10. Contained Rock Asphalt Mats
◻It is constructed by placing dense/open–graded aggregate layers in
between two asphalt layers. Properly designed asphalt concrete is
placed above the sub-grade. This asphalt concrete will reduce the
vertical compressive strain on soil sub–grade and protect from surface
water.

11. Road Construction Layers (Road Pavement Layers)
◻Following are pavement layers in road construction,
Compacted subgrade (150 – 300mm).
Sub-base Course (100 – 300 mm)
Base Course (100 – 300 mm)
Prime Coat
Binder Coat (50 -100 mm)
Tack Coat
Surface Course (25 – 50 mm)
Seal Coat.

12. Flexible Pavement Road Construction Layers

13. Compacted Sub-grade (150 – 300 mm)
The compacted subgrade is a base of all pavement layers. All the above
pavement layers transfer the stress to this layer. So, it is essential to ensure
that soil sub–grade is not overstressed. Therefore, it should be properly
compacted to the desired density, near the optimum moisture content.

14. Sub-base Course (100 – 300 mm)
◻It is a layer of material below the base course.
◻Its major role to provide structural support, improve drainage, and reduce
the intrusion of fines from the sub-grade in the pavement structure.
◻In the case of the base, the course is open graded then the sub-base course
with more fine material can be utilized as filler between sub–grade and the
base course.
◻A sub–base is not strictly needed or used.
◻For example, road pavement made on high quality, hard sub-grade may not
need the additional features offered by a sub-base course. In such situations,
the sub-base course can be avoided.

15. Base Course (100 – 300 mm)
◻It is a layer of materials just below the surface of the binder course and it provides
additional load distribution and contributes to the sub-surface drainage.
◻The different materials are used for base courses such as crushed stone, crushed slag,
and other untreated or stabilized materials.

16. Prime Coat
◻A prime coat is applied by spreading low viscous cutback bitumen to
an absorbent surface like granular bases on which the binder layer is
placed.
◻It is primly used to provide a bond between two layers.
◻A prime coat is able to penetrate into the below layers, plug the voids,
and form a watertight surface.

17. Binder Course (50 -100 mm)
◻The Binder coat has the bulk of the asphalt concrete structure. Its main function is to
distribute the load to the base course.
◻The binder course primly consists of aggregate mixed with low asphalt and doesn’t
require quality as high as the surface course.
◻Replacement of some part of the surface course by the binder course results in a
more economical design.

18. Tack Coat:
◻In tack coat, a little amount of asphalt is applied to the surface.
◻It is generally asphalt emulsion diluted with water.
◻Its main function is to provide proper bonding between two layers of
binder course and must be thin, uniformly cover the entire surface,
and set very fast.

19. Surface Course (25 – 50 mm)
◻It is the main layer that bears the direct traffic load and generally contains superior
quality materials. The surface course is generally constructed with graded asphalt
concrete (AC). The functions and requirements of this layer are:
This course offers major characteristics like friction, smoothness, drainage, etc. Also, it prevents
the entry of excess water into the underlying base, sub–base, and sub–grade,
It should be provided with a hard surface to resist the distortion under traffic and provide a smooth
and skid–resistant riding surface,

20. Seal Coat
◻The seal coat is a thin layer with water–proof the surface and provides
skid resistance.

21. Rigid Pavements
◻Rigid pavements are cable to transfer wheel load to a wider area as it
has good flexural strength.
◻In rigid pavement, there are not many layers of materials as in the
case of flexible pavement.
◻In rigid directly placed on a well–compacted subgrade or on a single
layer of granular or stabilized material.
◻As there is only a single layer between the concrete and the
sub–grade, this layer can be called a base or sub–base course.

22. ◻In rigid, the vehicular traffic
load is transferred through slab
action, and the road behaves
like an elastic plate resting on a
viscous medium. It is
constructed by using plain
cement concrete. Generally, its
design is analyzed by plate
theory instead of layer theory,
assuming an elastic plate
resting on a viscous
foundation.

23. ◻The plate theory assumes that the road pavement slab is a
medium–thick plate that is plane before loading and to remain plane
after loading. Pavement slab experiences bending due to wheel load
and temperature variation and the resulting tensile and flexural stress.
◻Rigid pavements can be classified into four types,
Jointed plain concrete pavement (JPCP),
Jointed reinforced concrete pavement (JRCP),
Continuous reinforced concrete pavement (CRCP), and
Pre-stressed concrete pavement (PCP).

24. Jointed Plain Concrete Pavement
◻This type of rigid pavement is
constructed using plain cement
concrete with closely spaced
contraction joints.
◻JPCP does not contain any steel
reinforcement.
◻In this dowel, steel bars are
generally used for load transfer
across joints.
◻It has joint spacing around 5 to
10m.

25. Jointed Reinforced Concrete Road
◻Jointed reinforced concrete pavements
(JRCP) contain steel mesh reinforcement
(sometimes called distributed steel).
◻In JRCP, designers intentionally increase the
joint spacing and include reinforcing steel to
hold together mid-panel cracks.
◻The spacing between transverse joints is
typically 30 ft (9 m) or more with some
agencies using a spacing as great as 100 ft
(30.5 m).
◻Today only a handful of agencies employ
this design due to performance issues caused
by the embedded steel being incapable of
holding together mid-panel cracking and the
resultant erosion/faulting of such cracks.

26. Continuous Reinforced Concrete Road
◻Continuously reinforced concrete
pavements (CRCP) is a type of concrete
pavement that does not require any
transverse contraction joints.
◻Transverse cracks are expected in the
slab, usually at intervals of 1.5 - 6 ft (0.5
- 1.8 m).
◻CRCP is designed with enough
embedded reinforcing steel
(approximately 0.6-0.7% by
cross-sectional area) so that cracks are
held together tightly.
◻It can demonstrate superior long-term
performance (typical design service lives
are 30-40 years) and cost-effectiveness.
Transverse Bar Assembly

27. Prestressed Concrete Pavements
◻Prestressed concrete pavements are designed and produced to be
prestressed to bear tensile forces caused by external loads by various live
objects such as vehicles on the roads or aircraft in the airports.
◻Prestressed concrete pavements well achieve the due performance in their
relatively thinner thickness design.
◻As compared to asphalt pavements, prestressed concrete pavements are
more resistant to airplanes' or vehicles' wheel trails and thus cause less wear
and tear to themselves. Maintenance costs reduction is therefore realized.
◻Prestressed concrete pavements are flexible and resilient, thus applicable to
bad ground conditions.

28. Prestressed Concrete Pavements
◻It is speedy construction and
has lower user impact cost.
◻PPCP is comparatively
sustainable.

29. OTHER INFRASTRUCTURE
PROJECTS

30. Types of Infrastructure Projects
◻Aviation Infrastructure
Aviation infrastructure projects develop and maintain airplanes and airports.
Constructing an airport – like any architectural undertaking – is a complex business,
involving a whole host of stakeholders, from designers and contractors to construction
managers and executives.
Increasingly, airport operators are turning to large-scale technology to make sure projects
run as efficiently as possible and – most important of all – are completed on time.
◻Communications Infrastructure
The communications infrastructure sector focuses on the connection between
government agencies, businesses, and the nation through wireless, cable, satellite and
other technologies.
Private and government sectors work together, ensuring that outages are fixed and
updates keep wireless networks streamlined.

31. Types of Infrastructure Projects
◻Power and Energy Infrastructure
The electrical infrastructure oversees projects that deal with power
including; electrical lines, power grids, and innovations in alternative
energy.
◻Railroad Infrastructure
The sector is responsible for innovating and safeguarding trains, subways,
and light rail systems. This includes track layout, steel supplies, bridges and
tunnels.

32. Types of Infrastructure Projects
◻Water Infrastructure
Water infrastructure works to create sustainable water projects to purify
water supplies from waste, and make it safe for drinking.
◻Hazardous Waste Management
Hazardous waste construction finds and disposes of hazardous materials to
protect the environment. Solid and hazardous waste bi-products, such as
sewage remnants and other industrial leftovers, are transported to
designated landfills hazardous waste facilities. Tanks, drip pads and
incinerators are used to treat, recycle or dispose of.