PAVEMENT Hardcore TEGARTurapan is Layered Structure Consisting of a Slab Surface Layer and the Base...
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rigid pavement is a layered structure consisting of a layer of reinforced concrete slab surface and the
base or sub-base built on the subgrade.
Lebuhraya Air Keruh
–Pagoh.
•Lebuhraya Kuala Lumpur
–Tanjung Malim.
•Lebuhraya Gurun
Bukit Kayu Hitam.
Mass concrete
Mass concrete brings with it many challenges, among them the generation of high heat and problems that
can stem from it. While creating these projects can be difficult, careful design of mass concrete can
minimize or eliminate issues, and new research points to approaches that will allow us to create bigger
projects than ever before.
Jointed Reinforced Concrete Pavement
Jointed reinforced concrete pavement (JRCP, see Figure 1) uses contraction joints and reinforcing
steel to control cracking. Transverse joint spacing is longer than that for JPCP and typically ranges
from about 7.6 m (25 ft.) to 15.2 m (50 ft.). Temperature and moisture stresses are expected to
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cause cracking between joints, hence reinforcing steel or a steel mesh is used to hold these cracks
tightly together. Dowel bars are typically used at transverse joints to assist in load transfer while the
reinforcing steel/wire mesh assists in load transfer across cracks.
Continuous reinforce concrete pavement
Continuously reinforced pavement is pavement in which the continuity of the longitudinal reinforcing steel
is interrupted only at structures or at the ends of the projects. There are no transverse joints other than
construction joints and expansion joints at structures. The whole idea of continuously reinforced
pavement is based essentially on the "so let is crack" philosophy rather than the fussy concept of avoiding
cracks at any price. The important difference, however, is that a continuously reinforced pavement is
designed to keep the cracks tightly closed so that the slab will retain its structural integrity. In an
unreinforced slab cracks which occur will normally widen and get progressively worse under the effects of
traffic and climatic conditions. Fortunately, the amount of reinforcement needed to control the cracking is
relatively low if the length of the slab is short. But as the length of the slab increases the amount of steel
needed also increases. This is the main reason why the length of conventional slabs has always stayed
within 40 to 100 feet. It has simply proved more economical from a first cost standpoint. However, the
steel is not directly proportional to the slab length as is usually assumed in the design of conventional
jointed reinforced pavement. As a matter of fact, the relationship is a parabolic function with the steel
increasing at a progressively decreasing rate as the slab length increases and reaching a maximum at
slab length of 600 to 800 feet. It has also been found that as the amount of steel in the slab is increased,
the number of cracks also increases. Theoretically, this is highly desirable because it means that stresses
due to any cause will be distributed more evenly among the cracks and no single crack will then show a
tendency to open excessively. An excessive number of cracks has no real influence on the structural
efficiency of the slab. The design, therefore, should include only the optimum amount of steel that will (1)
cause sufficient cracks to occur and (2) ensure that they will remain tightly closed under service.
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6_body.htm
Prestressed Pavement
The PCP concept incorporates prestressing in both the transverse and longitudinal direction in
the form of pretensioning and/or post-tensioning. As discussed in the previous chapter,
prestressing provides numerous benefits for long-term pavement performance. Prestressing
induces a compressive stress in the slab, helping to reduce or even eliminating the occurrence of
cracking, while also reducing the required slab thickness.
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In general, the precast panels are pretensioned along the long axis of the panel (transverse
pavement direction) during fabrication, and post-tensioned together along the short axis
(longitudinal pavement direction) after installation, as will be described below. Transverse
pretensioning not only provides the necessary permanent prestress in the pavement slab, but also
permits longer and thinner precast panels to be used as it helps counteract lifting and handling
stresses. Likewise, the longitudinal post-tensioning not only provides the necessary permanent
prestress, but also provides load transfer between the panels.
The post-tensioning system used for the longitudinal tendons is a bonded post-tensioning system.
After the longitudinal post-tensioning tendons are tensioned, grout is pumped into the ducts to
bond the strands to the precast panels. A bonded post-tensioning system provides continuity
between the prestressing strand and concrete, reducing the amount of non-prestressed steel
required in the panels. This continuity also permits individual panels to be sawcut and removed
from the pavement, if necessary, without compromising the integrity of the entire longitudinal
post-tensioning system. Grouting also provides an additional layer of corrosion protection for the
post-tensioning tendons, which is critical in colder climates where deicing salts are used
http://www.fhwa.dot.gov/pavement/concrete/pubs/hif08009/hif08009.pdf
FIXED FORM PAVING
In fixed form paving, side forms are used to hold fresh PCC in place at the proper grade and
alignment until it sets and hardens. These forms may also serve as tracks for various
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pieces of placing and finishing equipment. Fixed form paving is most appropriate for small
jobs (see Figure 7.110), complicated geometry pavements or variable width pavements,
however it can be used for large jobs as well (see Figure 7.111). Particular advantages of
fixed form paving are (ACPA, 1995):
Tight tolerances and side clearances. Existing curbs or other features can beused as forms.
Custom geometry . Forms can be placed in just about any pavement geometry,
which allows for multiple changes in pavement width, smooth curves, blockouts
and other abnormalities.
Better construction staging. Forms can be placed such that staged construction
can be used to maintain traffic flow or intersection use (see Figure 7.112).
Less expensive equipment and mobilization. Forms and equipment are less
expensive than slipform paving equipment. If paving operations are small
enough, this cost savings can more than offset the higher production rates of
slipform paving.
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Figure 7.110 (top left):
Small Fixed Form Job
Figure 7.111 (top right):
Large Fixed Form Job
Figure 7.112 (right):
Construction Staging Using Fixed Form Paving
This section presents PCC forms, placement, consolidation, finishing and curing as they are
typically done in fixed form paving. Often more than one of these steps can be performed
by the same piece of equipment, such as a vibrating screed, which serves to strike off andconsolidate the fresh PCC, or a traveling carriage paver which can perform all three steps.
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SLIPFORM PAVING
Slipform paving is defined as a process used to consolidate, form into geometric shape and
surface finish a PCC mass by pulling the forms continuously through and surrounding the
plastic concrete mass.
Slipform paving is most appropriate for larger jobs that require high production rates.
Particular advantages of slipform paving are (ACPA, 1995):
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Uses low-slump PCC . Low-slump PCC (on the order of 0 - 75 mm (0 - 3 inches))
is necessary so that the fresh PCC is able to hold its shape once the slipform
paver has passed. Low slump PCC can be made with less water and usually has
higher compression and flexural strengths than comparable high slump mixes.
High productivity . Large jobs generally require high production rates in order to
be profitable. Slipform paving production rates are typically in the range of 65 -
100 m3 /hr (85 - 131 yd3 /hr) for mainline paving. That translates into between 70
- 90 m/hr (230 - 300 ft./hr) of 3.66 m (12 ft.) wide, 250 mm (10 inch) thick PCC
surface course.
Smooth riding surface. Automation and computer control allow slipform pavers
to produce very smooth riding surfaces (IRI on the order of 0.90 m/km or less).
This section presents PCC placement, consolidation, finishing and curing as it is typically
done in slipform paving. Most often, these steps are accomplished by three pieces of
equipment: theplacer/spreader (used for rough placement), the concrete paver (used for
final placement, consolidation and initial finishing), and the texturing and curing machine.
These machines usually travel together in series down the length of the project.
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.
Longitudinal Joints
The first signs of distress in a hot mix asphalt pavement occur at the weakest point in the
pavement, usually the longitudinal joint. Construction of durable longitudinal joints is critical to a
pavement‟s service life.
The optional methods for constructing longitudinal joints are butt joints and tapered wedge joints.
When using either method, the standard specification states that placement of the surface course
should be carefully planned to ensure that the longitudinal joints in the surface course will
correspond with the edges of the proposed traffic lanes. Refer to Standard Specifications §402-
3.09B for details of construction of butt and tapered joints.
The designer must include a special note in the project proposal that indicates if the longitudinal
pavement joint can be left exposed to traffic overnight. This requirement will help the Contractor
bid the contract accordingly. (Note: Refer to §619-3.01G3 for the case when the longitudinal joint
is the lane/shoulder joint. The Contractor shall provide traffic protection in accordance with the
provisions of Table 619-1 for drop-offs within three meters of the travel lanes, except bridge dropoffs or
other drop-offs in excess of 1.8 m deep). If the designer anticipates the longitudinal
pavement joint in excess of 30 meters can be left exposed to traffic overnight they should include
maintenance and protection of traffic requirements to alert drivers of the uneven edge. As a
minimum, W8-39, „UNEVEN LANES‟ signs should be posted on both sides of the roadway at a
maximum 300 meter spacing. Consideration should be given to include R4-10, „STAY IN LANE‟
signs. The Regional Traffic and Safety Unit should be consulted. An exposed longitudinal
pavement joint should not be allowed if it is expected that traffic will frequently change lanes. Under
no circumstances can traffic be allowed to travel over a longitudinal pavement joint constructed as
a butt joint. Minimizing damage to the shape of the joint (urban vs. rural projects) and the safety
of the motoring public must be considered in the decision to allow an exposed longitudinal
pavement joint. The following are examples of special notes for the designer to use:
• “During paving operations on this contract a longitudinal pavement joint length in excess of
30 meters at the end of the working day is prohibited.”
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• “Prior to paving operations on this contract, the contractor may request approval, in writing,
to leave exposed a longitudinal pavement joint in excess of 30 meters at the end of the work
day. Approval is contingent upon the use of Option B - Tapered Wedge Joint of Section 402-
3.09 Joints, of the Standard Specifications. Maintenance and protection of traffic
requirements to provide adequate, advanced warning to motorists must be provided as
detailed in these contract documents. As a minimum W8-39, „UNEVEN LANES‟ signs must
https://www.dot.ny.gov/divisions/engineering/design/dqab/cpdm/repository/chapter8.pdf
Cross Section of a Rigid Pavement
Figure shows a typical cross-section of
a rigid pavement
The pavement can be placed directly on
prepared subgrade or on a singular
layer of granular or stabilized material
The only layer of material under concrete
and above subgrade is called base
course or subbase
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