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TYPES OF JOINTS- SEMINAR PRESENTATION.pptx
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TYPES OF JOINTS- SEMINAR
PRESENTATION
-Jessica Goveas, 4SO17CV017
4th Year, Dept. of Civil Engineering, SJEC
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What are joints?
Joints are formed in concrete slabs as part of the process of constructing rigid
paving for roads. Joints are discontinuities in the pavement slab that are
necessary to allow for expansion, contraction and warping.
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EXPANSION JOINT
An expansion joint or movement joint is an assembly designed to hold parts
together while safely absorbing temperature-induced expansion and contraction of
building materials, and vibration, or to allow movement due to ground settlement or
seismic activity. They are commonly found between sections of buildings, bridges,
sidewalks, railway tracks, piping systems, ships, and other structures.
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Why are expansion joints used?
• If the natural temperature of the concrete is low i.e. concrete is laid down in the season of winter,
then the chances are there that concrete will undergo expansion in the summer season.
• Similarly, if the concrete is laid in the summer season then natural temperature of the concrete is
already high, so the concrete will contract in the season of the winter.
• Whether the concrete is going to expand or shrink, one has to provide the expansion or the
contraction joints respectively.
• Spacing of the expansion joints: The spacing of the expansion joint can be determined as
below:
(expansion) e = co-efficient of thermal expansion * Ls * (t2-t1)
we provide width of the joints double then ‘e’, 50% allowance is provided for the filler material.
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CONTRACTION JOINT
A contraction joint is a sawed transverse joint normally placed every 18 ft. to
control cracking due to pavement contraction caused by shrinkage and
temperature fluctuations. The plans for the particular contract are required to be
checked to verify the proper joint placement. The minimum/maximum joint spacing
is reviewed with the Area Engineer or District Construction Engineer so that joints
may be established in the initial pours that will complement adjacent pavements.
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Why are contraction joints used?
• A contraction joint is a sawed, formed, or tooled groove in a concrete slab that creates a
weakened vertical plane.
• It regulates the location of the cracking caused by dimensional changes in the slab.
• Unregulated cracks can grow and result in an unacceptably rough surface as well as water
infiltration into the base, sub-base and subgrade, which can enable other types of pavement
distress.
• Contraction joints are the most common type of joint in concrete pavements, thus the
generic term “joint” generally refers to a contraction joint.
• They are generally between 1/4 – 1/3 the depth of the slab and typically spaced every 3.1 –
15 m (12 – 50 ft.) with thinner slabs having shorter spacing
• Transverse contraction joints can be cut at right angles to the direction of traffic flow or at an
angle (called a “skewed joint”, see Figure 3).
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WARPING JOINT
A joint with the sole function of permitting warping of pavement slabs when
moisture and temperature differentials occur between the top and bottom of the
slabs.
Warping joints are provided along the longitudinal direction to prevent warping of
the concrete slab due to temperature and subgrade moisture variation.
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Why are warping joints used?
• During the mid-day, the top of the pavement slab has a higher temperature than
the bottom. This causes the top fibers of the slab to expand more than the
bottom fibers and the slab curls at the edge. This phenomenon is known as
warping down of the slab.
• Similarly, the slab warps up during midnight due to the higher temperature of the
bottom slab as compared to the top. Warping joints are provided to minimize the
stresses induced due to warping. These joints are also known as hinged joints.
Longitudinal joints with tie bars fall in this class of joints.
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CONSTRUCTION JOINT
Construction joints are provided whenever the construction work stops
temporarily. They can be either along the transverse or longitudinal direction.
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Why are construction joints used?
• A construction joint is a type of concrete joint that is used when a new section of
concrete is poured adjacent to another concrete section that has already set.
• The purpose of a construction joint is to allow for some horizontal movement,
while being rigid against rotational and vertical movement.
• Construction joints prevent the premature failure of the concrete structure.
• Construction joints can have several different geometries, including straight wall
butt joints and tongue and groove joints.
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LONGITUDIJNAL JOINT
A longitudinal joint consists of a tie bar placed at the mid-depth of a concrete
pavement and it is not intended for joint lateral movement.
Tie bars are commonly utilized at longitudinal joints or between an edge joint
and a curb or shoulder. Typically, tie bars are 12.5mm or 16mm in diameter and
between 0.6 and 1.0 m long.
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Why are construction joints used?
• Longitudinal joints are normally designed at a regular spacing e.g. 4.5m to
accommodate the effect of differential settlement of pavement foundation.
• When uneven settlement occurs, the tie bars in longitudinal joints perform as
hinges (Ministry of Transport (1955)) which allow for the settlement of concrete
carriageway.
• Moreover, it also serves to cater for the effect of warping of concrete due to
moisture and temperature gradients by permission of a small amount of angular
movement to occur so that stresses induced by restrained warping can be
avoided.
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What happens if these joints fail?
Improper method of sealing
or the absence of a sealant
can result in joint spalling.
It eventually leads to the
deterioration of joints and
leads to pavement failure.
FAULTING
If the joints are not laid properly
it will result in the settlement of
the pavement and the temp
and moisture changes will
cause curling of slab edges.
This will result in faulting.
This is also caused if the
joints are not laid properly.
Heavy repeated loads and
foundation support loss
across these joints may lead
to punch out and eventual
failure of the pavement.
JOINT SPALLING PUNCH OUT
LINEAR CRACKING
Is caused due to
repeated traffic loads and
due to thermal gradient.
D- CRACK
It is caused due to
freezing and thawing
action.
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Joints are the weakest areas in PCC pavement.
There is a discontinuity in the concrete at saw-cut
joints, and wheel load is not 100% transferred
from one slab to the next, which results in higher
wheel load stress. When incompressible
materials get into the joints, expansion of
concrete slabs during high seasonal/daytime
temperatures will squeeze the incompressible
materials, and high localized stresses will develop
in the concrete. Localized high concrete stresses
can cause spalling in the joints. Also, if a good
joint seal is not maintained, water can get into the
joint and cause rust problems in dowel bars
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In CPCD, any cracking, breaking, or spalling of slab
edges, on either side of a transverse joint, need to be
repaired. The repair can be full-depth repair (FDR) or half-
depth repair (HDR), depending on the extent of the
breaking or spalling. If the distress extends through the
depth of the slab or hinders the ability of dowel bars to
transfer load, FDR is required.
In CRCP, failures in transverse construction joints require
joint repairs. Additional longitudinal steel is used at the
transverse construction joints to accommodate large
concrete stresses, which requires special attention for
concrete consolidation under the longitudinal steel. If
proper consolidation is not provided at the transverse
joints, delamination and distress can result as shown in
Figure. Any repair of the transverse construction joints
requires FDR.
During the joint repair in CPCD, dowels need to be
provided at transverse joints and tie bars at longitudinal
joints.
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RECENTLY ASKED QUESTIONS:
1. With sketches describe the various types of joints and their requirements in a
Rigid pavement.
2. Explain the types and objectives of joints in a cement concrete pavement.
3. List the types of joints and explain briefly.
