Concrete Pavement Joints
November 30, 1990
- Transverse Contraction Joints
- Longitudinal Joints
- Construction Joints
- Expansion Joints
- Joint Construction
- PURPOSE. To provide guidance and recommendations relating to the
design and construction of joints in jointed Portland cement concrete pavements.
- CANCELLATION. Technical Advisory T 5140. 18, Rigid Pavement Joints,
dated December 15, 1980, is canceled.
- The performance of concrete pavements depends to a large extent upon
the satisfactory performance of the joints. Most jointed concrete pavement
failures can be attributed to failures at the joint, as opposed to inadequate
structural capacity. Distresses that may result from joint failure include
faulting, pumping, spalling, corner breaks, blowups, and mid-panel cracking.
Characteristics that contribute to satisfactory joint performance, such
as adequate load transfer and proper concrete consolidation, have been
identified through research and field experience. The incorporation of
these characteristics into the design, construction, and maintenance of
concrete pavements should result in joints capable of performing satisfactorily
over the life of the pavement. Regardless of the joint sealant material
used, periodic resealing will be required to ensure satisfactory joint
performance throughout the life of the pavement. Satisfactory joint performance
also depends on appropriate pavement design standards, quality construction
materials, and good construction and maintenance procedures.
- The most common types of pavement joints, which are defined by their
function, are as follows:
- (1) Transverse Contraction Joint - 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, and is by far the most common type of joint in concrete pavements.
- (2) Longitudinal Joint - a joint between two slabs which allows slab
warping without appreciable separation or cracking of the slabs.
- (3) Construction Joint - a joint between slabs that results when
concrete is placed at different times. This type of joint can be further
broken down into transverse and longitudinal joints.
- (4) Expansion Joint - a joint placed at a specific location to allow
the pavement to expand without damaging adjacent structures or the
- TRANSVERSE CONTRACTION JOINTS. The primary purpose of transverse
contraction joints is to control the cracking that results from the tensile
and bending stresses in concrete slabs caused by the cement hydration process,
traffic loadings, and the environment. Because these joints are so numerous,
their performance significantly impacts pavement performance. A distressed
joint typically exhibits faulting and/or spalling. Poor joint performance
frequently leads to further distresses such as corner breaks, blowups, and
mid-panel cracks. Such cracks may themselves begin to function as joints and
develop similar distresses. The performance of transverse contraction joints
is related to three major factors:
- Joint Spacing. Joint spacing varies throughout the country because of considerations of initial costs, type of slab (reinforced or plain), type of load transfer, and local conditions. Design considerations should
include: the effect of longitudinal slab movement on sealant and load
transfer performance; the maximum slab length which will not develop transverse
cracks in a plain concrete pavement; the amount of cracking which can
be tolerated in a jointed reinforced concrete pavement; and the use of
random joint spacings.
- (1) The amount of longitudinal slab movement that a joint experiences
is primarily a function of joint spacing and temperature changes.
Expansion characteristics of the aggregates used in the concrete and
the friction between the bottom of the slab and the base also have
an effect on slab movement.
- (a) Joint movement can be estimated by the following equation:
expected change in slab length, in inches.
C = the base/slab frictional restraint factor (0. 65 for stabilized
bases, 0. 8 for granular bases).
L = the slab length, in inches.
= the PCC
coefficient of thermal expansion (see Table 1 for typical values).
maximum temperature range (generally the temperature of the concrete
at the time of placement minus the average daily minimum temperature
in January, in °F) .
shrinkage coefficient of concrete (see Table 2 for typical values).
This factor should be omitted on rehabilitation projects, as shrinkage
is no longer a factor.
Typical Values for PCC Coefficient of Thermal Expansion () 
|Type of Coarse Aggregate
||PCC Coeff. of Thermal Expansion (10-6/°F)
- (b) While the above equation can be used to estimate anticipated
joint movements, it may be worthwhile to physically measure joint
movements in existing pavements. These measurements could provide
the designer with more realistic design inputs.
Typical Values for PCC Coefficient of
Shrinkage () 
|Indirect Tensile Strength (psi)
||PCC Coeff. of Shrinkage (in. /in. )
|300 (or less)
|700 (or greater)
- (2) For plain concrete slabs, a maximum joint spacing of 15 feet
is recommended. Longer slabs frequently develop transverse cracks.
It is recognized that in certain areas, joint spacings greater than
15 feet have performed satisfactorily. The importance of taking local
experience into account when selecting joint spacing (and designing
pavements in general) cannot be overstated. Studies have shown that
pavement thickness, base stiffness, and climate also affect the maximum
anticipated joint spacing beyond which transverse cracking can be
expected. Research indicates that there is a general relationship
between the ratio of slab length (L) to the radius of relative stiffness
() and the amount of transverse cracking
. This research shows that there is an increase in transverse cracking
when the ratio L/
exceeds 5. 0. Further discussion is provided in Attachment 1.
- (3) For reinforced concrete slabs, a maximum joint spacing of 30
feet is recommended. Longer slab lengths have a greater tendency to
develop working mid-panel cracks caused by the rupture of the steel
reinforcement. Studies have also shown that, as the joint spacing
increases above 30 feet, the rate of faulting increases and joint sealant
performance decreases .
- (4) Random joint spacings have been successfully used in plain undoweled
pavements to minimize resonant vehicle responses. When using random
joint spacings, the longest slab should be no greater than 15 feet,
to reduce the potential for transverse cracking. Some States are successfully
using a spacing of 12'-15'-13'-14'. Large differences in slab lengths
should be avoided.
- (5) While they do not affect joint spacing, skewed joints have been
used in plain pavements to provide a smoother ride. A skew of 2 feet
in 12 feet is recommended, with the skew placed so that the inside
wheel crosses the joint ahead of the outside wheel. Only one wheel
crosses the joint at a time, which minimizes vehicle response and
decreases stresses within the slab. Skewed joints are most commonly
used when load transfer devices are not present. While skewed joints
may be used in conjunction with load transfer devices, studies have
not substantiated that skewing doweled joints improves pavement performance
and are not recommended. Dowels in skewed joints must be placed parallel
to the roadway and not perpendicular to the joints.
- Load Transfer Across the Joint. Loads applied by traffic must
be effectively transferred from one slab to the next in order to minimize
vertical deflections at the joint. Reduced deflections decrease the potential for
pumping of the base/subbase material and faulting. The two principal methods
used to develop load transfer across a joint are: aggregate interlock;
and load transfer devices, such as dowel bars. It is recommended that
dowel bars be used.
- (1) Aggregate Interlock. Aggregate interlock is achieved through
shearing friction at the irregular faces of the crack that forms beneath
the saw cut. Climate, and aggregate hardness have an impact on load
transfer efficiency. It can be improved by using aggregate that is
large, angular, and durable. Stabilized bases have also been shown
to improve load transfer efficiency . However, the efficiency
of aggregate interlock decreases rapidly with increased crack width
and the frequent application of heavy loads to the point that pavement
performance may be affected. Therefore, it is recommended that aggregate
interlock for load transfer be considered only on local roads and
streets which carry a low volume of heavy trucks.
- (2) Dowel Bars. Dowel bars should be used on all routes carrying
more than a low volume of heavy trucks. The purpose of dowels is to
transfer loads across a joint without restricting joint movement due
to thermal contraction and expansion of the concrete. Studies have
shown that larger dowels are more effective in transferring loads
and in reducing faulting. It is recommended that the minimum dowel
diameter be D/8, where D is the thickness of the pavement. However,
the dowel diameter should not be less than 1 1/4 inches. It is also
recommended that 18-inch long dowels be used at 12-inch spacings.
Dowels should be placed mid-depth in the slab. Dowels should be corrosion-resistant
to prevent dowel seizure, which causes the joint to lock up. Epoxy-coated
and stainless steel dowels have been shown to adequately prevent corrosion.
- Joint Shape and Sealant Properties
- (1) The purpose of a joint sealant is to deter the entry of water
and incompressible material into the joint and the pavement structure.
It is recognized that it is not possible to construct and maintain
a watertight joint. However, the sealant should be capable of minimizing
the amount of water that enters the pavement structure, thus reducing moisture-related
distresses such as pumping and faulting. Incompressibles should be
kept out of the joint. These incompressibles prevent the joint from
closing normally during slab expansion and lead to spalling and blowups.
- (2) Sealant behavior has a significant influence on joint performance.
High-type sealant materials, such as silicone and preformed compression
seals, are recommended for sealing all contraction, longitudinal,
and construction joints. While these materials are more expensive,
they provide a better seal and a longer service life. Careful attention
should be given to the manufacturer's recommended installation procedures.
Joint preparation and sealant installation are very important to the
successful performance of the joint. It is therefore strongly recommended
that particular attention be given to both the construction of the
joint and installation of the sealant material.
- (3) When using silicone sealants, a minimum shape factor (ratio of
sealant depth to width) of 1:2 is recommended. The maximum shape factor
should not exceed 1:1. For best results, the minimum width of the
sealant should be 3/8 inch. The surface of the sealant should be recessed
1/4 to 3/8 inch below the pavement surface to prevent abrasion caused
by traffic. The use of a backer rod is necessary to provide the proper
shape factor and to prevent the sealant from bonding to the bottom
of the joint reservoir. This backer rod should be a closed-cell polyurethane
foam rod having a diameter approximately 25 percent greater than the
width of the joint to ensure a tight fit.
- (4) When using preformed compression seals, the joint should be designed
so that the seal will be in 20 to 50 percent compression at all times.
The surface of the seal should be recessed 1/8 to 3/8 inch to protect
it from traffic. Additional information can be obtained from FHWA
Technical Paper 89-04, "Preformed Compression Seals" 
for PCC pavement joints. "
- LONGITUDINAL JOINTS
- Longitudinal joints are used to relieve warping stresses and are generally
needed when slab widths exceed 15 feet. Widths up to and including 15
feet have performed satisfactorily without a longitudinal joint, although
there is the possibility of some longitudinal cracking. Longitudinal joints
should coincide with pavement lane lines whenever possible, to improve
traffic operations. The paint stripe on widened lanes should be at 12
feet and the use of a rumble strip on the widened section is recommended.
- Load transfer at longitudinal joints is achieved through aggregate interlock.
Longitudinal joints should be tied with tiebars to prevent lane separation
and/or faulting. The tiebars should be mechanically inserted and placed
at mid-depth. When using Grade 40 steel, 5/8-inch by 30-inch or 1/2-inch
by 24-inch tiebars should be used. When using Grade 60 steel, 5/8-inch
by 40-inch or 1/2-inch by 32-inch tiebars should be used. These lengths
are necessary to develop the allowable working strength of the tiebar.
Tiebar spacing will vary with the thickness of the pavement and the distance
from the joint to the nearest free edge. Recommended tiebar spacings are
provided in Table 3.
Table 3 Maximum Recommended Tiebar Spacings
- Tiebars should not be placed within 15 inches of transverse joints.
When using tiebars longer than 32 inches with skewed joints, tiebars should
not be placed within 18 inches of the transverse joints.
- The use of corrosion-resistant tiebars is recommended, as corrosion
can reduce the structural adequacy of tiebars.
- It is recommended that longitudinal joints be sawed and sealed to deter
the infiltration of surface water into the pavement structure. A 3/8-inch
wide by 1-inch deep sealant reservoir should be sufficient.
- CONSTRUCTION JOINTS
- Transverse Construction Joints
- (1) Transverse construction joints should normally replace a planned
contraction joint. However, they should not be skewed, as satisfactory
concrete placement and consolidation are difficult to obtain. Transverse
construction joints should be doweled as described in paragraph 4b(2)
and butted, as opposed to keyed. Keyed transverse joints tend to spall
and are not recommended.
- (2) It is recommended that transverse construction joints be sawed
and sealed. The reservoir dimensions should be the same as those used
for the transverse contraction joints.
- Longitudinal Construction Joints
- EXPANSION JOINTS
- Good design and maintenance of contraction joints have virtually eliminated
the need for expansion joints, except at fixed objects such as structures.
When expansion joints are used, the pavement moves to close the unrestrained
expansion joint over a period of a few years. As this happens, several
of the adjoining contraction joints may open, effectively destroying their
seals and aggregate interlock.
- The width of an expansion joint is typically 3/4 inch or more. Filler
material is commonly placed 3/4 to 1 inch below the slab surface to allow
space for sealing material. Smooth dowels are the most widely used method
of transferring load across expansion joints. Expansion joint dowels are
specially fabricated with a cap on one end of each dowel that creates
a void in the slab to accommodate the dowel as the adjacent slab closes
the expansion joint, as shown in Figure 2.
Figure 2 Expansion Joint Detail
- Pressure relief joints are intended to serve the same purpose as expansion
joints, except that they are installed after initial construction to relieve
pressure against structures and to alleviate potential pavement blowups.
Pressure relief joints are not recommended for routine installations.
However, they may be appropriate to relieve imminent structure damage
or under conditions where excessive compressive stresses exist. Additional
information can be obtained from the FHWA Pavement Rehabilitation Manual,
- 8. JOINT CONSTRUCTION
- Concrete Placement
- (1) A prepaving conference should be considered on all major paving
projects. This conference should include the project engineer and
the paving contractor and should discuss methods for accomplishing
all phases of the paving operation. The need for attention to detail
cannot be overstated.
- (2) When using dowel baskets, the baskets should be checked prior
to placing the concrete to ensure that the dowels are properly aligned
and that the dowel basket is securely anchored in the base. It is
recommended that dowel baskets be secured to the base with steel stakes
having a minimum diameter of 0. 3 inch. These stakes should be embedded
into the base a minimum depth of 4 inches for stabilized dense bases,
6 inches for treated permeable bases, and 10 inches for untreated
permeable bases, aggregate bases, or natural subgrade. A minimum of
8 stakes per basket is recommended. All temporary spacer wires extending
across the joint should be removed from the basket. Securing the steel
stakes to the top of the dowel basket, as opposed to the bottom, should
stabilize the dowel basket once these spacer wires are removed.
- (3) Dowels should be lightly coated with grease or other substance
over their entire length to prevent bonding of the dowel to the concrete.
This coating may be eliminated in the vicinity of the welded end if
the dowel is to be coated prior to being welded to the basket. The
traditional practice of coating only one-half of the dowel has frequently
resulted in problems, primarily caused by insufficient greasing and/or
dowel misalignment. The dowel must be free to slide in the concrete
so that the two pavement slabs move independently, thus preventing
excessive pavement stresses. Only a thin coating should be used, as
a thick coating may result in large voids in the concrete around the
- (4) The placement of concrete at construction joints is particularly
critical. Therefore, care must be taken to ensure that only quality
concrete is used in their construction; i. e. , do not use the first
concrete down the chute, nor the "roll" from the screed
to construct this type of joint. The concrete used to construct these
joints should be the same as for the remainder of the slab. The practice
of modifying the mix at the joints is not recommended.
- (5) Careful and sufficient consolidation of the concrete in the area
of the joints is essential to good joint performance. Load transfer
across a doweled joint is greatly affected by the quality of concrete
consolidation around the dowels. Consolidation also has a direct relationship
to concrete strength and durability. Concrete strength, in turn, has
a significant effect on the amount of spalling that occurs at the
- (6) The placement of dowels should be carefully verified soon after
paving begins. If specified tolerances are not being achieved, then
an evaluation of the dowel installation, concrete mix design, and
placement techniques must be made. Appropriate corrections should
be made to the paving process to ensure proper alignment of the load
- (7) When paving full-depth full-width, a mechanical prespreader and
finishing machine in the paving train can be used to reduce drag and
shear forces on the dowels.
- (8) In cases where separate concrete placement is made adjacent to
previously placed concrete, i. e. , truck climbing lanes or concrete
shoulders being placed after mainline pavement, it is important that
incompressibles do not enter the previously sawed transverse joint
reservoir or crack that typically forms below the transverse joint
reservoir. It is recommended that backer rod, tape, or other material
be placed on the vertical face of the transverse joint at the edge
of the pavement to prevent mortar from intruding into the existing
joint. Failure to keep incompressibles out could prevent the joint
from closing normally during slab expansion and may lead to delaminations
near the edge of the previously placed concrete.
- (1) It is recommended that all joints be sawed. The sawing of transverse
contraction and longitudinal joints should be a two-phase operation.
The initial sawing is intended to cause the pavement to crack at the
intended joint. It should be made to the required depth, as described
later, with a 1/8-inch wide blade. The second sawing provides the
necessary shape factor for the sealant material. This second sawcut
can be made any time prior to the sealant installation. However, the
later the sealant reservoir is made, the better the condition of the
joint face. Both sawcuts should be periodically checked to ensure
proper depth, as saw blades tend to wear, as well as ride up when
hard aggregate is encountered. Periodic measurement of blade diameter
is an excellent method to monitor random blade wear, particularly
when using gang saws.
- (2) Time of initial sawing, both in the transverse and longitudinal
directions, is critical in preventing uncontrolled shrinkage cracking.
It is very important that sawing begin as soon as the concrete is
strong enough to both support the sawing equipment and to prevent
raveling during the sawing operation. All joints should be sawed within
12 hours of concrete placement. The sawing of concrete constructed
on stabilized base must be sawed earlier. This is particularly critical
during hot weather. Once sawing begins, it should be a continuous
operation and should only be stopped if raveling begins to occur.
- (3) For transverse contraction joints, an initial sawcut of D/3 is
recommended, particularly for pavements with a thickness greater than
10 inches. In no case should the sawcut depth be less than D/4. Transverse
contraction joints should be initially sawed in succession. Skip sawing
is not recommended, as this practice results in a wide range of crack
widths that form beneath the sawed joints. These varied crack widths
affect the shape factors and may cause excessive sealant stresses
in those joints initially sawed. The dimensions of the final sawing
should be dependent upon the sealant type and the anticipated longitudinal
- (4) For longitudinal joints, a minimum initial sawcut depth of D/3
is recommended to ensure cracking at the joint. The maximum sawcut
depth should be such that the tiebars are not damaged. A final sawing
that provides a 3/8-inch wide by 1-inch deep sealant reservoir should
- (5) When a lengthy period is anticipated between the initial sawing
of the joint and the final sawing and sealing, consideration should
be given to filling the joint with a temporary filler. This filler
material should keep incompressibles out of the joint and reduce the
potential for spalling.
- (6) The use of plastic inserts is not recommended. Although a few
States have had success with these inserts, most States no longer
allow their use. Improper placement of plastic inserts has been identified
as a cause of random longitudinal cracking . It is also very difficult
to seal the joint formed by these inserts.
Anthony R. Kane
Associate Administrator for
DESIGN OF SLAB LENGTH
Studies have shown that pavement thickness, base stiffness, and climate affect
the maximum anticipated joint spacing beyond which transverse cracking can be
expected . Research indicates that there is a general relationship between
the ratio of slab length (L) to the radius of relative stiffness (_) and transverse
cracking. The radius of relative stiffness is a term defined by Westergaard
to quantify the relationship between the stiffness of the foundation and the
flexural stiffness of the slab. The radius of relative stiffness has a lineal
dimension and is determined by the following equation:
- = radius of relative stiffness (in. )
- E = concrete modulus of elasticity (psi.)
- h = pavement thickness (in. )
- µ = Poisson's ratio of the pavement
- k = modulus of subgrade reaction (pci.)
Research data indicates that there is an increase in transverse cracking when
the ratio L/ exceeds 5. 0. Using the criteria of a maximum L/ ratio of 5. 0, the allowable joint
spacing would increase with increased slab thickness, but decrease with increased
(stiffer) foundation support conditions. The relationship between slab length,
slab thickness, and foundation support for a L/ ratio of 5. 0 is shown below.
Attachment 1: Design of Slab Length
TIEBAR PULLOUT TESTS
Proper consolidation of the concrete around the tiebars is essential to the
performance of longitudinal construction joints. Adjacent lanes should not be
constructed until the project engineer has had opportunity to test the pullout
resistance of the tiebars. Acceptance of the tiebars should be based on the
results of the tests for resistance to pullout. The project engineer will select
15 tiebars from the first day's placement, after the concrete has attained a
flexural strength of 550 psi. The tiebars will be tested to 12,000 lbs. or to
a slippage of 1/32 inch, whichever occurs first. The average of the results
of these pullout tests, divided by the spacing of the tiebars, will be used
to determine the pullout resistance in lbs. per linear foot.
If the test results on the first day's placement are well within the test requirements
shown below, additional testing will be at the discretion of the project engineer
and will be based on comparison of the installation methods and spacings of
the first day's placement with subsequent placements.
If the results of the pullout tests are less than the minimum requirements
specified for the width of concrete being tied, the contractor shall install
additional tiebars to provide the minimum average pullout resistance required,
as directed by the project engineer. Testing of the supplemental tiebars will
be at the discretion of the Engineer.
Tiebars shall be installed by methods and procedures such that the tiebars
will develop the minimum average pullout resistance specified without any slippage
exceeding 1/32 inch in accordance with the following table:
|Tied Width of Pavement (Distance from Joint Being Constructed to Nearest Free Edge)
||Average Pullout Resistance of Tiebars, lbs. /L. F. of joint, minimum.
|12 feet or less
|Over 12 feet to 17 feet
|Over 17 feet to 24 feet
|Over 24 feet to 28 feet
|Over 28 feet to 36 feet
|Over 36 feet
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Association of State Highway and Transportation Officials, 1986.
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FHWA-RD-89-136, K. D. Smith, D. G. Peshkin, M. I. Darter, A. L. Mueller, and
S. H. Carpenter, March 1990.
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in Concrete Pavement, Federal Highway Administration, FHWA-ED-88-025, 1988.
7. "1984 Standard Specifications for Construction," Michigan Department
of Transportation, 1984.
8. "Design of Zero-Maintenance Plain Jointed Concrete Pavement,"
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9. "Design, Construction, and Maintenance of PCC Pavement Joints,"
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No. 19, Transportation Research Board, 1973.
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A. M. Ioannides, 1989.
12. "Relationship of Consolidation to Performance of Concrete Pavements,"
FHWA-RD-87-095, D. A. Whiting and S. D. Tayabji, 1987.
13. "The Design of Plain Doweled Jointed Concrete Pavement,"
K. Kelleher and R. M. Larson, 4th International Conference on Concrete Pavement
Design and Rehabilitation, 1989.
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Cement Association, IS059. 03P, 1980.
15. "The Benefits of Using Dowel Bars," Federal Highway Administration,
Pavement Division Technical Paper 89-03, 1989.
16. "Performance of Jointed Concrete Pavements, Volume III, Summary of
Findings," K. D. Smith, D. G. Peshkin, M. I. Darter, and A. L. Mueller,
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