U.S. patent application number 10/885823 was filed with the patent office on 2004-12-02 for system of protecting the edges of cast-in-place concrete slab on ground, construction joints.
This patent application is currently assigned to Permaban North America, Inc.. Invention is credited to Boxall, Russell, Harrison, Patrick, Parkes, Nigel A..
Application Number | 20040237434 10/885823 |
Document ID | / |
Family ID | 26905184 |
Filed Date | 2004-12-02 |
United States Patent
Application |
20040237434 |
Kind Code |
A1 |
Boxall, Russell ; et
al. |
December 2, 2004 |
System of protecting the edges of cast-in-place concrete slab on
ground, construction joints
Abstract
An improved joint edge assembly, of the type used in the
construction of concrete slabs, is disclosed. The assembly
comprises a longitudinal joint rail, preferably of steel, which is
supported off the ground by temporary formwork. The joint rail is
secured to the formwork by mounting brackets. The joint rail
comprises first and second joint edge members that are connected to
each other by connectors with self-release elements. A plurality of
studs extends downward and outward from each of the joint edge
members into the concrete slabs provide a positive mechanical
connection between the slab and the joint rail. As the concrete
shrinks during hardening, the self-release elements of the
connectors allow the joint to freely open. The joint edge assembly
thus provides a self-releasing expandable joint between adjacent
slab sections, and protects the edges of the adjacent slab sections
from damage. A dowel aligner may also be integrated into the
assembly, to allow proper positioning of dowels within the
slab.
Inventors: |
Boxall, Russell; (Matthews,
NC) ; Parkes, Nigel A.; (Tucker, GA) ;
Harrison, Patrick; (Prairie Village, KS) |
Correspondence
Address: |
BANNER & WITCOFF, LTD.
TEN SOUTH WACKER DRIVE
SUITE 3000
CHICAGO
IL
60606
US
|
Assignee: |
Permaban North America,
Inc.
Tucker
GA
|
Family ID: |
26905184 |
Appl. No.: |
10/885823 |
Filed: |
July 7, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10885823 |
Jul 7, 2004 |
|
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|
10210464 |
Jul 31, 2002 |
|
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|
6775952 |
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60309397 |
Aug 1, 2001 |
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Current U.S.
Class: |
52/364 ;
52/393 |
Current CPC
Class: |
E01C 11/08 20130101;
E04F 15/14 20130101; E01C 11/14 20130101 |
Class at
Publication: |
052/364 ;
052/393 |
International
Class: |
E01C 011/16 |
Claims
We claim:
1. An improved joint edge assembly for the construction of jointed
concrete slabs and protection of concrete slab joints, the concrete
slabs separating after pouring, the assembly comprising: a first
elongated joint edge member; a second elongated joint edge member;
connector or connectors that connect the joint edge members to each
other, said connector(s) also including release elements that
release the joint edge members from each other under the force of
the slabs separating; temporary formwork and formwork mounting
members; whereby the assembly of the joint edge members and
connectors may be placed for the joint edge members to form and
thereby protect edges of a concrete slab joint, whereby the slabs
may be poured, and the joint edge members may release from each
other under action of the slabs separating, to allow the joint
formed by the joint edge members to open and minimize slab cracking
at and adjacent the joint during separation, and whereby the
formwork mounting members may be mounted on the temporary formwork
and may support the assembly in position for the joint edge members
to form the edges of the concrete slab.
2. The apparatus of claim 1 further comprising a dowel aligner
connected to the temporary formwork, extending into the region
where the first concrete slab is to be poured, whereby the dowel
aligner permits the placement of dowels prior to the pouring of the
adjacent concrete slab.
3. An improved joint edge assembly as in claim 1 further comprising
a plurality of anchors extending from each side of the joint edge
assembly into the regions where the adjacent slabs are to be
poured.
4. An improved joint edge assembly as in claim 3, wherein the
plurality of anchors are comprised of at least one steel stud with
an expanded head.
5. A method of forming an improved joint edge utilizing an improved
joint edge assembly, for the construction of jointed concrete slabs
and protection of concrete slab joints, the concrete slabs
separating, the assembly comprising a first elongated joint edge
member, a second elongated joint edge member, each side of the form
assembly being anchored into the regions where the adjacent slabs
are to be poured, joint edge members connected to each other,
connected using release element(s) that release the joint edge
members from each other under action of the slabs shifting, and a
dowel aligner connected to temporary formwork, extending into the
region where the first. concrete slab is to be poured, whereby the
dowel aligner permits the placement of dowels prior to the pouring
of the adjacent concrete slab, the method comprising: placing the
assembly of the joint edge members and connecting means for the
joint edge members to form and thereby protect edges of a concrete
slab joint, pouring the slabs to the joint edge members, and
allowing the joint edge members to release from each other under
action of the slabs shifting with the anchors embedded therein and
under action of the releasing elements of the connectors, allowing
the joint formed by the joint edge members to open and minimize
slab cracking at and adjacent to the joint during shifting and
subsequently protecting the joint edge.
6. An article made according to the method of claim 5.
7. An improved apparatus for constructing, protecting, and
preserving concrete slab joint edges, the assembly comprising:
joint edge members forming the respective edges of the concrete
slabs; one or more connectors that connect the joint edge members,
the connector or connectors having release elements, allowing the
joint edge members to separate while the concrete is shrinking
during construction or shifting after construction; temporary
formwork and formwork mounting members; whereby joint edge members
are placed opposite to one another on temporary formwork to act as
the concrete slab edges prior to pouring the concrete, whereby the
connectors minimize cracking in the concrete slabs by allowing the
joint edge members to separate from one another while the concrete
shrinks during hardening; whereby the connectors minimize cracking
in the concrete slabs by allowing the joint edge members to move
relative to one another while the concrete slabs shift after
hardening; whereby the joint edge members form the edge of the
concrete slabs and protect the concrete slab edges from cracking or
chipping after hardening;
8. The apparatus of claim 7 further comprising a dowel aligner
connected to the temporary formwork, extending into the region
where the first concrete slab is to be poured, whereby the dowel
aligner permits the placement of dowels prior to the pouring of the
adjacent concrete slab.
9. An improved joint edge assembly as in claim 7 further comprising
a plurality of anchors extending from each side of the joint edge
assembly into the regions where the adjacent slabs are to be
poured.
10. An improved joint edge assembly as in claim 9, wherein the
plurality of anchors are comprised of at least one steel stud with
an expanded head.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of, and claims benefit
of, U.S. patent application Ser. No. 10/210,464, filed, Jul. 31,
2002, incorporated herein by reference, which is based on, and
claims the benefit of, U.S. Provisional Application Ser. No.
60/309,397, filed on Aug. 1, 2001, entitled "System of Protecting
the Edges of Cast in Place Concrete Slab on Ground, Construction
Joints."
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to the construction of
concrete slabs. More particularly, the invention relates to an
improved joint edge assembly that protects the joint edges and
allows the joint to self-open as the concrete shrinks during
hardening.
[0004] 2. Related Art
[0005] For logistical and technical reasons, concrete floor slabs
are made up of a series of individual blocks. The interface where
one block meets another is termed a joint. Freshly placed concrete
shrinks considerably as it hardens as the chemical reaction between
the cement and the water occurs, i.e., hydration. As the concrete
shrinks, tensile stress accumulates in the concrete, therefore, the
joints should be free to open and thus allow shrinkage to occur
without damaging the slab.
[0006] The joint openings, however, create discontinuities in the
slab surface, which can cause the wheels of forklift trucks and
other vehicles to impact the joint edges and chip small pieces of
concrete from the edge of each slab. This damage to the edges of
slabs is commonly referred to as "joint spalling." Joint spalling
often interrupts the normal working operations of many facilities
by slowing down forklift and other truck traffic, and/or causing
damage to trucks and the carried products. Severe joint spalling
can even cause loaded forklift trucks to be overturned and can be
dangerous to employees. Furthermore, joint spalling can be very
expensive to repair.
[0007] For these reasons, it is advantageous to protect the joint
edges against spalling with steel bars or angles. Commonly used
details illustrating the use of hot rolled steel bars (or angles)
are shown in the American Concrete Industry (ACI) technical manuals
302 and 360. However, the standard installation procedure for these
steel bars or angles is both time-consuming and expensive. The
conventional procedures typically includes the following steps: (1)
a temporary edge form is erected; (2) the first bar (or angle) is
attached to the edge form; (3) the first concrete slab is cast; (4)
the form is removed; (5) the second bar (or angle) is tack welded
to the first; (6) the second concrete slab is cast; and (7) the
tack welds are removed by grinding. Importantly, the quality
control of the tack welding and the timing of the tack weld
grinding are critical to the joint performance. If a weld is not
completely removed by grinding, or if grinding is not completed
shortly after the second slab is cast, then the joint remains
locked together and tensile stress accumulates in the slabs, which
often leads to unacceptable slab cracking.
[0008] For at least the foregoing reasons, an improved joint edge
assembly that protects the joint edges of the concrete slab, and
allows the joint to self-open as the concrete shrinks during
hardening would be desirable.
SUMMARY OF THE INVENTION
[0009] The invention is an improved joint edge assembly that
protects the joint edges of concrete slabs and allows the joint to
self-open as the concrete shrinks during hardening. The apparatus
comprises a longitudinal joint rail, made up of two elongated joint
edge members. The elongated joint edge members are typically steel
bar sections, but can be any similar suitable material. The
sections are connected to one another along their length by two
sets of connectors. The first set secures the sections during
shipping and placement, and are removed before pouring the adjacent
concrete slab. The second set of connectors remain throughout the
concrete pouring operation and include release elements that
self-release the joint edge members from each other under the force
of the slabs shrinking during hardening, thus allowing the joint to
open. The joint rail is supported above the ground surface by a
mounting bracket attached to temporary formwork seated on the
ground surface. A plurality of studs extend from the elongated
joint edge members into the region where the slab is to be poured
such that, upon hardening of the concrete slab, the studs are
integrally cast within the body of the slab. One or more dowel
aligners may be integrated into the form assembly to allow dowels
to be accurately positioned within the adjacent slab sections.
Alternatively, a base and sleeve may be used where a load plate is
employed between adjacent slabs rather than dowels.
[0010] When the first of the adjacent slab sections is poured, the
claimed form assembly restrains the wet concrete. Preferably, studs
extending from the longitudinal joint rail become embedded in the
concrete slab, providing a positive mechanical connection between
the slab and the form assembly when the concrete hardens. Before
pouring the adjacent slab, the connectors used to secure the
longitudinal joint rail during shipping and placement are removed
such that the connectors containing the self-release elements
remain. This step is best taken after the concrete has hardened
sufficiently to support the longitudinal joint rail. Further, at
this point the dowels or load plates are placed, if desired, using
the aligners that were cast into the first concrete slab. After
pouring the adjacent slab, the studs extending from the
longitudinal joint rail into the adjacent slab region become
embedded in the adjacent concrete slab, providing a positive
mechanical connection between the adjacent slab and the form
assembly. As the chemical reaction between the cement and the water
occurs, i.e., hydration, the concrete hardens and shrinks. As the
slabs shrink away from one another, the self-release elements allow
the elongated joint edge members to separate from one another. If
desired, the gap formed by the separated joint edge members may be
filled with a sealant.
BRIEF DESCRIPTION OF THE DRAWING
[0011] FIG. 1 of the drawing is a plan view of concrete slab with
joints at the interface of the individual blocks.
[0012] FIG. 2 of the drawing is a cross section view of the joint
edge assembly constructed in accordance with the present
invention.
[0013] FIG. 2A is a detail of FIG. 2 showing the factory assembled
form assembly and the dowel aligner.
[0014] FIG. 3 is a cross section of the completed joint edge
constructed in accordance with the present invention showing the
placement of the dowels between concrete slabs.
[0015] FIG. 4 is a perspective view of the joint rail in the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] A preferred design for a form assembly made in accordance
with the claimed invention is shown in FIGS. 1, 2, 2A, 3, and 4. In
FIG. 2A, the preferred embodiment of the form assembly 200 is
shown. Referring to FIG. 2, the form assembly 200 includes a
longitudinal joint rail 201, which is comprised of two joint edge
members 202, 203. The joint edge members 202, 203 are typically
steel bar sections, but any other suitable steel section, such as
an angle section, can be used. FIG. 4 shows the three, dimensional
components of the joint rail 201, the longitudinal dimension 401,
the major latitudinal dimension 402, and the minor latitudinal
dimension 403. In situ, the longitudinal dimension 401 is oriented
along the length of the joint 101 between adjacent concrete slab
sections 100 (shown in FIG. 1) and parallel to the ground surface
260, which defines a generally flat reference plane. The major
latitudinal dimension 402, when in situ, extends generally
perpendicular to the reference plane 260 and the minor latitudinal
dimension 403, when in situ, extends generally parallel to the
reference plane 260. The steel rails, i.e., joint edge members 202,
203, are oriented, when in situ, with the major latitudinal
dimensions 402 thereof adjacent to each other.
[0017] In the preferred embodiment, holes 410 (shown in FIG. 4) are
drilled through the joint rail 201 at longitudinal intervals, so
that a connector, typically a bolt, 213 can be passed through the
joint rail 201. As shown in FIG. 2, a bolt 213 passes through the
holes 410 of the joint rail 201 in a direction generally parallel
to the minor latitudinal dimension 403. The bolt 213 is generally
permanently affixed to the first joint edge member 202 by any
suitable means such as welding the head of the bolt 210 to the
first joint edge member 202. The connectors 211, 212 that secure
the joint edge members 202, 203 and the mounting bracket 230 are
affixed in the reverse order that they are removed. I.e., the
shipping/placement connectors 212 are affixed last because they are
removed first in the field. Therefore, the second joint edge member
203 is first secured to the first joint edge member 202 by
connectors 211 that will allow the joint edge members 202, 203 to
self-release under the force of the concrete slabs 250, 350
shrinking during hardening. The details of the self-release
connectors 211 are presented below.
[0018] The mounting bracket 230 shown in FIG. 2 is next secured to
the joint rail 201 by the shipping/placement connectors 212. The
mounting bracket 230 is of any suitable configuration to secure the
joint rail 201 to the temporary formwork 235. The temporary
formwork 235 is typically comprised of standard 2" lumber sections
selected according to the design thickness of the concrete slabs
250, 350. The mounting bracket 230 is designed such that the form
assembly 200 can be temporarily affixed to the temporary formwork
235, so that the edge of the temporary formwork 235 aligns with the
interface of the first and second joint edge members 202, 203. The
shipping/placement connectors 212 are typically comprised of steel,
and secure the form assembly from the time of assembly until the
temporary formwork 235 is removed in preparation for pouring the
adjacent concrete slab 350.
[0019] Also shown in FIG. 2 are anchors 220, 225 that are
permanently affixed to the joint edge members 202, 203, typically
by welding, in order to provide a positive mechanical connection
between the concrete slabs 250, 350 and the joint edge members 202,
203. The anchors 220, 225 are typically comprised of headed steel
studs. The studs 220, 225 and heads of the steel studs 221, 226
extend downward and outward from the joint rail 201 such that when
the concrete slabs 250, 350 are poured, the studs 220, 225 and
heads of the steel studs 221, 226 are embedded within the concrete
slab. Although a headed stud is preferred, a non-headed stud may be
used. Alternatively, the anchor may have ridges or a rough surface
to help concrete adhere to the anchor during hardening. As used
herein, the term anchor or stud generally includes any structure
that projects from the rail assembly to become embedded in the
slab, positively connecting the slab to the form assembly.
[0020] Ideally, the form assembly 200 shown in FIG. 2A is factory
assembled to exacting tolerances. This improves the levelness
across joints 101, and makes the finishing of the adjacent concrete
slabs easier.
[0021] To use the assembly, the factory assembled form assembly 200
is secured to the temporary formwork 235 in the field by any
suitable means. The temporary formwork is aligned and fixed in
position with stakes 236 or any other suitable member. As in any
concrete slab construction, the alignment of the formwork is
essential to insuring the desired finished product. One or more
dowel aligners 242 (see FIG. 2A) may be integrated into the form
assembly to permit dowels 340 (see FIG. 3) to be accurately
positioned within the adjacent concrete slab sections. Each dowel
aligner 242 comprises a dowel sleeve 240 and a dowel support member
241 attached to the temporary formwork 235. The dowel sleeve
permits a dowel 340 to be installed parallel to the minor
latitudinal dimension 403 after the first concrete slab 250 has
begun to harden and the temporary formwork 235 is removed.
Alternatively, a base and sleeve may be used where a load plate is
employed between adjacent slabs rather than dowels. As used herein,
the dowels generally include any structure that projects from one
concrete slab to an adjacent concrete slab, positively connecting
the two slabs.
[0022] Once the form assembly 200 is properly secured and aligned,
the first concrete slab 250 is poured. The studs 220 extending from
the first joint edge member 202 become embedded in the wet
concrete, and provide a positive mechanical connection between the
concrete slab 250 and the joint edge member 202 when the concrete
hardens. Once the concrete slab 250 has hardened sufficiently, the
shipping/placement connectors 212 are removed followed by the
stakes 236, the mounting brackets 230, the temporary formwork 235,
and the dowel support members 241. After positioning the dowels 340
in the dowel sleeves 240, the adjacent concrete slab 350 is poured
and finished such that the studs 225 and heads of the steel studs
226 extending from the second joint edge member 203 become embedded
in the wet concrete of the adjacent concrete slab 350.
[0023] As the chemical reaction between the cement and the water in
the adjacent concrete slab 350 occurs, i.e., hydration, the
concrete hardens and shrinks. This chemical reaction is ongoing in
the first concrete slab 250 also, as the process continues for an
extended period of time. As the slabs 250, 350 shrink away from one
another, the self-release elements in the connectors 211 allow the
elongated joint edge members 202, 203 to separate from one another.
If desired, the gap formed by the separated joint edge members 202,
203 can be filled with an appropriate sealant.
[0024] In the preferred embodiment, the connectors 211 that allow
the joint edge members 202, 203 to self-release under the force of
the concrete slabs 250, 350 shrinking during hardening are
comprised of nylon nuts or other suitable material. The nylon nuts
are suitably chosen according to the design tensile strength of the
concrete such that the nylon nut yields under the shrinkage stress.
Note that the design tensile strength is variable according to the
conditions and application of the concrete slabs 250, 350. As the
concrete slabs 250, 350 shrink, the studs 220, 225, which are
embedded in the concrete slabs 250, 350 pull the joint edge members
202, 203 apart. In the properly compatible design configuration,
the nylon nut yields under the shrinkage stress of the concrete,
and is stripped off the bolt 213, i.e., the threads of the nylon
nuts are sheared as the joint edge members 202, 203 separate.
[0025] While in the foregoing, there have been described various
preferred embodiments of the present invention, it should be
understood to those skilled in the art that various modifications
and changes can be made without departing from the scope of the
invention as recited in the claims. An effort has been made to
prepare claims commensurate in scope with this description without
any failure to claim any described embodiment and within the best
abilities of the inventors to foresee any modifications or
changes.
* * * * *