Note: Descriptions are shown in the official language in which they were submitted.
METHOD OF FABRICATING A CONCRETE SLAB SYSTEM
[0001] [Deleted].
Cross-reference to Related Patent Applications
[0002] [Deleted]
Field of the Invention
[0003] The invention relates generally to concrete slab fabrication, and
more
particularly to a method for fabricating a high-quality-finish concrete slab
system that
also provides functionality during a building's construction phase.
Background of the Invention
[0004] A building's concrete slab/floor (hereinafter referred to as
"slab") is
often the showpiece of a building and must be smooth and flat in order to
safely
support foot and vehicular traffic during the building's life. However, a
building's
concrete slab is usually poured and finished early on in a building's
construction
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thereby subjecting the slab to a barrage of construction processes that damage
the
slab's finish physically and cosmetically. Such damages can be difficult or
impossible to repair thereby leaving the finished building slab in a
physically and/or
cosmetically damaged state when the building is brand new.
[0005] A common construction process that subjects a concrete slab to
substantial abuse is known as tilt-up or tilt-wall construction. Tilt-up or
tilt-wall
construction is a well-known approach to the construction of concrete
buildings and
structures. In general, tilt-wall construction involves the horizontal
fabrication of
concrete wall panels on a horizontal concrete casting bed, followed by the
raising or
tilting of the concrete wall panels into vertical orientations on top of a
footing. For
most tilt-wall construction, some (or substantially all) of a building's
interior concrete
slab is poured and finished to its finished grade prior to the casting of the
wall
panels with portions of the slab near the building's perimeter serving as the
casting
bed regions for the fabrication of concrete wall panels. The portion of the
slab
serving as the casting bed regions is subjected to heavy construction traffic
and
abuse during tilt-wall fabrication and erection operations. As a result, it is
difficult or
impossible to provide a high-quality-finish concrete slab that was previously
used as
a tilt-wall construction casting bed.
Summary of the Invention
[0006] Accordingly, it is an object of the present invention to provide a
method
for fabricating a high-quality-finish concrete slab system.
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[0007] Another object of the present invention is to provide a high-quality-
finish concrete slab system that also provides functionality and advantages
during a
building's construction phase without jeopardizing the slab's ultimate high-
quality
finish.
[0008] Still another object of the present invention is to provide a method
of
constructing a concrete slab system that supports tilt-wall construction and
ultimate
slab applications.
[0009] Other objects and advantages of the present invention will become
more
obvious hereinafter in the specification and drawings.
[0010] In accordance with the present invention, a method of fabricating a
concrete slab system includes the step of placing a bed of a first concrete on
a
base. The bed has a top surface, a bottom surface, and edge surfaces. The bed
is
exposed to a drying environment wherein the top surface develops shrinkage
cracks
and portions of the bed separate from the base. A force is applied to the top
surface at the portions of the bed separated from the base to induce non-
shrinkage
cracks in the bed. The non-shrinkage cracks extend to the bed's bottom
surface.
Non-concrete material is placed on the bed's top surface and on each of its
edge
surfaces. The non-concrete material and bed are covered with a second concrete
having stretchable fibers mixed therein.
Brief Description of the Drawings
[0011] Other objects, features and advantages of the present invention will
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become apparent upon reference to the following description of the preferred
embodiments and to the drawings, wherein corresponding reference characters
indicate corresponding parts throughout the several views of the drawings and
wherein:
[0012] FIG. 1 is a side sectional view of a concrete slab system in
accordance
with an embodiment of the present invention;
[0013] FIG. 2 is a sectional plan view of the concrete slab system taken
along
line 2-2 in FIG. 1;
[0014] FIG. 3 is an isolated and enlarged view of a portion of the concrete
slab system's bed taken along line 3-3 in FIG. 2;
[0015] FIG. 4 is a side sectional view of a concrete slab system in
accordance
with another embodiment of the present invention;
[0016] FIG. 5A is a schematic cross-sectional view of a building site with
a
structure's footing above the structure's proposed finished floor grade level;
[0017] FIG. 5B is a schematic cross-sectional view of a building site with
a
structure's footing below the structure's proposed finished floor grade level;
[0018] FIG. 5C is a schematic cross-sectional view of a building site with
a
structure's footing at the structure's proposed finished floor grade level;
[0019] FIG. 6A is a schematic cross-sectional view of a below-grade bed in
accordance with an embodiment of the present invention;
[0020] FIG. 6B is a plan view of the footing and the below-grade bed taken
along line 6-6 in FIG. 6A;
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[0021] FIG. 7 is a schematic cross-sectional view of a below-grade bed that
has dried and cured to thereby experience shrinkage cracks and curl;
[0022] FIG. 8 is an enlarged cross-sectional view of a portion of the below-
grade bed with shrinkage cracks and induced cracks in accordance with the
present
invention;
[0023] FIG. 9 is a schematic cross-sectional view of the below-grade bed
covered with a single-layer of a non-concrete material in accordance with an
embodiment of the present invention;
[0024] FIG. 10 is a schematic cross-sectional view of the below-grade bed
covered with multi-layers of a non-concrete material in accordance with
another
embodiment of the present invention;
[0025] FIG.11 is a schematic cross-sectional view of the below-grade bed,
non-concrete material, and concrete covering deposited thereon in accordance
with
an embodiment of the present invention; and
[0026] FIG. 12 is a schematic cross-sectional view of a completed concrete
slab system in accordance with an embodiment of the present invention.
Detailed Description of the Invention
[0027] Referring now to the drawings, simultaneous reference will be made
to
FIGs. 1-3 where FIGs. 1-2 illustrate a concrete slab system 10 in accordance
with
an embodiment of the present invention. It is to be understood that the
elements of
system 10 are drawn to illustrate the novel features of system 10 and are not
drawn
CA 2961764 2017-03-22
to scale. In general and as will be explained further herein, a portion of
system 10
provides functionality during a building's construction phase, while the
entirety of
system 10 is the building's concrete slab system that has a high-quality
finish
defined by a smooth, flat, and virtually blemish-free top surface.
[0028] Concrete slab system 10 includes a concrete bed 20, a non-concrete
material 30, and a concrete covering 40. The top or exposed portion of
concrete
covering 40 defines the top/finished surface 12 of system 10 whereas the
bottom
portions of concrete covering 40 are in contact with non-concrete material 30
and
can define a portion of the bottom 14 of system 10.
[0029] Concrete bed 20 can be made from a variety of types of concrete
materials or mixes. One of the great advantages of the present invention is
that bed
20 can be made using concrete materials that decrease a project's cost, while
also
providing functionality during a building's construction phase and a stable
support
for the remaining elements of system 10. Some exemplary concrete
materials/mixes that can be used for bed 20 include, but are not limited to,
conventional region-specific concrete mixes, high fly ash content concrete
mixes,
high "ground granulated blast furnace slag" (GGBFS) content concrete mixes,
Portland and non-Portland cement concrete mixes, recycled concrete mixes, etc.
Each of the above-noted concrete mixes can be a fiber-free or non-fibrous
concrete
mix thereby making bed 20 a cost-effective element of system 10. However, it
is to
be understood that bed 20 could include additives such liquid additives and/or
fibers
without departing from the scope of the present invention.
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[0030] Following a wet placement of bed 20 on a base 100 (e.g., the ground,
bed of stones, etc.), bed 20 begins to dry and cure. As bed dries/cures, any
of the
above-described concrete mixes will undergo shrinkage to thereby naturally
develop
shrinkage cracks 24 (e.g., hairline cracks that are generally visible but have
no
measurable width) originating in the top surface 22 of bed 20. That is,
shrinkage
cracks 24 occur spontaneously as a consequence of the natural volume reduction
of
bed 20 without any human and/or machine interaction. Shrinkage cracks 24
generally extend minimally or just partially into the thickness of bed 20 from
top
surface 22. In addition to the development of naturally-occurring shrinkage
cracks
24 during the natural shrinking of bed 20, bed 20 will experience naturally-
occurring
curl at any edges thereof as the concrete mix dries and cures. As will be
explained
further later herein, concrete curl is defined by the raising of concrete's
edge regions
away from the surface of the base on which concrete is placed such that a gap
forms between the bottom of any curled concrete and the base on which it has
been
placed. Since bed 20 is to be placed early on in a building's construction,
bed 20
will have a sufficient amount of time to experience the natural occurrence of
both
shrinkage cracking and curl at its edge regions.
[0031] In accordance with the present invention and as will be explained
further below, concrete bed 20 is purposefully processed to generate induced
cracks
26 (i.e., via purposeful human and/or machine interaction with top surface 22
as
opposed to the above-described naturally-occurring shrinkage cracks 24)
therein
prior to completing system 10 with non-concrete material 30 and concrete
covering
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40. More specifically and with additional reference to the isolated portion of
bed 20
shown in FIG. 3, each non-shrinkage-based induced crack 26 is V-shaped in
cross-
section and extends to the bottom surface 28 of bed 20. Each induced crack 26
is
clearly visible at top surface 22 and has a width "W" at the bed's top surface
22 that
is greater than the width of any shrinkage crack 24 at top surface 22. As a
result of
induced cracks 26, bed 20 breaks at induced cracks 26 to define broken regions
20B of bed 20 with the bottoms of broken regions 20B adjacent to each induced
crack 26 being placed in contact with base 100 as illustrated in FIG. 3.
Induced
cracks 26 will be located all around a perimeter region of bed 20 as
illustrated in
FIG. 2. Moreover and in general, induced cracks 26 will be in bed 20 at any
edge
region or location where bed 20 exhibited curl as bed 20 dried and cured.
[0032] Non-concrete material 30 is disposed on top surface 22 of bed 20 as
well as any exposed edge surfaces 20E of bed 20. Material 30 provides both
friction
reduction and bond prevention between bed 20 and concrete covering 40.
Material
30 can be a single layer as shown in FIG. 1 or multiple layers (e.g., layers
30A and
30B as shown in FIG. 4) of a non-concrete material such as, but not limited
to,
sheet(s) of plastic (e.g., polymers such as polyethylene), layer(s) of a spray-
on non-
concrete material (e.g., TEFLON or other lubricant), and combinations thereof.
While the particular thickness of material 30 is not a limitation of the
present
invention, typical thicknesses range from approximately 1 mil to approximately
20
mils.
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[0033] Covering bed 20 and non-concrete material 30 is concrete covering 40
whose top surface 42 defines the ultimate finished top surface 12 of concrete
slab
system 10. In general, concrete covering 40 is a concrete mix with stretchable
fibers 44 mixed therein. The concrete mix can include a variety of concrete
mixes
such as those described above. Stretchable fibers 44 can include polymer
fibers,
metal fibers, or combinations thereof. The lengths of the fibers and the
amount of
stretch associated therewith can be selected to satisfy the needs of a
particular
application. The amount of stretchable fibers 44 mixed in concrete covering 40
is
generally expressed as a weight per cubic yard of concrete covering 40.
Suitable
weight amounts of stretchable fibers 44 range from 3-65 pounds per cubic yard
of
concrete covering 40. Lower weight amounts are generally associated with
polymer
fibers while higher weight amounts are generally associated with metal fibers.
[0034] Concrete covering 40 includes stretchable fibers 44 to decrease the
elastic modulus of concrete covering 40 when it hardens. If using only polymer
fibers,
approximately 3-9 pounds of stretchable fibers 44 will typically be mixed into
each
cubic yard of the concrete so that it will be flexible enough after setting to
eliminate
curl of concrete slab system 10. Such polymer fibers could be polymer
macrofibers
that range in length from approximately 0.5 inches to approximately 2.5
inches. The
fibers could be all the same length or different lengths without departing
from the
scope of the present invention.
[0035] The above-described bed 20 can define or substantially define a
building's floor footprint. However, the above-described bed 20 could also be
a
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smaller portion of the building's floor footprint as is sometimes the case in
tilt-wall
construction. In either case, the method used to fabricate concrete slab
system 10
is essentially the same as will be described herein below.
[0036] The present invention includes a novel concrete slab system
construction method that produces the resulting and novel concrete slab system
described above. By way of an illustrative example, the fabrication method
will be
described as part of one type of a tilt-wall construction methodology.
However, it is
to be understood that the present invention is not limited to use in tilt-wall
construction as the present invention's concrete slab system can be fabricated
during any building construction methodology. The present invention is
particularly
well-suited to the construction of a high-quality-finish and curl-free
concrete slab
system.
[0037] Prior to describing the fabrication method, reference is made to
FIGs.
5A-5C where exemplary footings are illustrated and are referenced by numeral
200.
As is known in the art, footings 200 provide the in-ground support for a
structure's
walls (e.g., concrete wall panels erected using tilt-wall construction
techniques). The
particular materials used for footings 200 as well as their particular
construction are
not part of the present invention or a limitation of the present invention. In
general,
footings 200 define the outer perimeter of a structure.
[0038] Each footing 200 extends some depth into a surrounding ground
environment 202 of the building site with the top supporting surface 200A of
each
footing 200 being above the structure's proposed finish floor grade level 300
(FIG.
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5A), below the structure's proposed finish floor grade level 300 (FIG. 5B), or
at the
structure's proposed finish floor grade level 300 (FIG. 5C) depending on the
needs
of the particular construction project. The region between the illustrated
footings
200 will become the interior of a structure to be built using footings 200. It
is to be
understood that additional footings (not shown) can be formed between the
illustrated footings 200 to provide support for interior walls, columns, etc.
[0039] When a concrete slab of the present invention is to be constructed,
the
ground environment 202 between footings 200 needs to be excavated to a level
below that of what will be finished concrete floor slab. For example and with
reference to FIG. 6A, ground environment 202 is excavated or dug out below a
level
(referenced by dashed line 300) that defines what will become the top surface
of a
finished concrete floor slab system for the particular project. The base of
the
excavated region defines the above-described base 100 for the concrete slab
system of the present invention.
[0040] In accordance with the present invention, a bed 20 of concrete in
its
plastic state is deposited on base 100 with the top surface 22 of bed 20 being
below
the level 300 of the top surface of the finished concrete slab system. In
general,
bed 20 is of a width "Bw" and thickness "B-r" to support the construction of
concrete
tilt-walls thereon. Bed 20 can be formed just inside the entire periphery of
the
structure to be built on footings 200 as illustrated in FIG. 6B. Bed 20 can be
offset
from footings 200 by a gap 50 sufficient to support the raising of tilt-walls
from bed
20 as is known in the art of tilt-wall construction. Bed 20 can define a frame
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surrounding a region of base 100 that remains exposed as illustrated in the
example
shown in FIGs. 6A and 6B. However, it is to be understood that bed 20 can also
be
a contiguous bed that substantially covers base 100 except for gap 50 as
needed
for tilt-wall construction. In either case, the distance "D" between top
surface 22 and
finished slab level 300 will be filled with the above-described novel layered
structure
that includes the above-described non-concrete material 30 and concrete
covering
40 to complete the finished concrete slab system as will be described further
herein.
For the above-described concrete covering 40, the distance D is generally on
the
order of approximately 2.5 to approximately 4 inches.
[0041] Concrete tilt-wall panels (not shown in FIGs. 6A and 6B) are
fabricated
on top surface 22 of bed 20 and raised onto footings 200 as is known in the
art. It is
to be understood that the fabrication, tilting/raising, and ultimate anchoring
of such
tilt-wall panels is not a limitation of the present invention. Accordingly,
and with
reference to FIG. 7, concrete tilt-wall panels 400 are shown positioned on
footings
200. For clarity of illustration, no additional supports, anchoring, etc., are
shown.
[0042] Bed 20 can be made using any of the various concrete mixes
described above. As also mentioned above, these types of concrete mixes tend
to
exhibit curl when they dry/cure as illustrated in FIG. 7. Since bed 20 will
typically
have had a substantial amount of time to dry/cure during the tilt-wall
construction
process, FIG. 7 depicts bed 20 as it will appear after a typical tilt-wall
construction
process is complete. More specifically, a dried/cured bed 20 will naturally
develop
shrinkage cracks as described above and will naturally tend to be pulled up
and
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away from base 100 (i.e., referred to a "curl" in the art) at least around the
periphery
as well as any edge regions of bed 20. As a result of such curling, air spaces
or
gaps 21 are defined between portions of the bottom surface 28 of bed 20 and
base
100, and raised edges 23 are defined at top surface 22 about the periphery of
bed
20 as well as any other edge regions of bed 20. Gaps 21 and/or raised edges 23
can be the source of crack formation in any concrete topping product applied
to top
surface 22.
[0043] Once tilt-wall panels 400 are vertically erected as shown, bed 20 no
longer needs to function for purposes of tilt-wall construction. At this point
or any
point thereafter in the building's construction, bed 20 is ready to be
processed for
purposes of becoming part of the finished concrete slab system whose top
surface
will be coincident with finished slab level 300. An advantage of the present
invention's fabrication process and resulting concrete slab system is that the
final
processing steps used to create the completed concrete slab system can occur
as a
final building construction process thereby preventing construction abuse of
the
high-quality-finish concrete slab system.
[0044] As a first step in the slab system completion process, gaps 21
and/or
raised edges 23 (illustrated in FIG. 7) must be eliminated. To do this, bed 20
is
subjected to a purposefully-applied and directed force "F" impinging on top
surface
22 at least along the perimeter regions of bed 20 and any other area where
curl is
exhibited or suspected. The application of force F causes the creation of
induced
cracks 26 and broken regions 20B as described above and illustrated in FIG. 8.
The
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application of force F to bed 20 can be carried out by human and/or machine
interaction with top surface 22 of bed 20 to include one or more of manual
means,
mechanized means such as driving a piece of heavy road construction equipment
(e.g., a roller/compactor) on top surface 22, or using any other suitable
force
application technique(s) that purposefully creates non-shrinkage-based induced
cracks 26 and broken regions 20B thereby eliminating gaps 21 under bed 20 as
well
as raised edges 23 at top surface 22.
[0045] Referring additionally now to FIG. 9, the next step in the
construction
method of the present invention is the placement of non-concrete material 30
on top
surface 22 and on all edge surfaces 20E of bed 20. Non-concrete material 30 is
any
sheet(s) and/or coating(s) having the attributes described previously herein.
For
example, material 30 can be a sheet or sheets of polymer material (e.g.,
polyethylene) whose thickness can generally range from approximately 1 mil to
approximately 20 mils. Material 30 can be a single layer as shown in FIG. 9,
but
could also be realized using multiple layers such as layers 30A and 30B as
shown in
FIG. 10. Additional friction reduction is achieved by a multi-layer material
30 since
layers 30A/30B will readily slide relative to one another.
(0046] After material 30 is in place, concrete covering 40 in a plastic
state
thereof is deposited on bed 20 and material 30, as well as the regions within
and
outside of the confines of bed 20, in order to define a complete concrete slab
system whose top surface is coincident with finished slab level 300. The
placing of
concrete covering 40 can be accomplished using one or more wet concrete
14
would be understood in the art. For example, for the frame-type of bed 20 in
the
illustrated example, forms (not shown) could be placed around the inner and
outer
perimeters of bed 20, and concrete covering 40 could then be poured/deposited
between the forms and on top of non-concrete material 30 up to finished slab
level
300 as illustrated in FIG. 11. Then, additional amounts of concrete covering
40 can
be poured/deposited in gap 50 and within the region bounded by bed 20 up to
finished slab level 300 as illustrated in FIG. 12.
[0047] The advantages of the present invention are numerous. The finished
top surface of the concrete slab system need never exposed to the abuse of
construction events such as tilt-wall construction. Further, the concrete slab
system's topping can be poured/finished after a structure's roof is installed
thereby
minimizing or eliminating exposure of the slab system's finish surface to
environmental abuse. The use of a curl-free concrete covering in combination
with
the friction-reducing non-concrete barrier on the flat, induced-crack bed
ensures the
curl-free attributes of the concrete covering will not be compromised.
[0048] Although the invention has been described relative to specific
embodiments thereof, there are numerous variations and modifications that will
be
readily apparent to those skilled in the art in light of the above teachings.
It is therefore
to be understood that, within the scope of the appended claims, the invention
may be
practiced other than as specifically described.
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