U.S. patent application number 11/207909 was filed with the patent office on 2006-04-06 for unitized fibrous constructs having functional circumferential retaining elements.
Invention is credited to Gene Lamb, Paul Schmidt.
Application Number | 20060070341 11/207909 |
Document ID | / |
Family ID | 35968191 |
Filed Date | 2006-04-06 |
United States Patent
Application |
20060070341 |
Kind Code |
A1 |
Schmidt; Paul ; et
al. |
April 6, 2006 |
Unitized fibrous constructs having functional circumferential
retaining elements
Abstract
A unitized fibrous construct for providing reinforcement to
castable structures, such as cementitious structures is claimed.
The construct includes a bundle of reinforcing fibers or filaments
that are held in place prior to addition to the cementitious
mixture by a retaining element. The retaining element is of such a
composition that upon release into the cementitious mixture it
provides reinforcing capability to the cement structure. As such,
the construct adds additional reinforcing capability and diminishes
the likelihood of detrimental side-effects attributed to retaining
elements that otherwise dissolve or disperse in the cementitious
mixture.
Inventors: |
Schmidt; Paul; (Pretty
Prairie, KS) ; Lamb; Gene; (Kingman, KS) |
Correspondence
Address: |
WOOD, PHILLIPS, KATZ, CLARK & MORTIMER
500 W. MADISON STREET
SUITE 3800
CHICAGO
IL
60661
US
|
Family ID: |
35968191 |
Appl. No.: |
11/207909 |
Filed: |
August 19, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60603091 |
Aug 20, 2004 |
|
|
|
Current U.S.
Class: |
52/600 |
Current CPC
Class: |
C04B 2103/0051 20130101;
C04B 20/0048 20130101; E04C 5/076 20130101; C04B 2103/0077
20130101; C04B 40/0039 20130101; C04B 40/0039 20130101 |
Class at
Publication: |
052/740.1 |
International
Class: |
E04C 3/30 20060101
E04C003/30 |
Claims
1. A unitized fibrous construct for reinforcing a cementitious
mixture, the construct comprising: a plurality of reinforcing
filaments or fibers oriented in a generally parallel relationship
such that the plurality of reinforcing filaments or fibers form a
unit having a circumferential exterior surface; and a retaining
element that surrounds at least a portion of the circumferential
exterior surface and retains the plurality of reinforcing filaments
or fibers prior to adding the construct to the cementitious
mixture, wherein the retaining element serves as a reinforcing
element in the cementitious mixture.
2. The construct of claim 1, wherein the plurality of reinforcing
filaments and the retaining element are formed of similar
materials.
3. The construct of claim 1, wherein the plurality of reinforcing
filaments further comprise a plurality of continuous reinforcing
filaments.
4. The construct of claim 1, wherein the plurality of reinforcing
fibers further comprises a plurality of finite staple length
reinforcing fibers.
5. The construct of claim 1, wherein the plurality of reinforcing
filaments further comprises a plurality of fibrillated reinforcing
filaments.
6. The construct of claim 1, wherein the plurality of reinforcing
filaments or fibers is further defined as being imparted with
tension to impart greater dispersion upon addition to the
cementitious mixture.
7. The construct of claim 1, wherein the plurality of reinforcing
filaments or fibers further comprise splittable reinforcing
filaments or fibers.
8. The construct of claim 1, wherein the plurality of reinforcing
filaments or fibers further comprise a super absorbent polymer
composition.
9. The construct of claim 1, wherein the retaining element further
comprises a splittable filament or fiber retaining element.
10. The construct of claim 1, wherein the retaining element further
comprises a super absorbent polymer composition.
11. The construct of claim 1, wherein the retaining element
circumscribes no more than 80% of the total surface area of the
circumferential exterior surface.
12. A unitized fibrous construct for reinforcing a cementitious
mixture, the construct comprising: a plurality of reinforcing
filaments or fibers oriented in a generally parallel relationship
such that the plurality of reinforcing filaments or fibers form a
unit having a circumferential exterior surface; and a retaining
element formed of one or more splittable filaments that surrounds
at least a portion of the circumferential exterior surface and
retains the plurality of reinforcing filaments or fibers prior to
adding the construct to the cementitious mixture.
13. The construct of claim 12, wherein the plurality of reinforcing
filaments or fibers further comprise filaments or fibers having a
composition similar to the retaining element.
14. The construct of claim 12, wherein the plurality of reinforcing
filaments or fibers further comprise a plurality of fibrillated
reinforcing filaments.
15. The construct of claim 14, wherein the fibrillated filaments
are further defined as being imparted with tension.
16. The construct of claim 12, wherein the plurality of reinforcing
filaments or fibers further comprise a super absorbent polymer
composition.
17. The construct of claim 12, wherein the plurality of reinforcing
filaments or fibers further comprise a plurality of splittable
reinforcing filaments.
18. A unitized fibrous construct for reinforcing a cementitious
mixture, the construct comprising: a plurality of reinforcing
filaments or fibers oriented in a generally parallel relationship
such that the plurality of reinforcing filaments or fibers form a
unit having a circumferential exterior surface; and a retaining
element formed of a super absorbent polymer composition that
surrounds at least a portion of the circumferential exterior
surface and retains the plurality of reinforcing filaments or
fibers prior to adding the construct to the cementitious
mixture.
19. The construct of claim 18, wherein the plurality of reinforcing
filaments or fibers further comprise filaments or fibers having a
composition similar to the retaining element.
20. The construct of claim 18, wherein the plurality of reinforcing
filaments or fibers further comprise a plurality of splittable
reinforcing filaments or fibers.
21. The construct of claim 18, wherein the plurality of reinforcing
filaments or fibers further comprise a super absorbent polymer
composition.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims benefit of U.S. provisional
application No. 60/603,091, filed on Aug. 20, 2004.
FIELD OF THE INVENTION
[0002] The present invention is directed to unitized fibrous
constructs for reinforcing castable mixtures, such as cementitious
matrices or mixtures and, more particularly a unitized fibrous
construct in which the circumferential retaining element that
retains a bundle of reinforcing fibers or filaments also serves as
a reinforcing element upon mixture into the castable mixture.
BACKGROUND OF THE INVENTION
[0003] Many proposals have been made to reinforce, strengthen,
and/or reduce cracking during curing or otherwise beneficially
alter the properties of castable mixtures, such as cementitious
mixtures, by applying and/or incorporating various types of fibrous
components, including asbestos, glass, steel, as well as synthetic
polymer fibers to aqueous based concrete mixes prior to the curing
of the concrete. The types of polymer fibers in use or proposed for
use include those composed of natural and synthetic composition. As
is evident in the prior art, individual fibrous components are well
known in terms of their performance modifying attributes.
Relatively large diameter fibers, for example, in excess of 40 to
60 microns in diameter, can be added to a cementitious mixture such
as a wet concrete blend, dispersed in the blend by mechanical
agitation, followed by pouring and curing of the concrete. Large
diameter fibers serve to reinforce the concrete after it has been
cured, by providing additional tensile strength and minimizing
impact damage and crack propagation. Small diameter fibers,
typically less than 30 to 40 microns in diameter, and having a
relatively high surface area, are commonly added to concrete mixes
in order to reduce the development of small elastic shrinkage
cracks in the concrete during the curing period. The problem of
crack development is known to occur as a result of uneven curing of
the concrete. The fibrous components used typically in the practice
of reinforcing cementitious mixtures include specifically
thermoplastic synthetic fibers of finite staple length, such as
polypropylene staple fibers.
[0004] Due to the variable and unpredictable form conventional
reinforcing fibrous components have heretofore been provided for
end-use consumption, such as at a construction work-site, the
accurate and reproducible dosing of reinforcing fibrous component
into sequential batches of cementitious mixtures has been dubious
at best. Further complicating the actual utilization of the
reinforcing fibrous components, numerous synthetic thermoplastic
polymers used in the formation of suitable staple fibers are
inherently hydrophobic in nature. As a result, difficulties can
arise in obtaining a uniform dispersion and blending of the
reinforcing fibrous component throughout hydrous cementitious
mixtures using conventional mixing equipment.
[0005] Prior attempts to address the issue described have focused
on the use of binding agents. U.S. Pat. No. 5,399,195, entitled,
"Fibres and material comprising the same", issued on Mar. 21, 1995,
in the name of inventors Hansen et al., discloses the addition of
small amounts of fine (less than 30 microns) polymer fibers to
concrete. During production, the filaments are treated with a
topical wetting agent. After the filaments are chopped into
staple-length fibers, the wetting agent holds or binds the staple
fibers together in the form of micro-bundles. The micro-bundles
remain relatively stable during handling, and when the fibers are
added to the concrete mix, the wetting agent promotes dispersion of
the fibers. U.S. Pat. No. 6,258,159, entitled, "Product and method
for incorporating synthetic polymer fibers into cement mixtures",
issued on Jul. 10, 2001, in the name of inventor Pyle, attempts to
address the forming of micro-bundles of fibers by incorporation of
binding agents into the staple fibers themselves during the
melt-extrusion process.
[0006] The use of binding agents, whether internal or externally
applied, while improving in-part issues inherent of individual
staple fibers, such practices have not obviated such problems as
random agglomerate size, and further, the use of binding agents has
introduced additional problems. Most notably, the corresponding
performance of the binding agent is based upon application of the
binding agent to the reinforcement fibrous components such that the
binding agent is both uniformly applied to the majority of the
fibers so as to obtain equivalency within the batch, and that no
excess binding agent is introduced as such will adversely effect
the ability of the reinforcement fibrous components to disengage
and distribute homogeneously. One other determent encountered in
the use of binding agents is that air is often entrained within the
micro-bundles upon application and agglomeration of the staple
fibers. When such micro-bundles are subjected to mechanical mixing,
the entrained air is released as a foam, which reasonably
compromises the ability of the cementitious mixture to cure
uniformly.
[0007] Cellulosic tapes have also been utilized to retain
reinforcement fibers; however, such tapes can become problematic
for a cementitious matrix or mixture as well. See for example U.S.
Pat. No. 5,807,458, entitled, "Reinforcing Elements for Castable
Compositions", issued Sep. 15, 1998, in the name of inventors
Sanders et al. The cellulose tape is prone to degradation in the
alkaline environment of the mixture. Degradation of the tapes may
introduce void spaces within the mixture which can negatively
impact uniform curing of the cement. Further, the wet cellulose
tapes can promote mold growth within the mixture that can lead to
cracks in the setting mix.
[0008] More recently, circumferential binding elements have been
utilized to provide temporary retention of fibrous constructs, as
disclosed in commonly assigned U.S. Patent Publication
2004/0244653, entitled "Unitized Fibrous Concrete Reinforcement",
filed on Dec. 9, 2004, in the name of inventors Schmidt et al,
which is herein incorporated by reference as if set forth fully
herein. Heretofore, the circumferential binding element was
purposeful as a retaining element, but did not contribute
incremental functionality within the cementitious matrix.
[0009] As is evident in the industry, an unmet need exists for a
means of introducing reinforcing fibrous components into a
cementitious mixture such that the reinforcing fibrous components
exhibit the attributes of uniform and predictable presentation for
use, while the circumferential retaining elements, which
temporarily bind the oriented fibrous components, further provide
an advantageous and incremental performance within the cementitious
matrix.
SUMMARY OF THE INVENTION
[0010] The present invention is directed to unitized fibrous
constructs for reinforcement in a castable compound, such as a
cementitious matrices or mixtures. The invention provides for a
construct that includes a bundle of reinforcing fibers or filaments
surround, at least partially, by a retaining element, which also
serves the dual purpose, upon addition to the cementitious mixture,
of acting as a reinforcing element. In this regard, the retaining
element does not need to dissolve or otherwise be dispersible upon
addition to the cementitious mixture. As such, degradation issues
with dispersible materials are eliminated, such as issues related
to void spaces in the mixture and possible mold issues leading to
crack propagation. In addition, by creating a construct in which
the retaining element serves as a reinforcing element further
strengthening and stability of the overall cementitious mixture is
imparted from a single unitized fibrous construct.
[0011] In one embodiment of the invention a unitized fibrous
construct for reinforcing a cementitious mixture includes a
plurality of reinforcing filaments or fibers oriented in a
generally parallel relationship such that the plurality of
reinforcing filaments or fibers form a unit having a
circumferential exterior surface. The unit will those typically
form the geometry of a cylindrical bundle of filaments or fibers,
although other geometries of the unit are herein contemplated and
within the bounds of the present invention. The construct also
includes a retaining element that serves as a reinforcing element
in the cementitious mixture. The retaining element surrounds at
least a portion of the circumferential exterior surface and retains
the plurality of reinforcing filaments or fibers prior to adding
the construct to the cementitious mixture. Thus, once the construct
is formed, the circumferential retaining element aids in
maintaining the integrity of the unitized fibrous construct, and
the fibrous component therein, for purposes of shipment,
measurement, and dosing into a cementitious mixture. Typically the
retaining element will be spirally wound around the plurality of
fibers or filaments, such that the retaining element provides
temporal retention of the bundle of fibers or filaments prior to
immersion in the cementitious mixture. In most instances, minimal
spiral winding is required, less than about 30% coverage of the
surface area of the circumferential exterior surface of the unit,
so as to insure that the fibers and filaments become free from
containment upon agitation in the cementitious mixture. Upon
mechanical agitation of the unitized fibrous construct in a
cementitious mixture, the circumferential retaining element is
disrupted, allowing for the homogenous release, distribution, and
dispersion of the reinforcing filaments and fibers into the overall
cementitious mixture and release of the circumferential retaining
element itself into the mixture, which also serves as a reinforcing
element.
[0012] Typically, the retaining element will be formed of a similar
material, and in some embodiments the identical material, as is
used to form the reinforcing fibers or filaments. The
circumferential retaining element may be selected from suitable
materials that are considered structurally beneficial to a
cementitious matrix by providing additional reinforcement, minimize
impact damage, and crack propagation. Such fibrous or filamentary
material at least partially or may entirely include super absorbent
polymers, splittable fiber or filaments, and fiber or filaments
with three-dimensionality, such as coiled or crimped. Further, such
materials may consist of thermoplastic, thermoset and partially
soluble resins, which are subject to mechanical failure when a
corresponding stress and/or solvency threshold is exceeded. The
material selected may also be mechanically modified, as exemplified
by fibrillation, drawing, perforation, crimping, embossing or
molding, so as to exhibit performance attributes in the
cementitious matrix such as a reinforcement or elastic shrinkage
crack reduction.
[0013] Various geometries may be employed in the application of the
circumferential retaining element, including without limitation,
continuous or discontinuous filaments, ribbons, or sheets, which
circumscribe the combined, essentially parallel reinforcing fibrous
components. It is within the purview of the present invention that
the composition of the circumferential retaining elements and of
one or more of the reinforcing fibrous components need not
necessarily be the same.
[0014] It is further within the purview of the present invention
that the retaining element may be placed under additional tension
by means of twisting the retaining element. Placing additional
tension on the retaining element facilitates the mechanical removal
of the retaining element upon mechanical agitation, which then
enhances the fiber distribution within a cementitious mixture.
[0015] It is also noted that while the present embodiment includes
a single retaining element it is possible, and within the inventive
concepts herein disclosed, for more than one retaining element to
be used in connection with a single unitized reinforcing construct.
For example, two reinforcing elements may be spirally wound around
the unit of fibers or filaments in a double-helix type
arrangement.
[0016] The reinforcing filaments are continuous filaments and in
fiber embodiments the fibers are finite staple-length fibers.
Additionally, the reinforcing filaments may be characterized as
fibrillated reinforcing filaments. The reinforcing filaments or
fibers may be imparted with tension during processing to insure
that the degree of dispersion necessary occurs once the bundle of
filaments or fibers are free from retention within the cementitious
mixture. In alternate embodiments the reinforcing filaments or
fibers may be splittable filaments or fibers or may be formed from
a super absorbent polymer composition.
[0017] In another embodiment the unitized fibrous construct for
reinforcing a cementitious mixture includes a plurality of
reinforcing filaments or fibers oriented in a generally parallel
relationship such that the plurality of reinforcing filaments or
fibers form a unit having a circumferential exterior surface. The
construct also includes a retaining element formed of one or more
splittable filaments that surround at least a portion of the
circumferential exterior surface and retains the plurality of
reinforcing filaments or fibers prior to adding the construct to
the cementitious mixture. Typically, the splittable filaments will
provide reinforcing capabilities once they have been added to the
cementitious mixture
[0018] The reinforcing filaments or fibers may have a composition
similar to or identical to the composition of the splittable
filament retaining element. Additionally, the plurality of
reinforcing filaments or fibers may be defined as fibrillated
reinforcing filaments, which may be imparted with tension to
further encourage dispersion upon release from the retaining
element. The reinforcing filaments or fibers may further be defined
as being formed from a super absorbent polymer composition.
[0019] In yet another embodiment the unitized fibrous construct for
reinforcing a cementitious mixture includes a plurality of
reinforcing filaments or fibers oriented in a generally parallel
relationship such that the plurality of reinforcing filaments or
fibers form a unit having a circumferential exterior surface. The
construct also includes a retaining element formed of a super
absorbent polymer composition that surrounds at least a portion of
the circumferential exterior surface and retains the plurality of
reinforcing filaments or fibers prior to adding the construct to
the cementitious mixture. Typically, the super absorbent polymer
composition retaining elements will provide reinforcing
capabilities once they have been added to the cementitious
mixture.
[0020] The reinforcing filaments or fibers may have a composition
similar to or identical to the composition of the super absorbent
polymer composition retaining element. Additionally, the plurality
of reinforcing filaments or fibers may be defined as fibrillated
reinforcing filaments, which may be imparted with tension to
further encourage dispersion upon release from the retaining
element. The reinforcing filaments or fibers may further be defined
as being formed from a super absorbent polymer composition.
[0021] Thus, the present invention is able to provide for a
cementitious reinforcing construct that includes a retaining
element that imparts reinforcing structure into the cementitious
mixture. Such a construct benefits from not having a retaining
structure that disperses or otherwise dissolves in the aqueous
cementitious mixture and imparts possible negative side-effects to
the cementitious mixture, such as voids, strength reducing mold and
the like. Additionally, the reinforcing aspect of the retaining
element provides for a construct that is able to provide additional
per unit reinforcement of the cement mixture.
BRIEF DESCRIPTION OF THE DRAWING
[0022] FIG. 1 is an illustrative embodiment of the unitized fibrous
construct of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0023] While the present invention is susceptible of embodiments in
various forms, hereinafter the present invention is described by
presently preferred embodiments with the understanding that the
present disclosure is to be considered as an exemplification of the
invention, and is not intended to limit the invention to the
specific embodiment illustrated.
[0024] Referring to FIG. 1, therein is illustrated an embodiment of
a unitized fibrous construct of the present invention. The unitized
fibrous construct is added to a castable mixture, such as a
cementitious mixture to provide added reinforcement, resulting in
greater strength, stability and crack-resistance. The unitized
fibrous construct 10 is defined herein as a construct including a
plurality of oriented reinforcing continuous filaments or finite
staple length fibers 12. The filaments or fibers 12 are arranged in
a general parallel relationship such that the filaments or fibers
form a bundle. While the bundle will typically have a general
cylindrical shape, the bundle may also have any other shape, for
example oval, square, triangular, etc. The plurality of filaments
or fibers 12 will be bundled such that they form a circumferential
exterior surface 14.
[0025] The construct further includes one or more retaining
elements 16 that surround at least a portion of the circumferential
exterior surface 14 and serve to retain the reinforcing filaments
or fibers 12 prior to adding the construct 10 to a castable
mixture, such as a cementitious mixture. The retaining element will
serve as a reinforcing element upon once added to the castable
mixture, such as a cementitious mixture.
[0026] In order for the retaining element 16 to serve as a
reinforcing element upon addition to the castable mixture the
retaining element will typically be formed of a similar, and in
some embodiments identical, fibrous or filamentary material,
denier, and length as the reinforcing fibers or filaments 12.
Further still, in alternate embodiment the retaining element 16 may
be of a dissimilar fibrous or filamentary material, denier, and
length as the reinforcing fibers or filaments 12. In those
embodiments in which the retaining element is a dissimilar fibrous
or filamentary material compared to the reinforcing fibers or
filaments, the retaining element will be formed of a material that
allows for the retaining element to provide reinforcing
characteristics upon addition to the castable mixture.
[0027] Typically, the unitized fibrous construct of the present
invention is formed from a plurality of reinforcing fibrous or
filamentary components and one or more circumferential retaining
elements. The composition of such reinforcing fibers and
circumferential retaining element may be formed from any suitable
synthetic polymers, including, but not limited to, thermoplastic
and thermoset polymers, including polyesters, polyolefins, such as
polypropylene and polypropylene copolymers, polyethylene and
polyethylene copolymers, polyamides, polyimides, polylactic acid,
polyhydroxyalkanoate, polyvinyl alcohol, ethylene vinyl alcohol,
polyacrylates, copolymers thereof, and the combinations thereof.
Additionally the reinforcing fibers or filaments and the
circumferential retaining element may be formed from any suitable
natural fibers, including, but not limited to rayon, cotton, pulp,
flax, and hemp and the combinations thereof. A particularly
preferred embodiment of the present invention is directed to
reinforcing fibers or filaments including polyolefin thermoplastic
resins.
[0028] In one embodiment of the invention the retaining element
that surrounds a portion of the exterior surface includes
splittable filaments, which may be of similar or dissimilar
polymeric composition in relation to the reinforcing fibers or
filaments. Suitable splittable fibers are taught in U.S. Pat. No.
6,838,402, issued on Jan. 4, 2005, in the name of inventors Harris,
et al.; U.S. Pat. No. 6,746,766, issued on Jun. 18, 2004, in the
name of inventors Bond, et al.; U.S. Pat. No. 6,743,506, issued on
Jun. 1, 2004, in the name of inventors Bond et al.; and U.S. Pat.
No. 6,444,312, issued on Sep. 9, 2002, in the name of inventor
Dugan, all of which are herein incorporated by reference as if set
forth fully herein.
[0029] In embodiments in which the retaining element is splittable
filaments, the plurality of reinforcing filaments may be
fibrillated, wherein the filaments may be fibrillated by any
conventional fibrillation technique, such as by mechanical
fibrillation described in U.S. Pat. No. 3,302,501, issued on Feb.
7, 1967, in the name of inventor Greene; U.S. Pat. No. 3,496,260,
issued Feb. 17, 1970, in the name of inventors Guenther et al.;
U.S. Pat. No. 3,550,826, issued Dec. 29, 1970; in the name of
inventor Salmela; and U.S. Pat. No. 3,756,484, issued Sep. 4, 1973,
in the name of inventor Guenther, or by fluid and sonic
fibrillation as disclosed in U.S. Pat. No. 3,345,242, issued Oct.
3, 1967, in the name of inventor Rasmussen, all of which are hereby
incorporated by reference as if set forth fully herein. In
addition, the reinforcing filaments may be imparted with tension by
way of twisting the filaments as well. Tension imparted in the
reinforcing filaments will cause greater dispersion of the
filaments once the retaining element has been removed from the
construct/bundle of filaments.
[0030] Additionally, in embodiments in which the retaining element
is splittable filaments, the plurality of reinforcing fibers or
filaments may be formed from a super absorbent polymer composition.
Exemplary super absorbent polymers are disclosed in U.S. Pat. No.
5,145,609, issued Sep. 8, 1992, in the name of inventor Chambers;
U.S. Pat. No. 4,820,773; issued Apr. 11, 1989, in the name to
inventors Alexander et al.; and U.S. Pat. No. 4,645,039, issued
Mar. 31, 1997; in the name of inventor Brandt et al., all of which
are herein incorporated by reference as if set forth fully
herein.
[0031] In another embodiment of the invention the retaining element
that surrounds a portion of the exterior surface may include a
super absorbent polymer composition. Exemplary super absorbent
polymers are disclosed in the previously referenced and
incorporated patents.
[0032] In those embodiments in which the retaining element is
formed of a super absorbent polymer composition, the reinforcing
fibers may include splittable fibers. Suitable splittable fibers
are taught in the previously referenced and incorporated
patents.
[0033] According to the present invention, the retaining element
surrounds at least a portion of the circumferential exterior
surface of the construct. Once formed, the retaining element aids
in maintaining the integrity of the unitized fibrous construct, and
the reinforcing fibrous component therein, for the purposes of
shipment, measurement, and dosing into a cementitious mixture. Upon
mechanical agitation, and optionally exposure to appropriate
solvents, the unitized fibrous construct in a cementitious mixture,
the retaining element are disrupted, allowing for the homogenous
release, distribution, and disbursement of the reinforcing fibrous
component into the overall cementitious mixture. The unitized
fibrous construct of the present invention is believe to reduce
plastic shrinkage cracking by at least 10% per ASTM 1399, Obtaining
Average Residual Strength of Fiber Reinforced Concrete.
[0034] A number of suitable methodologies exist for the formation
of unitized fibrous constructs in accordance with the present
invention. A preferred, though non-limiting, method is taught in
part by U.S. Pat. No. 4,228,641, issued on Oct. 1, 1980, in the
name of inventors O'Neil, this patent is herein incorporated by
reference as if set forth fully herein. The '641 O'Neil patent
teaches a twine including a core bundle of synthetic monofilaments
circumscribed by a synthetic material in a thin band form spirally
wound about the monofilaments. It has been found by the inventors
of the present invention that by practice of the method taught in
the '641 O'Neil patent, with subsequent and repeated scission of
the continuous twine construct at or between each iteration of the
spiral winding that finite length unitized fibrous constructs are
formed which are suitable for practice in light of the present
invention.
[0035] The dimensions of the retaining element is defined in terms
of the overall circumference of the exterior surface formed by the
reinforcing fibers or filaments, as based on the quantity and
relative denier of the individual reinforcing fibrous components,
and of length, as based on the greatest finite staple length of the
cumulative combination of reinforcing fibrous components. Suitable
overall circumferences and lengths of the circumferential retaining
elements formed in accordance with the present invention may
reasonably range from 3 mm to 150 mm and from 8 mm to 100 mm,
respectively. In a presently preferred embodiment for standard
practices, circumferential retaining elements exhibit an overall
diameter of between 3 mm and 30 mm and lengths of between 12 mm and
50 mm may be utilized. Further, the circumferential retaining
elements may exhibit a width preferably about 1%-50% of the total
diameter of the unitized fibrous construct, more preferably about
3%-40% of the total diameter of the unitized fibrous construct, and
most preferably about 5%-30% of the total diameter of the unitized
fibrous construct. Further still, the circumferential retaining
element is preferably about 2%-50% by weight of the unitized
construct including parallelized reinforcement fibers, more
preferably of about 6%-40% by weight of the unitized construct, and
most preferably of about 8%-30% weight of the unitized
construct.
[0036] The circumferential retaining element may include one or
more continuous or discontinuous filaments, ribbons, or sheets of
varying thicknesses that retain the reinforcing fibrous components
by a plurality of wrapping techniques so as to expose more or less
fiber to the external environment. For instance, two thin
circumferential retaining elements may be used in a double helix
wrapping technique, whereby two circumferential retaining elements
criss-cross back and forth about the circumference of the fibrous
components.
[0037] Thus, the present invention is able to provide for a
cementitious reinforcing construct that includes a retaining
element that imparts reinforcing structure into the cementitious
mixture. Such a construct benefits from not having a retaining
structure that disperses or otherwise dissolves in the aqueous
cementitious mixture and imparts possible negative side-effects to
the cementitious mixture, such as voids, strength reducing mold and
the like. Additionally, the reinforcing aspect of the retaining
element provides for a construct that is able to provide additional
per unit reinforcement of the cement mixture.
[0038] From the foregoing, it will be observed that numerous
modifications and variations can be affected without departing from
the true spirit and scope of the novel concept of the present
invention. It is to be understood that no limitation with respect
to the specific embodiments illustrated herein is intended or
should be inferred. The disclosure is intended to cover, by the
appended claims, all such modifications as fall within the scope of
the claims.
* * * * *