WO2000006851A1

WO2000006851A1 - Concrete reinforcing system having non-corrosive bendable flanges

Info

Publication number: WO2000006851A1
Application number: PCT/US1999/016436
Authority: WO
Inventors: William M. Stecker
Original assignee: Surface Technologies, Inc.
Priority date: 1998-07-27
Filing date: 1999-07-20
Publication date: 2000-02-10
Also published as: AU5116799A

Abstract

Non-corrosive concrete reinforcing systems include a plurality of elongated non-corrosive flanges, transverse partitions, and a holder for maintaining the flanges in spaced-apart, substantially parallel relationship. Each holder includes a plurality of slots, each of which is configured to removably secure a longitudinal edge of a respective one of the flanges. At least one of the flange faces may have a non-planar surface portion for improving concrete adhesion thereto.

Description

CONCRETE REINFORCING SYSTEM HAVING NON-CORROSIVE BENDABLE FLANGES

Field of the Invention

The present invention relates generally to reinforcing systems and, more particularly, to reinforcing systems for strengthening concrete.

Background of the Invention Concrete and other masonry or cementitious materials have high compressive strength, but relatively low tensile strength. When concrete is employed as a structural member, such as in a building, bridge, pipe, pier, culvert, or the like, it is conventional to incorporate reinforcing members to enhance the tensile strength of the structure. Historically, the reinforcing members are steel or other metal reinforcing rods or bars, i.e., "rebar" .

Such reinforcing members may be placed under tension to form prestressed concrete structures .

Although steel and other metals can enhance the tensile strength of a concrete structure, they are susceptible to oxidation. For example, ferrous metal rusts by the oxidation thereof to the corresponding oxides and hydroxides of iron by atmospheric oxygen in the presence of water. When it is poured, concrete is normally at a pH of 12 to 14 (i.e., at high alkalinity) due to the presence of hydroxides of sodium, potassium, and calcium formed during the hydration of the concrete. As long as a pH in this range is maintained, steel within the concrete is passive, which may result in long-term stability and corrosion resistance. Exposure to a strong acid, or otherwise lowering the pH of concrete, can cause steel contained in concrete to become corroded. For example, chlorine ions permeating into the concrete can cause corrosion. Sources of chlorine ions include road salt, salt air in marine environments, and salt -contaminated aggregate (e.g., sand) used in making the concrete. When the reinforcing steel corrodes, it can expand and create internal stresses in the concrete. These internal stresses can lead to cracking, and ultimately disintegration, of the concrete. Moreover, cracking and crumbling concrete may expose additional steel to atmospheric oxygen, water, and sources of chlorine ions .

Various solutions to the corrosion problem of steel rebar have been offered. Non-corrosive coatings on the concrete, the steel rebar, or both have been proposed. For example, U.S. Patent No. 5,271,193 to Olsen et al . proposes a steel-reinforced concrete product, such as a manhole cover, having a coating of a corrosion-resistant gel coat layer and an intermediate layer of fiberglass between the concrete and the gel coat layer. The gel coat layer is described as being a "hardenable polymeric fluid material." U.S. Patent No. 4,725,491 to Goldfein proposes steel rebar members having chemical conversion iron oxide coatings, such as black iron oxide. U.S. Patent No. 5,100,738 to Graf proposes steel rebar having an outer layer of a synthetic material (e.g., epoxy resin) and an intermediate layer of aluminum or aluminum alloy between the outer layer and the steel. Unfortunately, in general these exemplary coatings tend to be expensive and have received mixed results and acceptance .

There has also been interest in replacing steel with various fiber-reinforced resins. For example, U.S. Patent No. 5,580,642 to Okamoto et al . proposes a reinforcing member for civil and architectural structures made from a mixture of reinforcing fibers and thermoplastic fibers. U.S. Patent No. 5,613,334 to Petrina proposes a non-metallic laminated composite reinforcing rod for use in reinforced or prestressed concrete. A corrosion- resistant fiber-reinforced rebar, disclosed in U.S. Patent No. 5,650,109 to Kaiser et al . comprises a fiber reinforced thermoset core and an outer cladding formed of sheet molding compound (SMC) . These materials are formed into rebar through modified pultrusion processes .

Some rebar components are desirably curved or bent in order to follow the contour of the surrounding concrete structures. Unfortunately, rebar formed from fiber-reinforced resins may be difficult to bend in the field without causing the rebar to crack or break. Forming non- linear articles via pultrusion processes may also be troublesome. Because pultrusion involves pulling material through an elongated heated die which at least partially cures, and therefore stiffens, the pultruded article, establishing bends or curves in the articles without sacrificing the advantages provided by pultrusion may be problematic.

Summary of the Invention

It is therefore an object of the present invention to provide non-corrosive reinforcing structures for use within concrete structures.

It is also an object of the present invention to provide non-corrosive reinforcing structures for use within concrete that increases the strength of concrete . It is another object of the present invention to provide non-corrosive reinforcing structures that are easily bendable into various configurations .

These and other objects of the present invention are provided by a reinforcing system for concrete including a plurality of elongated non- corrosive flanges, and a non-corrosive holder for maintaining the flanges in spaced-apart, substantially parallel relationship. Each flange has opposite faces, opposite longitudinal edges, and opposite ends. The holder includes a plurality of slots, each of which is configured to removably secure a longitudinal edge of a respective one of the flanges. According to one aspect of the present invention, a longitudinal edge of each flange includes an enlarged portion. Each slot in a holder includes an enlarged portion configured to receive the enlarged longitudinal edge portion of a respective flange.

At least one of the flange faces may have a non-planar surface portion for improving concrete adhesion thereto. The non-planar surface portion may be added during or after flange-forming operations. Preferably, at least one of the flanges is formed from fiber-reinforced thermosetting resin material. Fibers within the resin material may be formed from glass, carbon, metal, aromatic polyamides, polybenzimidazoles, aromatic polyimides, polyethylene, nylon, and blends and hybrids thereof, and preferably are unidirectional. A flange holder may be formed from a non- corrosive material different from the flange material. Exemplary materials include thermoplastics, aluminum, and the like. Furthermore a concrete reinforcing system may include a plurality of holders along a span of flanges for maintaining the flanges in spaced-apart, substantially parallel relationship.

A concrete reinforcing system may include one or more transverse partitions intersecting and cooperating with one or more flanges. Slots may be provided in both transverse partitions and flanges to permit cooperation therebetween. Slots in a flange holder may also be configured to receive both longitudinal edges of a respective flange. Furthermore, slots in a flange holder may be configured to removably secure two flanges in end-to-end abutting relationship. According to another aspect of the present invention, a reinforced structure of cementitious material includes a mass of cementitious material; a plurality of elongated non-corrosive flanges; and holders for removably securing the flanges in spaced- apart, substantially parallel relationship. Exemplary cementitious materials within which the present invention may be utilized includes, but is not limited to, Portland cement.

The present invention is advantageous because the non-corrosive flange and holder materials are resistant to harsh environmental conditions. Furthermore, a reinforcing structure having the same cross-sectional area as a round rebar structure has more surface area than the corresponding round rebar structure, and is stronger. Also, concrete flows easily around the thin flanges and transverse partitions. Flanges according to the present invention can be bent into various configurations by hand in the field, thereby decreasing the time required to install a reinforcing structure prior to pouring concrete.

Brief Description of the Drawings Fig. 1 is a perspective view of a concrete reinforcing system, according to aspects of the present invention. Figs. 2A and 2B illustrate cross-sectional views of different flange embodiments of a concrete reinforcing system according to the present invention.

Fig. 3 illustrates a flange holder configured to removably secure two flanges in end-to-end abutting relationship .

Fig. 4 illustrates transverse partitions intersecting and cooperating with flanges of a concrete reinforcing system according to the present invention. Fig. 5 is a cross-sectional view of the concrete reinforcing system in Fig. 4 taken along lines 5-5.

Fig. 6 illustrates non-planar portions on the face of a flange. Fig. 7 illustrates a non-planar sinusoidal pattern for the face of a flange according to an embodiment of the present invention.

Fig. 8 is a cut-away plan view of a concrete reinforcing system according to the present invention embedded in concrete.

Detailed Description of the Invention

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout .

Referring now to Fig. 1, a non-corrosive, concrete reinforcing system 10, according to an embodiment of the present invention, is illustrated. The illustrated concrete reinforcing system 10 includes a plurality of elongated, non-corrosive flanges 12 arranged in spaced-apart, face-to-face, substantially parallel relationship by a flange holder 14. Each flange 12 has opposite faces 16a, 16b, opposite longitudinal edges 18a, 18b, and opposite ends 20a, 20b. As will be described in detail below, each flange 12 is preferably formed from a noncorrosive material, such as, but not limited to, fiber-reinforced thermosetting resin. Reinforcing structures according to the present invention may be configured by hand in the field into various configurations without requiring the use of complex bending tools and the like. It is to be understood that different numbers and configurations of flanges 12 and holders 14 may be utilized without departing from the spirit and intent of the present invention. The present invention is not limited to reinforcing structures having a particular number of flanges or to flanges spaced-apart substantially equidistantly . Multiple flange holders 14 can be used to achieve virtually any desired flange configuration.

In the illustrated embodiment, flange holder 14 includes an upper portion 22 and a lower portion 24, each of which serves as means for removably securing a plurality of flanges 12 in spaced-apart, substantially parallel relationship. Flange holder upper and lower portions 22, 24 each have multiple slots 26 configured to receive a respective flange longitudinal edge. The slots 26 in the lower portion 24 are configured to receive longitudinal edges 18b, and the slots 26 in the upper portion 22 are configured to receive longitudinal edges 18a, as illustrated. Referring now to Figs. 2A and 2B, cross- sectional views of different flange embodiments are illustrated. In Fig. 2A, the longitudinal edges of the illustrated flange 12 are enlarged with respect to the thickness of the flange. In Fig. 2B, the illustrated flange 12 has a constant thickness. Slots in a particular flange holder are preferably configured to have a mating configuration for the longitudinal edges of the flanges to be secured therein. For example, the holder slots 26 illustrated in Fig. 1 have an enlarged portion 27 for receiving the enlarged longitudinal edges of the illustrated flanges 12. The longitudinal edges of flanges utilized according to the present invention may have many configurations and are not limited to those illustrated. It is to be understood that the upper and lower portions 22, 24 of the flange holder 14 may be utilized in accordance with the present invention either separately or jointly. In addition, the upper and lower portions 22, 24 of the flange holder 14 may be joined together to form a unitary holder. The longitudinal edges 18a and 18b may be snapped into respective upper and lower portion slots 26. Alternatively, the end portion 20a of each flange 12 may be inserted into a respective slot 26. According to another embodiment, each slot 26 within a flange holder 14 may be configured to receive both longitudinal edges 18a, 18b of a respective flange 12. As illustrated in Fig. 3, a flange holder slot 26 also may be configured to removably secure two flanges 12 in end-to-end abutting relationship.

Referring now to Figs. 4 and 5, transverse partitions 30 may intersect and cooperate with the flanges 12 of the non-corrosive, composite reinforcing system 10. The transverse partitions 30 facilitate maintaining the flanges 12 in substantially equidistant, spaced-apart relationship and provide additional strength to the reinforcing system 10. In the illustrated embodiment, each transverse partition 30 has slots 31 therein which cooperate with respective slots 33 in each of the flanges 12.

However, the present invention is not limited to the illustrated embodiment. Transverse partitions having various configurations may be utilized and various ways of joining the transverse partitions with the flanges may be utilized. In addition, various numbers of transverse partitions may be utilized, without limitation. Preferably, the transverse partitions are formed from the same or similar non- corrosive material to that of the flanges. A particularly preferred material is fiber-reinforced thermosetting resin.

Preferably, the flanges 12 have relatively thin cross-sectional dimensions (i.e., thickness) to facilitate bending. Listed below in Table 1 are exemplary thicknesses for various sizes of flanges.

Table 1

Flange Width Flange Thickness 2.25 inches 0.098 inch 2.0 inches 0.075 inch

1.625 inches 0.060 inch 0.50 inch 0.050 inch

The thin cross section of a flange creates a high modulus to volume ratio in plane with the width of the flange. Furthermore, reinforcing structures according to the present invention have greater surface area than conventional round rebar even though the cross- sectional area may be the same. As set forth in Table 2 below, four flanges of various sizes are compared with round rebar having the equivalent cross-sectional area.

Table 2

Size Cross-Sect. Area Surface Area

Flanged 2.25"x2.25' .44 in 9.39 in' Round 0.75" OD 44 in-^* 2.36 in²

Flanged 2 . 0 "x2 . 0 " 31 in' 8 . 3 i ' Round 0 . 625 " OD 31 in" 1 . 96 in² Flanged 1.625 "xl .625" .25 in² 6.74 in²

Round 0.50" OD .25 in² 1.57 in²

Flanged 0.50"x0.50" .11 in² 4.2 in² Round 0.375" OD .11 in² 1.17 in²

In contrast with round rebar, more surface area is available for concrete to adhere to using the flanged reinforcing structure of the present invention. Referring now to Fig. 6, portions of a flange face may be non-planar as a result of crimping, embossing, and similar operations. In the illustrated embodiment of Fig. 6, the face portions 40 of a flange 12 have a generally crimped configuration. The crimped, non-planar flange surface increases adhesion of concrete to the flange 12. Flange strength is increased, as well. Those skilled in this art will appreciate that non-planar flange surfaces can take any number of configurations known to those skilled in this art to improve the mechanical bond between the flange

12 and a surrounding concrete structure. For example, Fig. 7 illustrates a sinusoidal pattern 41 for face portions of a flange 12, according to another embodiment of the present invention. Portions of a flange face may be sprayed with material to form a non- planar surface thereon for improving concrete adhesion thereto. Various types of materials may be utilized, including thermoplastic and thermosetting materials. Referring now to Fig. 8, a reinforced concrete structure 50 according to aspects of the present invention is illustrated. The reinforced concrete structure 50 contains a non-corrosive, reinforcing system 10 surrounded by a mass of cementitious material 52. Exemplary cementitious materials include Portland cement, as well as sand, water and aggregate mixtures. The illustrated reinforcing structure 10 is bent approximately 90° to conform with the shape of the concrete structure 50. Reinforcing structures according to the present invention can conform to virtually any concrete configuration desirable.

The present invention also anticipates that the flanges, holders, and/or transverse partitions of reinforcing structures according to the present invention may include various types of connectors for connecting additional flanges, holders and/or transverse partitions thereto. Accordingly, multiple reinforcing structures can be can be linked together.

Flange Holder Materials

Preferably, flange holders according to the present invention are formed from non-corrosive materials such as thermoplastics, aluminum, and the like. Furthermore, various techniques may be utilized to manufacture flange holders, according to the present invention. Flange holder material strength should be sufficient to resist deformation caused by the forces of concrete being poured thereon. Flange holders according to the present invention also may be formed from flexible material to facilitate bending. Flange Materials Flanges may be fabricated via various methods. A particularly preferred fabrication method includes pultrusion, as described in co-pending and co- assigned patent application number

(attorney docket number 5460-52), which is incorporated herein by reference, in its entirety. Conventional pultrusion processes involve drawing a bundle of reinforcing material (e.g., glass filaments or fibers) from a source thereof, wetting the fibers and impregnating them (preferably with a thermosettable polymer resin) by passing the reinforcing material through a resin bath in an open tank, pulling the resin-wetted and impregnated bundle through a shaping die to align the fiber bundle and to manipulate it into the proper cross-sectional configuration, and curing the resin in a die mold while maintaining tension on the filaments. Because the fibers progress completely through the pultrusion process without being cut or chopped, the resulting products generally have exceptionally high tensile strength in the longitudinal (i.e., in the direction the filaments are pulled) direction. Exemplary pultrusion techniques are described in U.S. Patent Nos . 3,793,108 to Goldsworthy; 4,394,338 to Fuway; 4,445,957 to Harvey; and 5,174,844 to Tong, the disclosures of which are incorporated herein by reference in their entirety.

Preferably, reinforcing fibers utilized within the flanges are unidirectional. Unidirectional fibers are preferably oriented to be substantially parallel with the longitudinal direction of each flange. In this configuration, the fibers can enhance the tensile and flexural strength and rigidity of a flange. In addition, it is preferred that unidirectional fibers are located along or near the surface of each flange. By having fibers along the surface of a flange, contact can be made directly between the concrete and the fibers. Contact between the concrete and the fibers increases the strength of the flange. Accordingly, the more fibers at the surfaces of each flange, the stronger the reinforcing structure is within concrete. A fibrous mat is also contemplated . Preferably, a thermosetting resin is used to form the flanges. The term "thermosetting" as used herein refers to resins which irreversibly solidify or "set" when completely cured. Suitable thermosetting resins include unsaturated polyester resins, phenolic resins, vinyl ester resins, polyurethanes, and the like, and mixtures and blends thereof. Particularly preferred thermosetting resins are ATLAC™ 31727-00 and POLYLITE™ 31041-00, available from Reichhold Chemicals, Inc., Research Triangle Park, North Carolina. Additionally, the thermosetting resins useful in the present invention may be mixed or supplemented with other thermosetting or thermoplastic resins. Exemplary supplementary thermosetting resins include epoxies . Exemplary thermoplastic resins include polyvinylacetate, styrene-butadiene copolymers, polymethylmethacrylate, polystyrene, cellulose acetatebutyrate, saturated polyesters, urethane- extended saturated polyesters, methacrylate copolymers, polyethylene terephthalate (PET) , and the like in a manner known to one skilled in the art.

Unsaturated polyester, phenolic and vinyl ester resins are the preferred thermosetting resins of the present invention, such as described in U.S. Patent No. 5,650,109 to Kaiser et al . , the disclosure of which is incorporated herein by reference in its entirety. Suitable unsaturated polyester resins include practically any esterification product of a polybasic organic acid or anhydride and a polyhydric alcohol, wherein either the acid or the alcohol, or both, provide the reactive ethylenic unsaturation. Typical unsaturated polyesters are those thermosetting resins made from the esterification of a polyhydric alcohol with an ethylenically unsaturated polycarboxylic acid. Examples of useful ethylenically unsaturated polycarboxylic acids include maleic acid, fumaric acid, itaconic acid, dihydromuconic acid and halo and alkyl derivatives of such acids and anhydrides, and mixtures thereof. Exemplary polyhydric alcohols include saturated polyhydric alcohols such as ethylene glycol , 1 , 3-propanediol , propylene glycol, 1 , 3-butanediol , 1,4- butanediol, 2-ethylbutane-l , 4-diol , 1 , 5-pentanediol , 1 , 6-hexanediol , 1 , 7-heptanediol , 1 , 8-octanediol , 1,4- cyclohexanediol , 1 , 4-dimethylolcyclohexane, 2,2- diethylpropane-1 , 3-diol , 2 , 2-diethylbutane-l , 3-diol , 3- methylpentane-1, 4-diol , 2 , 2-dimethylpropane-l , 3 -diol , 4 , 5-nonanediol , diethylene glycol, triethylene glycol, dipropylene glycol, glycerol , pentaerythritol , erythritol , sorbitol, mannitol, 1,1,1- trimethylolpropane, trimethylolethane, hydrogenated bisphenol-A and the reaction products of bisphenol-A with ethylene or propylene oxide.

The flange resin can be formed by the addition of recycled PET, such as from soda bottles to the base resin prior to polymerization. PET bottles can be ground and depolymerized in the presence of a glycol, which produces an oligomer. The oligomer can then be added to a polymerization mixture containing polyester monomer and polymerized with such monomer to an unsaturated polyester. Unsaturated polyester resins can also be derived from the esterification of saturated polycarboxylic acid or anhydride with an unsaturated polyhydric alcohol. Exemplary saturated polycarboxylic acids include oxalic acid, malonic acid, succinic acid, methylsuccinic acid, 2 , 2-dimethylsuccinic acid, 2,3- dimethylsuccinic acid, hydroxylsuccinic acid, glutaric acid, 2-methylglutaric acid, 3-methylglutaric acid, 2 , 2-dimethylglutaric acid, 3 , 3-dimethylglutaric acid, 3 , 3 -diethylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, tetrabromophthalic acid, tetrahydrophthalic acid, 1 , 2-hexahydrophthalic acid, 1 , 3-hexahydrophthalic acid, 1 , 4-hexahydrophthalic acid, l , l-cyclobutanedicarboxylic acid and trans-1,4- cyclohexanedicarboxylic acid.

Unsaturated polyhydric alcohols which are suitable for reacting with the saturated polycarboxylic acids include ethylenic unsaturation-containing analogs of the above saturated alcohols (e . g . , 2-butene-l , 4- diol) .

Suitable phenolic resins include practically any reaction product of a aromatic alcohol with an aldehyde. Exemplary aromatic alcohols include phenol, orthocresol, metacresol, paracresol , Bisphenol A, p- phenylphenol , p-tert-butylphenol , p-tert-amylphenol , p- tert-octylphenol and p-nonylphenol. Exemplary aldehydes include formaldehyde, acetaldehyde, propionaldehyde, phenylacetaldehyde, and benzaldehyde . Particularly preferred are the phenolic resins prepared by the reaction of phenol with formaldehyde.

Suitable vinyl ester resins include practically any reaction product of an unsaturated polycarboxylic acid or anhydride with an epoxy resin. Exemplary acids and anhydrides include (meth) acrylic acid or anhydride, α-phenylacrylic acid, α- chloroacrylic acid, crotonic acid, mono-methyl and mono-ethyl esters of maleic acid or fumaric acid, vinyl acetic acid, cinnamic acid, and the like. Epoxy resins which are useful in the preparation of the polyvinyl ester are well known and commercially available. Exemplary epoxies include virtually any reaction product of a polyfunctional halohydrin, such as epichlorohydrin, with a phenol or polyhydric phenol. Suitable phenols or polyhydric phenols include for example, resorcinol, tetraphenol ethane, and various bisphenols such as Bisphenol-A, 4 , 4 ' -dihydroxydiphenyl- sulfone, 4,4' -dihydroxy biphenyl , 4,4' -dihydroxydi- phenylmethane, 2 , 2 ' -dihydroxydiphenyloxide, and the like.

Typically, the resin also includes a vinyl monomer in which the thermosetting resin is solubilized. Suitable vinyl monomers include styrene, vinyl toluene, methyl methacrylate, p-methyl styrene, divinyl benzene, diallyl phthalate and the like.

Styrene is the preferred vinyl monomer for solubilizing unsaturated polyester or vinyl ester resins.

The thermosetting resin may be thickened during the manufacturing process of the flanges. The term "thickened" as used herein relates to an increase in viscosity of the resin such that the resin is transformed from a liquid to a nondripping paste form. This is often achieved by partial curing or so-called "B-staging" the resin. The term "partial curing" as used herein refers to incompletely polymerizing the resin by initiating polymerization and subsequently arresting the polymerization or controlling the polymerization so that full cure occurs at a later time . Thickening or partial curing may be achieved in a variety of ways. For example, the thermosetting resin may be thickened by the inclusion of a thickening agent. Suitable thickening agents are commonly known to those skilled in the art and include crystalline unsaturated polyesters, polyurethanes, alkali earth metal oxides and hydroxides, and polyureas . Often, the thickening agent cooperates with the conditions within a shaping fixture (such as a shaping die) to thicken or partially cure the thermosetting resin. The conditions within the fixture which are required to effect the thickening or partial cure of the thermosetting resin are dependent upon the thickening agent employed, and are discussed in detail below.

Suitable resins employing a crystalline polyester thickening agent are described in U.S. Patent No. 3,959,209 to Lake, the disclosure of which is incorporated herein by reference in its entirety. Typically, in an embodiment of the present invention wherein the thermosetting resin is thickened with a crystalline polyester, the thermosetting resin comprises a thermosetting resin solubilized in a vinyl monomer. The crystalline polyesters useful in the present invention are generally ethylenically unsaturated, and react with the vinyl monomer, although one skilled in the art will appreciate that saturated crystalline polyesters may also be employed.

Methods of preparing crystalline polyester are well known in the art and include polyesterifying a symmetrical, aliphatic diol with fumaric acid, lower alkyl esters of fumaric acid, or symmetrical saturated diacids such as terephthalic acid, isophthalic acid and sebacic acid. Maleic anhydride or maleic acid or lower alkyl esters of maleic acid may also be used in the presence of an appropriate catalyst. Likewise, mixtures of fumaric acid or esters with maleic anhydride or maleic acid or its esters may also be used. Exemplary crystalline polyesters which may be employed in the present invention include polyfumarates of 1,6- hexanediol , neopentyl glycol, bis- (hydroxyethyl) resorcinol , ethylene glycol, 1,4- butanediol, 1 , 4-cyclohexanediol , 1 , 4-cyclohexanedi- methanol , or bis- (hydroxyethyl) hydroquinone .

The amount of crystalline polyester added to the thermosetting resin will vary depending upon the particular thermosetting resin employed. Typically, about 2 to about 80 percent by weight of crystalline polyester is required to thicken about 20 to about 98 percent by weight of a thermosetting resin.

The thermosetting resin may also be thickened with polyurethanes . Exemplary thermosetting resin thickened with a polyurethane are described in U.S. Patent No. 3,886,229 to Hutchinson, the disclosure of which is incorporated herein by reference in its entirety. Typically, in the embodiment of the invention wherein the thermosetting resin is thickened with a polyurethane, the first resin material comprises a thermosetting resin solubilized in a vinyl monomer.

The polyurethanes useful in the present invention typically comprise the reaction product of a polyol and an isocyanate compound. The polyol may be saturated or unsaturated. Exemplary saturated polyols include ethylene glycol, propylene glycol, butane- 1,4- diol , pentane-1 , 5-diol , hexane-1 , 6-diol , di (ethylene glycol), and di (propylene glycol) . Polymers of glycols may also be employed. Exemplary polymers include poly (ethylene glycol), poly (propylene glycol), and poly (butylene glycol) and polyols of functionality greater than two, for example, glycerol , pentaerythritol , and trialkylol alkanes, e.g., trimethylol propane, triethylol propane, tributylol propane and oxyalkylated derivatives of said trialkylol alkanes, e.g., oxyethylated trimethylol propane and oxypropylated trimethylol propane.

In an embodiment wherein the thermosetting resin is thickened with a polyurethane including an unsaturated polyol, the unsaturated polyol crosslinks the urethane groups with the ethylenically unsaturated polyester and vinyl monomer of the thermosetting resin. Exemplary unsaturated polyols include polyesters, and vinyl esters. In one particularly preferred embodiment, the unsaturated polyol is a diester of propoxylated bisphenol-A.

The isocyanate compound employed to produce a polyurethane thicknering agent is typically a polyisocyanate . The polyisocyanate may be aliphatic, cycloaliphatic or aromatic or may contain in the same polyisocyanate molecule aliphatic and aromatic isocyanate groups, aliphatic and cycloaliphatic isocyanate groups, aliphatic cycloaliphatic and aromatic isocyanate groups or mixtures of any two or more polyisocyanates .

Exemplary polyisocyanates include 4,4'- diphenylmethane diisocyanate, 2 ,4-toluene diisocyanate, 2,6-toluene diisocyanate, isophorone diisocyanates (e.g., 3-isocyanatomethyl-3 , 5 , 5-trimethylcyclohexyl isocyanate) , tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate and octamethylene diisocyanate, and cycloaliphatic diisocyanates (e.g., 4 , 4 ' -dicyclohexylmethane diisocyanate) .

The polyurethane may be reacted with the thermosetting resin according to any method known to those skilled in the art. The amount of polyurethane added to the first resin material will vary depending upon the particular thermosetting resin employed.

Typically, the polyurethane comprises about 1 to about 60 percent by weight of the thermosetting resin.

The resin may also be thickened using a polyurea thickening agent. Suitable formulation of resins thickened with polyurea are described in U.S.

Patent No. 4,296,020 to Magrans, Jr., the disclosure of which is incorporated herein by reference in its entirety. Typically, in the embodiment of the invention wherein the resin material is thickened with polyurea, the resin material comprises a resin solubilized in a vinyl monomer. The polyureas useful in the present invention typically comprise the product of polyamines with polyisocyanates. The polyisocyanates useful in the present invention include those described above with reference to urethane thickeners. Aliphatic, cycloaliphatic and aromatic polyamines free of ethylenic saturation are preferred polyurea precursors in that they form individual polyurea chains which are relatively cross-linked with the polymer chain formed by the copolymerization of the ethylenically unsaturated resin and monomers in solution therewith. Aryl diamines and mixtures thereof such as metaphenylene diamine, paraphenylene diamine, naphthalene diamine, benzidene, bis(4-amino- phenyl) methane, 4 , 4 ' -diaminodiphenyl sulfone and halogenated derivatives such as those containing halogen on the benzenoid ring such as 3,3'- dichlorobenzidine, bis, 4-amino-2-chlorophenyl (sulfone), 4-bromo-l , 3 -phenylene diamine, to name a few, are operable.

Low molecular weight aliphatic and cycloaliphatic diamines are also suitably employed, such as: ethylene diamine, propylene diamine, hexamethylene diamine, trimethyl hexamethylene diamine, isophorone diamine, l-amino-3-amino-3 , 5 , 5-trimethyl cyclohexane, hydrogenated di- (aminophenyl) methane, hydrogenated methylene dianiline, diamino methane, and hydrogenated toluene diamine. The most useful of these are those that are liquids up to 75EC. For those which are solids under these conditions, vinyl monomer solutions can be employed to form the homogeneous mix rapidly. In addition, other suitable amines include polyoxyalklene polyamines and cyanoalkylated polyoxyalklene polyamines having a molecular weight of about 190 to about 2,000 with a preferred range of about 190 to about 1,000. These amines are prepared according to the procedure outlined in a U.S. Patent No. 4,296,020 to Magrans , Jr., the disclosure of which is hereby incorporated by reference in its entirety. The resin may also be thickened using alkali earth metal oxides or hydroxides . Typical thickeners of this type include calcium and magnesium oxides or hydroxides. The addition of these components to the resin will transform the liquid thermosetting resin to a semi-solid or solid form. The amount of oxide or hydroxide employed will vary depending upon the particular thermosetting resin employed. Typically, the alkali metal oxide or hydroxide comprises about 1 to about 15 percent by weight of the first resin material . The resin also may include an initiator system which cooperates with the conditions of a shaping die to thicken the resin by partially curing the resin. The initiator system may be present in addition to any of the foregoing thickening agents, or as an alternative thereto.

The initiator system may comprise any number of polymerization initiators. Where multiple polymerization initiators are employed, the initiator system typically comprises polymerization initiators which can be activated by different conditions. For simplicity, where multiple polymerization initiators are employed, we refer to the polymerization initiator requiring the least activation energy as the "first polymerization initiator" , and the initiator requiring the most activation energy as the "second polymerization initiator" . Any practical number of polymerization initiators having activation energies between the first and second polymerization initiators may also be incorporated into the thermosetting resin matrix. It should not be implied from the use of the terms "first" and "second" polymerization initiator that the invention is restricted to the use of no more than two polymerization initiators.

Polymerization initiators which are useful in the practice of the present invention typically include free-radical initiators. Typical free-radical initiators include peroxy initiators. The reactivity of such initiators is evaluated in terms of the 10 hour half-life temperature, that is, the temperature at which the half -life of a peroxide is 10 hours. Suitable first polymerization initiators include polymerization initiators having a low 10 hour half-life, i.e., a more reactive peroxide initiator, as compared to initiators having a higher 10 hour half -life. Suitable second polymerization initiators include polymerization initiators having a higher 10 hour half-life than the 10 hour half-life of the polymerization initiator selected as the first polymerization initiator. Exemplary free-radical initiators useful in the present invention include diacyl peroxides, (e.g., lauroyl peroxide and benzoyl peroxide) , dialkylperoxydicarbonates , (e.g., di(4-tert- butylcyclohexyl) peroxy dicarbonate) , tert-alkyl peroxyesters, (e.g., t-butyl perbenzoate) , di- (tert- alkyl) peroxyketals, (e.g., l,l-di-(t- amylperoxy) cyclohexane) , di-tert-alkyl peroxides, (e.g., dicumyl peroxide) , azo initiators, (e.g., 2,2'- azobis (isobutyronitrile) , ketone peroxides, (e.g., methylethylketone peroxide and hydroperoxides) . In an embodiment wherein the initiator system comprises only one polymerization initiator, the resin material preferably includes a vinyl monomer. The vinyl monomer and the polymerization initiator may be independently activated under different conditions thus permitting the partial polymerization of the resin.

The amount of polymerization initiator (s) used is dependent upon the number of initiators employed, the conditions at which the selected initiators will initiate polymerization, and the time desired for partial curing. Typically the amount of time desired for partial curing is a short period, i.e., less than 3 hours, and often less than 1 hour. In the embodiment wherein the resin includes only one polymerization initiator, the amount of the initiator is typically about 0.1 to about 10 percent by weight of the resin. In the embodiment wherein the resin includes two polymerization initiators, the amount used is about 0.01 to about 4 percent by weight of the first polymerization initiator and about 0 to about 5 percent by weight of the second polymerization initiator based on the weight of the resin.

The initiator system and amounts of each polymerization initiator incorporated into the resin should be such that as the resin impregnated reinforcing fibers are shaped in a shaping die, the conditions therein are sufficient to activate at least one, but preferably not all polymerization initiators, resulting in the partial polymerization of the resin. Typically, in the embodiment wherein the initiator system comprises only one polymerization initiator, the resin impregnated reinforcing fibers are shaped through a shaping die within which the reinforcing fibers are subjected to sufficient heat to activate the polymerization initiator without attaining the self- polymerization temperature of the resin. In an embodiment wherein multiple polymerization initiators are employed, typically the resin impregnated reinforcing fibers are shaped in a shaping die within which the reinforcing fibers are subjected to sufficient heat to activate at least one, and preferably the first, polymerization initiator to partially cure the resin.

The resin may also include other additives commonly employed in resin compositions, the selection of which will be within the skill of one in the art. For example, the cladding resin material may include reinforcing fillers, particulate fillers, selective reinforcements, thickeners, initiators, mold release agents, catalysts, pigments, flame retardants, and the like, in amounts commonly known to those skilled in the art. Any initiator may be a high or a low temperature polymerization initiator, or in certain applications, both may be employed. Catalysts are typically required in resin compositions thickened with polyurethane. The catalyst promotes the polymerization of NCO groups with OH groups. Suitable catalysts include dibutyl tin dilaurate and stannous octoate. Other commonly known additives which may desirably be incorporated into the resin material include pigments and flame retardants. Particulate fillers that can be used with the resin include inorganic fillers and organic fillers. Exemplary inorganic fillers include ceramic, glass, carbon-based inorganic materials such as carbon black, graphite, and carbonoyl iron, cermet, calcium carbonate, aluminum oxide, silicon dioxide, oxides of nickel, cobalt, iron (ferric and ferrous), manganese, and titanium, perlite, talc (hydrous magnesium silicate) , mica, kaolinite, nitrides of boron and aluminum, carbides of silicon, boron, and aluminum, zircon, quartz glass, aluminum hydroxide, gypsum, magnesite, ferrite, molybdinum disulfide, zinc carbonate, and blends thereof. Exemplary organic fillers include aramid and polyethylene terephthalete . These and other exemplary reinforcing materials are described in U.S. Patent Nos. 4,278,780 to Nishikawa et al . ; 4,358,522 to Shinohara et al . ; 5,011,872 to Latham et al . ; 5,234,590 to Etienne et al . ; and 4,947,190 to Murayama et al . Preferably, the resin includes a ceramic filler; i.e., a material that is the product of heated earthy raw materials in which silicon with its oxide and silicates, such as calcium silicate, wollastonite, beryl, mica, talc, and clays such as kaolinite, occupy a predominant position. See Hawley ' s Condensed Chemical Dictionary at 240 (11th ed. 1987) . A particularly preferred ceramic filler is KZ Ceramic Powder, a proprietary ceramic powder available from Ceramic Technologies Corporation, Rowley, Iowa. In one embodiment, the ceramic filler is advantageously blended with a calcium carbonate filler in a 3:1 blend. The filler can be supplied in many forms, including powder, fiber, sphere, bead, particle, flake, lamella, and the like.

Reinforcing Fibers Reinforcing fibers, which are impregnated with the resin, can comprise up to 75 percent fibers, and preferably comprise at least about 40 percent of a flange by weight. The reinforcing fibers are preferably glass fibers. Glass fibers are readily available and low in cost. A typical glass fiber is electrical grade E-glass. E-glass fibers have a tensile strength of approximately 3450 MPa (practical). Higher tensile strengths can be accomplished with S-glass fibers having a tensile strength of approximately 4600 MPa (practical) . The glass fiber can be treated to provide other properties such as corrosion resistance. Other suitable reinforcing fibers include carbon, metal, high modulus organic fibers (e.g., aromatic polyamides, polybenzimidazoles, and aromatic polyimides), and other organic fibers (e.g., polyethylene, liquid crystal and nylon) . Blends and hybrids of the various fibers can be used.

The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.

Claims

THAT WHICH IS CLAIMED IS:

1. A concrete reinforcing system comprising : a plurality of elongated non-corrosive flanges, each flange having opposite faces and opposite longitudinal edges; and means for removably securing said plurality of flanges in spaced-apart, substantially parallel relationship.

2. A concrete reinforcing system according to Claim 1 wherein at least one of said flanges comprises fiber-reinforced resin material .

3. A concrete reinforcing system according to Claim 1 wherein said flanges are spaced-apart substantially equidistantly.

4. A concrete reinforcing system according to Claim 1 wherein the longitudinal edges of each flange are substantially parallel .

5. A concrete reinforcing system according to Claim 1 wherein at least one of said flange faces comprises a non-planar surface portion for improving concrete adhesion thereto.

6. A concrete reinforcing system according to Claim 1 wherein said means for removably securing said plurality of flanges comprises means for maintaining adjacent flanges in spaced-apart, face-to- face relationship.

7. A concrete reinforcing system according to Claim 2 wherein fibers within said resin material are unidirectional .

8. A concrete reinforcing system according to Claim 2 wherein said resin material comprises thermosetting resin.

9. A concrete reinforcing system according to Claim 2 wherein said reinforcing fibers are selected from the group consisting of glass, carbon, metal, aromatic polyamides, polybenzimidazoles, aromatic polyimides, polyethylene, nylon, and blends and hybrids thereof .

10. A concrete reinforcing system according to Claim 1 wherein at least one of said longitudinal edges of each flange comprises an enlarged portion and wherein said means for removably securing said plurality of flanges comprises means for receiving an enlarged portion of a longitudinal edge of each respective flange.

11. A concrete reinforcing system according to Claim 1 further comprising at least one transverse partition intersecting at least one of said plurality of flanges and cooperating therewith.

12. A concrete reinforcing system according to Claim 7 wherein said unidirectional fibers are located along the faces of said flanges.

13. A concrete reinforcing system comprising : a plurality of elongated non-corrosive flanges, each flange having opposite faces, opposite longitudinal edges, and opposite ends; and a holder for maintaining said plurality of flanges in spaced-apart, substantially parallel relationship, said holder comprising a plurality of slots, each of said plurality of slots configured to removably secure a longitudinal edge of a respective one of said flanges.

14. A concrete reinforcing system according to Claim 13 wherein a longitudinal edge of each flange comprises an enlarged portion, and wherein each slot in said holder comprises an enlarged portion configured to receive the enlarged portion of a longitudinal edge of a respective flange.

15. A concrete reinforcing system according to Claim 13 wherein each slot of said holder is configured to receive both longitudinal edges of a respective flange.

16. A concrete reinforcing system according to Claim 13 wherein each of said plurality of slots is configured to removably secure two flanges in end-to- end abutting relationship.

17. A concrete reinforcing system according to Claim 13 further comprising at least one transverse partition intersecting at least one of said plurality of flanges and cooperating therewith.

18. A concrete reinforcing system according to Claim 17 wherein said at least one transverse partition comprises a slot therein for cooperating with a respective slot in said at least one of said plurality of flanges.

19. A concrete reinforcing system according to Claim 13 wherein at least one of said flange faces has a non-planar surface portion for improving concrete adhesion thereto.

20. A concrete reinforcing system according to Claim 13 wherein at least one of said flanges comprises fiber-reinforced resin material.

21. A concrete reinforcing system according to Claim 20 wherein fibers within said resin material are unidirectional .

22. A concrete reinforcing system according to Claim 20 wherein said unidirectional fibers are located along the faces of said flanges.

23. A concrete reinforcing system according to Claim 21 wherein said resin material comprises thermosetting resin.

24. A concrete reinforcing system according to Claim 21 wherein said reinforcing fibers are selected from the group consisting of glass, carbon, metal, aromatic polyamides, polybenzimidazoles, aromatic polyimides, polyethylene, nylon, and blends and hybrids thereof .

25. A concrete reinforcing system according to Claim 13 wherein said holder comprises a first material and wherein said plurality of flanges comprise a second material different from said first material.

26. A concrete reinforcing system according to Claim 13 wherein said first material is selected from the group consisting of thermoplastics and aluminum.

27. A concrete reinforcing system according to Claim 13 further comprising a plurality of holders for maintaining said plurality of flanges in spaced- apart, substantially parallel relationship.

28. A reinforced structure of cementitious material comprising: a mass of cementitious material; a plurality of elongated non-corrosive flanges, each flange having opposite faces and opposite longitudinal edges; and means for removably securing said plurality of flanges in spaced-apart, substantially parallel relationship .

29. A reinforced structure according to Claim 28 wherein said cementitious material comprises Portland cement.

30. A reinforced structure according to Claim 28 wherein said means for removably securing said plurality of flanges comprises means for maintaining adjacent flanges in spaced-apart, face-to-face relationship .

31. A reinforced structure according to Claim 28 wherein said flanges are spaced-apart substantially equidistantly.

32. A reinforced structure according to Claim 28 wherein the longitudinal edges of each flange are substantially parallel.

33. A reinforced structure according to Claim 28 wherein at least one of said flange faces has a non-planar surface portion for improving concrete adhesion thereto.

34. A reinforced structure according to Claim 28 wherein at least one of said flanges comprises fiber-reinforced resin material.

35. A reinforced structure according to Claim 34 wherein fibers within said resin material are unidirectional .

36. A reinforced structure according to Claim 34 wherein said resin material comprises thermosetting resin.

37. A reinforced structure- according to Claim 34 wherein said reinforcing fibers are selected from the group consisting of glass, carbon, metal, aromatic polyamides, polybenzimidazoles, aromatic polyimides, polyethylene, nylon, and blends and hybrids thereof .

38. A reinforced structure according to Claim 28 wherein at least one of said longitudinal edges of each flange comprises an enlarged portion and wherein said means for removably securing said plurality of flanges comprises means for receiving an enlarged portion of a longitudinal edge of each respective flange.

39. A reinforced structure according to Claim 28 further comprising at least one transverse partition intersecting at least one of said plurality of flanges and cooperating therewith.

40. A reinforced structure according to Claim 35 wherein unidirectional fibers are located along the faces of said flanges in contacting relationship with said cementitious material .

41. A reinforced structure according to Claim 28 wherein said means for removably securing said plurality of flanges comprises a first material and wherein said plurality of flanges comprise a second material different from said first material.

42. A reinforced structure according to Claim 41 wherein said first material is selected from the group consisting of thermoplastics and aluminum.