Patent Application
20190092686
The present disclosure relates to a composition and method for making silica-coated composite fibers for the reinforcement of concrete, as well as a method of reinforcing concrete and other building materials using such fibers.
Building materials such as concrete can be reinforced with fibers in order to overcome specific issues that can arise when using traditional reinforcement members, such as steel rebars and/or welded wire mesh. Fibers can introduce toughness (i.e., energy absorption capacity during failure) to concrete, overcoming its intrinsic brittleness and providing post-cracking strength under direct or indirect tensile stresses. The vast majority of conventional fibers used for concrete reinforcement are made out of low or high carbon content steel, or polymers such as polypropylene, polyvinyl alcohol, polyester, etc. However, these conventional fibers suffer from various limitations. Processability issues such as clustering during mixing, blockages during pumping, reduction of workability, and difficult compaction and finishing arise from the relatively high quantities required. Additionally, the cost-performance benefit of such conventional fibers is often less than that of traditional reinforcement members due to the relatively high quantities required.
Various exemplary embodiments of the present disclosure are directed to a composition and method for making composite fibers used in the reinforcement of concrete. The composite fibers disclosed herein comprise silica-coated glass fibers. The silica particles provide an improved interface between the composite fibers and the concrete matrix.
In accordance with some exemplary embodiments, composite fibers for the reinforcement of concrete are provided. The composite fibers comprise a plurality of glass fibers, wherein the glass fibers include a polymeric coating and a plurality of silica particles distributed over the surface of the glass fibers.
In accordance with some exemplary embodiments, a method of manufacturing composite fibers is provided. The method comprises providing a viscous monomeric/oligomeric coating composition, applying the viscous monomeric/oligomeric coating composition to a plurality of glass fibers to form coated fibers, applying a plurality of silica particles onto the surface of the coated fibers to form silica-coated fibers, and exposing the silica-coated fibers to either thermal energy or radiation to cure the monomeric/oligomeric coating composition and form composite fibers.
In accordance with some exemplary embodiments, a method of reinforcing concrete is provided. The method includes providing a viscous monomeric/oligomeric coating composition, applying the viscous monomeric/oligomeric coating composition to a plurality of glass fibers to form a plurality of coated fibers, applying a plurality of silica particles onto the surface of the plurality of coated fibers to form silica-coated fibers, exposing the plurality of silica-coated fibers to thermal energy or radiation to cure the monomeric/oligomeric coating composition and form a plurality of composite fibers, preparing a concrete composition, and mixing the plurality of composite fibers into the concrete composition.
The advantages of the inventive concepts will be apparent upon consideration of the following detailed disclosure, especially when taken in conjunction with the accompanying drawings wherein:
Compositions and methods for making composite fibers used in the reinforcement of concrete are described in detail herein. The composite fibers comprise a plurality of silica-coated glass fibers. These and other features of the composite fibers, as well as some of the many optional variations and additions, are described in detail hereafter.
Numerical ranges as used herein are intended to include every number and subset of numbers within that range, whether specifically disclosed or not. Further, these numerical ranges should be construed as providing support for a claim directed to any number or subset of numbers in that range. For example, a disclosure of from 1 to 10 should be construed as supporting a range of from 2 to 8, from 3 to 7, from 5 to 6, from 1 to 9, from 3.6 to 4.6, from 3.5 to 9.9, and so forth.
All references to singular characteristics or limitations of the present disclosure shall include the corresponding plural characteristic or limitation, and vice versa, unless otherwise specified or clearly implied to the contrary by the context in which the reference is made.
Exemplary composite fibers used in the reinforcement of concrete are disclosed in PCT/US2014/053655, which is incorporated herein by reference in its entirety. Composite fibers in accordance with this present disclosure may include any combination or sub combination of the features disclosed by the present application and/or the foregoing PCT application.
The term “fiber” as used herein, unless otherwise specified, refers to a collection of one or more monofilaments.
The term “polymeric coating” as used herein, unless otherwise specified, refers to a mixture of monomers and/or oligomers that are hardened by one of the curing methods described or otherwise suggested herein.
The term “impregnated” as used herein, unless otherwise specified, means partially or fully impregnated.
The term “radiation cured” as used herein, unless otherwise specified, refers to monomers and/or oligomers that have been polymerized with the help of radiation, preferably in the presence of a suitable catalyst.
The term “UV cured” as used herein, unless otherwise specified, refers to the polymerization of monomers and/or oligomers in the presence of UV radiation.
The term “polymer” as used herein, unless otherwise specified, includes the term “copolymer,” and, unless otherwise specified, the term “copolymer” refers to polymers made from any two or more different monomers, including, for example, terpolymers, pentapolymers, homopolymers functionalized after polymerization so that two or more different functional groups are present in the product copolymer, block copolymers, segmented copolymers, graft copolymers, and any mixture or combination thereof. The term “(co)polymer” as used herein means homopolymer or copolymer.
The term “composite fiber” as used herein, unless otherwise specified, refers to a collection of one or more fibers coated with a mixture of monomers and/or oligomers, and treated with the appropriate curing method to form a polymeric coating from the mixture of monomers and/or oligomers.
The term “equivalent diameter” as used herein, unless otherwise specified, means diameter as defined in the EN14889 Standard.
The term “concrete” as used herein, unless otherwise specified, means any type of building material containing aggregates embedded in matrix (the cement or binder) that fills the space among the aggregate particles and glues them together, e.g., Portland Cement based concrete, mineral mortar, or asphalt.
Disclosed herein are cured composite fibers coated with silica particles for the reinforcement of concrete. The exemplary composite fibers disclosed herein may be manufactured using any suitable type of fiber, such as, for example, a glass fiber. A liquid, or otherwise viscous, monomeric, or oligomeric coating composition may be prepared and applied to the surface of the glass fibers. The surface of the fibers are then further coated with particles such as silica particles. The coated fibers may then be exposed to thermal energy or radiation, such as UV radiation, which cures the coating composition to form a composite fiber.
In accordance with various exemplary embodiments, composite fibers are provided for the reinforcement of concrete. The length of the composite fibers may be any length suitable for the reinforcement of concrete, such as a length from about 10 mm to about 80 mm, from about 20 mm to about 60 mm, or from about 30 mm to about 50 mm. The equivalent diameter of the composite fibers may be from about 0.3 mm to about 2 mm, or from about 0.5 mm to about 1.3 mm. In some exemplary embodiments, the cured composite fibers have a surface roughness between 20 μm and 200 μm, as measured by microscope or SEM.
In some exemplary embodiments, the initial uncoated fibers are inorganic fibers such as glass fibers. Non-exclusive exemplary glass fibers include A-type glass fibers, C-type glass fibers, G-type glass fibers, E-type glass fibers, S-type glass fibers, Basalt fibers, E-CR-type glass fibers (e.g., Advantex® glass fibers commercially available from Owens Corning), R-type glass fibers, biosoluble glass fibers, alkali-resistant glass, or combinations thereof, all of which may be suitable for use as the reinforcing fiber. In some exemplary embodiments, an alkali-resistant (“AR”) glass fiber, such as Cem-FIL® available from Owens Corning, is suitable for use as the reinforcing fiber.
The diameter of the monofilaments forming the glass fiber may vary from about 10 microns to about 27 microns, or from about 13 microns to about 20 microns. The tex of the fibers (the linear mass in g/km) may be from about 136 tex to about 4800 tex. In some exemplary embodiments, the tex is in the range of about 400 tex to about 1200 tex.
In some exemplary embodiments, the glass fibers disclosed herein are impregnated with a monomeric and/or oligomeric coating that leads to a polymeric coating after curing. The polymeric coating may be a thermal or radiation cured coating, such as, for example, an IR-cured coating or a UV-cured coating. A wide range of radiation may be used, i.e., from UVC to visible light or high energy electron beam. UV curable monomers, oligomers, and polymers are known in the art. Particularly suitable UV curable monomers, oligomers, and polymers include acrylates, methacrylates, vinylethers, and vinyl derivatives based on polyurethane, epoxy, polyester, polyether structures with or without aliphatic, cycloaliphatic or aromatic backbones, and copolymers based on such structures. In some exemplary embodiments, the polymeric coating structure includes polyurethanes based on aromatic structure, alone or in a mixture with epoxy or polyether derivative. In some exemplary embodiments, the polymeric coating is based on epoxy-acrylate, whereas in other exemplary embodiments the polymeric coating is mainly obtained from polyurethane-acrylate.
In addition to the polymeric coating, the surface of the glass fibers disclosed herein are further coated with particles that may include, but are not limited to, silica, sand, alumina, zirconium oxide, and the like. In some exemplary embodiments, the glass fibers are further coated with silica particles. The size of the particles may vary depending on the desired final product characteristics. In some exemplary embodiments, the silica particles have a diameter of about 5 microns to about 150 microns. In some exemplary embodiments, the silica particles have a diameter of from about 20 microns to about 40 microns, or of about 20 microns. In some exemplary embodiments, the silica particles have a diameter greater than 100 microns.
An exemplary process for producing silica-coated composite fibers is shown in
In accordance with the exemplary process shown in
Prior to passing through the coating bath 6, the fiberglass roving 2 may optionally pass over one or more rollers 4 or through grooves, a comb, bars, magnetic or mechanic brakes, etc., to control the tension and help guide the fiberglass roving 2 into the coating bath 6 with minimal tangling and/or winding. It should be understood that a variety of suitable structures, apparatuses, and articles could be utilized to control the tension and guide the fiberglass roving 2 into the coating bath 6, and the present disclosure is not limited to the use of rollers 4 as illustrated in
In accordance with some exemplary embodiments, excess coating may be removed from the coated fiberglass through a variety of means, including, for example, passing the coated fiberglass through one or more forming dies 8, such as a wire forming die. The forming dies 8 may be tapered to progressively remove excess coating from the coated fiberglass and achieve a particular coating level. In some exemplary embodiments, the dies 8 may have a particular diameter and/or particular shape, such that the coated fiberglass exits the forming dies having the approximate diameter and shape of the final die. In one exemplary embodiment, the amount of coating on the coated fiberglass is controlled by a series of calibrated dies. For example, five dies of varying diameters may adjust the diameter of the coated fiberglass from 1.1 mm down to 0.7 mm (i.e., a 1.1 mm die, two 0.9 mm dies, and two 0.7 mm dies).
In accordance with the exemplary embodiment shown in
In accordance with the exemplary embodiment shown in
Though the silica particles have been described above as a secondary surface coating following the polymeric coating, the general inventive concepts disclosed herein are not limited to this embodiment. In some exemplary embodiments, the silica particles may be mixed within the monomeric/oligomeric coating, and the glass fibers may be impregnated or otherwise coated with this combined silica particle monomeric/oligomeric coating.
In some exemplary embodiments, after the curing step 12, the silica-coated composite fiber may be wound. The winder 14 may be a single winder, or may include multiple winders used in conjunction. The winder 14 may comprise any winder generally used in the art, such as an inside pull winder that is built on a rubber bladder, or an outside pull winder that is built on a cardboard core. In some exemplary embodiments, the silica-coated composite fiber may be wound at a speed from about 5 m/min to about 250 m/min to create a package having an outer diameter of up to about 1 meter.
Alternatively, the silica-coated composite fiber may be fed directly into a chopper 16 for the formation of a plurality of chopped composite strands. The chopper 16 may comprise any conventional cutting means, such as, for example, a blade cutter head that includes razor blades inserted into slots positioned at a distance corresponding to the length of a desired chopped strand. The chopped composite strands may be of any length desired for a particular application, such as, for example, from about 20 mm to about 50 mm, or from about 35 mm to about 40 mm.
In some exemplary embodiments, the silica-coated composite fiber is first wound by winder 14 and then later unwound for feeding into the chopper 16.
In some exemplary embodiments, the chopped composite strands disclosed herein may be used to reinforce concrete. The reinforced concrete may be formed by preparing a concrete (e.g., using a conventional method of forming concrete) followed by mixing the chopped composite strands into the concrete, thereby forming a composite fiber reinforced concrete. In some exemplary embodiments, the quantity of silica-coated composite fibers in the reinforced concrete is from about 2 kg to about 75 kg of composite fiber per cubic meter of concrete, or from about 5 kg to about 25 kg of composite fiber per cubic meter of concrete. In some exemplary embodiments, the quantity of silica-coated composite fibers in the reinforced concrete is from about 7.5 kg to about 12.5 kg of composite fiber per cubic meter of concrete.
In some exemplary embodiments, the silica-coated composite fibers disclosed herein are provided for the reinforcement of shotcrete, i.e., concrete that is projected against a wall at a high speed and pressure. Existing composite fibers used as reinforcement in conventional concrete may exhibit an undesirable “rebound effect” when used in shotcrete applications. The fiber lengths of existing composite fibers (from about 2.5 cm to about 4 cm) may contribute to this effect of the concrete rebounding from the wall against which it was projected.
The rebound effect causes a reduction in the level of concrete reinforcement that conventional composite fibers provide in shotcrete applications. This is because during the projection of the shotcrete, the reinforcement fibers hit the wall at a high speed (several meters per second). The conventional composite fibers are quite flexible, and essentially act as “springs” when they hit the wall. Because the surface of the conventional fibers is smooth, the rebound effect extracts the fibers from the concrete. The quantity of fibers lost by this effect is dependent on the projection speed, but may be up to 60%.
In contrast, the silica-coated composite fibers disclosed herein provide a surface which anchors the composite fibers in the projected cement, and avoids or lessens the undesirable rebound effect. To overcome the rebound effect in conventional applications, an increased amount of composite fibers must be used to achieve the desired mechanical properties in the reinforced concrete. However, the surface roughness provided by the silica particles coating the composite fibers disclosed herein overcomes or otherwise reduces this rebounding effect, and achieves the desired mechanical properties without necessitating a substantial increase in the number of composite fibers used.
In addition to improvements in overcoming the “rebound effect” in fresh cement, the silica particle coating on the composite fibers disclosed herein improves the adhesion between the concrete matrix and the composite fibers after the cement has dried. In some exemplary embodiments, the silica coating improves the adhesion between the concrete matrix and the composite fibers by at least 2 to 3 times that of otherwise identical composite fibers not coated with silica particles.
Other advantages of the composite fibers described herein include a high speed of dispersion during the mixing process, ease in achieving a uniform distribution of fibers in the concrete mass, reduced wearing of mixing and pumping systems, less risk of clogging pumping pipes and blockages when filling structural elements, and less risk of honeycombs and consequent durability issues when used in combination with conventional reinforcement. For example, steel fibers are made in a shape with a “hook” at each end to give a mechanical anchoring in the cement or concrete. That may generate problems that can be described as “urchin” like clusters, which can induce pump breaks and inhomogeneity of the reinforced concrete. With the silica coated fiberglass disclosed herein, it is possible to achieve similar mechanical properties without the above-described drawbacks of conventional systems.
In some exemplary embodiments, the composite fibers are corrosion resistant, and thus do not develop corrosion stains in case of exposed concrete surfaces. Additionally, the composite fibers make the hardened concrete easier to recycle than traditional steel fibers.
The general inventive concepts have been described above both generally and with regard to various specific exemplary embodiments. Although the general inventive concepts have been set forth in what are believed to be exemplary illustrative embodiments, a wide variety of alternatives will be apparent to those of skill in the art from reading this disclosure. The general inventive concepts are not otherwise limited, except for those instances when presented in specific claims. Additionally, the following examples are meant to better illustrate the present invention, but do not limit the general inventive concepts.
The following examples describe the performance of various exemplary embodiments of the silica-coated composite fibers of the present disclosure, as used for concrete reinforcement.
The composite fibers were prepared with Cemfil glass fibers available from Owens Corning. The exemplary AR glass fibers were 640 tex, 19 μm, with epoxy-based sizing. The coated fibers of both
The adhesion behavior of exemplary composite fibers were measured using the Pull Out Test on fresh cement. To conduct the Pull Out Test (Fresh Cement), a 1 L composite fiber-reinforced sample of fresh cement was prepared for each formulation, with a cement resistance Rc of 80 MPa. A 22 cm rod was prepared, and 15 cm of the rod was inserted vertically into each sample. The samples were thereafter evaluated for extraction strength, by extracting the rod after 10 minutes maturation of the cement, so that the cement sample was stabilized, but not solidified. The rod was extracted at a speed of 60 mm/mn, with the observed extraction strengths summarized in Table 1 below.
The results of the Pull Out Test show that the adhesion of the composite fibers with fresh cement (both at max strength and during extraction) is significantly higher for the exemplary product with silica particles (HDF 101) as compared to the product without silica particles (HDF 100). This increased adhesion with the cement leads to a lower loss of fibers during reinforced concrete projection.
Table 2 below lists various exemplary composite fiber compositions and resulting properties. Three exemplary cement batches were evaluated to determine the effects that modifying the surface roughness had on mechanical performance after hardening of the cement.
As shown in the data below, the mechanical performance of the silica-coated composite fiber reinforced concrete after hardening was substantially higher than the non-silica coated comparative samples.
Samples 36 and 42 from Table 2 were further evaluated at 21 days. Table 3 shows the positive impact on bonding between fibers and concrete increased as the concrete cured.
In order to confirm the stronger bonding observed in Example 3, two concrete batches (C30-37 according to EN 206) were mixed with either 10 kg of the composite fibers disclosed herein, or with 10 kg of conventional glass fibers having a smooth surface. After 28 days curing at 23° C. and 90% moisture, the specimens were 3 point bended according to the EN Standard 14651.
Table 4 shows the improved performance of the silica-coated composite fibers, as measured by the Pull Out Test described above:
In a fifth trial, two composite fiber-reinforced concrete batches were prepared according to the process disclosed herein and compared with a conventional, uncoated composite fiber-reinforced concrete batch. The composite fibers had a length of 40 mm, an aspect ratio of 70, and were dosed at 10 kg/m3 fiber in concrete (C30-37), having consistency S4. Specimen beams having dimensions of 10 cm×10 cm×40 cm were prepared and evaluated for flexural tensile strength according to EN 14651 standards. The samples were cured for 7 days prior to evaluation at 23° C. and 90% moisture.
EN 14651 Flexural Strength data was used to evaluate the Average Residual Strength (ARS). The ARS is the mean value of individual strengths at 0.4, 1.2, 2.0 and 2.8 mm of crack width opening (noted respectively called CMOD1, CMOD2, CMOD3, CMOD4). The ARS value shows the residual strength observed after a sample breaks, i.e., a residual “wrenching” strength required to pull out the embedded glass fibers from the matrix. The ARS value is applicable to evaluating industrial applications, for example the behavior of a material during an earthquake. As shown in Table 5, each exemplary batch showed an improved Average Residual Strength (measured in MPa) as compared to a conventional, non-silica coated composite fiber.
As used in the description of the invention and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. To the extent that the term “includes” or “including” is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed (e.g., A or B) it is intended to mean “A or B or both.” When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use. Also, to the extent that the terms “in” or “into” are used in the specification or the claims, it is intended to additionally mean “on” or “onto.” Furthermore, to the extent the term “connect” is used in the specification or claims, it is intended to mean not only “directly connected to,” but also “indirectly connected to” such as connected through another component or components.
Unless otherwise indicated herein, all sub-embodiments and optional embodiments are respective sub-embodiments and optional embodiments to all embodiments described herein. While the present application has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the application, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant's general disclosure herein.
This application claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 62/306,219, filed on Mar. 10, 2016, for SILICA-COATED COMPOSITE FIBER FOR THE REINFORCEMENT OF CONCRETE, the entire disclosure of which is fully incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US17/21476 | 3/9/2017 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62306219 | Mar 2016 | US |
