Reinforcing fibers and concrete products containing such reinforcing fibers

Abstract

Reinforcing fibers (3) which are formed from mineral fibers (4) having a coating (5), characterized in that the coating (5) - has at least one silicone polymer layer and at least one graphene layer or - has at least one graphene-containing silicone polymer layer or - has at least one silicone polymer layer, at least one graphene-containing silicone polymer layer and at least one graphene layer.

Description

[0001] The present invention relates to reinforcing fibers formed from mineral fibers having a coating. The invention further relates to a concrete product formed from at least one mixture of aggregate, cement, reinforcing fibers and water.

[0002] Concrete is known to be a strong but rather brittle material. It is also known that adding a reinforcing element to building materials such as cement products, bricks, asphalt, etc., improves the material's structural integrity and reduces the likelihood of cracking. Introducing a reinforcing element into concrete products mitigates the effects of the two main structural weaknesses: low tensile strength and low elongation during cracking. Such concrete, reinforced with fibers of various origins, is subsequently referred to as fiber-reinforced concrete.

[0003] The formation of non-structural shrinkage cracks in cement-bound concrete is due to the numerous microcracks that develop during the production of cement mortar products. Under further loading or the influence of the product's own weight, these microcracks begin to propagate, increasing in number and size, and transforming into larger non-structural shrinkage cracks that reduce the product's strength and durability. By preventing the propagation of microcracks, the effective strength of cement-bound products can be increased, thus extending their service life.

[0004] Numerous methods for producing high-strength concrete products are known in the prior art.

[0005] A number of such products are manufactured from fiber-reinforced concrete with metal fibers, as described in documents EA 201300703 A, EP 851957 B1, EP 1282751 B1, WO 84 / 02732 A1, and US 3942955 A. Products made from such concrete have high mechanical properties but one significant disadvantage: the metal fibers corrode over time and cease to perform their primary function. The thinner the metal fibers, the faster they fail.

[0006] To impart additional physical and mechanical strength to cement-based concrete products, various reinforcing components are used, such as metal reinforcements, minerals, and synthetic fibers. Synthetic fibers are known to be the most effective at preventing the development of non-structural shrinkage cracks from microcracks, as they are the thinnest of the listed reinforcing components and their size is comparable to that of microcracks.

[0007] Technical solutions using synthetic fibers, as described in US 6753081 B1, RU 2074153 C1, and DE 202022104639 U1, do not allow for a sufficient increase in the strength of fiber-reinforced concrete products to achieve high-strength concrete products capable of withstanding prolonged cyclic loading. This is because synthetic organic fibers do not adhere well to cement and have a significantly lower modulus of elasticity than glass fibers.

[0008] Concrete products that use glass fibers as reinforcing fibers have a number of advantages over products with other reinforcing additives. These include increased abrasion resistance, high resistance to chipping and impact, excellent sound insulation properties, and the ability to shield against radiation.

[0009] Since glass fibers have almost the same coefficient of thermal expansion as concrete, this prevents the formation of cracks during operation of both large-format and individual products. As a result, the tensile strength of the products increases almost fivefold and the compressive strength by up to 50%.

[0010] The advantages of glass fiber reinforced concrete products are listed in a number of the following publications: WO 2022242862 A1, CH 709929 A1, EP 2336437 A1, DE 102010018348 A1 and RU 123016 U1.

[0011] The practically only disadvantage of fiber-reinforced concrete products based on glass fibers is their low resistance to alkaline environments. When Portland cement is used as a binder, these fiber-reinforced concrete products are subject to chemical corrosion.

[0012] During the hydration of cement, hydroxides such as calcium hydroxide (Ca(OH)₂) are formed, creating an alkaline environment where the pH can reach values ​​of 12 to 13. Cement hydration is a long process, lasting for years, during which calcium hydroxide and other alkaline components are continuously formed.

[0013] Glass fibers used as reinforcing material in concrete are susceptible to degradation by alkalis produced during cement hydration. A high pH level causes chemical corrosion of the glass fibers, leading to their mechanical weakening and a reduction in the material's durability. Various protective coatings can be used to improve the alkali resistance of mineral fibers.

[0014] For example, in publication RU 2569140 C1, finely dispersed silicon dioxide (SiO2) is introduced into the mixture for the production of fiber-reinforced concrete products to increase the corrosion resistance of basalt fibers. This acts as a chemical buffer to reduce the influence of the alkaline environment on the basalt fibers.

[0015] In some cases, nanoscale silicon dioxide coatings are applied to mineral fibers.

[0016] The fiber-reinforced concrete product described in publication DE 202023103900 U1 has better performance characteristics compared to existing analogues, as graphene-coated basalt fibers are used as a reinforcing additive.

[0017] The main disadvantage of the technical solutions described above is the insufficient chemical protection of the glass fibers from the effects of an alkaline environment when fiber-reinforced concrete products are used under conditions of high humidity, as well as the limited resistance of products with basalt fiber reinforcement in seismically active areas over long periods of time.

[0018] This is because calcium hydroxide increases its activity under conditions of high humidity, and the protective graphene layer is gradually destroyed by the changing temperature gradient during the product's operation.

[0019] It is therefore an object of the present invention to propose reinforcing fibers with high resistance for the reinforcement of concrete products that can be used in areas with increased humidity and high seismic activity. It is further an object of the present invention to provide a concrete product that can be reliably used in areas with increased humidity and high seismic activity.

[0020] The problem is solved, firstly, by reinforcing fibers made of mineral fibers having a coating, wherein the coating has at least one silicone polymer layer and at least one graphene layer, or at least one graphene-containing silicone polymer layer, or at least one silicone polymer layer, at least one graphene-containing silicone polymer layer, and at least one graphene layer.

[0021] This can be practically achieved, for example, by applying a protective layer to the mineral fibers consisting of a mixture of liquid silicone polymer and an aqueous dispersion of at least one, preferably several, layers of graphene.

[0022] It has proven particularly advantageous to apply 3 to 25 layers of graphene, especially preferably 3 to 10 layers of graphene, to the silicone polymer layer.

[0023] The silicone polymer of the silicone polymer layer adheres particularly well to the mineral fibers, thus ensuring a strong bond between the coating and the mineral fibers, partly through the formation of new van der Waals forces. The graphene contained within and / or applied to the structure of the silicone polymer layer imparts strength and chemical resistance to the coating.

[0024] The reinforcing fibers according to the invention are not susceptible to chemical corrosion and a product reinforced with them itself exhibits hydrophobic properties.

[0025] In a preferred embodiment of the reinforcing fibers according to the invention, the mineral fibers are glass fibers and / or basalt fibers. While simple glass fibers without a coating are less resistant than basalt fibers without a coating, the reinforcing fibers according to the invention, regardless of whether they are based on glass fibers or basalt fibers, exhibit almost the same degree of alkali resistance due to the coating formed thereon according to the invention.

[0026] The problem is further solved by a concrete product which is formed from at least a mixture of aggregate, cement, reinforcing fibers and water, wherein the reinforcing fibers are mineral fibers with a coating which has at least one silicone polymer layer and at least one graphene layer, or has at least one graphene-containing silicone polymer layer, or has at least one silicone polymer layer, at least one graphene-containing silicone polymer layer and at least one graphene layer.

[0027] The concrete product according to the invention is a dense and strong monolithic product formed from standard raw materials such as aggregate, cement, and water, to which reinforcing fibers are added. Furthermore, the concrete product may contain additional ingredients.

[0028] The aggregate can consist of sand and / or gravel, for example. The cement acts as a binder and can be Portland cement, for example.

[0029] In an advantageous embodiment of the concrete product according to the invention, the coating initially comprises at least one, preferably only one, silicone polymer layer formed on the respective mineral fiber, on which at least one or more graphene layers are formed.

[0030] The respective graphene layer can be a layer containing graphene particles or other graphene components, or a closed graphene layer. The respective graphene layer preferably contains at least 90% graphene.

[0031] In another embodiment of the concrete product according to the invention, graphene can also be mixed into the silicone polymer layer and then applied to the respective mineral fiber.

[0032] In a further embodiment of the invention, at least one silicone polymer layer, a graphene-containing silicone polymer layer and at least one graphene layer can be formed on the respective mineral fiber.

[0033] As mentioned above, the silicone polymer of the silicone polymer layer adheres particularly well to the mineral fibers, thus ensuring a strong bond between the coating and the mineral fibers, partly through the formation of new van der Waals forces. Furthermore, the graphene contained in and / or applied to the silicone polymer layer gives the coating strength and chemical resistance.

[0034] The coating formed on the surface of the mineral fibers according to the invention, consisting of a composition of silicone polymer and at least one layer of graphene, forms an additional separating layer at the interface with the cement, which ensures sufficient adhesion to the cement matrix.

[0035] This film layer formed on the surface of the mineral fibers reduces the water requirement of the mineral fiber concrete and increases the density of the component composition of the concrete product.

[0036] The concrete product designed according to the invention can withstand high mechanical loads with minimal thickness. Furthermore, the concrete product according to the invention can be used reliably under conditions of increased seismic activity and humidity. The concrete product according to the invention is therefore primarily suitable for use in the building materials industry and can be used for the production of concrete products in civil, industrial, and road construction, including the use of nanotechnologies.

[0037] The concrete product according to the invention is preferably a building material. Such a building material is particularly suitable for the production of thin-walled and high-strength concrete products that can be used in areas with high seismic activity and increased humidity.

[0038] The present invention provides the prerequisites for the long-term chemical protection of mineral fibers and eliminates the shortcomings of the prior art, thereby improving the mechanical properties of fiber-reinforced concrete. The present invention enables the production of concrete products that can be used in high humidity and in seismically active regions.

[0039] In a preferred embodiment of the concrete product according to the invention, the reinforcing fibers are glass fibers and / or basalt fibers. This allows the proposed technical solution to produce high-strength glass fiber and / or basalt fiber-reinforced concrete products whose service life does not depend on ambient humidity.

[0040] In the present invention, the coating can be applied to the mineral fibers both during the production of the mineral fibers and during the production of the concrete product.

[0041] It has proven particularly advantageous if not just one graphene layer, but several graphene layers, such as 3 to 25 graphene layers, particularly preferably 3 to 10 graphene layers, are applied to the silicone polymer layer.

[0042] The respective graph position(s) preferably contain at least 90% graphs.

[0043] In advantageous embodiments of the present invention, the proportion of mineral fibers comprising the coating in the concrete product is in the range of 0.01 to 5 wt.%. Preferably, the proportion of mineral fibers comprising the coating in the concrete product is in the range of 0.1 to 0.7 wt.%.

[0044] It has also proven advantageous if the mineral fibers each have a length in the range of 0.1 to 50 mm. The length of the mineral fibers is preferably 5 to 8 mm.

[0045] Comparative tests on the alkali resistance of reinforcing fibers according to the proposed technical solution were conducted in comparison to uncoated mineral fibers and to mineral fibers coated only with graphene (i.e., without a silicone polymer layer). Glass fibers were used as the mineral fibers in the tests. These tests were carried out according to a standard method by immersing the respective fibers in a 10% NaOH solution at a temperature of 80°C for 14 days and subsequently determining their tensile strength.

[0046] The tensile strength values ​​of the glass fibers with the coating according to the proposed technical solution exceeded the tensile strength of the glass fibers coated only with graphene by a factor of 1.8 and that of the uncoated glass fibers by a factor of 11.

[0047] To compare the mechanical properties of glass fiber reinforced concrete products, one manufactured according to the proposed technical solution and the other containing only graphene-coated glass fibers as reinforcing fibers, samples were produced and their compressive and flexural strength determined 28 days after molding. The samples were stored at a relative humidity of 75%.

[0048] Furthermore, the strength properties of a concrete product manufactured according to the proposed technical solution and of a concrete product in which only graphene-coated glass fibers, and not polymer silicone-coated glass fibers, were used as reinforcing fibers, were determined for 28 days at a relative humidity of 100%.

[0049] The results of the comparative tests showed the following pattern: • The flexural and compressive strength of the concrete product according to the proposed invention is on average 18% and 9% higher, respectively, after 28 days at a relative humidity of 75% than that of the concrete product in which only graphene-coated glass fibers, and not polymer silicone-coated glass fibers, were used as reinforcing fibers. • The flexural and compressive strength of the concrete product according to the proposed invention is 34% and 21% higher respectively after 28 days at a relative humidity of 100% than that of the concrete product in which only graphene-coated glass fibers, and not polymer silicone-coated glass fibers, were used as reinforcing fibers.

[0050] The data obtained suggest that, at high humidity, the strength of the concrete product according to the invention significantly exceeds the strength of the concrete product in which only glass fibers coated with graphene and not with polymer silicone were used as reinforcing fibers.

[0051] Therefore, the concrete product according to the invention is able to function under conditions of increased seismic activity and high humidity without any deterioration of its mechanical properties. Furthermore, the concrete product according to the invention can be manufactured in a thinner thickness while maintaining consistently high strength properties.

[0052] Preferred embodiments of the present invention are shown in the figures, wherein Fig. Figure 1 schematically shows a section of the material of an embodiment of the concrete product according to the invention in a cross-sectional view, and Fig. Figure 2 schematically shows a perspective view of a reinforcing fiber designed according to the invention.

[0053] In Fig. Figure 1 schematically shows the structure of an embodiment of the concrete product 10 according to the invention. The concrete product 10 comprises at least an aggregate 1, cement 2, and reinforcing fibers 3 designed according to the invention in a hardened mixture.

[0054] In the Fig. In the example shown, the reinforcing fibers are mineral fibers in the form of glass fibers with a coating consisting of a silicone polymer layer and several graphene layers. However, basalt fibers can also be used as mineral fibers instead of or in addition to the glass fibers.

[0055] At the in Fig. In the embodiment shown in Figure 1, the silicone polymer layer, consisting of a liquid organic silicone polymer, and the graphene layers, formed from a graphene dispersion, were created during the manufacturing process of the reinforcing fibers. In alternative embodiments of the invention, the silicone polymer layer and the graphene layers can be applied to the mineral fibers before the reinforcing fibers 3 are mixed with the concrete ingredients.

[0056] Fig. Figure 2 shows a single reinforcing fiber 3. The reinforcing fiber 3 is a mineral fiber 4 provided with a coating 5. In the embodiment shown, the mineral fiber 4 is a glass fiber, but in other embodiments of the present invention it can also be a basalt fiber.

[0057] In the Fig. In the embodiment shown in Figure 2, the coating 5 is formed from a mixture of a liquid organic silicone polymer and a graphene dispersion. The graphene dispersion used is a dispersion of graphene and water, with the graphene content in the dispersion being in the range of 3 to 5 wt.%. The silicone polymer was premixed with the graphene dispersion before being applied to the mineral fibers 4.

[0058] In the Fig. In the embodiment shown in Figure 2, the coating 5 was applied directly to the glass fibers during glass fiber production, i.e., while the glass fibers were being drawn through a spinneret. For this purpose, the dispersion was introduced into a lubrication system of the glass fiber production plant. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EA 201300703 A

[0005] EP 851957 B1

[0005] EP 1282751 B1

[0005] WO 84 / 02732 A1

[0005] US 3942955 A

[0005] US 6753081 B1

[0007] RU 2074153 C1

[0007] DE 202022104639 U1

[0007] WO 2022242862 A1

[0010] CH 709929 A1

[0010] EP 2336437 A1

[0010] DE 102010018348 A1

[0010] RU 123016 U1

[0010] RU 2569140 C1

[0014] DE 202023103900 U1

[0016]

Claims

[1] Reinforcing fibers (3) formed from mineral fibers (4) having a coating (5), characterized by , that the coating (5) - has at least one silicone polymer layer and at least one graphene layer or - has at least one graphene-containing silicone polymer layer or - has at least one silicone polymer layer, at least one graphene-containing silicone polymer layer and at least one graphene layer. [2] Reinforcing fibers according to claim 1, characterized by , that the mineral fibers (4) are glass fibers and / or basalt fibers. [3] Reinforcing fibers according to claim 1 or 2, characterized by , that at least one graph layer has 3 to 25 graph layers. [4] Concrete product (10) consisting of at least a mixture of aggregate (1), cement (2), reinforcing fibers (3) and water, characterized bythat the reinforcing fibers (3) are mineral fibers (4) with a coating (5) which - has at least one silicone polymer layer and at least one graphene layer or - has at least one graphene-containing silicone polymer layer or - has at least one silicone polymer layer, at least one graphene-containing silicone polymer layer and at least one graphene layer. [5] Concrete product according to claim 4, characterized by , that the mineral fibers (4) are glass fibers and / or basalt fibers. [6] Concrete product according to one of claims 4 or 5, characterized by , that the proportion of the mineral fibers (4) provided with the coating (5) in the concrete product (10) is in a range of 0.01 to 5 wt.%. [7] Concrete product according to any one of claims 4 to 6, characterized by , that the mineral fibers (4) each have a length in the range of 0.1 to 50 mm. [8] Concrete product according to any one of claims 4 to 7, characterized by , that at least one graph layer has 3 to 25 graph layers.

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