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US-12623965-B2 - Concrete element and method for its production

US12623965B2US 12623965 B2US12623965 B2US 12623965B2US-12623965-B2

Abstract

What is shown and described is a concrete element including a core concrete layer and a face concrete layer, the face concrete layer being obtained by compacting and hardening a mixture containing a latent hydraulic binder and/or a pozzolanic binder, water, a granular material and an alkaline hardener, with the granular material having, at a screen hole width of 2 mm, a through fraction from 35.5 wt. % to 99.5 wt. % and, at a screen hole width of 0.25 mm, a through fraction from 2.5 wt. % to 33.5 wt. %, each based on the total weight of the granular material.

Inventors

  • Guido Volmer
  • Michael Metten

Assignees

  • METTEN TECHNOLOGIES GMBH & CO. KG

Dates

Publication Date
20260512
Application Date
20200820
Priority Date
20190913

Claims (20)

  1. 1 . A concrete element comprising a core concrete layer and a face concrete layer, the face concrete layer being obtained by compacting and hardening a mixture containing: a latent hydraulic binder and/or a pozzolanic binder, water, a granular material, and 3 wt. % to 5 wt. % of an alkaline hardener, based on the total weight of the mixture, with the granular material having, at a screen hole width of 2 mm, a through fraction from 35.5 wt. % to 99.5 wt. %, and at a screen hole width of 0.25 mm, a through fraction from 2.5 wt. % to 8.5 wt. %, each based on the total weight of the granular material, and wherein the alkaline hardener is selected from the group consisting of alkali metal oxides, alkali metal hydroxides, alkali metal carbonates, alkali metal silicates, alkali metal aluminates and mixtures thereof.
  2. 2 . The concrete element according to claim 1 , wherein the granular material has: at a screen hole width of 2 mm, a through fraction from 42.5 wt. % to 99.5 wt. %, and at a screen hole width of 0.25 mm, a through fraction from 2.5 wt. % to 8.5 wt. %, based on the total weight of the granular material.
  3. 3 . The concrete element according to claim 1 , wherein the granular material has a grain size number from 1.59 to 3.62.
  4. 4 . The concrete element according to claim 1 , wherein the mixture contains 55 wt. % to 80 wt. % of the granular material, based on the total weight of the mixture.
  5. 5 . The concrete element according to claim 1 , wherein the mixture contains 1 wt. % to 30 wt. % of a filler, based on the total weight of the mixture.
  6. 6 . The concrete element according to claim 5 , wherein the filler has, at a screen hole width of 0.025 mm, a through fraction from 63 wt. % to 99 wt. % and, at a screen hole width of 0.015 mm, a through fraction from 38 wt. % to 73 wt. %, based on the total weight of the filler.
  7. 7 . The concrete element according to claim 5 , wherein the filler is selected from the group consisting of fly ash, slag sand, rock powder, limestone powder, and mixtures thereof.
  8. 8 . The concrete element according to claim 1 , wherein the mixture contains 15 wt. % to 40 wt. % of latent hydraulic binder and/or pozzolanic binder, based on the total weight of the mixture.
  9. 9 . The concrete element according to claim 1 , wherein the latent hydraulic binder is selected from the group consisting of slag, blast furnace slag, electrothermal phosphorus slag, steel slag, and mixtures thereof and/or the molar ratio of (CaO +MgO):SiO 2 in the latent hydraulic binder ranges from 0.8 to 2.5.
  10. 10 . The concrete element according to claim 1 , wherein the pozzolanic binder is selected from the group consisting of amorphous silicon dioxide, precipitated silicon dioxide, pyrogenic silicon dioxide, microsilica, glass powder, fly ash, metakaolin, natural pozzolans, natural and synthetic zeolites, and mixtures thereof.
  11. 11 . The concrete element according to claim 1 , wherein the alkaline hardener is selected from the group consisting of alkali metal hydroxides, alkali metal silicates, and mixtures thereof.
  12. 12 . The concrete element according to claim 1 , wherein the mixture contains 3.15 wt. % to 4.85 wt. % of the alkaline hardener, based on the total weight of the mixture.
  13. 13 . The concrete element according to claim 1 , wherein the mixture contains 3 wt. % to 7 wt. % water, based on the total weight of the mixture.
  14. 14 . The concrete element according to claim 1 , wherein the mixture has hardening regulators.
  15. 15 . The concrete element according to claim 1 , wherein the mixture contains cement and/or one or more additives selected from the group consisting of gravel, grit, sand, perlite, kieselguhr, and vermiculite, and/or one or more additives selected from the group consisting of plasticizers, antifoam agents, water retention agents, dispersants, pigments, fibers, redispersible powders, wetting agents, impregnating agents, complexing agents, and rheology additives.
  16. 16 . The concrete element according to claim 1 , wherein the concrete element is a concrete block, a concrete slab, a concrete wall element, or a concrete step.
  17. 17 . A method for producing the concrete element according to claim 1 , comprising the following steps: a. preparing of a composition containing as components i. granular material, ii. optional pigment, iii. optional filler, iv. water, v. latent hydraulic binder and/or pozzolanic binder, and vi. alkaline hardener, wherein the alkaline hardener is selected from the group consisting of alkali metal oxides, alkali metal hydroxides, alkali metal carbonates, alkali metal silicates, alkali metal aluminates and mixtures thereof, b. mixing of the composition to obtain a mixture, that contains 3 wt. % to 5 wt. % of the alkaline hardener, based on the total weight of the mixture, c. filling of the mixture into at least one mold, and d. compacting of the mixture to obtain at least one green concrete element.
  18. 18 . The method according to claim 17 , wherein the components of the composition are metered in the order given.
  19. 19 . The method according to claim 17 , said method further comprising applying a grained material to the mixture before compacting said mixture in the at least one mold, the grained material comprising a litter component with a mean grain diameter of 0.1 to 5 mm in an amount of 65 to 95 wt. %, and a binder in an amount of 5 to 35 wt. %, based on the total composition of the grained material.
  20. 20 . The method according to claim 17 , wherein the surfaces and/or edges of the at least one green concrete element are processed with brushes and structured and/or roughened and/or smoothed and/or protrusions are reduced at the edges, and wherein a sealing and/or waterproofing agent is applied to the surface of the at least one green concrete element, and wherein the green concrete element is hardened to obtain a concrete element, wherein the concrete element is processed after it has hardened by grinding, blasting, brushing and/or structuring the concrete element.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is the United States national phase of International Application No. PCT/EP2020/073347 filed Aug. 20, 2020, and claims priority to German Patent Application No. 10 2019 124 726.8 filed Sep. 13, 2019, the disclosures of which are hereby incorporated by reference in their entirety. BACKGROUND OF THE INVENTION Field of the Invention The invention relates to a concrete element comprising a core concrete layer and a face concrete layer, the face concrete layer being obtained by compacting and hardening a mixture containing a latent hydraulic binder and/or a pozzolanic binder, water, a granular material and an alkaline hardener. The invention also relates to a method for producing the concrete element according to the invention. Description of Related Art Concrete elements such as concrete blocks, concrete slabs, concrete wall elements or concrete steps are often used due to their durability and lower price compared to stones, plates or steps made of natural stone. Concrete elements are usually produced by using cement as a binder. Various methods have been developed to enable the concrete elements to look decorative. For this purpose, among other things, pigment and/or natural stone aggregates and/or sands are usually added to provide color to the concrete element. Cement-containing concrete elements sometimes have the problem that they develop whitish spots on the surface over time. The color of colored concrete blocks may also fade. Both effects appear to be caused by the formation of lime. The whitish spots on the surface are attributed to lime efflorescence, which is formed by the reaction of calcium hydroxide transported to the surface with carbon dioxide. It is believed that the color fading is caused, among other things, by the fact that the pigment that has settled on the cement particles to provide color is slowly coated with calcium carbonate that forms. This is how the color impression of the pigment is slowly lost. Binders that are an alternative to cement are known. An example of such alternative binders is based on the chemical building blocks SiO2 in combination with Al2O3. Examples of such binders are latent hydraulic binders and pozzolanic binders. These are often referred to as “geopolymers.” EP 1 236 702 A1 describes for example a building material mixture containing water glass and a latent hydraulic binder. EP 1 236 702 A1 proposes to use the building material mixture as a mortar or filler. EP 1 081 114 A1 also describes a building material mixture for the production of chemical-resistant mortars, wherein the building material mixture contains water glass powder, at least one soluble water glass hardener, an inorganic filler and at least 10 wt. % of a latent hydraulic binder. WO 2014/067721 A1 discloses an aluminosilicate binder which is activated by alkaline substances. According to WO 2014/067721 A1, the aluminosilicate binder is suitable for fresh concrete, concrete parts, sprayed concrete, building adhesives and other applications. The production of concrete elements such as concrete blocks, concrete slabs, concrete wall elements or concrete steps places special demands on the concrete mix used, especially when compared to fresh concrete. When producing concrete elements, it is desirable to achieve the highest possible stability of the not yet hardened concrete blocks after as little time as possible so that they can be packed as quickly as possible. An additional requirement for the products that comprise a face concrete layer and core concrete is a high bond strength in order to prevent the face concrete layer from delaminating from the core under load. The adhesive tensile strength can be used to measure the resistance of the face concrete layer against a delamination from the core concrete of the concrete elements. If the adhesive tensile strength of the concrete elements is not high enough, the face concrete layer and core concrete can separate under load (delamination) or tear apart when the formwork is removed. This means that the concrete elements can be produced with a shorter cycle time and therefore more economically if they are designed with a sufficiently high adhesive tensile strength. In the course of the development of the present invention, it was found that concrete elements or layers of concrete elements which contain latent hydraulic binders and/or pozzolanic binders have a lower adhesive tensile strength under otherwise comparable production conditions and components than concrete elements which contain cement as a binder. SUMMARY OF THE INVENTION The object of the invention was therefore to provide aesthetically sophisticated concrete elements that change their appearance less over time and can be produced economically. In particular, concrete blocks are to be provided which show less staining and/or soiling on the surface and/or less color fading and/or have a sufficiently high adhesive tensile strength. Anot