Concrete element and method for its production
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.
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 . 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 . The concrete element according to claim 1 , wherein the granular material has a grain size number from 1.59 to 3.62.
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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . The concrete element according to claim 1 , wherein the mixture has hardening regulators.
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 . 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 . 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 . The method according to claim 17 , wherein the components of the composition are metered in the order given.
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 . 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.
21 . The method according to claim 19 , wherein the binder is an inorganic binder selected from the group consisting of cement, hydraulic lime, gypsum and water glass or
the binder is an organic binder selected from the group consisting of plastic dispersions, acrylate resins, alkyd resins, epoxy resins, polyurethanes, SolGel resin and silicone resin emulsions,
and/or said litter component has a mean grain diameter of 0.1 to 1.8 mm or from 1.2 to 5 mm,
and/or said litter component comprises one or more of a rock mixture, semi-precious stones, mica, metal chips, glass and plastic particles.
22 . The concrete element according to claim 19 , wherein the binder contained in the grained material is in an amount of 5 to 35 wt. %, based on the total composition of the grained material.
23 . The concrete element according to claim 1 , wherein the granular material has,
at a screen hole width of 2 mm, a through fraction from 72.5 wt. % to 97.5 wt. %, and,
at a screen hole width of 0.25 mm, a through fraction 2.5 to 8.5 wt. %, based on the total weight of the granular material.