Low-cement concrete composition, structure, structural component

Abstract

Low-cement concrete composition - with a solid component, wherein the solid component has a solid part, the solid part consisting of: - Cement, wherein the mass fraction of cement in relation to the total mass of the solid part is a maximum of 50 wt.%, - at least one virtually inactive first additive, and - at least one hydraulically latent or pozzolanic second additive; and - optionally with a liquid component.

Description

[0001] The present invention relates to the field of concrete technology. In particular, the present invention relates to a low-cement concrete composition, a structural component, and a structure.

[0002] Carbon dioxide (CO2) emissions represent one of the central challenges of our time. Worldwide, measures are being taken to reduce CO2 emissions in all industrial sectors and to establish sustainable production processes. In addition to the energy and transport sectors, the construction industry is increasingly coming into focus, as it contributes significantly to the global greenhouse gas balance. In particular, the production of cement, which serves as the main binding agent in concrete, generates large quantities of CO2.

[0003] Cement production is among the most energy-intensive and emission-intensive processes and contributes significantly to global CO2 emissions. This high CO2 intensity results from two aspects of the production process. The majority of emissions arise directly from the chemical transformation of the main raw material, limestone, which chemically consists of calcium carbonate. In the process known as calcination or deacidification, the calcium carbonate is thermally decomposed at high temperatures into calcium oxide and CO2, with CO2 being released as an unavoidable gaseous reaction product. This process is also referred to as clinker burning.

[0004] In addition to the process-related emissions from limestone deacidification, further significant amounts of CO2 are generated by the energy required for the clinker burning process. Generating the high temperatures necessary for the formation of hydraulically active clinker phases requires a considerable amount of thermal energy, which in conventional cement plants is also supplied by burning fossil fuels. Due to its availability and cost-effectiveness, coal remains the dominant energy source. Furthermore, the use of steel reinforcement in concrete also increases the overall CO2 balance.

[0005] The invention is therefore based on the objective of providing a concrete composition that enables a significant reduction in CO2 emissions without compromising the structural integrity and longevity of the structures built with these materials.

[0006] The problem underlying the invention is solved by a concrete composition having the features of claim 1.

[0007] The invention relates to a low-cement concrete composition with a solid component. The solid component comprises a solid part consisting of cement, wherein the mass fraction of cement is a maximum of 50 wt.% based on the total mass of the solid part, at least one, in particular nearly, inactive (inert) first additive, and at least one, in particular hydraulically latent and / or pozzolanic, second additive.

[0008] Due to the limitation of the cement mass fraction to 50 wt% of the total mass of the solids, CO2 emissions during the production of the concrete mix can be significantly reduced. Despite the low cement mass fraction, the provided concrete mix achieves high structural integrity and durability. This is a very surprising effect, as the cement mass fraction differs considerably from that of standardized concrete mixes. The low cement mass fraction is compensated for by the addition of at least one primary and at least one secondary additive (cement substitution), enabling comparable mechanical properties to be achieved with this concrete mix to those of conventional, standardized, high-cement concrete mixes.

[0009] Preferably, the concrete composition is a homogeneous mixture.

[0010] The low-cement concrete composition can exist in various states.

[0011] In some embodiments, the concrete composition comprises a liquid component, particularly water, in addition to the solid component. The solid component may be suspended in the liquid component. In these embodiments, the concrete composition may be, for example, fresh concrete or hardening concrete. Fresh concrete refers to the state of the concrete composition after mixing and before setting, in which the mass is still plastically workable. Hardening concrete refers to a concrete composition in the hydration phase, during which the concrete composition transitions into the solid state. Hardened concrete refers to the fully hardened building material with a fully developed structure and strength.

[0012] In some embodiments, the solid component comprises at least one additional solid besides the solid part. Possible additional solids will be discussed in more detail below.

[0013] In some other embodiments, the solid component is formed by the solid part. Therefore, no other solids are contained in the concrete composition besides the solid part.

[0014] In some embodiments, the solid part comprises only one first additive. Alternatively, several different first additives may be present. Preferred first additives are discussed in more detail below.

[0015] In some embodiments, the solid component contains only one second additive. Alternatively, several different second additives may be present. Preferred second additives are discussed in more detail below.

[0016] In some embodiments, the concrete composition is free of a liquid component. In these embodiments, the concrete composition can be, for example, hardened concrete or dry concrete. Hardened concrete refers to the hardened state of the concrete composition. Dry concrete refers to a powdered or granular dry mix that is activated with water at the place of use, thereby obtaining a concrete composition with a liquid component.

[0017] Concrete admixtures, or additives, are finely dispersed substances that influence certain properties of the concrete mix. These are primarily the workability of the fresh concrete and the strength and density of the hardened concrete. Admixtures are to be distinguished from concrete additives, as admixtures, unlike additives, are generally added in such large quantities that they must be taken into account in the material volume calculation.

[0018] DIN EN 206-1 / DIN 1045-2 classifies the group of additives into two types: Type 1: nearly inactive additives, Type 2: pozzolanic or latent hydraulic additives. The concrete composition according to the invention therefore comprises at least one first additive of Type 1 (nearly inactive first additive) and at least one second additive of Type 2 (latent hydraulic or pozzolanic additive). Additives of Type 2 may, provided their suitability has been demonstrated, be included in the water-cement ratio as an equivalent water-cement ratio. The water-cement ratio defines the mass ratio between water and cement. The equivalent water-cement ratio defines the mass ratio between water, cement, and eligible additives. The water-binder ratio defines the mass ratio between water and binder without including additives.

[0019] Inactive additives (type 1 additives), such as quartz flour, limestone flour, or pigments, do not react, or react only minimally, with cement and water and therefore do not interfere, or only minimally interfere, with hydration. Due to their particle size, composition, and shape, they serve to improve the aggregate structure in the fines range. They are added to concrete mixes to achieve a sufficient fines content for workability and a more compact structure. For the purposes of this disclosure, an inactive or nearly inactive substance is understood to be one that does not react at all, or reacts only minimally, compared to the second type 2 additive during the production of the concrete mix or the concrete itself.

[0020] Pozzolanic additives (type 2 additives) can be divided into natural pozzolans, such as trass, and synthetic pozzolans, such as fly ash or silica dust. They react with the calcium hydroxide produced during the hydration of cement paste, forming cement-like hardening products. These substances contribute to hardening and, due to their particle size, composition, and shape, improve the grain structure in the flour range.

[0021] Latent hydraulic substances (additives of type 2), such as granulated blast furnace slag, require an activator (calcium hydroxide or calcium sulfate) to then harden hydraulically themselves. Such substances also contribute to the hardening process.

[0022] The low-cement concrete composition may lie outside the normatively permissible range, but still exhibit durable and serviceable properties.

[0023] An advantageous aspect of the invention provides that the mass fraction of cement, based on the total mass of the solid component, is between 34.0 wt.% and 45.0 wt.%. This allows the optimum to be achieved while maintaining the opposing goals of CO2 reduction and the mechanical properties of the concrete. The mass fraction of cement, based on the total mass of the solid component, is preferably greater than 25 wt.%, in particular greater than 30 wt.%, and more preferably greater than 34.0 wt.%. The mass fraction of cement, based on the total mass of the solid component, is preferably less than 55 wt.%, in particular less than 50 wt.%, more preferably less than 45 wt.%, and further preferably less than 42 wt.%.

[0024] An advantageous aspect of the invention provides that at least one first additive is quartz flour and / or limestone flour. Quartz flour and limestone flour are finely ground mineral fillers that improve the packing density of the concrete by filling the voids between the coarser cement particles. This optimized particle size distribution results in a denser structure, leading to reduced porosity and thus increased durability of the concrete. Furthermore, the workability of the fresh concrete can be improved because the flours act as physical fillers and increase the cohesion of the concrete mix. This reduces segregation and improves pumpability.

[0025] An advantageous aspect of the invention provides that the mass fraction of the at least one first additive, based on the total mass of the solid component, is between 30.0 wt.% and 51.2 wt.%. This allows the concrete composition to be further optimized with regard to the objectives of CO2 reduction and maintaining mechanical properties. The mass fraction of the at least one first additive, based on the total mass of the solid component, is preferably greater than 20.0 wt.%, in particular greater than 25.0 wt.%, and more preferably greater than 30.0 wt.%. The mass fraction of the at least one first additive, based on the total mass of the solid component, is preferably less than 60.0 wt.%, in particular less than 55.0 wt.%, and more preferably less than 51.2 wt.%.If several first additives are present, the mass fractions disclosed above refer to the sum of the mass fractions of the first additives in relation to the total mass of the solid part.

[0026] An advantageous aspect of the invention is that at least one second additive is a synthetic pozzolan. Synthetic pozzolans improve concrete quality through their pozzolanic reactivity. Unlike inactive or inert fillers, these materials react chemically with the calcium hydroxide released during cement hydration, forming additional strength-enhancing phases. This significantly increases the final strength of the concrete. Furthermore, the pore structure can be refined, thus reducing permeability. From an ecological perspective, synthetic pozzolans offer the advantage of being industrial byproducts, and their use in concrete avoids the need for landfilling waste materials and reduces the cement content, thereby lowering the concrete's CO2 footprint.

[0027] An advantageous aspect of the invention provides that at least one second additive is granulated blast furnace slag and / or fly ash and / or silica dust and / or silica suspension. Granulated blast furnace slag is produced by grinding granulated blast furnace slag and has latent hydraulic properties. Upon excitation, granulated blast furnace slag exhibits a cement-like strength profile, so that a portion of the cement can be replaced by the granulated blast furnace slag. Fly ash originates from, for example, bituminous coal and is thus an organic sediment that has been transformed into coal by geological processes. Fly ash is a fine-grained, artificial pozzolan consisting mainly of spherical, glassy particles, which is produced during the combustion of finely ground coal and has pozzolanic properties. Due to its particle shape and size distribution, as well as its pozzolanic properties, fly ash is a cement substitute.Silica dust is an extremely fine-grained, mineral additive that is produced during the manufacture of silicon and silicon products and has pozzolanic properties.

[0028] The mean particle size (D50) of the first additive, in particular limestone flour, is preferably in a range between 2 µm and 20 µm, in particular between 5 µm and 15 µm, preferably between 8 µm and 12 µm.

[0029] An advantageous aspect of the invention provides that the mass fraction of the at least one second additive, based on the total mass of the solid component, is between 14.6 wt.% and 31.3 wt.%. This allows the concrete composition to be further optimized with regard to the objectives of CO2 reduction and maintaining mechanical properties. The mass fraction of the at least one second additive, based on the total mass of the solid component, is preferably greater than 5.0 wt.%, in particular greater than 10.0 wt.%, and more preferably greater than 14.6 wt.%. The mass fraction of the at least one second additive, based on the total mass of the solid component, is preferably less than 40.0 wt.%, in particular less than 45.0 wt.%, and more preferably less than 31.3 wt.%.If several second additives are present, the mass fractions disclosed above refer to the sum of the mass fractions of the second additives in relation to the total mass of the solid part.

[0030] An advantageous aspect of the invention provides that the concrete composition should be at least 140 kg / m³ 3 and / or a maximum of 230 kg / m² 3 The concrete composition contains cement. Preferably, the concrete composition contains at least 100 kg / m³. 3 , in particular at least 120 kg / m² 3 , preferably at least 140 kg / m² 3 Cement. Preferably, the concrete composition has a maximum of 230 kg / m³. 3 , in particular a maximum of 220 kg / m² 3 , preferably a maximum of 210 kg / m² 3 , preferably a maximum of 200 kg / m² 3 Cement. In these embodiments, the concrete composition preferably includes a liquid component.

[0031] In one embodiment, at least one second additive is granulated blast furnace slag. It is conceivable that the concrete composition contains at least 100 kg / m³. 3 and / or a maximum of 210 kg / m² 3 The concrete composition contains blast furnace slag. In these embodiments, the concrete composition preferably includes a liquid component.

[0032] It is conceivable that the concrete composition, as a liquid component, is 150 L / m³. 3 The concrete composition contains water, particularly tap water. Preferably, the concrete composition contains at least 130 L / m³. 3 , in particular at least 140 L / m² 3 Water. Preferably, the concrete composition has a maximum water content of 170 L / m³. 3 , in particular a maximum of 160 L / m 3 Water.

[0033] An advantageous aspect of the invention provides that the solid component further comprises fibers. Steel fibers, in particular high-performance steel fibers, and / or polypropylene (PP) fibers can be used as fibers. The steel fibers increase the tensile strength of the concrete. Thus, the use of steel reinforcement can be reduced or even completely dispensed with if further evidence can be provided. The concrete composition can be at least 30.0 kg / m³. 3 , in particular at least 35.0 kg / m² 3 Contains steel fibers. The concrete composition can have a maximum of 60.0 kg / m³. 3 , in particular a maximum of 50.0 kg / m² 3 Contains steel fibers. The PP fibers increase the fire resistance of the concrete. The concrete composition can contain at least 0.9 kg / m³. 3 , in particular at least 1.5 kg / m² 3 Contains PP fibers. The concrete composition can have a maximum of 2.0 kg / m³. 3 , in particular a maximum of 2.5 kg / m² 3contain PP fibers.

[0034] An advantageous aspect of the invention provides that the mass ratio between the liquid component and the cement (water-cement ratio) is between 0.8 and 1.25. Preferably, the mass ratio between the liquid component and the cement is greater than 0.6, in particular greater than 0.7, and more preferably greater than 0.8. Preferably, the mass ratio between the liquid component and the cement is less than 1.4, in particular less than 1.3, and more preferably less than 1.25.

[0035] An advantageous aspect of the invention provides that the mass ratio between the liquid component and the solid component (water-binder ratio) is between 0.34 and 0.43. Preferably, the mass ratio between the liquid component and the solid component is greater than 0.25, in particular greater than 0.30, and more preferably greater than 0.34. Preferably, the mass ratio between the liquid component and the solid component is less than 0.50, in particular less than 0.45, and more preferably less than 0.43.

[0036] An advantageous aspect of the invention provides that the mass fraction of the solid part is at least 70 wt.% in relation to the total mass of the solid component.

[0037] Preferably, the mass fraction is between 70 wt.% and 95 wt.%. Preferably, the mass fraction of the solid component is greater than 50 wt.%, in particular greater than 60 wt.%, and preferably greater than 70 wt.%. Preferably, the mass fraction of the solid component is less than 98 wt.%, in particular less than 96 wt.%, and preferably less than 95 wt.%.

[0038] An advantageous aspect of the invention provides that a primary second additive is granulated blast furnace slag and a secondary second additive is fly ash, wherein the mass ratio between the granulated blast furnace slag and the fly ash is in a range between 4:1 and 2:1, in particular between 3.5:1 and 2.5:1, preferably 3:1. Preferably, the mass ratio between the granulated blast furnace slag and the fly ash is greater than 2:1, in particular greater than 2.4:1 and more preferably greater than 2.8:1. Preferably, the mass ratio between the granulated blast furnace slag and the fly ash is less than 4:1, in particular less than 3.6:1 and more preferably less than 3.2:1. The mean particle size (D50) of the mixture of the primary and secondary second additives is preferably in a range between 5 µm and 30 µm, in particular between 10 µm and 20 µm. The mixture of the two second additives preferably comprises SiO2, Al2O3, CaO, MgO and / or Fe2O3.

[0039] The concrete mix, particularly the solid component, may contain additional admixtures such as plasticizers, sealants, and / or setting accelerators. The solid component may also contain sand, gravel, and / or crushed aggregate.

[0040] It is advantageous if the hardened concrete produced from the concrete mix has a compressive strength after 7 days of more than 30 MPa, in particular more than 35 MPa, preferably more than 40 MPa, preferably more than 45 MPa, and / or after 28 days of more than 50 MPa, in particular more than 55 MPa, preferably more than 60 MPa, preferably more than 65 MPa. It is also advantageous if the hardened concrete produced from the concrete mix has a compressive strength after 7 days of less than 60 MPa, in particular less than 55 MPa, preferably less than 50 MPa, and / or after 28 days of less than 90 MPa, in particular less than 85 MPa, preferably less than 80 MPa, preferably less than 75 MPa.

[0041] It is advantageous if the hardened concrete produced from the concrete mix has a modulus of elasticity after 2 days of more than 15 GPa, in particular more than 20 GPa, preferably more than 25 GPa, and / or after 7 and / or 28 days of more than 30 GPa, in particular more than 35 GPa, preferably more than 37 GPa. It is also advantageous if the hardened concrete produced from the concrete mix has a modulus of elasticity after 2 days of less than 32 GPa, in particular less than 28 GPa, and / or after 7 and / or 28 days of less than 44 GPa, in particular less than 42 GPa, preferably less than 40 GPa.

[0042] The problem underlying the invention is also solved by a building component or a building with the features of claim 14.

[0043] The invention relates to a structural component, in particular a tunnel lining segment, or a structure, in particular a tunnel comprising several tunnel lining segments, which is made from a previously described concrete composition. A tunnel lining segment is a precast concrete element used in tunnel construction and, in particular, has a partially arched cross-section. A tunnel can be composed of a plurality of tunnel lining segments. Consequently, structural components and structures can be manufactured in a stable, durable, and low-CO2 manner.

[0044] Another aspect concerns a method for producing a previously described concrete composition in a mixing device, comprising the steps of: mixing the liquid and solid components in the mixing device to produce the concrete composition; and discharging the concrete composition. Due to the low cement content, a low-CO2 concrete composition is obtained. The cement substitution using the first and second additives maintains the mechanical properties required for the construction of structures despite the reduction in cement.

[0045] To achieve this, all components of the solid part can first be premixed and then mixed with the liquid component. Specifically, all components of the solid component can first be premixed and then mixed with the liquid component. Alternatively, all components of the solid part can first be premixed and then mixed with the liquid component or a portion of the liquid component, followed by the addition of the remaining components of the solid component and, if applicable, the remaining portion of the liquid component. It is also conceivable that the remaining components of the solid component are first premixed with (a portion of) the liquid component and then mixed with the solid part.

[0046] The concrete mix is ​​preferably used to manufacture a tunnel lining ring. Such a concrete mix is ​​called tunnel lining concrete.

[0047] In a specific embodiment, the concrete composition comprises the following components: - 150 kg / m 3 Cement, - 135 kg / m 3 a mixture consisting of blast furnace slag and fly ash, - 130 kg / m 3 Limestone flour - 50 kg / m 3 silica suspension - 4.2 kg / m² 3 Flow agent - 3.0 kg / m 3 Hardening accelerator, - 40.0 kg / m² 3 steel fibers, - 1.5 kg / m 3 PP fibers, and - Water.

[0048] In another specific embodiment, the concrete composition comprises the following components: - 180 kg / m 3 Cement, - 120 kg / m 3a mixture consisting of blast furnace slag and fly ash, - 100 kg / m 3 Limestone flour - 2-4 kg / m 3 Flow agents, and - Water.

[0049] In another specific embodiment, the concrete composition comprises the following components: - 140 kg / m 3 Cement, - 210 kg / m 3 a mixture consisting of blast furnace slag and fly ash, - 60 kg / m 3 Limestone flour - 2-4 kg / m 3 Flow agents, and - Water. 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 non-patent literature

[0000] DIN EN 206-1 / DIN 1045-2

[0018]

Claims

[1] Low-cement concrete composition - with a solid component, wherein the solid component has a solid part, the solid part consisting of: - Cement, wherein the mass fraction of cement in relation to the total mass of the solid part is a maximum of 50 wt.%, - at least one virtually inactive first additive, and - at least one hydraulically latent or pozzolanic second additive; and - optionally with a liquid component. [2] Concrete composition according to claim 1, wherein the mass fraction of cement, based on the total mass of the solid part, is between 34.1 wt.% and 45.0 wt.%. [3] Concrete composition according to any of the preceding claims, wherein at least one first additive is quartz flour or limestone flour. [4] Concrete composition according to one of the preceding claims, wherein the mass fraction of the at least one first additive is between 30.0 wt.% and 51.2 wt.% in relation to the total mass of the solid part. [5] Concrete composition according to any of the preceding claims, wherein at least one second additive is synthetic pozzolan. [6] Concrete composition according to one of the preceding claims, wherein at least one second additive is granulated blast furnace slag, fly ash and / or silica dust. [7] Concrete composition according to one of the preceding claims, wherein the mass fraction of the at least one second additive is between 14.6 wt.% and 31.3 wt.% in relation to the total mass of the solid part. [8] Concrete composition according to any of the preceding claims, wherein the concrete composition is at least 140 kg / m³ 3 and a maximum of 230 kg / m² 3 It contains cement. [9] Concrete composition according to any one of the preceding claims, wherein the solid component further comprises: - High-performance steel fibers; and - PP fibers. [10] Concrete composition according to one of the preceding claims, wherein the mass ratio between the liquid component and the cement is between 0.8 and 1.

25. [11] Concrete composition according to one of the preceding claims, wherein the mass ratio between the liquid component and the solid component is between 0.34 and 0.

43. [12] Concrete composition according to one of the preceding claims, wherein the mass fraction of the solid component is at least 70 wt.%, preferably between 70 wt.% and 95 wt.%. [13] Concrete composition according to one of the preceding claims, wherein a primary second additive is granulated blast furnace slag and a secondary second additive is fly ash, wherein the mass ratio between the granulated blast furnace slag and the fly ash is in a range between 4:1 and 2:

1. [14] Structural component, in particular tunnel lining ring, or structure, in particular tunnel, made from a concrete composition according to any one of claims 1 to 13.