Concrete element and paving stone as well as methods for CO2 storage

Abstract

The invention relates to a concrete element (20) or a paving stone (30), a manufacturing method and a manufacturing device relating thereto. It is proposed that at least the amount of CO2 generated during the production of the concrete element (20) is bound in the concrete element (20), the concrete element (20) being designed to incorporate the CO2 during a hardening process. In addition, the invention relates to a method (10) for producing a concrete element, wherein at least an amount of CO2 that arises during the production of the concrete element (20) or paving stone (30) is incorporated during a hardening process, in particular a carbonation hardening. Furthermore, a manufacturing device for carrying out the process (10) is proposed, wherein a device for directly supplying the CO2 from a vent of a material production plant into a chamber (16) for hardening the at least one concrete element (20) or paving stone (30) is provided.

Description

[0001] The invention relates to a concrete element and a paving stone. The invention further relates to a method for manufacturing a concrete element or a paving stone. STATE OF THE ART

[0002] In the production of concrete elements or paving stones, the hardening process is a crucial step. Hardening determines aspects such as the strength, durability, and appearance of the concrete element or paving stone. One of the simplest methods for hardening is drying in an open racking system.

[0003] The hydration process underlying hardening (reduction of water in the cement) is highly dependent on environmental conditions, so that uneven hydration can occur if the cement is simply dried in a racking system. Therefore, hardening preferably takes place in special hardening chambers, which can be sealed and insulated. Advantageously, the environmental conditions can be controlled within a chamber.

[0004] It has been observed that concrete elements or paving stones can absorb CO2 from the ambient air during the curing process, and possibly even beyond. This can be achieved particularly through carbonation curing, which allows CO2 to be permanently bound within the concrete elements or paving stones.

[0005] However, in a typical hardening process, the incorporation of CO2 is usually limited to a maximum of 11 kg / m³. 2 CO2 or 11 kg / m² 3CO2 is limited.

[0006] It remains essential to reduce CO2 emissions. Therefore, it is advantageous to sequester a larger amount of CO2. This is because the production of cement, the basic material for concrete elements, is a very CO2-intensive process. The production of 1 kg of cement releases approximately 0.5 to 0.9 kg of CO2. The cement industry is responsible for around 8% of global CO2 emissions. This high CO2 output is primarily due to the production of cement clinker in rotary kilns.

[0007] The object of the invention is therefore to provide a concrete element, a paving stone, and a method that can achieve this object. In particular, the object of the invention is to incorporate the storage of a higher quantity of CO2 in a concrete element or paving stone during production, especially at least a quantity of CO2 that is generated during the production of the base material, particularly cement. Advantageously, at least the quantity of CO2 that is released during the manufacturing process of the concrete element or paving stone can be reintegrated.

[0008] The aim is to maximize carbonation hardening and thus achieve maximum CO2 uptake and binding. This should be achieved even when uptake is difficult due to a closed and, in particular, water-impermeable product surface and storage for curing on a production board.

[0009] This problem is solved by a concrete element or paving stone, a manufacturing process, and a manufacturing device according to the independent claims. Advantageous embodiments are the subject of the dependent claims. REVELATION OF THE INVENTION

[0010] The invention relates to a concrete element. It is proposed that at least the amount of CO2 generated during the production of the concrete element is bound in the concrete element, wherein the concrete element is designed to bind the CO2 during the hardening process.

[0011] The invention further relates to a paving stone. It is proposed that at least the amount of CO2 generated during the production of the paving stone is bound in the paving stone, wherein the paving stone is designed to bind the CO2 during the hardening process.

[0012] In a preferred embodiment, the concrete elements or paving stones have a closed surface, which is particularly impermeable to water. This prevents water penetration and also prevents the leaching of the incorporated CO2.

[0013] In a preferred embodiment, the concrete elements or paving stones have a facing layer and a core concrete layer, wherein the core concrete layer particularly has a reduced proportion of fines and / or contains open-pore concrete. Open-pore concrete describes a property of lightweight concrete in which the aggregates (such as expanded clay) are only partially cemented with a thin layer of cement paste, so that many voids (pores or cavities) are formed between them. This results in a low density, low weight, and good insulating properties without significantly impairing the strength. In this embodiment, the core concrete layer, which generally comprises at least 60-80% of the volume and weight of the concrete element or paving stone, particularly has a CO2-storing property, wherein the facing layer can also consist of ordinary material.It may be equipped with additional properties regarding improved IR reflectivity, abrasion resistance, optical properties, and catalytic properties.

[0014] The invention further relates to a method for producing a concrete element. It is proposed that a quantity of CO2 generated during the production of a concrete element, particularly during the cement production required for this purpose, be at least partially incorporated into the concrete element during a hardening process. The CO2 incorporation method can vary technically; that is, parameters such as CO2 content and temperature can vary depending on the concrete element being produced.

[0015] The invention further relates to a method for manufacturing a paving stone. It is proposed that a quantity of CO2 generated during the production of a paving stone be incorporated into the paving stone during a hardening process.

[0016] According to the invention, a "negative CO2 balance" can therefore be achieved, for example. Accordingly, a purification process of the ambient air can also take place according to the invention.

[0017] The invention thus relates to products which, due to their geometry or composition, are particularly suitable for absorbing CO2. The aim is to maximize the amount of CO2 that can be absorbed, whereby it is not necessarily required to absorb the entire amount of CO2 generated during the production of the cement or concrete product.

[0018] Preferably, the amount of CO2 generated during production is at least 30 kg to 150 kg, and in particular 50 kg to 150 kg. According to the invention, this amount of CO2 can be stored or incorporated, at least partially, into the concrete element or paving stone during the production of the base material, especially cement.

[0019] With the method according to the invention or with the concrete element or paving stone according to the invention, in particular a quantity of 20-25 kg / m² can be produced. 2 CO2 or 20-25 kg / m² 3 CO2 is incorporated in a manner many times higher than with known methods or prior art bricks. In other words, the invention enables the production of a "green brick".

[0020] According to the invention, for example, concrete elements or paving stones with a thickness of 5 cm to 7 cm, in particular 5.8 cm, can be produced. Other thicknesses are also conceivable.

[0021] In another embodiment, concrete elements or paving stones can be manufactured that contain a recycled content of at least 20%, in particular 30% to 50%, preferably 40% of the material used. This further improves the CO2 balance.

[0022] In contrast to drying, the main difference between hardening and hardening is that drying merely reduces the water content of the concrete block, while hardening increases the strength and resistance of the concrete block.

[0023] The hardening process can be, in particular, carbonation hardening. In heated hardening chambers, where moisture and / or CO2 can be added, the hardening of the concrete elements or paving stones can be intensified by increased carbonation. Therefore, the CO2 concentration in the air within the chamber is preferably increased. Different carbonation depths can be achieved with carbonation hardening. For example, with optimized CO2 levels, concrete mix design, and hardening time, the carbonation depth can reach up to 1 cm.

[0024] Another advantage of carbonation hardening is that well-carbonated surfaces give the product, i.e., concrete element or paving stone, a denser surface, which can largely prevent efflorescence and increase long-term color stability. In other words, the open-pore structure of the material can be utilized during the hardening process when CO2 is incorporated.

[0025] Carbonation hardening technology uses CO2 to harden concrete blocks or other concrete elements and permanently binds it into the concrete block through the chemical reaction with calcium hydroxide to form calcium carbonate.

[0026] In a preferred embodiment, the paving stone or concrete element can have a facing layer and a core concrete layer, wherein the core concrete layer particularly has a reduced fines content and / or contains open-graded concrete. In open-graded concrete, the aggregate particles are of uniform size. This results in small contact points or contact areas between the particles and creates air voids that are not filled with concrete. These voids give the concrete an overall rougher surface. In particular, the core concrete can consist of open-graded concrete. The core concrete layer particularly has a reduced water-cement ratio and / or a reduced fines content.

[0027] In a preferred embodiment, the core concrete layer can be designed to bind the CO2 during a hardening process, particularly via the side surfaces of the concrete element or paving stone. Thus, the four side surfaces of the core concrete layer can serve to absorb the CO2. If the concrete elements are more slab-like, with the side surfaces widely spaced, it is advantageous to provide a base profile to utilize the entire interior of the core concrete layer for CO2 absorption. This allows the bearing surface of the concrete element or paving stone to also be used for CO2 absorption when it is stored on a transport unit. Profiling therefore maximizes the product surface area.

[0028] In particular, concrete elements and paving stones of varying geometries can therefore be implemented while maintaining maximum carbonation capacity, and especially the core concrete layer of the entire concrete element or paving stone can be fully used for CO2 absorption. A familiar appearance can be maintained, as a dense, visually appealing, and waterproof, and at least partially colored, facing layer is still required.

[0029] For example, for paving stones or concrete elements with a raised and / or recessed curb in a range of, in particular, 8 cm to 50 cm, this can be achieved using a core concrete mix with a low porosity and reduced fines content. Specifically, a core mix with a high porosity is used, preferably with a maximum aggregate size of 8 mm to 16 mm.

[0030] By using "sharp" quartz sands instead of natural sands, the proportion of fine particles can be further reduced. In particular, the grading curve can be shifted to a range of 2 mm to 5 mm.

[0031] It is still conceivable that recycled concrete (RC concrete) will be used. In particular, concrete mixes that allow for a reduction in the water-cement ratio can be employed.

[0032] Implementing at least one of these factors, and thus adapting the concrete mix design, can lead to sufficient CO2 penetration, particularly via the flanks or side surfaces. The invention specifically aims to propose a method and a device for utilizing and permanently incorporating CO2 from the cement industry. Insights into this were gained from research on carbon dioxide reduction through low-lime clinker and carbonation hardening during concrete production. The invention can be applied on an industrial scale. In particular, the invention contributes to achieving the strategic goal of the German Federal Government's Carbon Management Strategy (CMS), with special reference to emissions that are difficult or impossible to avoid.

[0033] In a preferred embodiment, once a target concentration of CO2 has been reached, at least one environmental parameter can be controlled and / or maintained over a period of time.

[0034] In a preferred embodiment, the hardening process can take place in a chamber, which is hermetically sealed and flooded with CO2. A sealed chamber advantageously allows the CO2 concentration within the chamber to be set or controlled. For example, the chamber can be flooded with CO2 until a desired concentration is reached. Likewise, CO2 can be removed from the chamber in a controlled manner.

[0035] For example, a chamber can be provided in which at least one concrete element or paving stone is arranged. Preferably, however, a multiple of paving stones or concrete elements are provided within a single chamber. It is also conceivable that several chambers, in particular two or more, are provided, which can also be interconnected. This allows all chambers to be controlled or regulated simultaneously. A "ProCarbonCure system with four QUATRO double chambers" can be used as an example.

[0036] In a preferred embodiment, pre-storage can take place at 25 °C and 50% relative humidity for 3 hours. Pre-storage refers specifically to storage that occurs prior to the actual storage in which the CO2 is incorporated. This pre-storage can, for example, take place under near-room climate conditions, where a room climate of approximately 23 °C to 25 °C, 45% to 55% relative humidity, and 50% CO2 can be observed.

[0037] In a preferred embodiment, after pre-storage, the chamber can be flooded with CO2, particularly up to a CO2 concentration of 50%, and preferably over a period of 2 hours. The CO2 flooding can be continuous. For example, a continuous supply of CO2 can be set so that a CO2 concentration of 50% is reached after 2 hours. It is also conceivable that CO2 is supplied continuously, with a CO2 concentration of 50% being reached before or after a period of 2 hours. Accordingly, the period can be adjusted and does not have to be two hours.

[0038] The CO2 can be blown into the chamber. Alternatively or additionally to the circulation of the CO2 in the chamber, a device, in particular a blower or similar, can be provided.

[0039] In particular, the CO2 can be supplied directly from the concrete production or material production of the chamber.

[0040] In a preferred embodiment, the material can then be stored at 25 °C, 50% relative humidity, and 50% CO2, particularly for a period of at least 10 hours, preferably for a period of 19 hours. Preferably, after 19 hours, the process has progressed to such an extent that the amount of CO2 is stored in the concrete element or paving stone.

[0041] In a preferred embodiment, the CO2 concentration can then be lowered and the at least one paving stone or concrete element removed from the chamber. Preferably, a plurality of elements or stones are hardened simultaneously in the chamber and can therefore be removed at the same time.

[0042] In a preferred embodiment, the at least one paving stone or the at least one concrete element can have a facing layer and a core concrete layer, wherein the core concrete layer in particular has a reduced fines content and / or contains porous concrete, wherein the facing layer is applied before hardening.

[0043] In a preferred embodiment, the amount of CO2 can be incorporated via the side surfaces of the core concrete layer. The core concrete layer serves in particular to absorb CO2, as already described with regard to the concrete product or the paving stone. The features and advantages already mentioned therefore also apply to the process.

[0044] In a preferred embodiment, the amount of CO2 absorbed by the concrete element or paving stone can be determined by the porosity of the side surfaces of the core concrete layer and / or by the geometry of a base profile. In particular, a base profile can be provided for slab-shaped elements, as already described with regard to the concrete product or paving stone. The aforementioned features and advantages therefore also apply to the process. According to the invention, the entire process, including pre-storage, can last for a period of 24 hours. Accordingly, the concrete element or paving stone can be removed from storage after approximately 24 hours and subjected to a packaging process.

[0045] The invention further relates to a manufacturing device for implementing the process. This device includes a means of directly feeding CO2 from a flue, in particular a chimney or chimney, into the chamber during material production, preferably raw material production, especially cement production. The device can advantageously be retrofitted into existing plants. The CO2 to be used in this plant can, for example, be taken from cement production as a raw material, since CO2 is captured there and thus explicitly falls under those difficult or unavoidable CO2 emissions that the CMS targets.

[0046] CO2 can be separated from the exhaust gas stream of a cement clinker kiln using amine scrubbing technology. This includes both the unavoidable, process-related CO2 emissions generated during calcination in cement clinker production, and the fuel-related emissions from the energy sources used in the kiln.

[0047] The energy demand, especially the specific energy demand per unit of concrete block produced, can amount to, for example, 479.4 kW. Since not all components are always operating simultaneously, full power is not always required. Therefore, this value can only serve as an estimate of the upper limit of the energy demand. Assuming operation for 200 days a year and 8 hours a day, this maximum electrical output would result in an energy demand of 767.4 MWh. Advantageously, the electricity is generated by wind turbines. Wind power does not produce CO2 during operation. Even considering a life-cycle analysis of wind turbines and a corresponding CO2 factor of approximately 10 grams per kWh, realistic operation of the plant would result in only a few tons of CO2 per year. DRAWINGS

[0048] Further advantages become apparent from the accompanying drawings and drawing descriptions. The drawings illustrate exemplary embodiments of the invention. The drawing, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations. These include: Fig. 1: a schematic representation of a possible sequence of the method according to the invention; Fig. 2: a possible embodiment of a chamber as it can be used according to the invention; Fig. 3 - 7: different possible designs of concrete elements or paving stones. Fig. 8: a concrete element or paving stone in a drying chamber; Fig. 9: a concrete element or paving stone arranged on a transport unit.

[0049] Fig. Figure 1 shows a possible sequence of a method 10 according to the invention. In step A, pre-storage can take place, wherein the at least one concrete element 20 or the at least one paving stone 30 can be stored, for example, for 3 hours at a room temperature of 25 °C and 50% relative humidity. This can take place, in particular, in a chamber 16, as exemplified in Figure 1. Fig. Figure 2 illustrates this process. The at least one paving stone or concrete element can remain in chamber 16, where, in step B, storage can take place at 25 degrees Celsius, 50% relative humidity, and 50% CO2. For this purpose, chamber 16 can, for example, be flooded with CO2 for a period of 2 hours until a CO2 concentration of 50% is reached. Other timeframes are also conceivable. During storage in step B, the at least one concrete element or paving stone can remain in chamber 16 for 19 hours. Subsequently, in step C, removal from chamber 16 can take place. In step C, for example, the remaining CO2 can first be released from chamber 16. The at least one paving stone or concrete element can then be subjected to a packaging process.The process, therefore, could take 24 hours for steps A to C, for example. Other process durations are also conceivable.

[0050] As in Fig. As shown in Figure 2, chamber 12 can also be designed to hold several concrete elements 20 or paving stones 30. The concrete elements 20 or the paving stones 30 can, for example, be stored on a pallet 18. Alternatively, several pallets 18 can be stacked on top of each other, for example, using racking elements, so that a plurality of concrete elements or paving stones can be arranged in chamber 16.

[0051] The concrete elements 20 can be any type of concrete element, such as palisade stones, kerbstones, L-shaped stones and the like.

[0052] The device and / or method are based in particular on the industrial application of amine scrubbing technology, which can be used to separate CO2 from the exhaust gas stream of a cement clinker kiln. These emissions consist of two-thirds process-related emissions generated during the production of cement clinker through the deacidification of calcium carbonate, as well as the associated fuel-related emissions released from the energy sources used to operate the kiln.

[0053] In the production of concrete blocks, curing is a crucial process step that determines strength, durability, and appearance. Several methods exist for this in the current state of the art. The simplest method is drying the blocks in an open racking system. However, the underlying hydration process, i.e., the reaction between cement and water, is highly dependent on environmental conditions, which can lead to inconsistent results with this method. Therefore, curing is often carried out in special curing chambers. These are sealed and insulated and can be equipped with heating and humidity control to precisely manage the environmental conditions required for the desired result.

[0054] It has been observed that concrete absorbs CO2 from the ambient air during the curing process and even beyond. During carbonation curing, the cement does not react exclusively with water, but also hardens through reaction with CO2. Specifically, the reaction with water, the hydration of the cement, produces calcium hydroxide (Ca(OH)2), which then reacts further with any existing CO2 to form calcium carbonate (CaCO3). This calcium carbonate is sparingly soluble and forms a hard layer with a penetration depth that depends on the process parameters. The CO2 is thus permanently bound.

[0055] The carbonated concrete products manufactured using the method or device can be labelled as "CO2 bricks" or with an additional "CO2-reducing" label. The invention makes it possible, in particular, to produce low-lime cement clinker for the direct avoidance of CO2 emissions in clinker production. With regard to carbonation hardening, therefore, it is essential to analyze and optimize both the process of CO2 absorption into the concrete and, relatedly, to identify and develop those clinker and cement types that are particularly well-suited for carbonation hardening and exhibit the highest possible CO2 binding potential.

[0056] The concrete elements or paving stones can be stored in special curing chambers. These can be sealed airtight and then flooded with CO2. Once the target concentration is reached, the ambient parameters can be regulated and maintained for the required duration by the automatic process control system. Afterwards, the CO2 concentration can be reduced and the stones removed. Carbonation therefore represents an additional process step in concrete block production.

[0057] A concrete block plant can produce, for example, 185,000 tons of concrete products for garden and landscape construction annually. Of this, approximately 75,000 tons can be wall panels and palisades, and approximately 110,000 tons high-quality concrete block products. From this product portfolio, the concrete blocks are ideally suited for carbonation curing technology because they offer a large surface area to volume ratio. This is important because the incorporation of CO2 from the atmosphere of the special curing chamber occurs via diffusion into the surface of the already formed concrete blocks.

[0058] With this invention, at least 50% of the annual production of a concrete block manufacturing plant can be processed after commissioning. This allows, for example, the initial use of 55,000 tons of concrete blocks for carbonation hardening. Specifically, 30–50 kg of CO2 per cubic meter of concrete block can be incorporated. The exact amount can depend on the cement clinker or cement types used, the optimal process parameters, and the objective of complete carbonation of the concrete. Furthermore, it is conceivable that volumes of 50–150 kg of CO2 per cubic meter of concrete block can be achieved, particularly when using clinker-rich CEM-I cement types.

[0059] Further experience and optimization, as well as new insights and developments in clinker and cement, will enable even higher input rates. For example, the amount of concrete blocks used for carbonation can be gradually increased by optimizing the process steps involved in exposing the concrete blocks to CO2. From an initial 55,000 tons of concrete blocks per year, a total of 65,000 tons per year could be achieved by 2030, and then 80,000 tons per year by 2033.

[0060] The Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. Figure 7 shows embodiments of concrete elements 20, in particular designed as paving stones 30. In the Fig. 3 and Fig. Figure 6 shows a view from the left in figure (a), a view from the right in figure (b), a view from the rear in figure (c), and a view from the front in figure (d). The paving stone 30 according to the Fig. 3, Fig. 4 to Fig. For example, 5 may have a core concrete layer.

[0061] The paving stone 30 according to the Fig. 6 and Fig. 7 can have a core concrete layer 14 and a facing layer 12. The paving stones 30 can have different ribs or spacers on their sides, which ensure a gap between the paving stones 30. The paving stones 30 can also have grooves on their underside, as for example in Fig. 5 shown.

[0062] Fig. Figure 8 shows a concrete element or paving stone in a drying chamber. The concrete element 20 or paving stone 30 has a core concrete layer 14 and a facing layer 12. The concrete element 20 or paving stone 30 is arranged on a transport unit 19.

[0063] In Fig. Figure 8(a) shows the situation before the absorption of CO2 from the ambient air of the drying chamber by the concrete element 20 or the paving stone 30. The CO2 is therefore represented as a dotted area. The arrows indicate that CO2 can enter the core layer 14 through the side surfaces and a bottom surface of the concrete element 20 or paving stone 30. For example, the transport unit 19 may be designed to be porous, allowing the CO2 to enter the core concrete layer 14 through the transport unit 19. Alternatively or additionally, the transport unit may have openings, in particular formed by holes and / or slots. This also allows the transport unit 19 to be permeable.

[0064] Typically, concrete products carbonate to a depth of approximately 1 cm at the edges, whereby CO2 can only be bound or absorbed to a depth of 1 cm. The invention enables complete carbonation, thereby maximizing the amount of bound CO2 in concrete products, in addition to improving technical properties such as reducing efflorescence, increasing color brilliance, and increasing strength through carbonation hardening. Fig. Figure 8(b) shows the situation where the CO2 is absorbed in the core concrete layer 14. The entire core concrete layer 14 can serve to absorb CO2, and it may be fully carbonated. A residual amount of CO2 may remain in the ambient air, which can be released from the drying chamber.

[0065] Since slabs, due to their geometry, do not have sufficient flank area or sufficiently large side surfaces, it is advantageous for "through-carbonation" if a base profile is provided, as in Fig. Figure 9 shows that the panels can be profiled on their underside during the manufacturing process, for example, using a so-called drawing die. This profiling allows CO2 to flow through the resulting profile channels under the underside of the core concrete layer 14 during carbonation, which can advantageously lead to complete CO2 absorption penetrating all the way to the product core.

[0066] According to the invention, paving stones or concrete elements that differ from those shown can be used, such as, in particular, palisade stones, L-shaped stones, kerbstones and the like. REFERENCE MARK LIST 10 procedures 12. Front layer 14 Core concrete layer 16th Chamber 18 pallets 19 transport units 20 concrete elements 30 paving stones A Upstream storage B Storage C Expansion

Claims

Concrete element (20), characterized in that at least the amount of CO2 generated during the production of the concrete element (20) is bound in the concrete element (20), wherein the concrete element (20) is designed to bind the CO2 during a hardening process. Paving stone (30), characterized in that at least the amount of CO2 generated during the production of the paving stone (30), in particular during the cement production required for this purpose, is bound in the paving stone (30), wherein the paving stone (30) is designed to bind the CO2 during the hardening process. Concrete element (20) according to claim 1 or paving stone (30) according to claim 2, characterized in that it has a closed surface which is in particular designed to be impermeable to water. Concrete element (20) or paving stone (30) according to one of the preceding claims, characterized in that it has a facing layer (12) and a core concrete layer (14), wherein the core concrete layer (14) in particular has a reduced fines content and / or contains open-pore concrete. Concrete element (20) or paving stone (30) according to claim 4, characterized in that the core concrete layer is designed to incorporate the CO2 during a hardening process, in particular via side surfaces of the concrete element (20) or paving stone (30). Method (10) for producing a concrete element (20), in particular according to one of claims 1 or 3 to 5, characterized in that at least an amount of CO2 that arises during the production of a concrete element (20) is at least partially incorporated into the concrete element (20) during a hardening process, in particular a carbonation hardening process. Method (10) for producing a paving stone (30), in particular according to one of claims 2 to 5, characterized in that at least an amount of CO2 that arises during the production of a (30) paving stone is at least partially incorporated into the paving stone (30) during a hardening process, in particular a carbonation hardening process. Method (10) according to one of claims 6 or 7, characterized in that after reaching a target concentration of CO2, at least one environmental parameter is controlled and / or maintained over a period of time. Method (10) according to claims 6 to 8, characterized in that the hardening process takes place in a chamber (16), wherein the chamber (16) is hermetically sealed and flooded with CO2. Method (10) according to one of claims 6 to 9, characterized in that a pre-storage (A) takes place at 25 °C and 50% relative humidity for 3 hours. Method (10) according to claims 9 and 10, characterized in that after pre-storage (A) the chamber (16) is flooded with CO2, in particular up to a concentration of 50% CO2, and preferably over a period of 2 hours. Method (10) according to claim 11, characterized in that storage (B) is subsequently carried out at 25 °C, 50% room humidity and 50% CO2, in particular for a period of at least 10 hours, preferably for a period of 19 hours. Method (10) according to claim 12, characterized in that the concentration of CO2 is subsequently lowered and the at least one paving stone (30) or the at least one concrete element (20) is removed from the chamber (16). Method (10) according to claim 12, characterized in that the at least one paving stone (30) or the at least one concrete element (20) is subsequently removed from the chamber (16), and the excess CO2 is discharged from the chamber (16). Method (10) according to one of claims 6 to 14, characterized in that the at least one paving stone (30) or the at least one concrete element (20) has a facing layer (12) and a core concrete layer (14), wherein the core concrete layer (14) in particular has a reduced fines content and / or contains open-pore concrete, wherein the facing layer (14) is applied before hardening. Method (10) according to claim 15, characterized in that the amount of CO2 is incorporated via the side surfaces of the core concrete layer (14). Method (10) according to claim 15 or 16, characterized in that an amount of CO2 absorbed in the concrete element (20) or paving stone (30) is determined by a porosity of the side surfaces of the core concrete layer (14) and / or by a geometry of a floor profiling. Concrete element (20), in particular paving stone (30), characterized in that it is manufactured according to a method according to one of claims 6 to 17. Manufacturing device for carrying out the method (10) according to one of claims 6 to 17, characterized in that a device for directly supplying the CO2 from a vent of a material production plant into a chamber (16) for hardening the at least one concrete element (20) or paving stone (30) is provided.

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