Mixture for producing concrete or mortar, or additive for cement-containing products

Abstract

The invention relates to a mixture for producing concrete, the mixture containing biochar, in particular pyrolized biochar, to fresh concrete / mortar or a cured concrete product produced from the mixture, and to the use of biochar as aggregate in concrete / mortar for reducing the net CO2 emissions of the concrete production, in particular for reaching a net CO2 emission of the concrete and mortar production of net-zero or below. The invention relates in particular to a mixture of biochar and cement.

Description

[0001] Mixture for the production of concrete or mortar or additive for cement-containing products

[0002] The present invention relates to a mixture for producing fresh concrete of various types. Furthermore, the invention relates to all hardened concrete products or a cured concrete product made from the mixture.

[0003] Concrete and mortar have long been known as versatile building materials. One disadvantage of using concrete or mortar as building materials is the relatively high CO2 emissions associated with their production. A lot of CO2 is generated, particularly during the production of the cement used in concrete and mortar. Reduction approaches such as the use of alternative binding agents or recycled concrete are being intensively pursued by the construction industry. A further reduction in CO2 emissions is of great economic and ecological interest.

[0004] The object of the present invention was to provide a solution for improving the net effect on the climate in the area of ​​cement-containing products.

[0005] According to the invention, this object is achieved by a mixture according to claim 1. The mixture according to the invention is a mixture for producing concrete or mortar of all kinds. The mixture contains biochar. The plants used to produce the biochar remove CO2 from the atmosphere as they grow. By incorporating biochar into concrete, large amounts of carbon can be stably bound for a long time. In this way, the CO2 emissions that occur during the production of other components of the concrete or mortar, such as cement, can be at least partially compensated for, but complete compensation or overcompensation is also possible. The inventors have recognized that the use of the mixture according to the invention in the production of concrete results in concrete products with material properties that are particularly useful in the construction industry. The mixture according to the invention can in particular contain pyrolyzed biochar.Biochar can be produced, for example, by pyrolyzing plant material at temperatures between 350°C and 1000°C, while removing oxygen. The plant material can be a waste product from agriculture or forestry, for example, or it can come from plants cultivated specifically to bind CO2. Biochar can be present as an additive in any form (pure, mixed, conditioned, loaded, etc.).

[0006] Examples of the invention result from the features of the dependent claims 2 to 9. In one embodiment of the mixture, the

[0007] Biochar in grains of the grain size range 0 - 10 mm, especially 0 - 6 mm.

[0008] These grain size ranges for the biochar granules can be achieved, for example, by breaking up larger pieces and / or possibly additionally by sieving with a corresponding mesh size. The inventors recognized that fresh concrete with a grain size range containing larger grains, e.g., up to 30 mm, is difficult to process, including difficult to pump, and that the larger biochar pieces have a strong tendency to float to the top. By reducing the maximum grain size to a maximum of 10 mm or smaller, fresh concrete becomes more workable and stable.

[0009] As an alternative, it is also conceivable to grind the biochar into much smaller grains, which can create a filler effect in the concrete.

[0010] In one embodiment, the mixture comprises, e.g., in combination with a binder, an activator with a hydraulic effect. A hydraulic effect is understood to mean the effect that enables the concrete to harden under water, i.e., in the absence of air, without contact with carbon dioxide from the air. Various substances are known that have such a hydraulic effect or that have it in combination with the cement. The activator in the present embodiment, for example, with an additive of types I and II according to SN EN 206, can in particular be an activator from the group comprising

[0011] - lime,

[0012] - Puz zolane ,

[0013] - glass powder,

[0014] - Stone flour,

[0015] - ground mixed concrete granulate, or

[0016] - Water glass (soda water glass, potassium water glass or lithium water glass or a mixture of these).

[0017] In one embodiment of the mixture containing an activator, the activator is incorporated into pores of the biochar and / or applied to the surface of the biochar. In this embodiment, the large internal surface area of ​​pyrolyzed biochar can be used to great advantage by loading this surface with an auxiliary substance which simplifies the production of concrete / mortar and improves its durability. This means that the biochar is conditioned or loaded biochar. In an alternative, the mixture consists of the biochar loaded with the activator. This mixture can, for example, be stored and delivered separately and can be mixed with other components of the concrete in a subsequent production step of a concrete product.In one embodiment, the mixture already includes other components for concrete production, for example, a complete cement mixture including the activator. In one embodiment of the mixture, the biochar has a carbon mass fraction of at least 85%, is essentially free of polycyclic aromatic carbons (PAHs), and is essentially free of heavy metals.

[0018] Concrete products made from such a mixture can be used without hesitation in areas where there is direct physical contact with the concrete product. Furthermore, the recycling of such concrete products is not complicated by the biochar content, as there is no risk of heavy metals or polycyclic aromatic carbons escaping from the biochar during extraction and reuse. It is particularly advantageous if the biochar meets the conditions for EBC certification (European Biochar Certificate) or is EBC certified. This certification defines, among other things, limit values ​​for heavy metals and PAHs that are tailored to the intended use.Limit values ​​are defined differently depending on the intended use (for the EBC-Agro, EBC-Urban, and EBC-Consumer Materials classes). The EBC-Consumer Materials class is defined so that the corresponding products are suitable for direct skin contact or contact with food. There are stricter limit values ​​for individual substances for EBC-AgroBio and even stricter ones for EBC-Feed.

[0019] The compound used in the mixture according to the invention

[0020] Biochar can, for example, comply with the limit values ​​for heavy metals according to the following table, which corresponds to the requirements for the EBC-Consumer Materials class (unit in g per tonne of dry matter (DM)): Compliance with stricter limits, such as those specified for the EBC-AgroBio class, also improves the resulting concrete product in terms of potential applications and ease of recycling. The biochar used can, for example, also comply with the limit for polycyclic aromatic hydrocarbons (PAH) of a maximum of 6.0 g t-1 DM.

[0021] Compliance with additional requirements for EBC certification leads to a more favorable carbon footprint. No fossil fuels may be used for heating during the pyrolysis of EBC biochar, and the resulting pyrolysis gases must be recovered and burned. The pyrolysis gases must not escape into the atmosphere. Using EBC biochar ensures that the production of biochar has no climate-damaging side effects.

[0022] In variants of embodiments, the mixture contains a low dosage of 1-5%, based on the cement, or a high dosage of up to 30%, for a wide range of applications.

[0023] In one embodiment, the mixture comprises a first weight fraction of biochar and a second weight fraction of cement, wherein the ratio of the first weight fraction to the second weight fraction is at least 1:8 and wherein the ratio in particular does not exceed 1:1. The ratio of the first weight fraction to the second weight fraction can in particular be in the range 1:5 to 1:3.

[0024] The inventors have recognized that for relevant types of cement, the net CO2 emissions of approximately 4 kilograms of cement can be offset to net zero with one kilogram of biochar. With a ratio of the first weight share to the second weight share of at least 1:8, a significant portion of the climate impact of cement production is already offset. Conversely, to ensure that the properties of the concrete are not impaired by an excessive proportion of biochar, the ratio of 1:1 should not be exceeded. Adjustments of the ratio to the type of cement and to other aggregates in the concrete are possible within the stated ratio, whereby the

[0025] Inventors have recognized that a weight ratio of between 1 : 5 and 1 : 3 is a favorable compromise between reduced net CO2 emissions and properties of the resulting concrete product for many applications.

[0026] Surveys on the production process for biochar have shown that 2.61 kg of CO2 equivalent of carbon can be bound per kilogram of biochar. For the cement used in the example below, the CO2 emissions from cement production are 0.66 kg CO2 equivalent per kg of cement. In this case, 1 kg of biochar compensates for 3.9 kg of cement. The influence of the aggregate and admixtures has not yet been taken into account in this consideration. The use of recycled concrete, for example, or rock that has only been transported a short distance, can of course have an additional positive effect on the overall CO2 footprint. With the greenhouse gas emissions mentioned, a weight ratio of 1:3, for example, can achieve net-negative CO2 emissions.

[0027] In one embodiment, the mixture further contains a stabilizer to ensure the balance between sedimentation stability and flowability of the concrete. Such a stabilizer prevents biochar grains from floating upwards in the mixed fresh concrete. The stabilizer can, in particular, be a viscosity modifier in the form of a high-molecular-weight, synthetic copolymer. The stabilizer can be added to the mixture, for example, in the form of an aqueous solution of the high-molecular-weight, synthetic copolymer.

[0028] The inventors have recognized that, for example, the product "MasterMatrix SDC 100", marketed by MBCC Group, which is an aqueous solution of a high-molecular, synthetic copolymer, is suitable as a stabilizer in the mixture according to the invention and effectively improves the cohesion and stability of the fresh concrete with the biochar portion produced on the basis of the embodiment of the mixture.

[0029] In another embodiment, the mixture consists of biochar and cement.

[0030] This design has the advantage that an improved CO2 balance or even CO2 neutrality can be achieved with a cement mixture according to this

[0031] The mixture according to this embodiment could then be described as "CO2-neutral cement." Another aspect of adding biochar is that it allows for a certain amount of cement to be saved.

[0032] This means that the mix is ​​provided without aggregates, sand and stones, etc. In this case, there is no need for the time-consuming addition of biochar in the concrete plant. By adding the mix according to this embodiment, the mixing processes in the concrete plant can take place as if conventional cement were being added. The biochar in this mix can be pure biochar or, in particular, it can also be conditioned or loaded biochar in the sense discussed above. The biochar can therefore be loaded with an additive that supports and enhances the hydraulic process. The biochar can be loaded with CO2, which, in addition to binding carbon in the biochar, further improves the CO2 balance of the mixture.To produce the mixture according to this embodiment, biochar can be added to cement clinker before grinding, and then the cement clinker and biochar can be ground together. Alternatively, biochar can also be mixed with ground cement clinker to obtain the mixture according to this embodiment. The grain size of the biochar can, for example, be in the range of 0.001 mm to 40 mm. In particular, the grain size of the biochar can be in the range of the fineness of the ground cement, i.e., approximately 0.045 mm.

[0033] In one embodiment of the mixture, the mixing ratio is between 10 kg of biochar to 1000 kg of cement and 300 kg of biochar to 1000 kg of cement.

[0034] The inventors have recognized that, based on the mixture with this range of biochar and cement ratios, concrete products can be obtained that exhibit a very favorable carbon dioxide balance while simultaneously meeting the usual requirements for concrete products. This mixture, which can be sold, for example, in standard cement packaging units, is very easy to handle and requires no further adjustment of concrete production processes.

[0035] Features of the discussed embodiments can be combined as desired.

[0036] The invention further relates to fresh concrete or mortar or a hardened concrete product according to claim 10 or claim 11, wherein the fresh concrete or the hardened concrete product is produced from the mixture according to the invention.

[0037] In one embodiment, the cured concrete product contains a mass fraction of biochar per volume of the cured concrete product that is in the range of 40 to 100 kg / m3. In particular, the mass fraction of biochar per volume of the cured concrete product can be in the range of 75 to 90 kg / m3.

[0038] The inventors have recognized that in the above-mentioned ranges, acceptable building material properties can be combined with a favorable CCh balance in a surprisingly simple manner for the mass fraction of biochar relative to the volume of the hardened concrete product.

[0039] The invention further relates to a use of biochar according to claim 12, namely the use of biochar as an additive in concrete or in mortar for reducing the net CO2 emissions of concrete production, in particular for achieving a net CO2 emissions of concrete production of net zero or below.

[0040] The following specific example of a concrete mix combines features of several of the above-discussed designs (quantities given in kilograms per cubic meter of concrete product):

[0041] - Cement: 300 kg / m 3

[0042] - Pyrolized biochar in EBC quality: 80 kg / m 3

[0043] - Aggregate size 0-32 mm

[0044] In this concrete recipe, the ratio of the first weight portion (vegetable charcoal) to the second weight portion (cement) is 1:3.75. Admixtures, such as stabilizers or superplasticizers, can be added to the cement in a proportion of a few percent by weight, based on the weight of the cement. For example, the product "Master Matrix SDC 100" can be added as a stabilizer at a proportion of 0.2 percent by weight. For example, a superplasticizer based on polycarboxylates can also be added to improve the flow properties. For example, the product "Glenium Sky 767" can be added as a superplasticizer at a proportion of 0.8 percent by weight.

[0045] Primary material, e.g. clean gravel, can be used in the mixture, the fresh concrete and the ready-mixed concrete products according to the present invention. An improvement of the ecological balance is possible in a simple way by using recycled material within the scope of the invention, e.g. by

[0046] Addition of concrete granulate or mixed demolition granulate.

Claims

Patent claims 1. Mixture for the production of concrete or mortar, wherein the mixture contains biochar, in particular pyrolyzed biochar.

2. Mixture according to claim 1, wherein the biochar is in the form of grains with a grain size range of 0 - 10 mm, in particular 0 - 6 mm, or smaller.

3. Mixture according to one of claims 1 or 2, wherein the mixture comprises an activator with a hydraulic effect, in particular wherein the activator is from the group comprising lime, pozzolans, glass flour, stone flour, ground mixed concrete granules, or water glass.

4. Mixture according to claim 3, wherein the activator is introduced into pores of the biochar and / or applied to the surface of the biochar.

5. Mixture according to any one of claims 1 to 4, wherein the biochar has a carbon mass fraction of at least 85%, wherein the biochar is substantially free of polycyclic aromatic hydrocarbons and wherein the biochar is substantially free of heavy metals.

6. Mixture according to any one of claims 1 to 5, wherein the Mixture for a wide range of applications, low Dosage of 1-5%, based on the cement, or high dosage up to 30%.

7. Mixture according to any one of claims 1 to 6, wherein the mixture further comprises a stabilizer which ensures the balance between sedimentation stability and flowability, in particular a stabilizer in the form of a high molecular weight synthetic copolymer.

8. Mixture according to any one of claims 1 to 7, wherein the mixture consists of biochar and cement.

9. Mixture according to claim 8, wherein the mixing ratio is between 10 kg of biochar to 1000 kg of cement and 300 kg of biochar to 1000 kg of cement.

10. Fresh concrete or mortar or hardened concrete product made from the mixture according to any one of claims 1 to 9.

11. Cured concrete product according to claim 10, wherein the mass fraction of biochar per volume of the cured concrete product is in the range of 40 to 100 kg / m³, in particular wherein the mass fraction of biochar per Volume of the hardened concrete product in the range of 75 to 90 kg / m3 is the value.

12. Use of biochar as an aggregate in concrete or mortar to reduce the net CO2 emissions of concrete production, in particular to achieve net CO2 emissions of concrete production of net zero or below.