Process for producing hydrothermally hardened aerated or foamed concrete moldings and aerated or foamed concrete molding produced according to the process

Abstract

The invention relates to a process for producing hydrothermally hardened aerated or foamed concrete moldings, in particular in the form of areated or foamed concrete blocks, and an aerated or foamed concrete molding produced according to the process.

Description

[0001] Process for the production of hydrothermally cured aerated or foamed concrete moldings and aerated or foamed concrete moldings produced by the process

[0002] The present invention relates to a process for producing hydrothermally cured aerated or foamed concrete moldings, in particular in the form of aerated or foamed concrete blocks. Particularly preferred are aerated concrete blocks of standardized grades regarding strength and bulk density according to DIN EN 771-4:2015-11 in combination with DIN 20000-404:2018-04 with bulk densities of 305 to 1000 kg / m³. 3 However, non-standardized bricks can also be produced, e.g. with a density between 200 and < 305 kg / m 3 and aerated or foam concrete insulation material, preferably aerated or foam concrete insulation boards, with a bulk density between e.g. 70 and < 200 kg / m 3 , preferably 70 and 150 kg / m 3Furthermore, reinforced aerated or foam concrete precast elements with bulk densities such as standardized or non-standardized aerated or foam concrete blocks can also be manufactured.

[0003] Furthermore, the invention relates to such a porous or foam concrete molded body produced by means of the method.

[0004] Aerated concrete moldings consist of hydrothermally cured, porous calcium silicate hydrate material. They are produced from an aqueous mixture or fresh concrete mass containing at least one CaO component reactive in the hydrothermal process and at least one SiO2 component reactive in the hydrothermal process, a blowing agent, in particular aluminum powder and / or paste, and optionally, particularly inert, additives. Furthermore, the fresh concrete mass often contains at least one admixture, e.g., a plasticizer and / or a dispersant. The pourable or ready-to-cast fresh concrete mass is poured into a mold, allowed to expand and stiffen, cut, and then subjected to steam curing. In contrast to conventional, non-autoclaved concrete, aerated concrete material does not contain coarse aggregates with a grain size > 2.0 mm.

[0005] To produce hydrothermally cured foam concrete moldings, pre-formed foam is mixed into the fresh concrete mass instead of the foaming agent, or the fresh concrete mass containing a foaming agent is directly foamed by stirring, and then the pourable or ready-to-cast fresh concrete mass is poured into the mold. In both cases, the foaming process is omitted.

[0006] Conventional porous and foam concrete moldings therefore essentially consist of a solid web structure, which generally consists primarily of calcium silicate hydrate phases (CSH phases). "Primarily" means that the solid web structure consists of more than 50 mass% of the CSH phases, based on its dry mass. At high densities, e.g., > 650 kg / m 3, the content can also be below 50 mass%. The solid web framework can also contain, for example, residual quartz grains and possibly the inert additives. The residual quartz grains and the inert additives are embedded in the CSH phases. The solid web framework has webs that surround the pores (= macropores) artificially created by porosification or the addition of foam or foaming. In addition, the solid web framework has nano-, gel- and micropores that are embedded in or distributed within the CSH phases. The nano-, gel- and micropores are part of the solid web framework. The CSH phases of the solid web framework thus function as a binding phase in the solid web framework. They are largely cryptocrystalline to crystalline, usually CSH(I) and mainly 11 Å tobermorite.

[0007] Aerated or foam concrete blocks are building blocks made of aerated or foam concrete material. These generally unreinforced aerated or foam concrete blocks are primarily used as masonry units. Depending on the manufacturing tolerances, they are also referred to as aerated or foam concrete blocks or blocks. Reinforced aerated or foam concrete preforms are primarily used as large-format aerated or foam concrete components.

[0008] As already explained, porous or foam concrete moldings with very low bulk density are used as porous or foam concrete insulation bodies, preferably in the form of porous or foam concrete insulation boards.

[0009] Currently, aerated concrete blocks of standardized grades (EN 771-4 2015-1 1 and DIN 20000-404:2018-04) with bulk densities < 800 kg / m 3usually manufactured using so-called lime-cement formulations. Lime-cement formulations contain cement, usually Portland cement (CEM I), as both a CaO and SiO2 component. However, lime-cement formulations can also contain other standardized (e.g., CEM II or CEM III) or non-standardized cements. In addition to the cement, quicklime and / or hydrated lime are also included as a CaO component. In addition to the cement, lime-cement formulations also contain another SiO2 component, e.g., ground quartz, preferably ground sand, or fly ash. Furthermore, lime-cement formulations usually contain a sulfate carrier in the form of anhydrite and / or gypsum. The sulfate carrier in the cement acts as a setting regulator and is already contained in the cement. For standardized cements, the SO2 content is specified in DIN EN 197-1:2011-11. However, an additional sulfate carrier is usually added to the aerated concrete mixture.

[0010] Furthermore, pure lime formulations for the production of aerated concrete moldings are also known in the field. These lime formulations contain only quicklime and / or hydrated lime as the CaO component, but no cement or cement clinker. Consequently, they do not contain a sulfate carrier as a setting regulator. Generic lime formulations are known, for example, from WO 2009 / 121635 A1.

[0011] In addition, both lime-cement and lime formulations often contain aerated concrete aggregate. The aerated concrete aggregate is also known in the industry as aerated concrete flour or aerated concrete chippings. The aerated concrete aggregate typically comes from ongoing production. This means that scrap material and / or material from overproduction is crushed, usually using a roller crusher, screened, and used to manufacture new aerated concrete moldings. The aerated concrete aggregate is typically screened to achieve a consistent grain distribution with a maximum grain size of < 1200 μm.

[0012] Furthermore, for environmental reasons, efforts are being made to use aerated concrete material from demolition and dismantling projects for the production of aerated concrete moldings.

[0013] (https: / / www.bauhandwerk.de / news / ytong-startschuss-fuer-porenbeton-recycling-im-werk-wedel_3197859.html). The aerated concrete material must be recycled separately and is also crushed and sieved to a grain size of 0-1 mm. The reuse of recycled aerated concrete material contributes significantly to improving the carbon footprint.

[0014] Furthermore, other processes for the (re)use of aerated concrete aggregates are known:

[0015] DE 10 2006 049 836 A1 discloses the production of a hydraulic binder from construction waste, e.g., for the production of hydrothermally produced building materials, such as aerated concrete or sand-lime brick. The construction waste contains calcium silicate hydrates or cement stone as the binding phase and aggregates. According to the process of DE 10 2006 049 836 A1, fillers are first separated, and the remaining material is thermally treated to form a hydraulically active phase. For this purpose, the construction waste is crushed to a grain size of < 10 mm, the binding phase of the construction waste is enriched by sieving and / or sifting, and then heated to 600 to 800 °C for a period of 0.25 to 10 hours. According to DE 10 2006 049 836 A1, the construction waste can also be aerated concrete rubble.The binder-rich fine fraction is also obtained by sieving and / or classifying a grain fraction < 0.063 mm from the construction waste crushed to grain sizes < 10 mm.

[0016] In addition, the binder can be used to produce hydrothermally produced building materials, e.g. aerated concrete or sand-lime brick.

[0017] CN 113213846 A discloses a cement mortar containing crushed, calcined, and ground aerated concrete powder. Crushing initially produces aerated concrete granulate with a grain size of < 0.16 mm. Subsequent calcination and grinding activate the aerated concrete powder, making it a suitable replacement for cement.

[0018] CN 111439964 A discloses a dry mortar mixture containing aerated concrete waste, which has been ground into a powder with a grain size of < 45 pm. The aerated concrete waste is thermally treated at 700 to 900°C.

[0019] DE 20 2018 105 762 U1 discloses a concrete mixture in which the hydraulic binder is replaced by aerated concrete waste, which has a sieve residue of < 50% at a 45 pm sieve.

[0020] Aerated and foam concrete blocks exhibit good physical properties as building materials. In particular, aerated and foam concrete blocks exhibit high compressive strengths with a relatively low bulk density and low thermal conductivity. The so-called A-number is derived from a calculated relationship between the compressive strength and the dry bulk density. This represents the relative compressive strength of the aerated or foam concrete block. The higher the A-number, the better the compressive strength level. The A-number is calculated as follows:

[0021] A-number [ - ] = Compressive strength [N / mm 2 ] / ((Dry density [kg / dm 3 ]) 2 ■ 0.016 [Ndm 6 / mm 2 kg 2 ])

[0022] The goal in the production of aerated concrete moldings is always to achieve the lowest possible thermal conductivity while maintaining the best possible strength properties. To reduce thermal conductivity, it is known, for example, to use limestone flour as an additive in the production of aerated or foam concrete. Limestone flour is chemically inert and autoclave-resistant. The specific surface area of ​​the commonly used limestone flour is 4000–6000 cm2. 2 / g according to Blaine. The addition of limestone powder also reduces shrinkage and sorption moisture because it is incorporated into the solid web structure, thus reducing the CSH phases. This simultaneously reduces the compressive strength (A-number).

[0023] DE 10 2013 011 742 A1 also discloses the addition of PCC instead of natural, ground limestone powder. This slightly reduces thermal conductivity while maintaining strength.

[0024] DE 20 2008 017 703 U1 also addresses the reduction of thermal conductivity. According to DE 20 2008 017 703 U1, this is achieved by the solid web framework containing up to 10 mass % residual quartz grains and / or rock grains. This results in particular from the use of quartz powder with a Blaine specific surface area of ​​at least 6000 cm2. 2 / g and a corresponding autoclaving time.

[0025] The object of the present invention is to provide a sustainable process for producing a porous or foam concrete material with good strength properties.

[0026] Furthermore, a porous or foam concrete molded body produced by the process with good strength properties is to be provided.

[0027] These objects are achieved by a method having the features of claim 1 and a porous or foam concrete molded body having the features of claim 26. Advantageous developments of the invention are characterized in the respective subsequent subclaims. Within the scope of the invention, it was surprisingly discovered that activated fine powder, which is produced by dry grinding a starting grain comprising at least one porous or foam concrete grain, can improve the strength of a porous or foam concrete molded body compared to the use of a conventional porous or foam concrete grain. The activated fine powder then comprises at least one activated porous and / or foam concrete fine powder.

[0028] In dry grinding, a bulk material or loose solid mixture is ground. In wet grinding, however, the material is mixed with a liquid, and a suspension or slurry is ground in the mill.

[0029] Within the scope of the invention, it was surprisingly discovered that the strength of a porous or foam concrete molded body can be improved if the conventionally used porous or foam concrete grain is ground very finely.

[0030] This can compensate for or at least reduce the loss of strength that normally occurs when using aerated concrete aggregate.

[0031] The cause of this effect has not yet been conclusively clarified. It is assumed to be a mechanochemical activation process of the mineral surfaces. Mineral transformations may also occur during grinding.

[0032] The aerated or foamed concrete molding according to the invention is produced in a conventional manner from a fresh concrete mass comprising at least one hydrothermally reacting CaO component, at least one hydrothermally reacting SiO2 component, optionally at least one setting regulator, water, and at least one blowing agent or prefabricated foam or foaming agent. According to the invention, the fresh concrete mass also comprises at least one finely ground, activated aerated and / or foamed concrete fine powder.

[0033] As is usual in the production of aerated or foamed concrete, all components used for the fresh concrete mass preferably have a grain size of < 2 mm, determined according to DIN EN 1015-1:2007-05.

[0034] In the context of the invention, all components used for the fresh concrete mass preferably have a grain size of < 1 mm, preferably < 500 pm, particularly preferably < 150 pm, determined according to DIN EN 1015-1:2007-05.

[0035] The fresh concrete mass preferably contains Portland cement clinker flour. Portland cement clinker flour provides CaO and SiO2 for the reaction in the autoclave. It is therefore both a CaO and SiO2 component.

[0036] In addition, the at least one setting regulator is preferably a sulfate carrier, preferably anhydrite and / or hemihydrate and / or gypsum.

[0037] For the purposes of the invention, a sulfate carrier is understood to mean a raw material consisting of alkali metal sulfate or alkaline earth metal sulfate, preferably calcium sulfate. Of course, these raw materials may contain minor components or impurities. Minor components are undesirable and should therefore be interpreted as impurities.

[0038] In contrast, raw materials which contain sulfate minerals or sulfate compounds only as minor components are not referred to as sulfate carriers in the context of the invention.

[0039] Portland cement (CEM I) according to DIN EN 197-1:2011-11 is preferably used for the production of the fresh concrete mass. Portland cement is known to comprise Portland cement clinker and at least one sulfate carrier, in particular anhydrite and / or hemihydrate and / or gypsum. As a (further) SiO2 component, the fresh concrete mass preferably also comprises ground quartz, preferably ground quartz sand, and / or amorphous silica, preferably microsilica.

[0040] The quartz, preferably the quartz sand, preferably makes up the predominant proportion (i.e. > 50 mass%) of the SiO2 in the fresh concrete mass.

[0041] In addition, the fresh concrete mass preferably contains quicklime and / or hydrated lime as an additional CaO component.

[0042] The fresh concrete mass may also contain other inert additives known in the art, preferably natural, ground limestone flour and / or precipitated calcium carbonate (PCC).

[0043] The fresh concrete mass may also contain at least one additive known in the art, preferably a flow agent and / or a dispersant and / or a sedimentation inhibitor. The flow agent is preferably polycarboxylate ether (PCE). The dispersant is preferably polyacrylate (PAR) or an acrylic polymer or copolymers. The sedimentation inhibitor is preferably modified starch.

[0044] According to the invention, the grinding of the porous and / or foam concrete grains can be carried out either by grinding a starting grain which consists exclusively of porous and / or foam concrete grains or the starting grain has at least one further dry component of the fresh concrete mass.

[0045] According to a first embodiment of the invention, the starting grain contains only or exclusively at least one aerated and / or foamed concrete grain and no other components. The proportion of aerated and / or foamed concrete grain in the starting grain is thus 100 mass%, based on the dry mass of the starting grain. This starting grain is then ground into pure, activated aerated and / or foamed concrete fine powder.

[0046] Alternatively, in addition to the at least one aerated or foamed concrete grain, the starting grain comprises at least one further dry component of the fresh concrete mass, preferably at least one hydrothermally reacting CaO component and / or at least one hydrothermally reacting SiO2 component. This starting grain is thus ground into an activated fine flour mixture containing at least one activated aerated or foamed concrete fine flour.

[0047] Preferably, the starting grain comprises, in addition to the at least one aerated or foamed concrete grain, quicklime and / or Portland cement (CEM I).

[0048] The proportion of porous and / or foamed concrete aggregate in the starting aggregate is preferably 50 to 90 mass%, more preferably 70 to 80 mass%, based on the dry mass of the starting aggregate. The lower limit is determined by the formulation and the binder content.

[0049] The at least one aerated or foamed concrete grain used for the starting grain size preferably has a dgo value < 10 mm, preferably < 5 mm, particularly preferably < 2 mm, determined by means of the sieve passage according to DIN EN 1015-1:2007-05.

[0050] Unless otherwise stated, grain sizes are determined within the scope of the invention by means of sieve passage according to DIN EN 1015-1:2007-05.

[0051] The porous or foam concrete grain preferably has a maximum grain size of < 12 mm, preferably < 6 mm, particularly preferably < 3 mm.

[0052] Furthermore, the aerated or foamed concrete aggregate is preferably coarse-grained, meaning it also contains grains with a grain size > 125 pm, preferably also grains with a grain size > 250 pm. The aerated or foamed concrete aggregate therefore contains a coarse grain content.

[0053] In addition, the aerated or foamed concrete aggregate preferably has a bulk density of 400 to 700 g / l, preferably 450 to 600 g / l, according to DIN EN 1097-3:1998-06.

[0054] The aerated or foamed concrete aggregate used is preferably a by-product from the aerated or foamed concrete production process, which has been mechanically crushed into the aerated or foamed concrete aggregate with the specified grain size, preferably using a crusher. This by-product is, in particular, technological waste.

[0055] Alternatively, the aerated or foamed concrete grain is recycled material, which has also been mechanically crushed, preferably using a crusher, into the aerated or foamed concrete grain with the specified grain size. The recycled material can also be recarbonated. Furthermore, it is known that it may contain adhering plaster and mortar residues. The advantage of the grinding according to the invention is that homogenization occurs, and the adhering plaster and mortar residues are finely crushed and distributed.

[0056] Of course, the aerated or foam concrete aggregates can also be produced by mechanical crushing of specially manufactured aerated or foam concrete moldings.

[0057] In addition, it can also be aerated concrete material which was produced according to the process according to EP 3 789 362 A1 or according to WO 2009 / 121635 A1.

[0058] The aerated or foamed concrete aggregate is also first dried before grinding at a temperature of 100 to 300°C, preferably 105 to 200°C, particularly preferably 105 to 120°C, to expel physically bound water. The residual moisture content after drying is < 5 mass%, preferably < 2 mass%, particularly preferably < 0.5 mass%, determined according to DIN EN ISO 17892-1: 2022-08.

[0059] Further thermal treatment of the aerated or foamed concrete grains and / or the activated aerated or foamed concrete fine powder is not carried out within the scope of the invention. In particular, calcination at elevated temperatures is not carried out. The at least one aerated or foamed concrete grain and / or the activated aerated or foamed concrete fine powder are therefore not exposed to temperatures above 300°C before the production of the fresh concrete mass. This also serves, in particular, to prevent the tobermorite from transforming at excessively high temperatures.

[0060] The dry grinding of the mechanically crushed starting grain is also carried out in a mill, preferably in a drum mill, preferably in the form of a ball mill, and / or a roller mill.

[0061] Within the scope of the invention, it was also surprisingly discovered that a certain proportion of activated aerated or foamed concrete fine powder is advantageous. The fresh concrete mass preferably contains 10 to 35 mass-%, more preferably 10 to 30 mass-%, particularly preferably 10 to 25 mass-%, very particularly preferably 15 to 25 mass-%, of activated aerated or foamed concrete fine powder, based on the solids content (= total solids) in the fresh concrete mass. The solids content is understood to be the sum of all solids, i.e. the mass of the freshly dosed dry matter as well as the dry matter contained in the returned sludge. The solids contained in admixtures or additives, such as flow agents or dispersants, and in the blowing agent or foaming agent are not included in the total solids; their content is related to the solids content.

[0062] The proportion of activated aerated or foamed concrete fines includes any portion contained in the return sludge, even if the activated aerated or foamed concrete fines are added with the return sludge rather than in the form of fines. This is because the activated aerated or foamed concrete fines are present in the return sludge in a finely dispersed form.

[0063] It was surprisingly found that, for example, with a content of 40 mass % of activated aerated or foamed concrete fine powder, no improved compressive strengths could be achieved compared to the use of 40 mass % of non-activated aerated or foamed concrete grains.

[0064] This could result from the fact that there is too little binder, which has a greater impact on the activated porous or foam concrete fine powder due to the high fineness and the associated high active surface than on the coarser, non-activated porous or foam concrete grain.

[0065] In addition, the minimum proportion of activated porous or foam concrete fine powder should be 10 mass% in order to achieve a significant technical effect and be economically interesting.

[0066] According to the invention, the starting grain is milled until the activated fine flour has a Blaine value, determined according to DIN 196-6:2019-03, of 9 000 to 22 500 cm 2 / g, preferably 13 000 to 22 500 cm 2 / g, preferably 14,000 to 22,000 cm 2 / g, particularly preferably 14 000 to 21 500 cm 2 / g.

[0067] Preferably, the starting grain is also milled until the activated fine flour has a BET surface area, determined according to DIN ISO 9277: 2014- 01 , of 30 to 45 m 2 / g, preferably 34 to 40 m 2 / g.

[0068] As already explained, the fresh concrete mass preferably contains Portland cement clinker flour as CaO and SiO2 components.

[0069] The fresh concrete mass preferably has a Portland cement clinker powder content of 5 to 45 mass%, preferably 10 to 40 mass%, particularly preferably 15 to 35 mass%, based on the total solids content of the fresh concrete mass.

[0070] The fresh concrete mass may also contain residual sludge. The dry matter contained in the residual sludge consists of hydrate phases formed from the binder components and, if necessary, inert substances such as aerated concrete powder or rock powder. The hydrate phases have already reacted to such an extent that they no longer contribute to the green strength. They only react further during hydrothermal curing in the autoclave.

[0071] The fresh concrete mass preferably contains 2 to 30 mass%, preferably 2 to 20 mass%, particularly preferably 5 to 15 mass%, of return sludge (dry mass), based on the solids content in the fresh concrete mass.

[0072] The return sludge stabilizes the fresh concrete mass and the green porous or foam concrete molding.

[0073] The fresh concrete mass preferably also contains 25 to 80 mass%, preferably 30 to 70 mass%, particularly preferably 35 to 60 mass%, of ground quartz, based on the solids content of the fresh concrete mass. This ensures, in particular, the formation of a sufficient amount of CSH phases.

[0074] Fly ash as a SiO2 component is preferably not included because it has a different solubility than quartz and the CSH phase formation is generally poorer.

[0075] The fresh concrete mass preferably also contains 5 to 40 mass%, preferably 5 to 30 mass%, particularly preferably 10 to 25 mass%, of quicklime, based on the solids content of the fresh concrete mass. This ensures, in particular, the formation of a sufficient amount of CSH phases. The W / F ratio (water / solids ratio) of the fresh concrete mass is also preferably 0.5 to 1.2, preferably 0.5 to 1.1, particularly preferably 0.6 to 0.9, and most particularly preferably 0.6 to 0.8.

[0076] Optionally, the fresh concrete mass also contains 0 to 20 mass%, preferably 0 to 17 mass%, particularly preferably 0 to 10 mass%, of inert additives, in particular rock flour, based on the solids content of the fresh concrete mass. The rock flour is preferably limestone flour. The limestone flour can, for example, also result from the addition of a Portland limestone cement, in particular a CEM II according to DIN EN 197-1:2011-11.

[0077] Advantageous compositions or recipes of the fresh concrete mass are given in the following table (values ​​in mass%, based on the total dry mass (=sum of solids) of the fresh concrete mass; admixtures and the foam component are considered (unless otherwise stated) as they are available or on the market [not their active ingredient content] and are additively based on the dry mass):

[0078]

[0079] The solids contents listed in the table above do not necessarily add up to 100 mass%. Rather, other components may also be included. Consequently, each component and each range disclosed in the table is considered advantageous in its own right. Furthermore, the lower and upper limits of the ranges specified for the individual components can be combined.

[0080] For example, it may also contain fired clays and / or calcined clays. The aluminum component can be aluminum powder, paste, or suspension in a conventional manner. The proportions listed in the table represent the solids or active ingredient content of the respective aluminum component.

[0081] In addition, an aluminum component or, alternatively, a foam component or a foaming agent is always present. Aluminum components, foam components, and foaming agents are thus used alternatively.

[0082] Furthermore, it is preferred if the fresh concrete mass contains Portland cement clinker and at the same time quicklime and / or hydrated lime.

[0083] As already explained, the production of the porous or foam concrete moldings according to the invention is carried out in the usual way:

[0084] Basically, the fresh concrete mass is first produced, which contains at least one hydrothermally reacting CaO component, at least one hydrothermally reacting SiO2 component, preferably reclaimed sludge, at least one blowing agent or pre-formed foam or a foaming agent, and water. According to the invention, the fresh concrete mass also contains at least one activated porous or foamed concrete fine powder.

[0085] Production preferably takes place as usual, by first mixing the recycled sludge with water, then adding the inert components, followed by the binder, and finally the aluminum component. The activated fine powder is preferably added together with the binder.

[0086] The fresh concrete mass is poured into a casting mold. If reinforced aerated concrete molds are to be produced, reinforcement can be suspended in the casting mold. Alternatively, the reinforcement can be suspended in the casting mold after the mold has been filled with fresh concrete. In the case of the production of aerated concrete molds, the casting mass is allowed to expand.

[0087] In the production of foam concrete molds, the foaming process is eliminated. To produce foam concrete molds, either the fresh mass containing a foaming agent is whipped to form the foam, or the pre-formed foam is mixed in. This occurs before the fresh mass is poured into the mold.

[0088] The casting compound is then allowed to harden into a green porous or foam concrete cake.

[0089] After stiffening, the aerated or foam concrete cake is cut into individual aerated or foam concrete moldings in a conventional manner.

[0090] The cut porous or foam concrete moldings are then hydrothermally cured in the autoclave in a conventional manner under saturated steam conditions.

[0091] For example, autoclaving is carried out with a holding phase of 6 to 12 hours at a temperature of 180 to 190 °C.

[0092] The start-up and shut-down phases are preferably linear, with no intermediate stop phases. In addition, the start-up and shut-down phases each last, for example, 1.5 to 6 hours. In a very preferred autoclave operating mode, the autoclave process begins with a vacuum phase. After the autoclave is closed, the air is pumped out until a negative pressure of, for example, 0.4 bar is reached. This process takes, for example, 20 - 30 minutes. Steam is then fed into the autoclave, and the start-up phase begins. In another preferred operating mode, the air present in the autoclave is reduced by pressure-free purging with steam. This process takes, for example, 20 - 30 minutes.As already explained, it has been found according to the invention that the fresh concrete mass and the aerated or foamed concrete cake can be easily processed and that the aerated and / or foamed concrete moldings produced according to the invention have good strength properties despite the addition of aerated or foamed concrete fine powder.

[0093] As already explained, a measure of the strength of aerated and foam concrete forms is the so-called A-number, which indicates the compressive strength relative to the bulk density. The A-number is derived from a calculated relationship between the compressive strength and the dry bulk density. It represents the relative compressive strength of the aerated or foam concrete form. The higher the A-number, the better the compressive strength level.

[0094] Preferably, the porous or foam concrete moldings according to the invention have an A-number of 900 to 2700 []. The compressive strength is determined for porous or foam concrete moldings with a dry bulk density of 0 to 150 kg / m 3 according to DIN EN 826:2013-05 after drying at 40°C to constant mass and for aerated or foam concrete bodies with a dry bulk density po > 150 kg / m 3 Tested for mass constancy on a cube with an edge length of 100 mm according to DIN EN 772-1: 2011-07 after drying at 50°C.

[0095] Preferably, the porous or foam concrete moldings according to the invention also have a compressive strength of 0.1 to 10.0 N / mm 2 The compressive strength of porous or foam concrete bodies with a dry density po of up to 150 kg / m 3 according to DIN EN 826:2013-05 after drying at 40°C to constant mass and for aerated or foam concrete bodies with a dry bulk density po > 150 kg / m 3tested on a cube with an edge length of 100 mm according to DIN EN 772-1: 2011-07.

[0096] If the porous or foam concrete shaped bodies according to the invention are, preferably unreinforced, porous or foam concrete shaped blocks, they preferably have a compressive strength of 1.0 to 10.0 N / mm 2 , preferably from 1.5 to 8.0 N / mm 2 , particularly preferably from 2.0 to 7.0 N / mm 2 , tested on a cube with an edge length of 100 mm according to DIN EN 772-1 : 2011-07.

[0097] If the porous or foam concrete shaped bodies according to the invention are porous or foam concrete insulating bodies, in particular porous or foam concrete insulating panels, they preferably have a compressive strength of 0.1 to 0.7 N / mm 2 , preferably from 0.1 to 0.5 N / mm 2 , particularly preferably from 0.2 to 0.4 N / mm 2 , according to DIN EN 826:2013-05 after drying at 40°C to constant mass.

[0098] In addition, the porous or foam concrete moldings according to the invention preferably have a dry bulk density po of 70 to 800 kg / m 3 , according to DIN EN 772-13: 2000-09 or DIN EN 1602: 2013-05.

[0099] If the aerated or foamed concrete moldings according to the invention are, preferably unreinforced, aerated or foamed concrete molding blocks, they preferably have a dry bulk density po of 151 to 800 kg / m 3 , preferably from 220 to 800 kg / m 3 , particularly preferably from 255 to 600 kg / m 3 , according to DIN EN 772-13: 2000-09.

[0100] If the porous or foam concrete shaped bodies according to the invention are porous or foam concrete insulating bodies, in particular porous or foam concrete insulating boards, they preferably have a dry bulk density po of 70 to 150 kg / m 3 , preferably from 80 to 120 kg / m 3 , particularly preferably from 85 to 115 kg / m 3 , according to DIN EN 1602: 2013-05.

[0101] Preferably, the aerated or foam concrete moldings also have a thermal conductivity X, dry, unit of 0.039 to 0.180 W / (m K), according to DIN EN 12664: 2001-05 and DIN EN 12667: 2001-05. If the aerated or foam concrete moldings according to the invention are, preferably unreinforced, aerated or foam concrete molded blocks, they preferably have a thermal conductivity X10, dry, unit of 0.060 to 0.180 W / (m K), preferably of 0.065 to 0.160 W / (m K), particularly preferably of 0.070 to 0.140 W / (m K), according to DIN EN 12664: 2001-05 and DIN EN 12667: 2001-05.

[0102] If the porous or foam concrete shaped bodies according to the invention are porous or foam concrete insulating bodies, in particular porous or foam concrete insulating panels, they preferably have a thermal conductivity X , dry, unit of 0.039 to 0.055 W / (m K), preferably of 0.041 to 0.049 W / (m K), particularly preferably of 0.042 to 0.048 W / (m K), according to DIN EN 12664: 2001-05 and DIN EN 12667:2001-05.

[0103] In the following, the invention will be illustrated by means of some embodiments.

[0104] Examples of implementation:

[0105] In the examples, aerated concrete molds were produced using different formulations. The aerated concrete molds were always manufactured as follows:

[0106] The test samples were mixed with a dissolver mixer at 550 rpm (disk diameter 12 cm) in a 20 l stirred vessel as follows:

[0107] 1. Place water and, if necessary, return sludge and, if necessary, additives in the mixing vessel

[0108] 2. Add quartz flour, mixing time 30 seconds

[0109] 3. Addition of the binding agents (quicklime, cement, microsilica), if necessary activated aerated concrete fine flour or activated fine flour mixture, if necessary aerated concrete grain, mixing time 30 seconds

[0110] 4. Addition of aluminum in suspension (100 ml), mixing time 20 seconds 5. Pour into a polystyrene container with lid

[0111] The test specimens from test series 0 to 8 and 10 to 12 were demolded after 3-4 hours (at 20°C), transferred to the hardening base, and then autoclaved. The test specimens from test series 9 (insulating board) were demolded after 24 hours (at 25°C), transferred to the hardening base, and then autoclaved.

[0112] The autoclaving of test series 0 to 8 and 10 to 12 began with a vacuum phase lasting 30 minutes, during which a pressure of 0.4 bar was a bs. The pressure was then increased linearly to 12 bar over 1.5 hours. a bs increased, maintained for 7 hours and then, also linearly, reduced to ambient pressure over 1.5 hours.

[0113] The autoclaving of test series 9 (insulation board) began with a vacuum phase lasting 30 minutes, during which a pressure of 0.4 bar was a bs. The pressure was then increased linearly to 12 bar over 6 hours. a bs increased, maintained for 6 hours and then, also linearly, reduced to ambient pressure over 6 hours.

[0114] The following raw materials were used to conduct the tests:

[0115] Table 1 : Raw materials used

[0116] Table 2: Additives used Production of return sludge:

[0117] The return sludge was produced from non-steam-cured porous concrete moldings.

[0118] The test samples were mixed with a dissolver mixer at 550 rpm (disk diameter 12 cm) in an 80 l stirred vessel as follows: 1 . Place water in the mixing vessel.

[0119] 2. Add quartz flour, mixing time 30 seconds.

[0120] 3. Add the binders and activated aerated concrete fine flour and / or activated fine flour mixture; mix for 30 seconds. 4. Add the aluminum in suspension (100 ml); mix for 20 seconds.

[0121] 5. Force the mixture up in the mixing container.

[0122] 6. After approximately 1 hour, the swollen cake was gradually suspended in water to form a suspension with a density of 1.3 kg / L. The residual sludge density (liter weight) was determined using a measuring cylinder and laboratory balance (mass per volume). The suspension was then stirred for 18 hours before use. During the 18 hours, the suspension may have thickened further. Therefore, immediately before use, the residual sludge density was measured again and, if necessary, diluted with water to a density of 1.3 kg / L or corrected.

[0123] Production of dried aerated concrete (AAC) and wet

[0124] Aerated concrete aggregate (PBKf euC ht):

[0125] The production of the aerated concrete aggregates was initially carried out analogously to the production of aerated concrete moldings from the following recipe:

[0126] Table 3: Recipe for the production of aerated concrete aggregates

[0127] The steam-cured aerated concrete molded bodies were sawn into prisms with maximum dimensions of 40 mm x 50 mm x 500 mm using a band saw. The prisms and any small sawdust were crushed in a jaw crusher (from Fa.

[0128] Retsch, type BB1). The crushed material was sieved through a 1 mm sieve. The fraction < 1 mm formed the aerated concrete grain size. A composite sample was prepared from all small-scale test specimens.

[0129] The portion for the small-scale tests with moist aerated concrete aggregates (PBKfeucht) was separated. The moisture content was determined (12.5 wt% H2O) according to DIN EN ISO 17892-1: 2022-08.

[0130] The portion for the production of the activated fine powder and for the test series with conventional dried aerated concrete aggregate (AAC) was dried at 105°C in a drying oven until constant mass was reached.

[0131] Table 4: Results of the measurements of the properties of the starting material of the aerated concrete aggregate (PBK)

[0132] Production and specification of aerated concrete aggregates (PBKp rO d) from ongoing production:

[0133] The aerated concrete grain size (PBKp rO d) came from ongoing production at the Xella aerated concrete plant in Brück. This material consisted of scrap material and / or overproduction. The material was crushed using a roller crusher and sieved to a particle size of < 1500 pm.

[0134] The aerated concrete grain size (PBKp rO d) had the following main components in mass%:

[0135] Table 5: Main components of the aerated concrete aggregate (PBKprod) from current production [1] Determined by X-ray fluorescence analysis using an AXIOS PW 4400 from PANalytical BV

[0136] [2]Determined by infrared spectrometry using an Eitra CS-2000 from Eitra GmbH Pi Determined according to DIN EN 196-2:2013-10

[0137] Production of activated fine flour:

[0138] The aerated concrete grains prepared as above were dried to constant weight in a drying cabinet at a temperature of 105°C for 2 days before grinding.

[0139] To produce pure activated aerated concrete fine meal (PBFM), the aerated concrete grains were each dry ground individually.

[0140] For the production of the activated fine flour mixture (FMM) containing the activated aerated concrete fine flour, a starting grain was produced which contains the aerated concrete grain (PBK) and the Portland cement or

[0141] White fine lime or quartz flour or microsilica in different proportions and this initial grain size was ground.

[0142] The grinding was carried out in a drum mill with the following properties:

[0143] Table 6: Properties of the drum mill and process parameters

[0144] Drum mill

[0145] Manufacturer WELTE a) Grinding technology, Cologne

[0146] Year of construction 1995

[0147] Type designation WGN-WGT 100

[0148] Armor rubber

[0149] Mill diameter 46.5 cm

[0150] Mill length 48 cm

[0151] Rotation speed 48 rpm

[0152] Type of grinding: dry grinding

[0153] Ground material mass as specified

[0154] Grinding balls

[0155] Manufacturer CeramTec GmbH, Plochingen

[0156] Material AI2O3

[0157] Purity 92%

[0158] Classification

[0159] Total grinding mass 70000 g

[0160] Proportion of ball 0 = 40 mm 50%

[0161] Proportion of ball 0 = 30 mm 30%

[0162] Proportion of ball 0 = 20 mm 20 % a) Company liquidation 1998, service by AAM Mahltechnik GmbH, Cologne

[0163] Table 7: Process parameters of the grinding process

[0164] Grinding time fin the mass of ground material rule)

[0165] [min] [g]

[0166] 120 7500

[0167] Production of “Durox flour”:

[0168] The production of the "Durox flour" for the 7th test series is analogous to the production of the activated fine flour mixture. The mill parameters (including ball loading), grinding time, and mass of ground material are identical. In this case, however, the binder (white fine lime) was ground with the dry quartz flour. Production of preheated aerated concrete grain (PBK900) and the aerated concrete fine flour produced from the preheated aerated concrete grain (PBFM900):

[0169] For the 11th test series, the aerated concrete aggregate dried at 105°C was additionally baked for 24 h at 900°C and a portion of it was ground (identical procedure as for the aerated concrete aggregate treated at 105°C).

[0170] Measurements carried out:

[0171] The dry bulk density according to DIN EN 772-13:2000-09, the cube crush strength according to DIN EN 772-1:2011-07 and DIN EN 826:2013-05, from which the A-number and partly the thermal conductivity X10, dry, unit according to DIN EN 12664: 2001-05 and DIN EN 12667:2001-05 as well as partly the tensile strength according to DIN EN 1607:2013-05 were determined for the produced aerated concrete moldings.

[0172] In addition, the Blaine value according to DIN 196-6:2019-03 and, in part, the BET surface area according to ISO 9277:2022-11 of the activated aerated concrete fine meal and the activated fine meal mixture used were determined.

[0173] In addition, the mineralogical phase composition was determined in a series of experiments using X-ray diffraction. This was done as follows:

[0174] The aerated concrete molds were molded using commercially available

[0175] Drilling dust was taken from a pillar drill (HSS drill bit, diameter 24 mm). These powder samples were first dried for 24 h at 40°C in a drying cabinet. For the subsequent wet grinding, 10 wt.% internal standard zincite (ZnO from JT Baker Avantor Performance Materials, Inc.) was added to each sample, corresponding to 1.8 g of substance and 0.2 g of ZnO. Wet grinding in the micron mill (McCrone micronising mill) was carried out in 10 ml of 2-propanol for 4 1 min in PVC grinding bowls with ZrO2 grinding cylinders. The ground material was rinsed, rinsed four times with 5 ml of 2-propanol each (AnalaR NORMAPUR, VWR), and filtered for 24 h through hard filter paper (84 g / m 2, No. 1291; Sartorius) was filtered under a fume hood and dried at room temperature (20°C). The powder, brushed off the filter paper and homogenized for 2 minutes in an agate mortar, was pressed into a diffractometer powder tablet (backloading method). A powder tablet was prepared and measured from each sample taken.

[0176] The samples were measured on a Panalytical MPD Pro diffractometer. Qualitative phase determination was performed using Panalytical HighScorePlus software. The measurement conditions and further information are listed in Table 8. Table 8: Measurement conditions and further information

[0177] Quantitative determination was performed using the Rietveld method. Bruker AXS Topas (version 5) was used as the evaluation software. To determine the amorphous phase content, 10 wt.% zinc oxide (see above) was added to the sample as an internal standard and subtracted accordingly during the evaluation. The remaining phases, including X-ray amorphous phases, were normalized to 100%. The following structures from the ICSD database (Inorganic Crystal Structure Database, as of 2016) were used to evaluate the quantitative phase content:

[0178] 11Ä-Tobermorite (# 92943)

[0179] Quartz (# 34636)

[0180] Anhydrite (# 15876)

[0181] Bassanite (# 69090) Hydroxylellestadite (# 156173) Zincite (# 65120) 1. Test series:

[0182] In the first series of tests, aerated concrete molded bodies of the density class 400 kg / m 3All aerated concrete fresh masses according to the invention also contained 10 mass % activated aerated concrete fine powder. The aerated concrete fresh mass of the reference aerated concrete molded body contained 10 mass % aerated concrete grain. The activated aerated concrete fine powder and the activated fine powder mixture were each produced as described above. The composition of the starting grain was varied for the fine powder mixtures. The grinding time in each case was 120 minutes.

[0183] Table 9: Compositions of the recipes of the 1st test series

[0184] + the amount of microsilica used was deducted from the quartz powder The results of the measurements of the properties of the 1st test series are in

[0185] Table 10 shows the results.

[0186] Table 10: Results of the measurements of the properties of the 1st test series

[0187] Table 10 clearly shows that the A-number for all aerated concrete moldings 1 BE according to the invention is significantly higher than the A-number of the reference aerated concrete body 1A. The addition of 10 mass % of activated aerated concrete fine powder thus increases the compressive strength level compared to the use of 10 mass % of conventional aerated concrete aggregate.

[0188] Second test series: The second test series was conducted analogously to the first. However, 20 wt.% activated aerated concrete fine powder and 20 wt.% conventional aerated concrete aggregate were used.

[0189] Table 11 : Compositions of the recipes of the 2nd test series The results of the property measurements of the second test series are shown in Table 12. Table 12: Results of the property measurements of the second test series

[0190] Table 12 clearly shows that the A-number for all aerated concrete moldings 2B-E according to the invention is significantly higher than the A-number of the reference aerated concrete body 2A. The addition of 20 wt.% activated aerated concrete fine powder thus also increases the compressive strength level compared to the use of 20 wt.% conventional aerated concrete aggregate.

[0191] 3rd series of experiments:

[0192] In the third test series, the content of activated aerated concrete fine powder was further increased and varied. Concentrations of 25 M.-

[0193] %, 30 wt.%, 35 wt.%, and 40 wt.%. The starting grains contained either exclusively aerated concrete grain or 75 wt.% aerated concrete grain and 25 wt.% quicklime. The grinding time was again 120 minutes.

[0194]

[0195] The results of the measurements of the properties of the 3rd test series are shown in Table 14.

[0196] Table 14: Results of the measurements of the properties of the 3rd test series Table 14 shows that the A-number is not improved at a content of 25 mass % activated aerated concrete fine powder if the starting aggregate consists of pure aerated concrete aggregate. If the starting aggregate consists of a mixture of aerated concrete aggregate and quicklime, the A-number is only slightly improved compared to the use of conventional, non-activated aerated concrete aggregate. This trend is even more pronounced at a content of 30 mass % activated aerated concrete fine powder. Even at this point, the A-number of the aerated concrete body in which the starting aggregate contains quicklime and aerated concrete aggregate is slightly lower than that of the aerated concrete body that only contains non-activated, conventional aerated concrete aggregate. This trend becomes more pronounced with increasing content of activated aerated concrete fine powder. With an addition of 40 mass %With a content of 10% of activated aerated concrete fines, the reference aerated concrete body with the conventional, non-activated aerated concrete grain has by far the best A-number. 4th test series:

[0197] In the fourth test series, the aerated concrete grain content in the starting aggregate was varied. Aerated concrete grain contents of 50 wt.%, 62.5 wt.%, and 75 wt.% were set. The starting aggregates also contained quicklime. The grinding time was again 120 minutes. The proportion of activated aerated concrete fine powder in the fresh concrete mass was 20 wt.%.

[0198] Table 15: Compositions of the recipes of the 4th test series

[0199] The results of the property measurements of the 4th test series are shown in Table 16.

[0200] Table 16: Results of the measurements of the properties of the 4th test series From Table 16 it is clearly evident that there is no tendency of the influence of the content of aerated concrete aggregate in the initial aggregate on the A-number of the aerated concrete body produced from it.

[0201] Fifth test series: In the fifth test series, the grinding time was varied. It was 60, 120, and 240 minutes. These tests were conducted both with a starting grain consisting exclusively of aerated concrete grain and with a starting grain containing 75% by mass of aerated concrete grain and 25% by mass of quicklime. The proportion of activated aerated concrete fine powder was 20% by mass.

[0202] Table 17: Compositions of the recipes of the 5th test series

[0203] The results of the property measurements of the 5th test series are shown in Table 18. Table 18: Results of the property measurements of the 5th test series

[0204] Table 18 and Figures 5 and 6 clearly show that after a certain grinding time has been exceeded, the strength properties of the aerated concrete molded bodies decrease again or do not improve further. This could be due to the material beginning to agglomerate. The Blaine values ​​decrease again.

[0205] 6th series of experiments:

[0206] In the 6th test series, an aerated concrete body with a density of 330 kg / m 3 and an aerated concrete molded body with a bulk density of 460 kg / m 3 The starting aggregates used each contained 75 wt.% aerated concrete aggregate and 25 wt.% Portland cement (CEM I).

[0207] In addition, two aerated concrete moldings were produced using return sludge (RS). These tests were carried out both with a starting grain consisting exclusively of the aerated concrete grain and with a starting grain containing 75 mass % of

[0208] Aerated concrete aggregate and 25 mass% quicklime.

[0209] The grinding time was 120 minutes in each case. The proportion of activated aerated concrete fine powder in the total aerated concrete mixture / return sludge

[0210] (batch) was 20 wt.% in each case. Table 19: Compositions of the formulations of the 6th test series

[0211] The results of the property measurements of the 6th test series are shown in Table 20. Table 20: Results of the property measurements of the 6th test series

[0212] Table 20 clearly shows that the A-number is improved even when using recycled sludge by using activated aerated concrete fines. 7th test series:

[0213] As part of the seventh test series, two aerated concrete molds were produced in which the quartz sand and quicklime were ground together before being added to the fresh concrete mass (Durox flour). In addition, an activated aerated concrete fine powder was used, which was produced by grinding a pure aerated concrete grain. The conventional, unground aerated concrete grain was used as a reference. Aerated concrete molds were also produced without the composite grinding of quartz sand and quicklime.

[0214] The grinding time was 120 minutes in each case. The proportion of activated aerated concrete material was 20 mass% in each case.

[0215] Table 21 : Compositions of the recipes of the 7th test series

[0216] The results of the property measurements of the 7th test series are shown in Table 22. Table 22: Results of the property measurements of the 7th test series

[0217] From Table 22 it is clearly evident that, on the one hand, the use of Durox flour already improves the A-number, but the activated aerated concrete fine flour improves the A-number even further.

[0218] 8th series of experiments:

[0219] In the 8th test series, aerated concrete moldings with different densities in the density range 300 - 600 kg / m 3 In addition, conventional dried aerated concrete aggregate, moist aerated concrete aggregate, activated aerated concrete fine meal, and activated fine meal mixture were used. Cement was also ground with aerated concrete aggregate. The content of activated aerated concrete fine meal or aerated concrete aggregate was 20 mass%, and the grinding time was 120 minutes.

[0220]

[0221] + Value based on dry mass at 105°C

[0222] ++ including the water content contained in the PBKfeucht

[0223] +++ Not measurable due to humidity

[0224] Table 24: Results of the measurements of the properties of the 8th test series

[0225] Table 24 clearly shows that the activated aerated concrete fine powder, regardless of whether it was ground alone or in combination, improves the A-number and thus the compressive strength level at all bulk densities. Furthermore, the A-number is worse when using the moist aerated concrete aggregates (8A and 8F) than when using the dried aerated concrete aggregates (8B and 8G).

[0226] 9th series of experiments:

[0227] In the ninth test series, low-density aerated concrete moldings (aerated concrete insulation bodies) were produced. Conventional dried aerated concrete aggregate, moist aerated concrete aggregate, activated aerated concrete fine meal, and activated fine meal mixture were also used. The content of activated aerated concrete fine meal or aerated concrete aggregate was 10.5 mass%, and the milling time was 120 minutes.

[0228] Furthermore, the tensile strength was also determined. Table 25: Compositions of the formulations of the 9th test series

[0229] Table 26: Results of the measurements of the properties of the 9th test series

[0230] Table 25 shows that the activated aerated concrete fine powder significantly improves the A-number, even at low bulk densities. Tensile strength is also improved. Tensile strength is by far the best when using the activated fine powder mixture. 10th test series:

[0231] In the 10th test series, conventional, dried aerated concrete aggregate, moist aerated concrete aggregate, activated aerated concrete fine flour and activated fine flour mixture were used again and aerated concrete moldings with a bulk density of around 350 kg / dm 3 The content of activated aerated concrete fine powder or aerated concrete grain was 20 mass%, and the grinding time was 120 minutes. The tensile strength was also determined.

[0232] Table 27: Compositions of the recipes of the 10th test series

[0233] + Value based on dry mass at 105°C

[0234] ++ including the water content contained in the PBKfeucht

[0235] +++ Not measurable due to humidity Table 28: Results of the measurements of the properties of the 10th test series

[0236] Table 28 shows that the activated aerated concrete fine powder improves not only the compressive strength (A-number) but also the tensile strength, even at higher densities. Furthermore, the use of moist aerated concrete aggregates impairs the strength properties.

[0237] 11th series of experiments:

[0238] In the 11th test series, conventional, dried aerated concrete aggregate, baked aerated concrete aggregate, activated aerated concrete fine meal, and activated aerated concrete fine meal produced from baked aerated concrete aggregate were used. The content of activated aerated concrete fine meal and aerated concrete aggregate was 14.8 mass%, and the grinding time was 120 minutes.

[0239] Table 29: Compositions of the recipes of the 11th test series

[0240] Table 30: Results of the measurements of the properties of the 11th test series Table 31 : Mineralogical phase composition of the 11th series experiments.

[0241] series of experiments

[0242] Table 30 shows that annealing reduces the A-number. This applies to both conventional aerated concrete aggregates and activated aerated concrete fines.

[0243] The phase formation (Table 31) was normal in each case, but the tobermorite content was lower in the samples with the annealed grain.

[0244] 12th test series: In the 12th test series, recycled aerated concrete aggregate and an activated fine powder mixture with activated aerated concrete fine powder, produced from recycled aerated concrete aggregate, were used. The content of activated aerated concrete fine powder and aerated concrete aggregate was 10 and 20 mass%, respectively, and the grinding time was 120 minutes.

[0245] Table 32: Compositions of the recipes of the 12th test series

[0246] Table 33: Results of the measurements of the properties of the 12th test series Table 33 shows that the A-number is improved when using activated aerated concrete fine powder compared to using the same amount of conventional aerated concrete aggregate. Furthermore, the A-number is worse when using 20 mass% conventional aerated concrete aggregate than when using 10 mass% conventional aerated concrete aggregate. Furthermore, the A-number when using 20 mass% activated aerated concrete fine powder is only slightly worse than when using 10 mass% conventional aerated concrete aggregate. Thus, a larger amount of aerated concrete aggregate can be recycled without significantly reducing the A-number. 13th test series:

[0247] In the 13th test series, aerated concrete aggregate from current production and activated aerated concrete fine powder produced from it were used. The content of activated aerated concrete fine powder and aerated concrete aggregate was 20 mass%, and the grinding time was 20 minutes.

[0248] Table 34: Compositions of the recipes of the 13th test series

[0249] The results of the property measurements of the 13th test series are shown in Table 35. Table 35: Results of the property measurements of the 13th test series

[0250] Table 35 shows that the A-number of the inventive aerated concrete body 13B is significantly higher than the A-number of the reference aerated concrete body 13A. The addition of 20 mass % of activated aerated concrete fine powder thus increases the compressive strength level compared to the use of 20 mass % of conventional aerated concrete aggregate from current production. The results of the 13th test series therefore also demonstrate the effect for a Blaine value of the activated fine powder in the inventive range of 9,000 to < 13,000 cm 2 / G.

[0251] Finally, it is pointed out that all mentioned, particularly claimed, features of the method and / or of the porous or foam concrete molded body are particularly advantageous in themselves and in any combination and are the subject of the present invention.

[0252] In addition, the upper and lower limits specified for each individual range can all be combined with one another according to the invention.

Claims

Claims 1. A process for producing hydrothermally cured porous or foam concrete moldings, comprising the following process steps: a) Producing a fresh concrete mass containing at least one hydrothermally reacting CaO component, at least one hydrothermally reacting SiO2 component, water, and at least one blowing agent or prefabricated foam or foaming agent, b) Optionally foaming the fresh concrete mass containing the foaming agent by stirring, c) Pouring the ready-to-cast fresh concrete mass into a casting mold, d) Optionally allowing the fresh concrete mass containing the blowing agent to expand, e) Allowing the fresh concrete mass to stiffen into a porous or foam concrete cake, f) Cutting the porous or foam concrete cake into individual porous or foam concrete moldings, g) Curing the porous or foam concrete moldings in an autoclave, characterized in that an activated fine powder is used to produce the fresh concrete mass,which contains at least one activated porous and / or foam concrete fine powder, wherein the activated fine powder has a Blaine value, determined according to DIN 196-6:2019-03, of 9 000 to 22 500 cm, 2 / g, preferably 13 000 to 22 500 cm 2 / g, preferably 14,000 to 22,000 cm 2 / g, particularly preferably 14 000 to 21 500 cm 2 / g, wherein the activated fine powder is produced by dry grinding a starting grain which exclusively comprises at least one porous and / or foam concrete grain or which comprises at least one porous and / or foam concrete grain and at least one further dry component of the fresh concrete mass.

2. A process for producing hydrothermally cured porous or foam concrete moldings, comprising the following process steps: a) Producing a fresh concrete mass containing at least one hydrothermally reacting CaO component, at least one hydrothermally reacting SiO2 component, water and at least one blowing agent or prefabricated foam or a foaming agent, b) Optionally foaming the fresh concrete mass containing the foaming agent by stirring, c) Pouring the ready-to-cast fresh concrete mass into a casting mold, d) Optionally allowing the fresh concrete mass containing the blowing agent to expand, e) Allowing the fresh concrete mass to stiffen to form a porous or foam concrete cake, f) Cutting the porous or foam concrete cake into individual porous or foam concrete moldings, g) Curing the porous or foam concrete moldings in an autoclave, characterized in thatthat for the production of the fresh concrete mass, an activated fine flour in the form of an activated fine flour mixture is used, which contains at least one activated porous and / or foam concrete fine flour, wherein the activated fine flour mixture is produced by grinding a starting grain which has at least one porous and / or foam concrete grain and at least one further dry component of the fresh concrete mass.

3. Process according to claim 1 or 2, characterized in that the activated fine flour has a BET surface area, determined according to DIN ISO 9277: 2014-01, of 30 to 45 m 2 / g, preferably 34 to 40 m 2 / g.

4. Method according to one of the preceding claims, characterized in that a fresh concrete mass is produced which has a content of activated aerated concrete fine powder and / or activated foam concrete fine powder of 10 to 35 mass%, preferably 10 to 30 mass%, particularly preferably 10 to 25 mass%, based on the solids content in the fresh concrete mass.

5. Method according to one of the preceding claims, characterized in that a porous and / or foam concrete grain is used which has a dgo value < 10 mm, preferably < 5 mm, particularly preferably < 2 mm, determined by means of the sieve passage according to DIN EN 1015-1:2007-05.

6. Method according to one of the preceding claims, characterized in that a porous and / or foam concrete grain is used which has a maximum grain size of < 12 mm, preferably < 6 mm, particularly preferably < 3 mm, determined by means of the sieve passage according to DIN EN 1015-1:2007-05.

7. Method according to one of the preceding claims, characterized in that a porous and / or foam concrete grain is used which has a coarse grain fraction comprising grains with a grain size > 125 pm, preferably grains with a grain size > 250 pm, determined by means of the sieve passage according to DIN EN 1015-1:2007-05.

8. Method according to one of the preceding claims, characterized in that the proportion of aerated concrete grain and / or foam concrete grain in the starting grain is 50 to 90 mass%, preferably 70 to 80 mass%, based on the dry mass of the starting grain.

9. Method according to one of the preceding claims, characterized in that the starting grain comprises, in addition to the at least one aerated or foam concrete grain, at least one hydrothermally reacting CaO component and / or at least one hydrothermally reacting SiO2 component, wherein the starting grain preferably comprises, in addition to the at least one aerated or foam concrete grain, quicklime and / or Portland cement (CEM I).

10. Method according to one of the preceding claims, characterized in that the at least one aerated or foamed concrete grain is dried before grinding at a temperature of 100 to 300 °C, preferably 105 to 200 °C, particularly preferably 105 °C to 120 °C, preferably to a residual moisture content of < 5 wt.%, preferably < 2 wt.%, particularly preferably < 0.5 wt.%, determined according to DIN EN ISO 17892-1: 2022-08. 11 . Method according to one of the preceding claims, characterized in that the at least one aerated or foamed concrete grain and / or the activated aerated or foamed concrete material are not exposed to temperatures above 300°C before the production of the fresh concrete mass.

12. Method according to one of the preceding claims, characterized in that the grinding of the starting grain takes place in a mill, preferably in a drum mill, preferably in the form of a ball mill, and / or in a roller mill.

13. Method according to one of the preceding claims, characterized in that a fresh concrete mass is produced which has Portland cement clinker as SiO2 and at the same time CaO component, wherein the fresh concrete mass preferably has a Portland cement clinker powder content of 5 to 45 mass%, preferably 10 to 40 mass%, particularly preferably 15 to 35 mass%, based on the solids content in the fresh concrete mass.

14. Method according to one of the preceding claims, characterized in that a fresh concrete mass is produced which has quartz as the SiO2 component, wherein the quartz preferably makes up the predominant proportion of SiO2 in the fresh concrete mass.

15. The method according to claim 14, characterized in that a fresh concrete mass is produced which has a quartz content of 25 to 80 mass%, preferably 30 to 70 mass%, particularly preferably 35 to 60 mass%, based on the solids content in the fresh concrete mass.

16. Method according to one of the preceding claims, characterized in that a fresh concrete mass is produced which has quicklime as CaO component, wherein the fresh concrete mass preferably has a quicklime content of 5 to 40 mass%, preferably 5 to 30 mass%, particularly preferably 10 to 25 mass%, based on the solids content in the fresh concrete mass.

17. Method according to one of the preceding claims, characterized in that a fresh concrete mass is produced which comprises return sludge, wherein the fresh concrete mass preferably has a return sludge content (dry mass) of 2 to 30 mass%, preferably 2 to 20 mass%, more preferably 5 to 15 mass%, based on the solids content in the fresh concrete mass.

18. Method according to one of the preceding claims, characterized in that a fresh concrete mass is produced with a water / solids ratio of 0.5 to 1.2, preferably 0.5 to 1.1, particularly preferably 0.6 to 0.9, most particularly preferably 0.6 to 0.

8.

19. Method according to one of the preceding claims, characterized in that all components mixed into the fresh concrete mass have a grain size of < 1 mm, preferably < 500 pm, particularly preferably < 150 pm, determined according to DIN EN 1015-1:2007-05.

20. Method according to one of the preceding claims, characterized in that Porous or foam concrete moldings with a thermal conductivity Xio, dry, unit of 0.039 to 0.180 W / (m K) can be produced. 21 . Method according to one of the preceding claims, characterized in that Porous or foam concrete moldings with a dry bulk density po of 70 to 800 kg / m 3 , according to DIN EN 772-13: 2000-09.

22. Method according to one of the preceding claims, characterized in that Porous or foam concrete moldings with a compressive strength of 0.1 to 10.0 N / mm 2 , are manufactured.

23. Method according to one of the preceding claims, characterized in that Porous or foam concrete moldings with an A number of 900 to 2700 [] can be produced.

24. Method according to one of the preceding claims, characterized in that Aerated or foam concrete blocks a) with a thermal conductivity X , dry, unit of 0.060 to 0.180 W / (m K), preferably of 0.065 to 0.160 W / (m K), particularly preferably of 0.070 to 0.140 W / (m K), according to DIN EN 12664: 2001-05, and / or b) with a dry bulk density po of 151 to 800 kg / m 3 , preferably from 220 to 800 kg / m 3 , particularly preferably from 255 to 600 kg / m 3 , according to DIN EN 772-13: 2000-09, and / or c) with a compressive strength of 1.0 to 10.0 N / mm 2 , preferably from 1.5 to 8.0 N / mm 2 , particularly preferably from 2.0 to 7.0 N / mm 2 , tested on a cube with an edge length of 100 mm in accordance with DIN EN 772-1 : 2011-07.

25. Method according to one of claims 1 to 23, characterized in that a) porous or foam concrete insulation bodies with a thermal conductivity Xio, dry, unit of 0.039 to 0.055 W / (m K), preferably of 0.041 to 0.049 W / (m K), particularly preferably of 0.042 to 0.048 W / (m K), according to DIN EN 12667:2001-05, and / or b) Aerated or foam concrete insulation bodies, in particular aerated or foam concrete insulation boards, with a dry bulk density po of 70 to 150 kg / m 3 , preferably from 80 to 120 kg / m 3 , particularly preferably from 85 to 115 kg / m 3 , according to DIN EN 1602: 2013-05, and / or c) aerated or foam concrete insulation bodies, in particular aerated or foam concrete insulation boards, with a compressive strength of 0.1 to 0.7 N / mm 2 , preferably from 0.1 to 0.5 N / mm 2 , particularly preferably from 0.2 to 0.4 N / mm 2 , according to DIN EN 826:2013, and conditioning at 40°C to constant mass.

26. Hydrothermally cured porous or foam concrete molding comprising a solid web framework surrounding pores resulting from a foam or produced by a blowing process, wherein the solid web framework comprises calcium silicate hydrate phases and micropores, characterized in that the porous or foam concrete molding is produced by a process according to one of claims 1 to 25 and preferably has the features of at least one of claims 20 to 25.

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