WO2024245795A1 - Process for producing hydrothermally hardened aerated or foamed concrete moldings and aerated or foamed concrete molding produced according to the process - Google Patents

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

Process for the production of hydrothermally hardened porous or foam concrete moldings and porous or foam concrete moldings produced by the process

The present invention relates to a method for producing hydrothermally hardened aerated or foamed concrete moldings, in particular in the form of aerated or foamed concrete blocks. Aerated concrete blocks of standardized quality classes with regard to 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/m ³ are particularly preferably produced. However, non-standardized blocks, e.g. with a bulk density between 200 and < 305 kg/m ³ and aerated or foamed concrete insulation material, preferably aerated or foamed concrete insulation boards, with a bulk density between e.g. 70 and < 200 kg/m ³ , preferably 70 and 150 kg/m ³ can also be produced. Furthermore, reinforced aerated or foamed concrete formwork components with bulk densities such as standardized or non-standardized aerated or foamed concrete blocks can also be manufactured.

In addition, the invention relates to such a porous or foam concrete molded body produced by means of the method.

Aerated concrete moldings consist of hydrothermally hardened, porous calcium silicate hydrate material. They are produced from an aqueous mixture or fresh concrete mass, which contains at least one CaO component that is reactive in the hydrothermal process and at least one SiO2 component that is reactive in the hydrothermal process, a blowing agent, in particular aluminum powder and/or paste, and optionally, in particular inert, additives. In addition, the fresh concrete mass often contains at least one additive, e.g. a flow agent and/or a dispersant. The pourable or ready-to-pour fresh concrete mass is poured into a mold, allowed to expand and stiffen, cut and then subjected to steam hardening. In contrast to conventional, non-autoclaved concrete, Aerated concrete material does not contain any coarse aggregates with a grain size > 2.0 mm.

To produce hydrothermally hardened foam concrete moldings, prefabricated foam is mixed into the fresh concrete mass instead of the foaming agent, or the fresh concrete mass containing a foaming agent is foamed directly by stirring and then the pourable or ready-to-cast fresh concrete mass is poured into the mold. In each case, the foaming process is omitted.

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

Aerated or foam concrete blocks are building blocks made of aerated and foam concrete material. The generally unreinforced aerated or foam concrete blocks are mainly used as masonry blocks. Depending on the manufacturing tolerances, they are also referred to as aerated or foam concrete plan blocks or blocks. Reinforced aerated or foam concrete moldings are mainly used as large-format aerated or foam concrete components.

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.

Currently, aerated concrete blocks of standardized quality classes (EN 771-4 2015-1 1 and DIN 20000-404:2018-04) with densities < 800 kg/m ³ are usually 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, the 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, the 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 level of the SOs content is specified in DIN EN 197-1:2011-11. However, an additional sulfate carrier is usually added to the aerated concrete mixture.

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

In addition, both the lime-cement formulations and the lime formulations often contain aerated concrete grains. The aerated concrete grains are also called aerated concrete powder or aerated concrete chippings in the technical field. Aerated concrete grains usually come from ongoing production. This means that waste material and/or material from overproduction that arises during production is broken, usually using a roller crusher, screened and used to produce new aerated concrete moldings. The aerated concrete grains are usually screened in such a way that they have a consistent grain distribution with a maximum grain size of < 1200 pm.

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.

(https://www.bauhandwerk.de/news/ytong-startschuss-fuer-porenbeton- recycling-im-werk-wedel_3197859.html). The aerated concrete material must be recycled in pure form and is also broken and sieved so that it has a grain size of 0-1 mm. The reuse of the recycled aerated concrete material contributes in particular to improving the CO2 balance.

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

DE 10 2006 049 836 A1 discloses the production of a hydraulic binding agent 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 a binding phase and additives. According to the process of DE 10 2006 049 836 A1, fillers are first separated and the remaining amount of material is thermally treated to form a hydraulically active phase. To do this, 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.

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

CN 113213846 A discloses a cement mortar that contains crushed, calcined and ground aerated concrete powder. During crushing, aerated concrete granulate with a grain size of < 0.16 mm is initially produced. The subsequent calcination and grinding activates the aerated concrete powder and can replace cement.

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

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% on a 45 pm sieve.

Aerated and foam concrete blocks have good building physics properties as a building material. In particular, aerated and foam concrete blocks have 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. It represents the relative compressive strength of the aerated or foam concrete block. The larger the A number, the better the compressive strength level. The A number is calculated as follows:

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

The aim in the production of aerated concrete moldings is always to achieve the lowest possible thermal conductivity with the best possible strength properties. In order to reduce thermal conductivity, it is known, for example, to use limestone powder as an additive in the production of aerated or foamed concrete. Limestone powder is chemically inert and autoclave-resistant. The specific surface area of the limestone powder commonly used is 4000-6000 cm 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 and the solid web structure therefore contains fewer CSH phases. This also causes a reduction in the compressive strength level (A number).

From DE 10 2013 011 742 A1 it is also known to add PCC instead of natural, ground limestone powder. This reduces the thermal conductivity slightly, but retains the strength.

DE 20 2008 017 703 U1 also deals with 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 specific surface area according to Blaine of at least 6000 cm ² /g and a corresponding autoclaving time.

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

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

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 further developments of the invention are characterized in the respective subsequent subclaims. Within the scope of the invention, it was surprisingly found 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 in comparison 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.

In dry grinding, a bulk material or a loose mixture of solids is ground. In wet grinding, however, the material to be ground is mixed with a liquid and a suspension or slurry is ground in the mill.

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.

This means that the loss of strength that normally occurs when using aerated concrete grains can be compensated or at least reduced.

The reason for this effect has not yet been fully clarified. It is assumed that it is a mechanochemical activation process of the mineral surfaces. Mineral transformations may also occur as a result of grinding.

The production of the porous or foam concrete molding according to the invention takes place in a manner known per se from a fresh concrete mass which has 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 a foaming agent. According to the invention, the Fresh concrete mass also contains at least one finely ground, activated porous and/or foam concrete powder.

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.

In the context of the invention, moreover, 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.

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

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

In the context of the invention, a sulfate carrier is understood to mean a raw material which consists of alkali sulfate or alkaline earth sulfate, preferably calcium sulfate. Of course, these raw materials can contain secondary components or impurities. Secondary components are undesirable and should therefore be interpreted as impurities.

In contrast, raw materials which contain sulfate minerals or sulfate compounds only as minor components are not referred to as sulfate carriers within the scope of the invention.

Portland cement (CEM I) in accordance with DIN EN 197-1:2011-1 1 is preferably used for the production of the fresh concrete mass. Portland cement is known to contain 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 contains ground quartz, preferably ground quartz sand, and/or amorphous silica, preferably microsilica.

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

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

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

The fresh concrete mass can 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.

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

According to a first embodiment of the invention, the starting grain therefore only contains at least one porous and/or foam concrete grain and no other components. The proportion of porous and/or foam concrete grain in the starting grain is thus 100% by mass, based on the dry mass of the starting grain. This starting grain is thus ground into pure activated porous and/or foam concrete fine powder.

Alternatively, in addition to the at least one porous 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 to an activated fine flour mixture which contains at least one activated porous or foamed concrete fine flour.

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

The proportion of porous and/or foam concrete grain in the starting grain is preferably 50 to 90 mass%, more preferably 70 to 80 mass%, based on the dry mass of the starting grain. The proportion is limited downwards by the recipe and the binder content it contains.

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

Unless otherwise stated, grain sizes are determined within the scope of the invention by means of sieve passage in accordance with DIN EN 1015-1:2007-05.

The porous or foamed concrete grain preferably has a maximum grain size of < 12 mm, preferably < 6 mm, particularly preferably < 3 mm.

Furthermore, the porous or foamed concrete grain is preferably coarse-grained, i.e. it also has grains with a grain size > 125 pm, preferably also grains with a grain size > 250 pm. The porous or foam concrete grain therefore has a coarse grain content.

In addition, the aerated or foamed concrete grain 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.

The aerated or foamed concrete grain used is preferably a by-product from the aerated or foamed concrete production, which has preferably been mechanically crushed by means of a crusher to form the aerated or foamed concrete grain with the specified grain size. The by-product is in particular technological breakage.

Alternatively, the porous or foam concrete grain is recycled material, which has also preferably been mechanically crushed using a crusher to form the porous or foam concrete grain with the specified grain size. The recycled material can also be recarbonated. It is also known that it can contain adhering plaster and mortar residues. The advantage of the grinding according to the invention is that homogenization takes place and the adhering plaster and mortar residues are finely crushed and distributed.

Of course, the aerated or foamed concrete grain can also be produced by mechanical crushing of specially manufactured aerated or foamed concrete moldings.

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.

The porous or foamed concrete grain is also dried before grinding at a temperature of 100 to 300°C, preferably 105 to 200°C, particularly preferably 105°C to 120°C, in order to remove physically bound to expel water. The residual moisture after drying is < 5 wt.-%, preferably < 2 wt.-%, particularly preferably < 0.5 wt.-%, determined in accordance with DIN EN ISO 17892-1: 2022-08.

Further temperature treatment of the porous or foam concrete grain and/or the activated porous or foam concrete fine powder does not take place within the scope of the invention. In particular, no calcination takes place at higher temperatures. The at least one porous or foam concrete grain and/or the activated porous or foam 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 avoid a transformation of the tobermorite at temperatures that are too high.

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.

In the context of the invention, it was also surprisingly discovered that a certain proportion of activated porous or foamed concrete fine powder is advantageous. The fresh concrete mass preferably contains 10 to 35% by mass, preferably 10 to 30% by mass, particularly preferably 10 to 25% by mass, very particularly preferably 15 to 25% by mass, of activated porous or foamed concrete fine powder, based on the solids content (= total solids) in the fresh concrete mass. The solids content is understood to mean the sum of all solids, i.e. the mass of the freshly dosed dry substances and the dry substances contained in the return 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.

The proportion of activated porous or foamed concrete fine powder includes any portion contained in the return sludge, even if the activated porous or foamed concrete fine powder in this case is not in the form of of a fine powder, but is added with the return sludge. This is because the activated porous or foam concrete fine powder is present in the return sludge in a finely distributed form.

Surprisingly, it was found that, for example, with a content of 40 mass % of activated aerated or foamed concrete fine powder, no improved compressive strengths can be achieved compared to the use of 40 mass % of non-activated aerated or foamed concrete grains.

This could result from the fact that there is too little binding agent, which has a greater effect 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.

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

According to the invention, the starting grain is ground 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, more preferably 14 000 to 22 000 cm ² /g, particularly preferably 14 000 to 21 500 cm ² /g.

Preferably, the starting grain is also ground 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.

As already explained, the fresh concrete mass preferably contains Portland cement clinker powder as CaO and SiO2 components.

Preferably, the fresh concrete mass 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.

The fresh concrete mass can also contain residual sludge. The dry substances contained in the residual sludge are hydrate phases formed from the binding agent components and possibly 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 hardening in the autoclave.

Preferably, the fresh concrete mass 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.

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

Preferably, the fresh concrete mass 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 in the fresh concrete mass. In this way, in particular, the formation of a sufficient amount of CSH phases can be ensured.

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

Preferably, the fresh concrete mass also contains 5 to 40 mass-%, preferably 5 to 30 mass-%, particularly preferably 10 to 25 mass-%, of quicklime based on the solids content in the fresh concrete mass. In this way, in particular, the formation of a sufficient amount of CSH phases can be ensured. The W/F value (water/solids value) of the fresh concrete mass is also preferably 0.5 to 1.2, more preferably 0.5 to 1.1, particularly preferably 0.6 to 0.9, most preferably 0.6 to 0.8.

If necessary, 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 powder, based on the solids content in the fresh concrete mass. The rock powder is preferably limestone powder. The limestone powder can, for example, also result from the addition of a Portland limestone cement, in particular a CEM II in accordance with DIN EN 197-1:2011-11.

Advantageous compositions or recipes of the fresh concrete mass are given in the table below (figures in % by 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 present or available on the market [not their active ingredient content] and additively based on the dry mass):

The solids contents given in the table above do not have to add up to 100% by mass. In fact, other components may also be included. Consequently, each component and each range disclosed in the table is considered advantageous in itself. In addition, the lower and upper limits of the ranges given for the individual components can be combined with one another.

For example, it may also contain fired clays and/or calcined clays. The aluminium component may be aluminium powder, paste or suspension in a conventional manner. The aluminium component shown in the table The stated proportion is the solid or active ingredient content of the respective aluminum component.

In addition, an aluminum component or alternatively a foam component or a foaming agent is always present. Aluminum components, foam components or foaming agents are therefore used alternatively.

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

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

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 return sludge, at least one blowing agent or prefabricated foam or a foaming agent and water. In addition, according to the invention, the fresh concrete mass contains at least one activated porous or foamed concrete fine powder.

The production preferably takes place in the usual way, by first mixing the sludge with the water, then adding the inert components, then the binding agent and then the aluminum component. The activated fine powder is preferably added together with the binding agent.

The fresh concrete mass is filled 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 also be suspended in the casting mold after the casting mold has been filled with the fresh concrete mass. In the case of the production of aerated concrete moldings, the casting compound is allowed to expand.

When producing foam concrete moldings, there is no need for foaming. To produce foam concrete moldings, either the fresh mass containing a foaming agent is whipped to form the foam or the pre-made foam is mixed in. This takes place before the fresh mass is poured into the mold.

The casting compound is then allowed to stiffen into a green porous or foam concrete cake.

After stiffening, the aerated or foamed concrete cake is cut into individual aerated or foamed concrete moldings in a conventional manner.

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

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

The start-up and shut-down phases are preferably linear, without intermediate stopping phases. The start-up and shut-down phases each last, for example, 1.5 to 6 hours. In a very preferred autoclave mode, the autoclaving begins with a vacuum phase. After the autoclave is closed, the air is pumped out of it 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 mode, the air in the autoclave is reduced by flushing it with steam without pressure. 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 processed without further ado 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.

As already explained, a measure of the strength of porous and foam concrete moldings is the so-called A-number, as it indicates the compressive strength in relation to the bulk density. The A-number is the result of a calculation of the compressive strength to the dry bulk density. It represents the relative compressive strength of the porous or foam concrete molding. The higher the A-number, the better the compressive strength level.

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

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 is tested for constant mass in the case of porous or foam concrete moldings with a dry bulk density po of up to 150 kg/m ³ in accordance with DIN EN 826:2013-05 after drying at 40°C and in the case of porous or foam concrete moldings with a dry bulk density po > 150 kg/m ³ on a cube with an edge length of 100 mm in accordance with DIN EN 772-1: 2011-07.

If the porous or foam concrete moldings according to the invention are preferably unreinforced porous or Foam concrete blocks preferably have a compressive strength of 1.0 to 10.0 N/mm ² , preferably 1.5 to 8.0 N/mm ² , particularly preferably 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.

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

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.

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 of 220 to 800 kg/m ³ , particularly preferably of 255 to 600 kg/m ³ , according to DIN EN 772-13: 2000-09.

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

Preferably, the porous 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 foamed concrete moldings according to the invention are preferably unreinforced aerated or foamed concrete molding 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), in accordance with DIN EN 12664: 2001-05 and DIN EN 12667:2001-05.

If the porous or foam concrete moldings according to the invention are porous or foam concrete insulation bodies, in particular porous or foam concrete insulation boards, 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), in accordance with DIN EN 12664: 2001-05 and DIN EN 12667:2001-05.

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

Examples of implementation:

In the examples, aerated concrete moldings were produced using different recipes. The aerated concrete moldings were always produced as follows:

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

1. Place water and, if necessary, residual sludge and, if necessary, additives in the mixing vessel

2. Addition of quartz powder, mixing time 30 seconds

3. Addition of 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

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

The test samples 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 samples from test series 9 (insulating board) were demolded after 24 hours (at 25°C), transferred to the hardening base and then autoclaved.

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 _abs was reached. The pressure was then increased linearly to 12 bar _abs over 1.5 hours, held for 7 hours and then reduced, also linearly, to ambient pressure over 1.5 hours.

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

The following raw materials were used to conduct the tests:

Table 1: Raw materials used

Herstellung Rückschlamm: Table 2: Additives used

Production of return sludge:

The return sludge was produced from non-steam-cured porous concrete molds.

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

2. Add quartz powder, mixing time 30 seconds.

3. Addition of the binding agents and activated aerated concrete fine powder and/or activated fine powder mixture, mixing time 30 seconds. 4. Addition of aluminium in suspension (100 ml), mixing time 20 seconds.

5. Force the mixture up in the mixing container.

6. After about 1 hour, the swollen cake was gradually mixed with water to form a suspension with a density of 1.3 kg/L. The density of the sludge (weight per liter) was determined using a measuring cylinder and laboratory scales (mass per volume). The suspension was then stirred for 18 hours before use. During the 18 hours, the suspension may thicken further. The density of the sludge was therefore measured again immediately before use and, if necessary, diluted or corrected with water to a density of 1.3 kg/L.

Production of dried aerated concrete (AAC) and wet

Aerated concrete grain size (PBKf _euC ht):

The production of the aerated concrete grains was initially carried out analogously to the production of aerated concrete moldings from the following recipe:

Table 3: Recipe for the production of aerated concrete aggregate

The steam-cured aerated concrete moldings 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 sawing residues were crushed in a jaw crusher (Fa.

Retsch, type BB1). The broken material was sieved through a 1 mm sieve. The fraction < 1 mm formed the aerated concrete grain. A mixed sample was prepared from all small test specimens.

The proportion for the small-scale tests with moist aerated concrete grains (PBKfeucht) was separated. The moisture content was determined (12.5 M.-% H2O) according to DIN EN ISO 17892-1: 2022-08.

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

Table 4: Results of the measurements of the properties of the starting material of the aerated concrete aggregate (AAC)

Production and specification of aerated concrete grains (PBKp _rO d) from ongoing production:

The aerated concrete grain (PBKp _rO d) came from ongoing production at the Xella aerated concrete plant in Brück. It was waste material from production and/or material from overproduction. The material was crushed using a roller crusher and sieved to a grain size of < 1500 pm.

The aerated concrete grain size (PBKp _rO d) had the following main components in mass-%:

^[1] Bestimmt mittels Röntgenfluoreszenzanalyse unter Nutzung eines AXIOS PW 4400 der Firma PANalytical B.V. Table 5: Main components of the aerated concrete aggregates (PBKprod) from current production

^[1] Determined by X-ray fluorescence analysis using an AXIOS PW 4400 from PANalytical BV

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

Production of activated fine flour:

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.

To produce pure activated aerated concrete fine powder (PBFM), the aerated concrete grains were each dry ground alone.

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

White fine lime or quartz powder or microsilica in different proportions and this initial grain size was ground.

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

Table 6: Properties of the drum mill and process parameters

drum mill

Manufacturer WELTE ^a) Mahltechnik, Cologne

built in 1995

Type designation WGN-WGT 100

armor rubber

mill diameter 46.5 cm

mill length 48 cm

rotation speed 48 rpm

Type of grinding Dry grinding

ground material mass as specified

grinding balls

Manufacturer CeramTec GmbH, Plochingen

material AI2O3

purity 92%

type

Total grinding mass 70,000 g

Proportion of ball 0 = 40 mm 50 %

Proportion of ball 0 = 30 mm 30 %

Proportion of ball 0 = 20 mm 20 % a) Company closed in 1998, service via AAM Mahltechnik GmbH, Cologne

Table 7: Process parameters of the grinding process

Grinding time fin the mass of ground material rule)

[min] [g]

120 7500

Production of “Durox flour”:

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 loading with balls), grinding time and mass of ground material are identical. In this case, however, the binding agent (white fine lime) was ground with the dry quartz flour. Production of heated aerated concrete grains (PBK900) and the aerated concrete fine powder produced from the heated aerated concrete grains (PBFM900):

For the 11th test series, the aerated concrete grain 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 grain treated at 105°C).

Measurements carried out:

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, and from this 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.

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

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

The aerated concrete molds were prepared using commercially available

Drilling dust was removed from a pillar drill (HSS drill, diameter 24 mm). These powder samples were first dried for 24 hours at 40°C in a drying cabinet. For the subsequent wet grinding, 10 mass % of internal standard zincite (ZnO from JT Baker Avantor Performance Materials, Inc.) was added to each sample, which corresponds 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 minutes in PVC grinding jars with ZrÜ2 grinding cylinders. The ground material was rinsed out, rinsed four times with 5 ml of 2-propanol (AnalaR NORMAPUR, VWR) each time and filtered for 24 hours over hard filter paper (84 g/m ² , No. 1291; Sartorius) under a fume hood and dried at room temperature (20°C). The powder was brushed off the filter paper and homogenized for 2 minutes in an agate mortar and pressed into a diffractometer powder tablet (backloading method). A powder tablet was prepared and measured from each material sample taken.

The samples were measured on a Panalytical MPD Pro diffractometer. The qualitative phase determination was carried out using the Panalytical HighScorePlus software. The measurement conditions and further information are listed in Table 8. Table 8: Measurement conditions and further information

The quantitative determination was carried out using the Rietveld method. Bruker AXS Topas (version 5) was used as the evaluation software. To determine the amorphous phase content, 10 mass % zinc oxide (see above) was added to the test preparation as an internal standard and subtracted accordingly during the evaluation. The remaining phases, including X-ray amorphous phases, are standardized to 100 %. To evaluate the quantitative phase composition, the following structures from the ICSD database (Inorganic Crystal Structure Database, as of 2016) were used:

11Ä-Tobermorit (# 92943)

quartz (# 34636)

anhydrite (# 15876)

Bassanite (# 69090) Hydroxylellestadite (# 156173) Zincite (# 65120) 1st test series:

In the first series of tests, aerated concrete moldings with a density class of 400 kg/m ³ were produced. All aerated concrete fresh masses according to the invention also contained 10 mass % of activated aerated concrete fine powder. The aerated concrete fresh mass of the reference aerated concrete molding contained 10 mass % of 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 was 120 minutes in each case.

Table 9: Compositions of the recipes of the 1st test series

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

Table 10 shows the results.

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

From Table 10 it can be clearly seen 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 increases the compressive strength level compared to the use of 10 mass% of conventional aerated concrete grain.

2nd test series: The 2nd test series was carried out in the same way as the 1st test series. However, 20 mass% of activated aerated concrete fine powder or 20 mass% of conventional aerated concrete grains were used.

Die Ergebnisse der Messungen der Eigenschaften der 2. Versuchsreihe sind in Tabelle 12 aufgeführt. Tabelle 12: Ergebnisse der Messungen der Eigenschaften der 2. Versuchsreihe

Table 11 : Compositions of the recipes of the 2nd test series

The results of the measurements of the properties of the 2nd series of tests are shown in Table 12. Table 12: Results of the measurements of the properties of the 2nd test series

It can be clearly seen from Table 12 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 mass % of activated aerated concrete fine powder also increases the compressive strength level compared to the use of 20 mass % of conventional aerated concrete grain.

3rd series of experiments:

In the third series of tests, the content of activated aerated concrete fine powder was further increased and varied. Contents of 25 M.-

%, 30 mass-%, 35 mass-% and 40 mass-%. The starting grain sizes contained either exclusively aerated concrete grain or 75 mass-% aerated concrete grain and 25 mass-% quicklime. The grinding time was again 120 minutes.

The results of the measurements of the properties of the 3rd series of tests are shown in Table 14.

Aus Tabelle 14 ist zu erkennen, dass die A-Zahl bei einem Gehalt von 25 M.-% aktiviertem Porenbetonfeinmehl nicht verbessert wird, wenn die Ausgangskörnung aus reiner Porenbetonkörnung besteht. Besteht die Ausgangskörnung aus einer Mischung aus Porenbetonkörnung und Branntkalk, wird die A-Zahl lediglich noch geringfügig verbessert im Vergleich zu der Verwendung der herkömmlichen, nicht aktivierten Porenbetonkörnung. Dieser Trend zeigt sich verstärkt noch bei einem Gehalt von 30 M.-% an aktiviertem Porenbetonfeinmehl. Bereits hier ist auch die A-Zahl des Porenbetonkörpers, bei dem die Ausgangskörnung Branntkalk und Porenbetonkörnung enthält, geringfügig geringer als bei dem Poren beton körper, der lediglich nicht aktivierte, herkömmliche Porenbetonkörnung enthält. Dieser Trend verstärkt sich mit zunehmendem Gehalt an aktiviertem Porenbetonfeinmehl. Bei einer Zugabe von 40 M.-% an aktiviertem Porenbetonfeinmehl hat der Referenz- Porenbetonkörper mit der herkömmlichen, nicht aktivierten Porenbetonkörnung mit Abstand die beste A-Zahl. 4. Versuchsreihe: 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 grain consists of pure aerated concrete grain. If the starting grain consists of a mixture of aerated concrete grain and quicklime, the A number is only slightly improved compared to the use of conventional, non-activated aerated concrete grain. This trend is even more pronounced at a content of 30 mass % activated aerated concrete fine powder. Even here, the A number of the aerated concrete body in which the starting grain contains quicklime and aerated concrete grain is slightly lower than in the aerated concrete body that only contains non-activated, conventional aerated concrete grain. This trend becomes more pronounced with increasing content of activated aerated concrete fine powder. With an addition of 40 mass% of activated aerated concrete fine powder, the reference aerated concrete body with the conventional, non-activated aerated concrete grain has by far the best A-number. 4th series of experiments:

In the fourth series of tests, the content of aerated concrete grain in the starting grain was varied. The contents were set at 50%, 62.5% and 75% by mass of aerated concrete grain. The starting grains 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% by mass.

Table 15: Compositions of the recipes of the 4th test series

The results of the property measurements of the 4th series of tests are shown in Table 16.

Aus Tabelle 16 ist gut zu erkennen, dass sich keine Tendenz des Einflusses des Gehalts an Porenbetonkörnung in der Ausgangskörnung auf die A-Zahl des daraus hergestellten Poren beton körpers zeigt. 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 grain in the initial grain on the A-number of the aerated concrete body produced from it.

5th test series: In the 5th test series, the grinding time was varied. It was 60, 120 and 240 minutes. These tests were carried out both with a starting grain consisting exclusively of aerated concrete grain and with a starting grain that contained 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.

Table 17: Compositions of the recipes of the 5th test series

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

It is clear from Table 18 and Figures 5 and 6 that after a certain grinding time has been exceeded, the strength properties of the aerated concrete moldings decrease again or do not improve any further. This could be because the material begins to agglomerate. The Blaine values decrease again.

6th series of experiments:

In the 6th test series, an aerated concrete molding with a bulk density of 330 kg/m ³ and an aerated concrete molding with a bulk density of 460 kg/m ³ were produced. The starting grains used each contained 75 mass % aerated concrete grain and 25 mass % Portland cement (CEM I).

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 %

aerated concrete grain and 25 mass-% quicklime.

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

(batch) was 20 mass-% in each case. Table 19: Compositions of the recipes of the 6th test series

The results of the measurements of the properties of the 6th test series are shown in Table 20. Table 20: Results of the measurements of the properties of the 6th test series

From Table 20 it is clearly evident that the A number is improved by using activated aerated concrete fine powder even when using return sludge. 7th test series:

As part of the 7th test series, two aerated concrete moldings were produced in which the quartz sand and the quicklime were mixed before being added to the Fresh concrete mass was ground together (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. In addition, aerated concrete bodies were produced without the composite grinding of quartz sand and quicklime.

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

Table 21 : Compositions of the recipes of the 7th test series

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

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

8th series of experiments:

As part of the 8th series of tests, aerated concrete moldings with different densities in the density range 300 - 600 kg/m ³ were produced. In addition, conventional, dried aerated concrete grain, moist aerated concrete grain, activated aerated concrete fine powder and activated fine powder mixture were used. In addition, cement was also ground with aerated concrete grain. The content of activated aerated concrete fine powder or aerated concrete grain was 20 mass% and the grinding time was 120 minutes.

+ Value based on dry matter at 105°C

++ including the water content contained in the PBKfeucht

+++ Not measurable due to humidity

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

It can be clearly seen from Table 24 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 densities. In addition, the A number is worse when using the moist aerated concrete grains (8A and 8F) than when using the dried aerated concrete grains (8B and 8G).

9th series of experiments:

As part of the 9th series of tests, aerated concrete moldings with a low bulk density (aerated concrete insulation bodies) were produced. In addition, conventional, dried aerated concrete grain, moist aerated concrete grain, activated aerated concrete fine powder and activated fine powder mixture were used. The content of activated aerated concrete fine powder or aerated concrete grain was 10.5 mass% and the grinding time was 120 minutes.

Furthermore, the tensile strength was also determined. Table 25: Compositions of the recipes of the 9th test series

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

Table 25 shows that the activated aerated concrete fine powder significantly improves the A number even at low densities. The tensile strength is also improved. The tensile strength is by far the best when using the activated fine powder mixture. 10th series of experiments:

In the 10th series of tests, conventional, dried aerated concrete grain, moist aerated concrete grain, activated aerated concrete fine powder and activated fine powder mixture were used again and aerated concrete moldings with a bulk density of around 350 kg/dm ³ were produced. 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.

Table 27: Compositions of the recipes of the 10th test series

+ Value based on dry matter at 105°C

++ including the water content contained in the PBKfeucht

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

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. In addition, the strength properties are impaired by the use of moist aerated concrete grains.

11th series of experiments:

In the 11th series of tests, conventional, dried aerated concrete grain, baked aerated concrete grain, activated aerated concrete fine powder and activated aerated concrete fine powder made from baked aerated concrete grain were used. The content of activated aerated concrete fine powder or aerated concrete grain was 14.8 mass% and the grinding time was 120 minutes.

Table 29: Compositions of the recipes of the 11th test series

Tabelle 31 : Mineralogische Phasenzusammensetzung der Versuche der 11.Table 30: Results of the measurements of the properties of the 11th test series

Table 31: Mineralogical phase composition of the 11th series of experiments.

series of experiments

Table 30 shows that baking reduces the A-number. This applies both to conventional aerated concrete grains and to activated aerated concrete fine powder.

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

12th test series: In the 12th test series, recycled aerated concrete grain and activated fine flour mixture with activated aerated concrete fine flour, made from recycled aerated concrete grain, were used. The content of activated aerated concrete fine flour and aerated concrete grain was 10 and 20 mass% and the grinding time was 120 minutes.

Table 32: Compositions of the recipes of the 12th test series

Aus Tabelle 33 ist zu erkennen, dass die A-Zahl bei Verwendung des aktivierten Porenbetonfeinmehls jeweils im Vergleich zur Verwendung der herkömmlichen Porenbetonkörnung in gleicher Menge verbessert wird. Zudem ist die A-Zahl bei Verwendung von 20 M.-% herkömmlicher Porenbetonkörnung schlechter als bei Verwendung von 10 M.-% herkömmlicher Porenbetonkörnung. Die A-Zahl bei Verwendung von 20 M.-% aktiviertem Porenbetonfeinmehl ist zudem nur geringfügig schlechter als bei Verwendung von 10 M.-% herkömmlicher Porenbetonkörnung. Es kann also eine größere Menge an Porenbetonkörnung wiederverwertet werden, ohne dass die A-Zahl zu sehr abgesenkt wird. 13. Versuchsreihe: 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 grain. In addition, the A number is worse when using 20% by mass of conventional aerated concrete grain than when using 10% by mass of conventional aerated concrete grain. The A number when using 20% by mass of activated aerated concrete fine powder is also only slightly worse than when using 10% by mass of conventional aerated concrete grain. This means that a larger amount of aerated concrete grain can be recycled without the A number being reduced too much. 13th series of experiments:

In the 13th series of tests, the aerated concrete grains from current production and the activated aerated concrete fine powder produced from them were used. The content of activated aerated concrete fine powder or aerated concrete grains was 20 mass% and the grinding time was 20 minutes.

Table 34: Compositions of the recipes of the 13th test series

The results of the measurements of the properties of the 13th series of tests are shown in Table 35. Table 35: Results of the measurements of the properties of the 13th series of tests

From Table 35 it can be seen that the A-number of the aerated concrete molded body 13B according to the invention 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 increases the compressive strength level compared to the use of 20 mass% of conventional aerated concrete grain from current production. The results of the 13th series of tests 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.

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.

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. Process for the production of hydrothermally hardened porous or foam concrete moldings, with 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) hardening 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 Contains 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 has at least one porous and/or foam concrete grain or which has at least one porous and/or foam concrete grain and at least one further dry component of the fresh concrete mass. 2. Process for the production of hydrothermally hardened porous or foam concrete moldings, with 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-pour 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) hardening the porous or foam concrete moldings in an autoclave, characterized in that an activated fine flour in the form of an activated fine flour mixture is used to produce the fresh concrete mass, which contains 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 powder 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 foamed 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 porous or foamed 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 porous or foamed concrete grain, quicklime and/or Portland cement (CEM I). 10. The method according to any one of the preceding claims, characterized in that the at least one porous 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 porous or foam concrete grain and/or the activated porous or foam 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 as 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 the 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 contains residual sludge, wherein the fresh concrete mass preferably has a residual 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 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, can be produced. 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 can be produced. 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 foamed concrete blocks a) with a thermal conductivity X , dry, unit of 0.060 to 0.180 W/(m K), preferably from 0.065 to 0.160 W/(m K), particularly preferably from 0.070 to 0.140 W/(m K), in accordance with 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 , in accordance with 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 up 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. 25. Method according to one of claims 1 to 23, characterized in that a) porous or foam concrete insulating 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 80 to 120 kg/m ³ , particularly preferably 85 to 115 kg/m ³ , in accordance with 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 0.1 to 0.5 N/mm ² , particularly preferably 0.2 to 0.4 N/mm ² , in accordance with DIN EN 826:2013, and conditioning at 40°C to constant mass. 26. Hydrothermally hardened porous or foam concrete molded body having a solid web structure which surrounds pores resulting from a foam or produced by a blowing process, wherein the solid web structure has calcium silicate hydrate phases and micropores, characterized in that the porous or foam concrete molded body 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.