DE102010062762B4 - Process for producing foam concrete and use of the process - Google Patents

Abstract

Process for the production of foam concrete with a dry density less than 400 kg / m3 comprising the steps a. Formation of a cement paste consisting of cement, water, a network agent, which is a mixture of negatively charged inorganic substances and organic substances with amide groups with corresponding counterions (cations), the divalent or trivalent cations or a mixture thereof and / or an organic Compound with excess positive charges from the class of the cationic surfactants and / or the quaternary ammonium compounds, and optionally at least one additive, by mixing the components in a mixer (1), b. Formation of a foam consisting of water, air and a protein-based foaming agent from nonpolar and polar amino acids using a foam generator (2), the foaming agent being a protein which is 50 to 80% by mass from the amino acids A (alanine), E (glutamic acid) , G (glycine), I (isoleucine), L (leucine), M (methionine), P (proline), Q (glutamine) and V (valine), with a molecular weight between 20,000 and ...

Description

The invention relates to a process for the production of foam concrete and its use.

Concrete is an artificial stone made from a mixture of cement, concrete aggregate and water - possibly also with concrete admixtures and concrete admixtures (concrete admixtures) - by hardening the cement paste (cement-water mixture) (DIN 1045). Cement is the hydraulic binder. The concrete properties are set by selecting the starting materials and their mixing ratio. For example, sand, gravel and / or grit are used as concrete aggregate. In the mortar, in contrast to the concrete, the aggregates used are finer, an addition of larger stones missing. Concrete in which the cement paste has not yet set is called fresh concrete, which has a fresh raw density. After the cement paste has set, the concrete is called hardened concrete. This has a solid or dry density. The bulk density is the density of a porous body based on the volume including the pore spaces. The counterpart to the bulk density is the non-porous true density.

The density of the concrete depends on the surcharge. For normal concrete, the dry bulk density is between 2000 and 2600 kg / m ³ . Concretes above 2600 kg / m ³ are referred to as heavy concrete, below 2000 kg / m ³ as lightweight concrete.

• 1. Zugabe leichter Gesteinskörnungen oder Zusatzstoffe zum Zementleim. Leichtbeton hat meist Zuschläge wie Blähton oder Bimsstein. Als Zusatzstoffe sind auch Blähglas und expandierte Polystyrolkugeln bekannt.
• 2. Zugabe von Substanzen, die unter Freisetzung von Gasen in oder mit dem Zementleim reagieren und so Poren bilden, d. h. chemisches Aufschäumen.
• 3. Einbringen und Stabilisieren von Luftporen in den Zementleim während der Herstellung, d. h. physikalisches Aufschäumen.

To reduce the dead weight of a construction, lightweight yet stable concretes are desirable. In order to achieve this, the highest possible proportion of air or gases is introduced into artificial stones, such as concrete or cement, in line with light and porous natural rocks. Essentially, three approaches are known for this purpose:

• 1. Addition of light aggregates or additives to the cement paste. Lightweight concrete usually has aggregates such as expanded clay or pumice. As additives and expanded glass and expanded polystyrene balls are known.
• 2. Addition of substances that react with the release of gases in or with the cement paste and thus form pores, ie chemical foaming.
• 3. Introduction and stabilization of air pores in the cement paste during manufacture, ie physical foaming.

Due to the high proportion of air or gas in the cement or concrete raw material can be saved and there are improved thermal insulation properties. With increasing air intake and thus increasing porosity, the fresh and dry bulk density of the concrete decreases.

The production of lightweight concrete with a density of less than 400 kg / m ³ is possible, but technically complex. Previously known are solutions in which organic materials such as expanded polystyrene (EPS) in the form of spheres with a diameter between 1 to 5 mm are used as a supplement. Known brand products that are based on this method include Poriment ^® P of Heidelberger Beton Group and Thermozell 250 and 400 from Thermozell GmbH, Glanegg, Austria. With this method, lower densities than 400 kg / m ³ can be achieved, for densities around 250 kg / m ³ , however, the cement paste must be additionally foamed. The achievable strengths are a maximum of 0.3 MPa.

Aerated concrete, formerly known as aerated concrete, is known, for example, under the brand names Ytong, Hebel, Porit, Greisel, H + H Celcon, Hansa, Solbet or Siporex. The proportion of aggregate in aerated concrete is usually low, which is why aerated concrete is basically no concrete as defined by DIN 1045. The porosity of aerated concrete is achieved by chemical foaming. This is usually hydrogen gas, which is produced by the catalytic cleavage of the mixing water in a strongly alkaline medium. The catalyst used here is aluminum powder. The result is a highly porous, mineral building material based on lime, lime cement or cement mortar, which is porosified by puffing and is generally subjected to steam hardening. Aerated concrete is therefore also known as Autoclaved Aerated Concrete (AAC) or Autoclaved Cellular Concrete (ACC).

The production of lightweight concrete or mineral foams by oxygen gas as a blowing agent using hydrogen peroxide is from the WO2007 / 134349A1 previously known.

Foamed concrete, in addition to steam-hardened aerated concrete another form of aerated concrete, is produced using foaming agents. Unlike chemical foaming, the physical foaming used to make foam concrete does not require blowing agents. The foam concrete is formed by introducing foam filled with air or gas into the cement paste or concrete. Physical foams are only conditionally stable. As in the case of chemical foams, the gas bubbles serve only temporarily as supporting bodies until a solid structure of solidity has formed. Foamed concrete consists of a cement paste or a cement aggregate glue. This includes cement, water, any additives and / or additives. During processing, the glue, mortar or concrete becomes one of one Foam generator of water, air and foaming agent prefabricated foam added and mixed.

Foaming agents based on surfactants or proteins are previously known. The effect of the foaming agent is based on the polar groups of the surfactant or protein molecules. Protein-based foaming agents are generally more stable than surfactant-based foams. When choosing the active ingredients, the influence on the cement chemistry and the rheological properties of the fresh concrete must be considered. The high ion concentration and the high pH in the cement paste can reduce or suppress the foaming effect of many surfactants or proteins. In the construction sector, almost exclusively hydrolysis products based on animal waste are used as protein foaming agents. Depending on the course of hydrolysis and, above all, on the available animal waste, a mixture of proteins of different molecular weights (3000 to 350,000 daltons) is produced.

From the WO2007 / 134349A1 It is known that foam concrete usually has dry bulk densities in the range of 400 to 2000 kg / m ³ , but foam concrete with a dry bulk density below 400 kg / m ^{3 is} considered to be extremely unstable.

From the dissertation of Dr.-Ing. Jens Uwe Pott "Development strategies for cement-bound foams", University of Hannover 2006, it is already known that in the production of stable cement foams air contents of up to 65 vol .-% can be achieved in the fresh state, resulting in a fresh raw density of about 0.60-0 , 65 g / cm ³ leads. Dehydration again reduced the apparent density during hardening by about 0.10-0.15 g / cm ³ . In exceptional cases even lower straw densities of up to 0.40 g / cm ^{3 could be} achieved; However, according to the dissertation, corresponding prisms had no technically usable strengths.

It is further known from the abovementioned dissertation that the boundary surfaces formed during the introduction of the foam into the cement paste can be stabilized by surface-active substances. These stabilizers are intended to prevent segregation and improve the homogeneity of fresh concrete, especially in the case of soft concrete consistencies. At the same time, the cohesion of the mixture is improved, which has a positive effect on the processing properties. A side effect of the rheological changes of the glues when using stabilizers is almost always an increased air-pore content, since the introduced in the mixing process air can escape worse by the better cohesion of the mixture.

• • natürliche Polymere wie z. B. Stärke, Biopolymere, natürliche Gummimodifikationen,
• • halbsynthetische Polymere wie z. B. Cellulose-Derivate und
• • synthetische Polymere wie z. B. Polyethylen-Oxid, Polyacrylate.

Stabilizers can be subdivided into the two main groups of organic polymers and fine-grained, high-water-retaining inorganic substances according to the active ingredients used, the organic polymers being able to be further subdivided into

• • natural polymers such. Starch, biopolymers, natural rubber modifications,
• • semi-synthetic polymers such. B. cellulose derivatives and
• • synthetic polymers such. For example, polyethylene oxide, polyacrylates.

In the field of concrete admixtures, stabilizers based on fine-grained, inorganic substances usually consist of aqueous dispersions of silica dusts or synthetic silicas.

From industrial practice, for example in the production of heat-insulating cement-based leveling without the use of polystyrene particles, it is known that the lowest possible dry bulk density of foam concrete is about 400-500 kg / m ³ .

Aerated concrete with dry bulk densities below 400 kg / m ³ can currently only be produced with very high process engineering effort, which brings ecological and economic disadvantages. In addition, aerated concrete is usually produced as finished parts, since the plants for the production of these aerated concrete, such as autoclaves, are localized.

The invention is therefore based on the object to provide a process for the production of foam concrete with a dry density of less than 400 kg / m ³ available, which is available on site and can be dispensed with a costly thermal aftertreatment.

• a. Bildung eines Zementleims bestehend aus Zement, Wasser, einem Netzwerkmittel, wobei es sich um ein Gemisch von negativ geladenen anorganischen Stoffen und organischen Stoffen mit Amidgruppen mit entsprechenden Gegenionen (Kationen) handelt, die zwei oder dreiwertige Kationen oder eine Mischung derselben und/oder eine organische Verbindung mit überschüssigen positiven Ladungen aus der Klasse der kationischen Tenside und/oder der quartären Ammoniumverbindungen umfassen, und gegebenenfalls mindestens einem Zusatzstoff, durch Mischen der Komponenten in einem Mischerb. Bildung eines Schaums bestehend aus Wasser, Luft und einem proteinbasierten Schaummittel aus unpolaren und polaren Aminosäuren mittels eines Schaumgenerators, wobei das Schaummittel ein Protein, welches zu 50 bis 80 Masse-% aus den Aminosäuren A (Alanin), E (Glutaminsäure), G (Glycin), I (Isoleucin), L (Leucin), M (Methionin), P (Prolin), Q (Glutamin) und V (Valin) besteht, mit einer Molmasse zwischen 20000 und 120000 Dalton und die restlichen 20 bis 50 Masse-% andere Aminosäuren sind, ist,
• c. Mischen des in Schritt a gebildeten Zementleims und des in Schritt b gebildeten Schaums im Mischer (1) und/oder in einem Fahrmischer (3),
• d. Trocknen des Schaumbetons.

To solve this problem, the invention provides a process for the production of foam concrete with the following steps:

• a. Forming a cement paste consisting of cement, water, a network agent, which is a mixture of negatively charged inorganic substances and organic substances having amide groups with corresponding counterions (cations), the divalent or trivalent cations or a mixture thereof and / or an organic Compound comprising excess positive charges from the class of cationic surfactants and / or the quaternary ammonium compounds, and optionally at least one additive, by mixing the components in a mixer b. Formation of a foam consisting of water, air and a protein-based foaming agent of non-polar and polar amino acids by means of a Foam generator, wherein the foaming agent comprises a protein containing from 50 to 80% by mass of the amino acids A (alanine), E (glutamic acid), G (glycine), I (isoleucine), L (leucine), M (methionine), P (Proline), Q (glutamine) and V (valine), with a molecular weight between 20,000 and 120,000 daltons and the remaining 20 to 50 mass% are other amino acids, is
• c. Mixing the cement paste formed in step a and the foam formed in step b in the mixer ( 1 ) and / or in a truck mixer ( 3 )
• d. Drying the foam concrete.

As additives or other hydraulic binder limestone, fly ash or lime are preferred. The setting and drying of the foam concrete can be carried out at room temperature. The mixer is preferably a planetary mixer with or without swirler.

The counterions of the network agent are selected from the group of Ba ²⁺ , Ca ²⁺ , Cu ²⁺ , Fe ²⁺ , Zn ²⁺ , B ³⁺ , Fe ³⁺ , Al ³⁺ and Cr ³⁺ . The network agent is preferably LithoFoam ^® NWF, particularly preferably LithoFoam ^® S NWF with a nitrogen content of at least 1% by mass and a density from 1.2 to 1.35 g / ml, all of which products of the company Dr. Lucà & Partner Ingenieurkontor GmbH.

The foaming agent is a protein which has negative charges in the alkaline cement paste which are utilized in the process of the present invention to produce a tight bond between the dissolved protein strands so that foam stability is significantly increased. As mentioned above, the foaming agent consists of 50 to 80% by mass of the amino acids A (alanine), E (glutamic acid), G (glycine), I (isoleucine), L (leucine), M (methionine), P (proline) , Q (glutamine) and V (valine), with a molecular weight between 20,000 and 120,000 daltons. The remaining 20 to 50 mass are other amino acids, preferably other canonical amino acids. The foaming agent is preferably LithoFoam ^® SL-200 L having a density of 1 to 1.2 g / ml and a pH value of 6.5 to 8, which is a product of the company Dr. Lucà & Partner Ingenieurkontor GmbH is.

In one of the steps a, b or c, a stabilizer can be metered in, the addition of the stabilizer preferably being carried out as an aqueous suspension to the cement paste in step a, particularly preferably to the water of the cement paste before step a.

The stabilizer is a sugar polymer with molecularly incorporated inorganic silicate-active elements, ie so-called network formers, such as calcium or aluminum compounds, or mixtures thereof, especially calcium or aluminum oxides or mixtures thereof, wherein the sugar polymers of glucose units having a molecular weight between 50,000 and 200,000 daltons, preferably 125000 to 150000 daltons exist. Preferably, the stabilizer LithoFoam ^® MRF is, particularly preferably LithoFoam ^® MRF 2000-S, with a dry bulk density of 0.1 to 0.5 g / ml, all of which products of the company Dr. Lucà & Partner Ingenieurkontor GmbH.

The foam formed in the foam generator has a density between 10 and 160 g / l, preferably 80 g / l. The working pressure of the foam generator is at most 1 bar, preferably less than 1 bar. Preferably, a low-pressure foam generator FG4 II industrial version of the Fa. Lucà & Partner Ingenieurkontor GmbH.

The total amount of water used, consisting of the mixing water of the cement paste and the water for foaming, can be treated immediately before use with a DC current of 10 to 50 mA, preferably 25 mA, per liter and minute.

To hydrophobize the dry foam concrete, the cement paste before foam addition a maximum of 5 kg of silicone oil with molecular weights between 5 and 5000 daltons, preferably 350 to 1000 daltons per cubic meter of cement paste, preferably in a proportion of 2 to 4 kg per cubic meter of cement paste via a metering pump 5 be added.

The inventive method is described below with reference to 1 and embodiments explained.

1 shows a flowchart of the process according to the invention.

Cement is mixed with water and a network agent in a mixer 1 mixed. Optionally, additives such as limestone, fine sand, fly ash with a grain size of <500 .mu.m, particularly preferably <50 .mu.m, are added to the cement paste. The cement paste preferably consists of at least 60% by mass of cement, more preferably from 80 to 95% by mass of cement. Baukalk is preferred as a further hydraulic binder. But also possible is a cement content of 100%. Optionally, the cement paste with a metering pump 4 a stabilizer is added. For hydrophobing can via a metering pump 5 Silicone oil be added to the mixer.

In a foam generator 2 a foam is formed from water, foaming agent and air, the density of the foam being 10 to 160 g / l, preferably 80 g / l. The foam generator 2 is working preferably at an operating pressure of a maximum of 1 bar.

In a truck mixer 3 gets the mix out of the mixer 1 with the foam generator 2 formed foam mixed and formed the flowable and pumpable fresh foam concrete.

The mixing processes in the mixer 1 and truck mixer 3 can also successively in the mixer 1 respectively.

From the truck mixer 3 is with a feed pump 6 the fresh foam concrete applied on site and then dried. The drying takes place at room temperature.

The method is particularly suitable for the cast-in-situ technique, preferably for Wandverfüllungen, as heat-insulating balance in the bottom area, preferably under flow screeds, or perimeter insulation, or for filling hollow elements, preferably hollow and perforated bricks of different materials, for backfilling other cavities , for floor and roof insulation, for block production and for panel production and as Isolierplattenzuschnitt with dry densities less than 200 kg / m ³ , preferably 100 to 150 kg / m ³ .

The method according to the invention will be further explained with reference to the following exemplary embodiments:

Embodiment 1

Dry target density: 230 kg / m ³
43 kg of water,
40 kg aqueous suspension LithoFoam ^® MRF,
180 kg cement of type CEM I 52.5 N of the cement grinding plant Königswusterhausen of HeidelbergCement ^® AG,
10 kg lime and
5 kg LithoFoam ^® NWF
are processed gravimetrically in a planetary mixer with or without swirlers in the order given to a homogeneous mixture. With further mixing, 804 liters of foam having a foam density of 80 g / l, consisting of 3.47 kg of foam concentrate and water are fed to the homogeneous mixture.

The result is a cubic meter of fresh foam concrete with a fresh raw density of 342 kg / m ³ and a dry density of 230 kg / m ³ at a strength of the hardened concrete of 0.3 MPa.

Embodiment 2

Dry target density: 130 kg / m ³
3 kg of water,
40 kg aqueous suspension LithoFoam ^® MRF,
100 kg cement of type CEM I 52.5 N of the cement grinding plant Königswusterhausen of HeidelbergCement ^® AG,
5 kg lime,
2 kg of silicone oil 350 from Obermeier and
5 kg LithoFoam ^® NWF
are processed gravimetrically in a planetary mixer with or without swirlers in the order given to a homogeneous mixture. With further mixing, 890 liters of foam with a foam density of 80 g / l, consisting of 3.84 kg foam concentrate and water, are added to the homogeneous mixture.

This results in one cubic meter of pumpable fresh foam concrete with a fresh bulk density of 226 kg / m ³ and a dry bulk density of 130 kg / m ³ at a strength of the hardened concrete of 0.2 MPa.

The pumpable fresh concrete is poured into molds, heated for 5 hours at 40 ° C, switched off and cut into plates of various dimensions with an automatic wire saw and used after further air drying as a foam concrete insulating plate.

Embodiment 3
Dry target density: 130 kg / m ³
3 kg of water, treated with a current of 25 mA per liter and minute,
40 kg aqueous suspension LithoFoam ^® MRF with water that has been treated with a current of 25 mA per liter and minute
100 kg cement of type CEM I 52.5 N of the cement grinding plant Königswusterhausen of HeidelbergCement ^® AG,
5 kg lime and
5 kg LithoFoam ^® NWF
are processed gravimetrically in a planetary mixer in the order given to a homogeneous mixture. To the homogeneous mixture are added, with further mixing, 890 liters of foam having a foam density of 80 g / l, consisting of 3.84 kg foam concentrate and water treated with a flow of 25 mA per liter and minute.

The result is a cubic meter pumpable fresh foam concrete with a fresh bulk density of 224 kg / m ³ and a dry bulk density of 130 kg / m ³ at a strength of 0.4 MPa.

The pumpable fresh foam concrete can be pumped as a heat-insulating leveling layer or poured into molds. When pouring into molds, it is heated for 5 hours at 40 ° C, switched off and cut into plates of various dimensions with an automatic wire saw and used after further air drying as a foam concrete insulating plate.

With the method according to the invention can be produced in industrial practice without high drying temperatures foam concrete with dry bulk densities between 60 and 400 kg / m ³ with the required technical strength and excellent thermal insulation properties.

The crosslinked foam has a much higher elasticity, which has a very positive influence on the mechanical strength of the finished foam cement and / or foam concrete.

Benefits arise in the foam concrete produced by the process according to the invention also because of the flowable and pumpable consistency of the fresh foam concrete and its Autonivellierfähigkeit. The inexpensive and universally applicable method results in numerous application possibilities. Examples of foam concrete applications include block making, panel production, floor and roof insulation and cast-in-situ wall filling.

Another advantage of the invention, inorganic and ecological foam concrete is not least its incombustibility. Also for the intended in the long run recycling of building materials, the foam concrete according to the invention is fully suitable because it contains no potential pollutants in contrast to organic foams and EPS foam concrete.

A further advantage of the method according to the invention for the production of foam concrete is the possibility of rendering it hydrophobic in a simple manner. It is known that oils, in particular silicone oils and or silicone oil emulsions, are used as antifoams in various industrial processes. Silanes also have a foam-destroying effect. Surprisingly, however, it was found that the addition of up to 5 kg of silicone oil per cubic meter of finished foam concrete does not destroy the foam produced and used according to claim 1. A good water repellency can already be achieved with 2 kg of a silicone oil per cubic meter of the foam concrete according to the invention.

LIST OF REFERENCE NUMBERS

1

mixer

2

foam generator

3

Truck mixer

4

metering

5

metering

6

feed pump

Claims (11)

Process for producing foam concrete having a dry density of less than 400 kg / m ^3, comprising the steps a. Forming a cement paste consisting of cement, water, a network agent, which is a mixture of negatively charged inorganic substances and organic substances having amide groups with corresponding counterions (cations), the divalent or trivalent cations or a mixture thereof and / or an organic Compound comprising excess positive charges from the class of cationic surfactants and / or quaternary ammonium compounds, and optionally at least one additive, by mixing the components in a mixer ( 1 b. Formation of a foam consisting of water, air and a protein-based foaming agent of non-polar and polar amino acids by means of a foam generator ( 2 ), wherein the foaming agent comprises a protein containing from 50 to 80% by mass of amino acids A (alanine), E (glutamic acid), G (glycine), I (isoleucine), L (leucine), M (methionine), P (Proline), Q (glutamine) and V (valine), with a molecular weight of between 20,000 and 120,000 daltons and the remaining 20 to 50% by weight of other amino acids, is, c. Mixing the cement paste formed in step a and the foam formed in step b in the mixer ( 1 ) and / or in a truck mixer ( 3 ), d. Drying the foam concrete. A method according to claim 1, characterized in that in the foam generator ( 2 ) has a density between 10 and 160 g / l, preferably 80 g / l. A method according to claim 1 or 2, characterized in that the counterions of the network agent are selected from the group of Ba ²⁺ , Ca ²⁺ , Cu ²⁺ , Fe ²⁺ , Zn ²⁺ , B ³⁺ , Fe ³⁺ , Al ³⁺ and Cr ^3+, and the network means preferably LithoFoam ^® NWF, particularly preferably LithoFoam ^® NWF is S, with a nitrogen content of at least 1% by mass and a density from 1.2 to 1.35 g / ml. Method according to one of claims 1 to 3, characterized in that the foaming agent is LithoFoam ^® SL-200 L with a density of 1 to 1.2 g / ml and a pH of 6.5 to 8. Method according to one of claims 1 to 4, characterized in that in one of the steps a, b or c, a stabilizer is added, wherein the addition of the stabilizer preferably as an aqueous suspension for cement paste in step a, particularly preferably to the water of the cement paste before step a, takes place. Method according to one of claims 1 to 5, characterized in that the stabilizer is a sugar polymer with molecularly incorporated inorganic silicate-active elements, wherein the sugar polymers of glucose units having a molecular weight between 50,000 and 200,000 daltons, preferably 125,000 to 150,000 daltons exist, and that the Stabilizer preferably LithoFoam ^® MRF, more preferably LithoFoam ^® MRF 2000-S, with a dry bulk density of 0.1 to 0.5 g / ml, is. Method according to one of claims 1 to 6, characterized in that the working pressure of the foam generator ( 2 ) Does not exceed 1 bar. Method according to one of claims 1 to 7, characterized in that for hydrophobing the dry foam concrete cement paste before foam addition a maximum of 5 kg of silicone oil with molecular weights between 5 and 5000 daltons, preferably 350 to 1000 daltons per cubic meter of cement paste, preferably in a proportion of 2 up to 4 kg per cubic meter of cement paste are added. Method according to one of claims 1 to 8, characterized in that one of the additives is limestone powder and is preferred as a further hydraulic binder Baukalk. Method according to one of claims 1 to 9, characterized in that as a mixer ( 1 ) a planetary mixer is used. Use of the method according to one of claims 1 to 10 for the cast-in-situ technique, preferably for Wandverfüllungen, as heat-insulating balance in the bottom area, preferably under flow screeds or as Perimeterdämmung, or for filling of hollow elements, preferably of hollow and perforated bricks different Materials for filling other cavities, for soil and roof insulation, for block production and for panel production and as Isolierplattenzuschnitt with dry densities less than 200 kg / m ³ , preferably 100 to 150 kg / m ³ .

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