WO2003106365A2

WO2003106365A2 - Lightweight concrete building component, especially for use in building construction, and method for increasing the compressive strength of a lightweight concrete building component

Info

Publication number: WO2003106365A2
Application number: PCT/EP2003/005974
Authority: WO
Inventors: Marco Schmidt; Mario Sandor; Paul Moll
Original assignee: Basf Aktiengesellschaft; Mbs Montan Brennstoffhandel & Schifffahrt Gmbh & Co. Kg
Priority date: 2002-06-12
Filing date: 2003-06-06
Publication date: 2003-12-24
Also published as: WO2003106365A3; AU2003238481A8; DE10226176A1; AU2003238481A1

Abstract

The invention relates to a lightweight concrete building component, especially for use in building construction, which is molded from an aqueous mixture of cement and an inorganic lightweight aggregate. The invention is characterized by adding to the aqueous mixture an aqueous polymer dispersion in an amount to give a solids content, based on the amount of cement, ranging from 0.01- 20 % by weight.

Description

Component made of lightweight concrete, in particular for building construction, and method for increasing the compressive strength of a component made of lightweight concrete.

The invention relates to a component made of lightweight concrete, in particular for building construction, and a method for increasing the compressive strength of such a component, according to the preamble of claims 1 and 11.

In the construction of buildings and masonry, components made of lightweight concrete or lightweight building blocks are used in a known manner today.

The use of lightweight concrete as the starting material for the shaped parts or components, which are generally referred to below as structural elements, not only offers the advantage over the heavier building blocks that a larger volume can be transported and processed due to the lower weight, but also that it also has excellent thermal insulation properties has. Due to the constantly tightening thermal insulation regulations, the use of components made of lightweight concrete in building construction is now indispensable.

The reduction in the density of the components made of lightweight concrete is achieved in that the starting material for the component consists of an aqueous cement-mortar mixture which is mixed with a lightweight aggregate. The lightweight aggregate is, for example, pumice, cottage pumice, perlite, expanded clay, expanded glass or expanded slate, etc., and has a significantly lower density than normal concrete made of sand, gravel and cement.

From AT 406 877 B, for example, a lightweight concrete building block is known which contains expanded glass or expanded clay as a light aggregate and is provided with corrugated tongue and groove depressions to improve the thermal insulation. For the production of the components from lightweight concrete, an aqueous and preferably barely spreadable mixture of cement and the lightweight aggregate is produced by stirring in a suitable processing device. The mixture is pressed into appropriate molds under pressure, and the finished components are then removed after the mold has hardened. In this case, the curing process can be accelerated if necessary by increasing the temperature.

By adding the lightweight aggregates, the compressive strength of the hardened lightweight concrete is reduced, whereby the bulk density for lightweight materials can range from 0.15 to 2.0 t / m ³ .

The reduction in compressive strength means that the lightweight concrete components can only be used to a limited extent in building construction.

Gross density and compressive strength are generally d. Usually in a fixed relationship to each other. An increase in the compressive strength of the lightweight concrete material for components with a given bulk density class can be achieved by adding the polymer additives listed below.

Accordingly, it is an object of the invention to provide a component made of lightweight concrete, in particular for building construction, with which a higher compressive strength can be achieved with the same bulk density class of lightweight concrete, and to provide a method with which the compressive strength of components made of lightweight concrete same bulk density class of lightweight concrete.

This object is achieved by the features of claims 1 and 11.

Further features of the invention are described in the subclaims. The component according to the invention made of lightweight concrete has the advantage that, compared to conventional components of the same bulk density, it can be used in the construction of high-rise buildings due to the increased pressure resistance, which also means that a reduction in the wall thickness with the same thermal insulation increases the size of the rebuilt Room with the same footprint of the building.

Another advantage is that the increased compressive strength of the lightweight concrete material in accordance with the invention does not change the thermal conductivity of the material. The hollow chambers e.g. in a hollow block according to the invention can therefore have a larger volume and the material thickness of the walls and webs in the interior of lightweight blocks can accordingly be chosen to be thinner. The heat flow e.g. Such a hollow block stone is therefore lower overall due to the lower material thickness of the webs. This makes it easier to meet the requirements of the new thermal insulation regulation. It does not matter whether the component according to the invention is produced as a solid block, hollow block or other cement-bound molded part, since the improved thermal insulation can also be achieved by a lower bulk density class.

The component according to the invention is preferably designed as a load-bearing wall or ceiling element which is used within a building construction, for example within a high-rise building. As the applicants have found, it is particularly advantageous here if the component is provided with cavities in its interior, which are delimited by thin webs, since the use of the mixture of inorganic lightweight aggregate, cement and polymer dispersion with the following still results Weight ratios described in more detail and a compressive strength in the range between 20 and 40 N / mm ^{2 give} a surprisingly good thermal insulation capacity with a comparatively small wall thickness and high load-bearing capacity of the component. Here, the wall element is particularly preferably designed as a hollow block. The method according to the invention also has the advantage that the compressive strength of the lightweight concrete can be increased in a process-technically simple manner by simply adding the substances described in more detail below when preparing the aqueous mixture.

The component according to the invention made of lightweight concrete, which is formed from an aqueous mixture of cement and an inorganic lightweight aggregate, is characterized in that the aqueous mixture further contains an aqueous polymer dispersion in an amount such that its solids content, based on the amount of cement, is in the range of 0.01 to 20% by weight. Within normal processing temperatures, the polymer dispersion also has the property that it can form a polymer film or has a liquefying effect.

According to a further embodiment of the concept on which the invention is based, the aqueous mixture of inorganic lightweight aggregate, cement and aqueous polymer dispersion additionally contains a polymeric flow agent, which further increases the pressure resistance of the component.

It is advantageous here if the polymer dispersion is present in such an amount that its solids content, based on the amount of cement, is in the range from 0.5 to 15% by weight, particularly preferably in the range from 1.0 to 10% by weight ,

The polymer dispersions which are suitable for this purpose are aqueous dispersions of polymers, copolymers of different monomers in particular being used in addition to homopolymers.

The solids content of these polymer dispersions is preferably 30 to 80, particularly preferably 45 to 75% by weight. High polymer solids contents can be set, for example, by the processes described in EP-A 37923. The polymer is a radical emulsion polymer. All monomers polymerizable by radical polymerization can be used to produce it. The polymer is generally composed of

- 80 to 100 wt .-%, preferably 85 to 99.9 wt .-%, based on the

Total weight of the monomers for the polymer, at least one ethylenically unsaturated main monomer and

- 0 to 20 wt .-%, preferably 0.1 to 15 wt .-%, based on the total weight of the monomers for the polymer, at least one ethylenically unsaturated

Comonomers.

Of course, several main monomers or comonomers can also be used in the polymer.

The main monomer is preferably selected from

- Esters from ß-monoethylenically unsaturated mono- or dicarboxylic acids, preferably having 3 to 6 carbon atoms, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid with -C ^ -, preferably - -

Alkanols. Such esters are in particular methyl, ethyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl and 2-ethylhexyl acrylate and / or methacrylate;

vinyl aromatic compounds, preferably styrene, α-methylstyrene, o-chlorostyrene, vinyltoluenes and mixtures thereof;

- Vinyl esters of -C ^ mono or dicarboxylic acids, such as vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl laurate and / or vinyl stearate;

butadiene: - Linear 1-olefins, branched-chain 1-olefins or cyclic olefins, such as. B. ethene, propene, butene, isobutene, pentene, cyclopentene, hexene or cyclohexene. Furthermore, metallocene-catalyzed oligoolefins with a terminal double bond, such as. B. oligopropene or

Suitable for oligohexene;

- acrylonitrile, methacrylonitrile;

- Vinyl and allyl alkyl ethers having 1 to 40 carbon atoms in the alkyl radical, where the alkyl radical can also carry further substituents, such as one or more hydroxyl groups, one or more amino or diamino groups or one or more alkoxylate groups, such as, for. B. methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether and 2-ethylhexyl vinyl ether, isobutyl vinyl ether, vinyl cyclohexyl ether, vinyl 4-hydroxybutyl ether,

Decyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether, 2- (diethyl-ammo) ethyl vinyl ether, 2- (di-n-butyl-amino) ethyl vinyl ether, methyl diglycol vinyl ether and the corresponding allyl ethers or mixtures thereof.

Particularly preferred main monomers are styrene, methyl methacrylate, n-butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, vinyl acetate, ethene and butadiene and mixtures of these main monomers.

The comonomer is preferably selected from

- Ethylenically unsaturated mono- or dicarboxylic acids or their anhydrides, preferably acrylic acid, methacrylic acid, methacrylic anhydride, maleic acid, maleic anhydride, fumaric acid and / or itaconic acid; - Acrylamides and alkyl-substituted acrylamides, such as. B. acrylamide, methacrylamide, N, N-dimethylacrylamide, N-methylol methacrylamide, N-tert-butylacrylamide, N-methymethacrylamide and mixtures thereof;

- Monomers containing sulfo groups, such as. B. allysulfonic acid, methallylsulfonic acid, styrenesulfonic acid, vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyloxybenzenesulfonic acid, their corresponding alkali metal or ammonium salts or mixtures thereof, and sulfopropyl acrylate and / or sulfopropyl methacrylate;

- C ₁ -C ₄ hydroxyalkyl esters of C ₃ -C ₆ mono- or dicarboxylic acids, in particular acrylic acid, methacrylic acid or maleic acid, or their derivatives alkoxylated with 2 to 50 moles of ethylene oxide, propylene oxide, butylene oxide or mixtures thereof or with 2 up to 50 moles of ethylene oxide, propylene oxide, butylene oxide or mixtures thereof alkoxylated C ^ C ^ alcohols with the acids mentioned, such as. B. hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, butanediol-l, 4-monoacrylate, ethyl diglycol acrylate, methyl polyglycol acrylate (11 EO), (meth) acrylic acid esters of C ₁₃ / C ₁₅ - reacted with 3, 5, 7, 10 or 30 mol ethylene oxide. Oxo alcohol or mixtures thereof;

- vinylphosphonic acids and their salts, vinylphosphonic acid dimethyl ester and other phosphorus-containing monomers;

- Alkylaminoalkyl (meth) acrylates or alkylaminoalkyl (meth) acrylamides or their quaternization products, such as. B. 2- (N, N-dimethylamino) ethyl (meth) acrylate or 2- (N, N, N-trimethylammonium) ethyl methacrylate chloride, 3- (N, N-dimenthylamino) propyl (meth) acrylate, 2-dimethylamino-ethyl (meth) acrylamide, 3-dimethylaminopropyl (meth) acrylamide, 3-trimethylammonium propyl (meth) acrylamide chloride and mixtures thereof; - Allyl esters of C ₁ -C ₃₀ monocarboxylic acids;

N-vinyl compounds, such as N-vinylformamide, N-vinyl-N-methylformamide, N-vinylpyrrolidone, N-vinylimidazole, l-vinyl-2-methylimidazole, l-vinyl-2-methylimidazoline, 2-vinylpyridine, 4- Vinyl pyridine, N-vinyl carbazole and / or N-vinyl caprolactam;

- diallyldimethylammonium chloride, vinylidene chloride, vinyl chloride, acrolein, methacolein;

- Monomers containing 1,3-diketo groups, such as. B. acetoacetoxy-ethyl (meth) acrylate or diacetone acrylamide, monomers containing urea groups, such as ureidoethyl (meth) acrylate, acrylamidoglycolic acid, methacrylamidoglycolate methyl ether;

- Monomers containing silyl groups, such as. B. trimethoxysilyl propyl methacrylate;

- Monomers containing glycidyl groups, such as. B. Glycidyl methacrylate.

Particularly preferred comonomers are hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, ethylenically unsaturated mono- or dicarboxylic acids, such as, for. As acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid and acrylamides such as. B. acrylamide, methacrylamide, N-tert. Butylacrylamide. The comonomers can also be used as mixtures of various such comonomers.

Particularly suitable polymer dispersions are acrylate dispersions, styrene-acrylate dispersions, styrene-butadiene dispersions and vinyl acetate dispersions. The polymer used for the polymer dispersion is preferably prepared by radical polymerization. Suitable polymerization methods, such as bulk, solution, suspension or emulsion polymerization, are known to the person skilled in the art.

The copolymer is preferably prepared by solution polymerization with subsequent dispersion in water or particularly preferably by emulsion polymerization, so that aqueous copolymer dispersions are formed.

The emulsion polymerization can be carried out batchwise, with or without the use of seed latices, with presentation of all or individual constituents of the reaction mixture, or preferably with partial presentation and replenishment of the or individual constituents of the reaction mixture, or according to the metering process without presentation.

The monomers can be polymerized in the emulsion polymerization as usual in the presence of a water-soluble initiator and an emulsifier at preferably 30 to 95 ° C.

Suitable initiators are e.g. B. sodium, potassium and ammonium persulfate, tert-butyl hydroperoxides, water-soluble azo compounds or redox mitiators such as H ₂ O ₂ / ascorbic acid.

As emulsifiers z. B. alkali metal salts of longer-chain fatty acids, alkyl sulfates, alkyl sulfonates, alkylated aryl sulfonates or alkylated biphenyl ether sulfonates. Other suitable emulsifiers are reaction products of alkylene oxides, in particular ethylene or propylene oxide, with fatty alcohols, acids or phenol, or alkylphenols.

In the case of aqueous secondary dispersions, the copolymer is first prepared by solution polymerization in an organic solvent and then with the addition of salt formers, e.g. B. of ammonia, containing carboxylic acid groups Copolymers dispersed in water without the use of an emulsifier or dispersing aid. The organic solvent can be distilled off. The preparation of aqueous secondary dispersions is known to the skilled worker and z. B. described in DE-A-37 20 860.

Regulators can be used in the polymerization to adjust the molecular weight. Are suitable for. B. -SH-containing compounds such as mercaptoethanol, mercaptopropanol, thiophenol, and thioglycolic acid esters.

The gel content of such radical polymers is preferably below 40% by weight, preferably below 30% by weight, particularly preferably below 20% by weight, based on the polymer. The gel content should preferably be above 5% by weight. The gel content is the content of insoluble components.

The gel content is determined and defined by the following method: The dispersion is dried at 21 ° C. to a film with a thickness of approx. 1 mm. One gram of the polymer film is placed in 100 ml of tetrahydrofuran and left at 21 ° C for one week. The solution or mixture obtained is then filtered with the aid of a fabric filter (mesh size 125 μm). The residue (swollen film) is dried at 21 ° C. in a vacuum drying cabinet for 2 days and then weighed. The gel content is the mass of the weighed residue divided by the mass of the polymer film used.

The monomer composition is generally chosen so that a glass transition temperature Tg in the range from -60 ° C. to + 150 ° C., in particular in the range from -50 ° C. to + 100 ° C., results for the polymer. The glass transition temperature Tg of the polymers can be determined in a known manner, for example by means of differential scanning calorimetry (DSC). The Tg can also be calculated approximately using the Fox equation. According to Fox TG, Bull. Am. Physics Soc. 1, 3, page 123 (1956) applies: 1 / Tg = X _J / TG _J + x ₂ / Tg ₂ + ... + x _n / Tg _n , where x _n for the mass fraction (% by weight / 100 ) of the monomer n, and Tg _{n is} the glass transition temperature in Kelvin of the homopolymer of Monomers is n. Tg values for homopolymers are listed in Polymer Handbook 3rd Edition, J. Wiley% Sons, New York (1989).

In the same way, within the framework of the idea on which the invention is based, it is possible to add the aqueous polymer dispersion to the aqueous mixture of organic lightweight aggregate and cement by adding dried polymer powder to the aqueous mixture.

If a polymeric superplasticizer is used, it is advantageous for the polymeric superplasticizer to be present in such an amount that its solids content, based on the amount of cement, is in the range from 0.01 to 5% by weight, in particular in the range from 0.1 is up to 2% by weight.

Suitable polymeric flow agents include Condensation products of naphthalene sulfonic acid and formaldehyde as well as condensation products of melamine sulfonic acids and formaldehyde, as well as polycarboxylates, lignin sulfonates, oxycarboxylates and glucosaccharides.

Further suitable polymeric flow agents are derived from water-soluble polymers with polyalkylene glycol ether side chains which are obtained by copolymerizing a) esters of the formula (I)

R ²

R ¹ CH C - C - O (A - O) _n R ³ (I),

O

in the R, R are the same or different and are H or CH ₃

A is an alkylene group with 2 to 4 carbon atoms or -CH ₂ -CH ₂ -CH ₂ -CH ₂ -,

R3 represents - to C ₅₀ alkyl or C _α to C ₁₈ - alkylphenyl and

n is a number from 2 to 300,

With

b) at least one monoethylenically unsaturated carboxylic acid or its salts

were obtained.

Such polymeric flow agents preferably have molar masses (M _w = weight average) of 15,000-650,000 and are, inter alia, by solution polymerisation of the monomers a) and b), if appropriate in the presence of initiators such as, for. B. organic peroxides and azo initiators available. The solution polymerization can also be carried out in the presence of suitable entraining agents and regulators.

Such flow agents are widely used in the concrete industry.

Examples:

Model systems were mixed in the laboratory and the compressive strength and the bending tensile strength of the lightweight materials were tested. Two systems are given here as examples. It was found that in a cement / pumice mixture, an addition of 10% of a carboxylated styrene-butadiene polymer based on the cement content increased the compressive strength by 251% and the bending tensile strength by 219%. The addition a styrene-acrylate dispersion consisting of butyl acrylate and styrene showed a similar tendency.

Styrofan D 750 aqueous dispersion from a carboxylated

Styrene-butadiene copolymer (registered trademark of BASF Aktiengesellschaft)

AcronaT S 702 aqueous dispersion, containing a copolymer of n-butyl acrylate and styrene (registered trademark of BASF Aktiengesellschaft)

W / Z: ratio (weight) water / cement

K / Z: ratio (weight) plastic (polymer) / cement

Composition:

When developing such a lightweight material, care must be taken to ensure that sensible quantity and volume ratios are maintained. It is to be assumed here that the lightweight aggregate is preferably packed as densely as possible and the cement paste or cement mortar fills the cavities in between. If too little light aggregate is used, the specific mass or bulk density is unnecessarily increased and thus the thermal insulation effect is reduced. If too much light aggregate is used, voids will result in the cement matrix, which weakens the overall structure and thus counteracts the surprising strength-increasing effect of the polymer additives.

Furthermore, the residual water content and the absorbency of the light aggregate used should preferably be taken into account, because it must also be taken into account in the total water content of the system. The following weight ratios were established in test series:

The density of the cement mortar is approximately 2.2 g / cm ³ .

The measured values are exemplary of the light aggregates or fillers used in the experiment. Depending on the quality and storage location, the bulk densities, residual water contents and grain composition can vary widely. The optimal ratio can preferably be determined by experiment.

Claims

Expectations

1. Component made of lightweight concrete, in particular for building construction, which is formed from an aqueous mixture of cement and an inorganic light aggregate, characterized in that an aqueous polymer dispersion is added to the aqueous mixture in such an amount that its solids content, based on the amount of cement is in the range of 0.01-20% by weight.

2. The component according to claim 1, characterized in that the aqueous polymer dispersion is added in such an amount that its solids content, based on the amount of cement, is in the range from 1.0 to 10% by weight.

3. Component according to one of the preceding claims, characterized in that the weight ratio of cement to light aggregate in the mixture is 1: 4 to 1: 5.

4. Component according to one of the preceding claims, characterized in that the weight ratios of inorganic light aggregate, cement and aqueous polymer dispersion in the aqueous mixture are such that the compressive strength of the component after curing of the lightweight concrete between 10 N / mm ² and 40 N / mm ² lies.

5. Component according to one of the preceding claims, characterized in that the polymer dispersion is a styrene-butadiene dispersion.

6. The component according to one of claims 1 to 4, characterized in that the polymer dispersion is an acrylate dispersion.

7. The component according to claim 1, characterized in that the aqueous mixture additionally contains a polymeric flow agent which is present in such an amount that its solids content, based on the amount of cement, is in the range of 0.1-2% by weight.

8. The component according to claim 7, characterized in that the polymeric flow agent is a polymer of esters of

(Meth) acrylic acid with polyalkylene glycol ether side chains.

9. Component according to one of the preceding claims, characterized in that the inorganic light aggregate is expanded clay and / or expanded slate and / or expanded glass and / or pumice and / or pumice and / or perlite.

10. The component according to one of the preceding claims, characterized in that it has cavities delimited by webs in its interior.

11. A method for increasing the compressive strength of a component made of lightweight concrete, which is formed from an aqueous mixture of cement and an inorganic lightweight aggregate, characterized in that the aqueous mixture before setting with an aqueous

Polymer dispersion is added in such an amount that its solids content, based on the amount of cement, is in the range of 0.01-20% by weight.

12. The method according to claim 11, characterized in that the weight ratios of inorganic light aggregate, cement and aqueous polymer dispersion in the aqueous mixture are selected in such a way that the pressure resistance of the component between 10 N / mm ² and 40 N after curing of the lightweight concrete / mm ² .

13. Use of an aqueous mixture of cement and an inorganic lightweight aggregate as lightweight concrete for structural elements, the aqueous mixture containing a polymer in such an amount that its solids content, based on the amount of cement, is in the range of 0.01-20% by weight , and the weight ratios of inorganic lightweight aggregate, cement and aqueous polymer dispersion in the aqueous mixture are of such a size that the compressive strength of the component after curing of the lightweight concrete is between 10 N / mm ² and 40 N / mm ² .