EP3307694A1

EP3307694A1 - High-performance concrete comprising aerogel pellets

Info

Publication number: EP3307694A1
Application number: EP16732969.7A
Authority: EP
Inventors: Barbara Milow; Lorenz Ratke; Torsten Welsch; Silvia Fickler; Martina Schnellenbach-Held; Jan-Eric Habersaat
Original assignee: Deutsches Zentrum fuer Luft und Raumfahrt eV; Universitaet Duisburg Essen
Current assignee: Deutsches Zentrum fuer Luft und Raumfahrt eV; Universitaet Duisburg Essen
Priority date: 2015-06-15
Filing date: 2016-06-13
Publication date: 2018-04-18
Also published as: DE102015210921A1; WO2016202718A1; US20180354849A1

Abstract

The invention provides an aerogel-concrete mixture, a high-performance aerogel concrete obtained therefrom, and a method for production thereof. The problem addressed by the present application is that of providing pressure-resistant but not very thermally conductive concretes, precast concrete components, screeds, screeds for precast components, (glassfibre-)reinforced concrete, fire protection panels, construction elements for thermal partition and blocks. The aerogel-concrete mixture contains: 10% to 85% by volume/m3 of aerogel pellets having a grain size in the range from 0.01 to 4 mm, 100 to 900 kg/m3 of inorganic hydraulic binder, 10% to 40% by weight based on the binder content of at least one silica gel suspension, 1% to 5% by weight based on the binder content of at least one plasticizer, 0.2% to 1% by weight based on the binder content of at least one stabilizer and 0% to 60% by volume/m3 of at least one lightweight aggregate. The method for producing an aerogel concrete with an aerogel-concrete mixture involves first mixing aerogel and any lightweight aggregates, then adding a water-silica mixture, a water-plasticizer mixture and the stabilizer, adding the inorganic binder during a suspension of mixing, and, after restarting the mixing, adding the remaining water and continuing to mix.

Description

HIGH PERFORMANCE CONCRETE CONTAINING AEROGEL GRANULATE

The invention relates to an airgel concrete mixture, a high-performance aerosol concrete obtained therefrom and a process for its production.

Since the beginning of the millennium, the requirements for thermal insulation of residential and non-residential buildings have led to a large number of further developments in the field of building materials for solid exterior walls. Should the national rules and standards contain the EU Directive on the Energy Performance of Buildings (Directive 2000/31 / EU on the Energy Performance of Buildings, Official Journal of the European Union) European Union L 153/13; 18.06.2010), the heat transfer coefficient requirements (such as the U-value in EnEv 2014 (Federal Ministry of Justice and Consumer Protection) Second Order amending the Energy Saving Ordinance, Federal Law Gazette, 2013, Part I No. 67 Bonn, 21.11.2013) are usually only possible by using masonry blocks with a low bulk density and, associated therewith, with low compressive strength, the heat is dissipated in i ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The thermal insulation walls are in the range λ = 0.06 W / (mK) to λ = 0.16 W / (mK) (Table 1, lines 1 to 6), so that usually wall thicknesses between 36.5 cm and 49 cm are required to the required U-values achieve.

Table 1: Bulk densities, thermal conductivities and compressive strengths of selected solid wall building materials

P [10 ³ - fk or λ

Material p (kg / m ³ ) MN m ² K /

(0ck (MPa) (W / (mK))

Wkg]

1 lightweight concrete block Bisomark

315-335 0.8 0.06 42.3 Hbn *

2 aerated concrete block Ytong PP

250 0.8 0.07 45.7 1.6-0.25 **

3 Poroton bricks S9-MW *** 810-900 4.2 0.09 57.6

4 aerated concrete block Ytong PP

400 1.8 0.10 45.0 2-0.40 **

5 lightweight concrete block bisoplan

600 2.5 0.14 29.8 14 *

6 Poroton Planziegel T16 *** 710-800 4,7 0,16 41,4

7 Sand-lime brick Silka KS L-R 0.56-

1210-1400 5,6 8,3 p 12-1,4 **** 0,70

8 0.89-

Lightweight concrete LC35 / 38 **** 1500-1600 35,0 26,2

1.00

9 Sand-lime brick Silka KS-R P 0.99-

1810-2000 10.5 5.9 20-2 0 **** 1.10

1 normal concrete C12 / 15

2200-2400 12.0 1.65-2.0 3.3 0

1

Reinforced concrete C30 / 37 ***** 2300-2400 30.0 2.3-2.5 5.7 1 * Bisotherm GmbH. Complete masonry program Bauen, Mülheim- Kärlich; , 2013.

** Xella Germany GmbH. Product Program 2015. Duisburg; , 2015.

*** Wienerberger GmbH. Price list 2014 Poroton brick systems. Hannover; , 2014.

**** DIN 4108-4: 2013-02 Thermal insulation and energy economy in buildings - Part 4: Hygrothermal design values. Berlin: Beuth Verlag; , 2013.

***** ISO 10456: 2010-05 Building materials and products - Hygrothermal properties - Tabulated design Berlin: Beuth Verlag; Of 2010.

The performance indicated in Table 1 is defined as the ratio between compressive strength in [MN / m ² ] and the product of bulk density p in [kg / dm ³ ] and thermal conductivity λ in [W / mK].

As can be seen from Table 1, the compressive strengths of these optimized with regard to a low thermal conductivity materials in the range f _k <4.7 MPa. Despite the large wall thicknesses, these building materials can therefore usually be used only for buildings with a low number of floors. If greater compressive strengths are required, this is usually due to the higher bulk densities and the associated higher thermal conductivities (Table 1, lines 7 to 11) Single-shell exterior wall construction no longer possible without further thermal insulation. In most cases, trays made of normal concrete, lightweight concrete or sand-lime brick with thermal insulation composite system or with core insulation and veneer (bivalve walls) are executed in this case.

The idea to embed airgel granules in a cement matrix became the first in Ratke L, the production and properties of a new lightweight concrete: airgel concrete. Concrete and reinforced concrete construction 103 (2008) Heft 4, P. 236 to 243 reports. In this case, predominantly superhydrophobic silica airgel granules having a particle size of 0.01 to 4.0 mm, a porosity> 90% and a particle bulk density of 120 to 150 kg / m ^{3 were} used, the normal-strength mixtures of CEM II 32.5 R, CEM I 42, 5R and CEM I 52, 5R were added. The airgel content was varied between 50% by volume and 75% by volume so that airgel concrete with densities 580 kg / m ³ <p <1,050 kg / m ^{3 was} produced. The results of the tests show the excellent building physics properties of this material. With a uniform distribution of 70 vol .-% airgel granules, a thermal conductivity of λ = 0.10 W / (mK) was measured. The airgel concrete thus has a thermal conductivity which is comparable to that of thermal insulation masonry (Table 1, lines 1 to 6). The average compressive strengths determined on prisms with an edge length of 40 mm were in the range of 0.6 ≦ / cm, prism4o ^ 1.5 MPa and thus clearly below the compressive strengths of the wall building materials listed in Table 1. The moduli of elasticity derived from the results of the compressive strength tests were between 52 MPa and 127 MPa. The performance of the airgel concretes according to the invention was preferably 9.3-10 ³ MNm ² K / Wkg. In the calculation, the Prism stability _C m, prism4o with the factor 0.9 to the Würfeldruckfestig ^¬ speed (150 mm edge length) f _cm converted.

DE 10 2006 033 061 A1, in particular from Example 1 in combination with paragraph [0036], discloses an airgel concrete mixture comprising Aerosil®, Portland cement, a dispersant in the form of a silica gel suspension, a concrete plasticizer and a lightweight aggregate in the form of Superlite® contains.

In Hub A., Zimmermann G., Knippers J., lightweight concrete with aerogels as a construction material. Beton- und Stahlbetonbau 108 (2013) No. 9, pp. 654 to 661, silica airgel granules were embedded in an unspecified ultra-high performance concrete (UHPC) matrix to improve the compressive strength of airgel concrete. The measured thermal conductivities were between λ = 0.06 W / (mK) for mixtures with a bulk density of p <400 kg / m ³ and λ = 0.10 W / (m-K) for mixtures with a bulk density of p = 570 kg / m ³ . The compressive strength for mixtures in the range 500 kg / m ³ <p <620 kg / m ³ was determined to be 1.4 <cm, prism4o ^ 2.5 MPa, so that in principle the intention posi tive ^¬ effect of UHPC matrix on the Compressive strength can be observed. The compressive strength of airgel concrete with p <400 kg / m ³ has not been investigated. Further results of the investigations in Hub et al. show that aerogonal concrete has a low modulus of elasticity (E _C m = 1100 MPa), a high frost resistance, a low thermal expansion coefficient (5.3 x 10 ^"6 1 / K), a high shrinkage (2.2 mm / m) and a very low bond stress (0.95 N / mm ² at a slip of 0.02 mm for reinforcing steel 0 8 mm). UHPC-based airgel concretes were 25.2-10 ^{~ 3} MNm ² K / Wkg.

The compressive strength, flexural strength and thermal conductivity of airgel concrete have also been described in Gao T., Jelle B.P., Gustavsen A., Jacobsen S., Airgel-incorporated concrete: An experimental study.

Construction and Building Materials 52 (2014), pp. 130-136. Hydrophoborated airgel granules with a grain size of 2 to 4 mm, CEM I 52.5 R, silica fume, plasticizer, sand and distilled water were used for the mixtures investigated. The water-binder value was set to 0.4, the volume of the surcharges (airgel and sand) to 60 vol .-%. Here, the airgel content varied between 0 and 60% by volume, which resulted in densities in the range of 1,000 kg / m ³ and 2,300 kg / m ³ . The most interesting mixture with an airgel content of 60% by volume were the results

λ = 0.26 W / (mK), _C m, prism4o = 8.3 MPa and = 1.2 MPa. Mathematical relationships were derived for the relationships between thermal conductivity and density as well as compressive strength and density. The performance of the airgel concretes according to the invention was preferably between 13.9-10 ^"3 and 28.7-10 ^{" 3} MNm ² K / Wkg.

Ng S., Jelle B.P., Sandberg L.I.C., Gao T., Wallevik O.H., Experimental investigations of airgel-incorporated ultra-high

Performance concrete. Construction and Building Materials 77 (2015), pp. 307-316 reports on further optimizations of airgel concrete. Here, 20 to 80 vol .-% airgel granules were embedded in a UHPC mixture, with an airgel content of 50 vol .-% is considered optimal. For this mixture, a bulk density of 1,350 kg / m ³ , a compressive strength of _C m, prism4o = 20 MPa and a thermal conductivity of λ = 0.55 W / (mK) determined. Thus, while a considerable increase in compressive strength was achieved, the thermal conductivity remained well above the previously determined values for aerated concrete. An increase of airgel to 70 vol .-% brought about a considerable reduction in the pressure resistance, by a factor of 4, with it (cm, prism4o = 5.8 MPa), but led only to an improvement of Wär ^¬ meleitfähigkeit 20% to λ = 0.44 W / (mK). For specimens made of parallel produced cement-silica mixtures, which were produced without the fine components (sand and fine sand) typical for UHPC, significantly lower compressive strengths and thermal conductivities were observed for the same airgel content. These cement-silica mixtures were made with an increased water-cement value of 0.60 as no flow agents were added. The performance of the present invention preferably Aerogelbetone 21,8- was between 10 ^-3 and 25,4- 10 ^-3 MNm ² K / Wkg.

So far, airgel concrete has shown excellent physical properties, but its low modulus of elasticity, high shrinkage, low bond stress and, in particular, compressive strength, which is still below that of brick or lightweight concrete masonry with comparable thermal conductivity (Table 1 = characteristic values), are one Application of airgel concrete for load-bearing walls of multi-storey buildings.

The object of the present invention is therefore to provide pressure-resistant but less thermally conductive concretes, concrete finished le, screeds, precast concrete, reinforced concrete (GRP), fire protection boards, thermal breakage components and bricks.

The above object is achieved in a first embodiment by an airgel concrete mixture comprising:

From 10 to 85, in particular 75,% by volume / m ^{3 of} airgel granules having a particle size in the range from 0.01 to 4 mm,

100, in particular 200 to 900 kg / m ^{3 of} inorganic hydraulic binder,

10, in particular 20 to 40 wt .-% based on the content of binder of at least one silica suspension,

1, in particular 2 to 5 wt .-% based on the content of binder at least one superplasticizer,

0.2 to 1 wt .-% based on the content of binder content of at least one stabilizer and

0, in particular 10 to 60% by volume / m ^{3 of} at least one light aggregate, for example light sands, expanded clay and / or expanded glass.

According to the invention, high-performance concretes are available in which "airgel concrete" is developed by embedding airgel granules in a high-strength cement matrix which combines the advantages of conventional concretes (high compressive strength, any formability) with the properties of a thermal insulation material which significantly surpasses the compressive strengths of conventional thermal insulation masonry with comparable thermal conductivities and is thus suitable for producing single-shell exterior walls of multi-storey buildings without further thermal insulation. Based on high performance concrete (HPC), ultra high performance concrete (UHPC) and lightweight concrete (LC) blend compositions, mixtures for airgel concrete are provided. The airgel concrete according to the invention has extraordinary thermal insulation properties and comparable compressive strength to normal concrete. The excellent thermal insulation properties are achieved by the use of airgel granulate in an amount of 10 vol.% To 85, preferably 70 vol .-% / m ³ , in particular 60 to 65, preferably 50 to 70 vol .-% / m ³ . The grain size of the airgel is 0.01 to 4 mm, in particular 1 to 4 mm. This grain size can be obtained by simple sieving. This fine particles, especially dust are removed. The presence of these fines leads to a deterioration of the compressive strength values.

In DE 10 2006 033 061 Al sand is added to the mixture, as is usually the case with the mixture of concretes and mortar. According to the invention, however, sand and coarse aggregates are preferably completely dispensed with (except mixtures with additional lightweight aggregates).

The composition of the individual components of the airgel concrete according to the invention takes place taking into account the known M ischungszusammensetzungen for HPC, UHPC and LC. The examined components are listed below:

• Portland cement,

Microsilica (dust and suspension),

• various common surcharges,

• quartz sand,

• concrete liquefier, • stabilizer,

Airgel granules,

• Water,

• Light surcharges (eg light sands, expanded clay, expanded glass).

The mixtures prepared and tested from these components are described below:

According to the invention, the influence of the components listed above was investigated. For this purpose, 25 mixtures (prismatic specimens) were prepared with the aim of increasing the compressive strength. The concentrations of the additives, the concrete liquefier, the microsilica and the Portland cement were varied. After that, the best mixtures were further optimized. For this purpose, cubic specimens with an edge length of 15 cm were tested in accordance with German standardization (EN 12390-3: 2009-7 Testing hardened concrete - Part 3: Compressive strength of test specimens, Berlin: Beuth Verlag, 2009). The following description refers to these optimized mixtures Ml to M7. l l.

Another important aspect for the development of the compressive strength of airgel concrete is the type of storage. Three different types of storage were considered during the tests: Dry storage at an ambient temperature of 20 ° C ± 2 ° C, mixed storage according to EN 12390-2 (EN 12390-2 Ber 1: 2012-02

Testing hardened concrete - Part 2: Making and curing specimens for strength tests. Annex NA. Berlin: Beuth Verlag; 2012) for six days under water at a water temperature of 20 ° C ± 2 ° C and the following 12 days in the air at an ambient temperature of 20 ° C ± 2 ° C. In Schachinger, I. Studies on high performance Fine-grain concrete. 38th DAfStb Research Colloquium. TU Munich; 2000 p. 55-66, positive effects of a heat treatment on the compressive strength of HPC are reported. Therefore, also a 24h sample cube was heat treated in a drying oven for 24 hours. All cubes were switched off at 24h in the concrete age before being stored under the three different storage conditions specified.

Three samples were required for each mixture and each type of storage. In addition, the compressive strength was determined as specified above in the concrete age of seven and 28 days. Therefore, a total of 18 specimens were prepared for each mixture.

In order to determine the influence of the heat treatment and the heat of hydration of the airgel concrete, the temperature during the hydration process was measured by a temperature sensor embedded in the core of the sample cube. For each mixture, three temperature measurements were made according to the three types of storage (Figure 1). Fig. 1 shows the temperature curves for the mixture MIO. During the first few hours, a significant increase in core temperatures was observed. After five to eight hours, the maximum temperature was reached. The high core temperature resulted from the high cement content and the addition of fumed silica (see also Held M. Hochfester Konstruktions-Leichtbeton, Beton 1996, 7: 411-415). The three temperature curves do not decrease as much as they rise. Irrespective of the maximum temperature, the core temperature for mixtures Ml to M13 after 26 h was between 20 ° C and 25 ° C. During this period, the air or water temperature between see 20 ° C and 25 ° C held. Therefore, it can be assumed that the hydration process was completed after 26 h.

The heat treatment of the sample cube is also shown in FIG.

The drying oven had an ambient temperature between 84 ° C and 93 ° C. The core temperature of the concrete cubes reached one

Maximum value of 80 ° C and depends mainly on the high cement content and the silica content. The influence of the selected heat treatment on the compressive strength is low.

The results of the compressive strength tests and the associated densities are listed in Table 2.

Table 2: Blend compositions, compressive strengths after 28

Days (7 days), thermal conductivities and performance of optimized mixtures

Mix M7.10 M7.8 Ml MIO M9 M7.7 M2 M7.5 M7.3 M7.1

Aerogelgehalt

77 70 60 60 60 65 60 60 55 45 [% by vol.]

CEM I 52.5 R

202.0 348.9 500.8 534.6 502.8 473.0 541.7 559.5 647.5 846.2 [kg / m ³ ]

Microsilica powder /

60.6 104.7 65.1 139.0 66.2 141.9 140.8 167.8 194.3 253.9 Suspension [kg / m ³ ]

Flow agent [kg / m ³ ] 9.1 15.7 19.0 19.0 19.3 21.3 19.0 25.2 29.1 38.1

Stabilizer [kg / m ³ ] 1.0 1.7 2.7 2.5 2.4 2.8 3.2 4.2

Water [kg / m ³ ] 80.8 94.2 204.1 97.9 190.5 71.0 97.0 69.9 68.0 50.8

dry bulk

487 690 850 860 880 888 1015 1133 1326 1450 p [kg / m ³ ]

Dry storage: f _cm

- - 7.4 8.9 9.9 - 11.5 - - - [MPa]

Heat treatment:

- - 7.8 10.0 9.5 - 12.7 - - - [MPa]

Mixed storage:

1.4 4.8 8.4 9.3 9.2 5.94 13.9 16.8 26.0 24.7 [MPa]

Mixed storage:

1.3 4.3 8.1 8.9 6.6 7.07 10.3 16.4 27.4 27.2 [MPa] Warm eitfahigkeit λ

0,168 "" ⁾ Ο, ΐδδ ^{** 1} 0,199 '"> - 0,19> 0,255 ^* ' [W / mK]

Efficiency P. _

64.4 55.6 33.6 - 77.6 76.9

[10 ³ - MNm ² K / Wkg] ''

^* 'HFM procedure

* ^* 'THB procedure

The given compressive strengths f _cm are defined as the average compressive strength of cube specimens with 150 mm edge length after 28 days, _C m, 7 as the average compressive strength of cubes specimens with 150 mm edge length after 7 days.

Most blends achieved the highest compressive strength on mixed storage. The early heat treatment did not lead to significantly higher compressive strengths. With regard to the compressive strengths after seven and 28 days, no clear trend could be observed.

A comparison between the values given in Table 2 with the values from the prior art (Table 1 and p. 4 to p. 7) clearly shows that the performance of the high-performance aerosol concrete according to the invention is in some cases considerably greater than in the case of the known lightweight construction materials and Aerogelbetonen. For the purposes of the invention, high-performance aerosol concrete is to be understood as meaning an airgel concrete which has a capacity of at least 30.0 - 10 ³ MNm ² K / Wkg.

The relationship between bulk density and compressive strength is plotted in FIG. 2 for 13 mixtures with mixed storage. For this purpose, a linear regression analysis was performed. The coefficient of determination was calculated to be 0.93, indicating a high correlation between Density and compressive strength shows. After Gibson LJ, Ashby MF Cellular Solids. Cambridge University Press. 2nd Edition. Cambridge; 1997; p. 213, the compressive strength of porous bodies can be calculated as a function of the bulk density. Here, the values of the Portland cement used were used for o and a _cr °. σ _σ = ο, 2. σΙ. {ρΐ _Ρΰ ψ ^Ι2) Equation (1)

Taking into account the investigations on airgel concrete from ratchet (loc.cit.), The exponent 3/2 in this equation should be replaced by%. Both functions are shown in FIG. In the experimental studies of the Institute for Solid Construction (IfM), most optimized mixtures achieved higher compressive strengths than due to Eq. (1) according to Ratke (loc.cit.) And Gao et al. (loc.cit) was to be expected. Fig. 3 shows the compressive strength of 13 mixtures in a concrete age of 28 days in relation to the bulk density.

The thermal conductivity of some mixtures (see Table 2) was determined using the Transient Hot Bridge (THB) or Heat Flow Meter (HFM) method. The results of the IfM and Gao et al. (loc.cit) are shown in FIG. A correlation between compressive strength and thermal conductivity is clearly visible. In both investigations, the thermal conductivity increases with increasing compressive strength (and bulk density). The test results from Gao et al. (loc.cit.) lie between 8 MPa and 62 MPa with associated thermal conductivities between 0.26 W / (m-K) and 1.9 W / (mK), while the compressive strengths and thermal conductivities determined according to the invention are between 1.4 MPa and 26 MPa or 0.082 W / (mK) and 0.255 W / (mK). That is, in the context of the present invention, smaller values for the thermal conductivity and thus better thermal insulation properties were found at comparable compressive strengths. Fig. 3 shows the relationship between compressive strength and thermal conductivity.

On the basis of the known formulations for HPC, UHPC and LC, according to the invention, airgel concrete having a compressive strength increase while maintaining good thermal insulation properties was obtained.

The compressive strength correlated with the bulk density and reached values up to 26.0 MPa. With regard to the compressive strengths after seven and 28 days, no clear trend could be observed. The thermal conductivities were determined to be 0.082 <λ <0.255 W / (m-K), which is equivalent to good thermal insulation properties.

In comparison with thermal insulation masonry, the high-performance aerosol concrete according to the invention has greater compressive strengths with comparable thermal conductivities.

Another embodiment of the invention is a process for producing airgel concretes using the above-described mixture with water. Here, the mixing order is of particular importance.

Mixtures for high-strength (HPC) and ultra-high-strength concretes (UHPC) are usually produced as described in the German Association of the German Cement Industry, Cement Information Sheet for Concrete Technology B 16 10.2002, High-Strength Concrete / High Performance Concrete. Leipzig 2002, is described: "In order to achieve optimum homogenization of particulate matter in particular, the dosing order of aggregates, cement, water and subsequently fly ash and silica fume suspension has proved favorable. For optimal effect of the additives should be dosed after the addition of water and silica fume. "Mixtures that were prepared in this way, as the current state of research and own investigations show, only low compressive strengths and efficiencies.

In contrast to this mixing sequence familiar to the person skilled in the art, the mixing regime in the process according to the invention was preferably changed as follows: Premixes of the liquid constituents are prepared in advance. For this purpose, 1/3 of the additional water with the solvent and 1/4 of the additional water with the

Silica suspension mixed. Thereafter, the airgel granules and - if present - the lightweight aggregates are mixed together. After a mixing time of about 30 to 60 seconds, the water-silica mixture is added. After a further 30-60 seconds of mixing, the water-solvent mixture and stabilizer are added to the mixture. Thereafter, the mixing process is stopped to fill the inorganic binder in the mixer. After re-mixing for 1-2 minutes, the silica slurry and the solvent dispensers are each charged with 50% by volume of the remaining

Addition water filled, flushed out and emptied into the mixer. The entire mixture is mixed for another 2-10 minutes before it can be processed. The blends prepared in this way surprisingly showed a considerably greater compressive strength and performance than when using conventional mixing regimes (see Table 2).

The addition water is metered so that water binder values (w / b values) of 0.15 to 1.00, in particular 0.20 to 0.60, preferably 0.28 to 0.35, result. For the calculation of the w / b value, here only the proportion of the hydraulic binder without further solid constituents, such as e.g. the silica, to set.

Particularly low w / b values and associated high compressive strengths are obtained by cooling the addition water before mixing with the solid components, in particular to a temperature of less than 10 ° C, more preferably less than 5 ° C.

Silica gel suspensions according to the present invention are commercially available and in particular comprise a highly reactive, high specific surface area, amorphous microsilica-water mixture, for example MC Centrilit Fume SX: Blaine value 20000, ie 4 to 5 times greater than cement / Binder.

The silica gel can be added in powder form or as a suspension, the solids content of the suspension usually being 50% by volume. That the silica suspension has an active substance content of 50% by volume and 50% by volume usually consists of water.

Plasticizers for the purposes of the present invention are commercially available and include in particular commercially available polycarboxylates, For example, Powerflow 3100: polycarboxylate ether with 30 wt.% solids content, high charge density and short side chains.

Stabilizers according to the present invention are commercially available and include in particular commercially available organic polymers, for example MC Stabi 520, water-absorbent and water-storing cellulose.

In addition to the abovementioned constituents of the airgel concrete mixture, the mixtures according to the invention may also contain other conventional concrete admixtures and concrete admixtures.

Concrete admixtures are defined in European Standards EN 934 "Additives for concrete, mortar and grout", which are mandatory in all CEN member countries Part 2 of EN 934 contains the definitions and requirements for concrete admixtures:

"A substance that is added during the mixing process of the concrete in an amount that one

Mass fraction of 5% of cement content in concrete

does not exceed, in order to change the properties of the concrete mixture in the fresh / and / or hardened state. "

EN 934-2 contains definitions and requirements for the following individual action groups:

• concrete liquefier,

• flow agent,

• stabilizer, • air entraining agents,

• accelerator: solidification accelerator and hardening accelerator,

• Retarder and

• sealant.

Sand (grain density p> 2000 kg / m ³ ) is generally not required, as it is replaced by airgel granules or / and lightweight aggregates. Light aggregates are to be understood as meaning lightweight aggregates or light sands with a grain density of p <2000 kg / m ³ .

Components of airgel concrete, which are produced with the specified mixture compositions and according to the described mixing regime, are surprisingly characterized in comparison to the heretofore known aerosol concrete by a very short hardening time and a very rapid strength development. Already after 15-30 minutes, a solidification of the fresh concrete is observed, and after about 26 hours, the hydration process is almost completely completed (see also Fig. 1), so that at this time the compressive strength already about 80% of the compressive strength after 28 Days.

The wall / ceiling elements according to the invention or bricks made of graded airgel concrete have a high load-bearing capacity and a low thermal conductivity. They thus allow the production of single-shell exterior wall constructions of multi-storey residential and non-residential buildings without additional thermal insulation, as required for example in thermal insulation systems (ETICS) or double-shell masonry with core insulation (see above). However, additional trays are equivalent to one greater production costs and thus higher costs. There are also constructive problems (fire protection for EPS and XPS insulation materials, fastening technology, façades,

Recyclability of ETICS).

For the purposes of the invention, "graded airgel concrete" is to be understood as meaning that components are produced from at least two layers of different mixtures of airgel concrete The first layer of aerogonal concrete is concreted, the second layer is produced immediately after the hardening of the first layer, while in the "fresh on solid" method the second layer is produced only after hardening of the first layer. Regardless of the method chosen, an end product is produced which has a multi-layered structure, the layers being connected to one another in terms of pressure, tension and shear.

The load bearing capacity and the thermal conductivity of wall constructions made of airgel concrete could be further optimized by using the building material airgel concrete graded or graded in this way (FIG. 4). Two approaches were followed: On the one hand, the wall elements were designed so that different layers of a material were arranged, whose composition was determined individually for each layer (graded mono-fabric component). This resulted in a building element for single-shell walls, which consisted of different layers, each of which primarily met the mechanical or building physics requirements. On the other hand, airgel concrete was used as the material for these different layers. Fikant had a better relationship between compressive strength and thermal conductivity than conventional wall building materials for massive exterior walls. For the base course, the above-mentioned high-performance aerosol concrete with high compressive strength (em = 25 MPa), but relatively low thermal conductivity (Λ = 0.25 W / (m-K)) was used, for the insulating layer an airgel concrete with sufficient compressive strength and very low thermal conductivity. In the production of prototypes according to the invention, airgel adhesives with f _cm = 2 MPa and λ = 0.09 W / (mK) were produced and used for the insulating layer.

A preferred feature of the present invention insofar is the combination of the aerogonal concrete known per se with the construction method of a graded building material. Functionally graded concretes, in which airgel concrete is used exclusively as a porous filler for non-structural areas of building components, have to be distinguished from this.

To meet the requirement for impact sound insulation in building construction, so-called "floating screeds" are used. These consist of a minimum of 35 to 75 mm thick layer of cement, calcium sulfate, mastic asphalt, magnesia or synthetic resin screed, which is arranged on a compressible, about 20 to 50 mm thick layer of insulating materials (EPS foam, mineral wool) , The thickness of the screed layer is to increase the size of the Heizrohrdurchmessers in the arrangement of underfloor heating, so that in practice screed thicknesses of more than 10 cm are observed. The density of the screed types listed above varies between 2.0 and 3.0 kg / dm ³ , hence the inherent load of the screed layers is between 0.7 kPa and about 3.0 kPa. The thermal conductivity of these screeds is between λ = 0.5 W / (mK), (magnesia screed) and λ = 1.4 W / (mK), (cement screed). Cement screeds are very resilient depending on the strength class, are also suitable for wet rooms, but tend to cracking and to the Aufschüsseln and require long drying times of several weeks or months (depending on the thickness). Anhydrite screeds have significantly shorter drying times of about a week, but are less resilient and not suitable for wet rooms. Mastic asphalt screeds reach their mechanical properties immediately after cooling and are very robust, have a good impact sound insulation, but in case of fire are critical (fire spread, toxic fire gases). Magnesia screeds are light and mechanically strong, but are also very sensitive to moisture. Resin screeds are resistant to water and many chemicals, dry very quickly and are mechanically very resilient, but are criticized for possible emission of pollutants. The use of airgel concrete as screed was previously not possible due to the low compressive and flexural tensile strengths.

The Aerogelestrich invention combines the advantages of said screeds, but it has none of the disadvantages mentioned. An important aspect of the present application is to use high performance aerated aerated concrete as a material for the production of floating screed - Aerogelestrich. This application of airgel concrete as a screed was made possible only by the development of the high performance aerosol concrete according to the invention and the associated improvement of the mechanical properties. The investigations according to the invention show that screed made of high-performance aerated concrete at high densities (about 0.5-1.0 kg / dm ³ ) has high pressure strength (up to about 10 MPa), sufficient bending tensile strength (about 2 - 3 MPa) and low thermal conductivities (A = 0.06 - 0.16

W / (m-K)). The bending tensile strength and the shrinkage or cracking behavior can be improved, for example, by adding glass fibers.

Airgel concretes dry within a few days and show only a low water absorption capacity after hardening. Aerogels are non-toxic, not carcinogenic and have been classified by the Federal Environmental Agency of the Federal Republic of Germany as "largely harmless material". Airgel concrete is an excellent fire protection material and has a high sound absorption.

Due to the low bulk density resulting in normal screed thickness dead loads between about 0.25 kPa and about 1.0 kPa. The reduced dead load means that the load-bearing components of a building are less stressed and therefore can be made leaner. Furthermore, this results in application potential when building in stock, where the screed can also be used in the form of prefabricated screed plates. Optionally, due to the low weight, low modulus and high sound absorption of Aerogelestrich in the context of the present invention, the compressible layer under the screed unnecessary, so that the screed can be applied directly to the floor slabs.

Prefabricated building boards made of high-performance aerated concrete are not only suitable as precast screed elements, but also as fire protection boards. Flammable components or components whose mechanical properties change under the influence of high temperatures in a safety-relevant manner, must be effectively protected against the effects of fire. The fire protection panels of airgel concrete according to the invention are applied as a cladding on the components to be protected. Due to the excellent fire protection properties of the material, the clad components are not only effectively protected from direct flames, but because of their extremely low thermal conductivity the temperature on the back of the panel remains so low in case of fire that the mechanical properties of the components to be protected are excluded.

Currently used fire protection boards are usually cement-bonded, glass-fiber reinforced construction boards, which mineral lightweight aggregates such as expanded clay are added, or

Calcium silicate boards. Although these plates effectively protect against direct flames, due to their thermal conductivity (about λ = 0.18 - 0.25 W / (mK)) in the event of fire on the back of the plate, they have temperatures that are particularly high for sensitive components such as CFK glued with epoxy resin. Fins or CFRP clutches can be harmful. Some of the known fire protection boards are also approved for use in direct weathering, ie outdoors, but have a high water absorption due to the strongly absorbent lightweight aggregates (about 0.5 g / cm ³ ). Gypsum-based fire protection boards are not suitable for outdoor use.

The fire protection panels made of airgel concrete according to the invention have a considerably reduced thermal conductivity compared to lightweight concrete panels. ability to (about λ = 0.06 - 0.17 W / (mK)). In fire tests, airgel concrete components have demonstrated their excellent fire protection properties. The temperatures on the back of the component are lower by a factor of 2 to 3 than with lightweight concrete components. Moreover, aerogels are hydrophobic at normal ambient temperatures, so airgel concrete is expected to have significantly lower water absorption than light concrete (about 0.1 g / cm ³ ). At high temperatures (for example in case of fire) the aerogels lose their hydrophobic character and behave hydrophilic. Used extinguishing water is then absorbed by the plates and leads to additional cooling of the plates. Airgel concrete has higher compressive strengths compared to lightweight concrete with the same thermal conductivity. The bending tensile strength can be improved by the addition of glass fibers and tailored to individual needs.

An essential further element of the invention is to combine the known fire protection advantages of airgel concrete with the field of application of conventional fire protection panels. This possible application results from the improvement of the mechanical properties of the above-mentioned high-performance aerosol concrete - airgel concretes produced to date have too low compressive and flexural strength.

Due to their special properties, fire protection panels made of airgel concrete can be made thinner than comparable lightweight concrete panels (weight saving, manageability) with the same performance. The production of fire protection boards of greater thickness, which exceed the properties of conventional boards, is also if possible. The significantly reduced temperatures on the back of the panel mean that airgel concrete fire protection panels can also be used in critical areas such as fire protection of CFRP fins, where low temperatures must be ensured even in case of fire due to the low glass transition temperatures of the epoxy resin used. Due to the described hydrophobic behavior, the panels are excellently suited for outdoor use, for example in the fire protection of bridge and engineering structures, which are reinforced with glued-on CFRP slats or steel straps, for example.

Components made of airgel concrete have, similar to construction elements made of lightweight or normal concrete, a high compressive strength in relation to the gross density, but only a (bending) tensile strength which is lower by a factor of 5 to 10. For use as components subject to bending stress, therefore, as with reinforced concrete, reinforcement must be arranged in the airgel concrete components, which absorb the planned tensile forces from bending or centric tension.

Previously produced airgel concretes were due to their low compressive strength and in particular the low bond stresses not suitable to be used as reinforced airgel concrete in bending stressed components. In addition, so far only the use of conventional reinforcing steel reinforcement has been investigated. The high-performance aerosol concrete according to the invention has significantly improved composite properties and can therefore be used as reinforced aerobic concrete. Reinforcing elements made of glass fiber reinforced plastic are used for this purpose according to the invention. Airgel concrete has been optimized so far mainly with regard to its compressive strength and thermal conductivity. The bending tensile strengths of these airgel concretes are too low for use in bending-stressed components. Therefore, studies were conducted on the use of glass fibers added to the airgel concrete during the mixing process as well as on the bonding behavior of conventional reinforced concrete reinforcement in airgel concrete. The use of glass fibers was accompanied by an improvement in the cracking behavior and an increase in bending tensile strength. However, an increase in bending tensile strength to an extent that would allow use in bending-stressed components, so far not documented. The known pull-out tests with reinforcing steel reinforcement show that the composite behavior of reinforcing steel in airgel concrete is only moderate. It has been found that the bond stresses are relatively small and the bond is essentially adhesion. This contradicts the load-bearing behavior of reinforced concrete components, where the adhesion component for the bond is almost insignificant and the bond predominantly occurs via friction (smooth reinforcing steel) or mechanical gearing (ribbed reinforcing steel). The use of reinforcing steel as reinforcement for airgel concrete components is very questionable against the background of these results. This is particularly true because a further elementary condition for the functioning of the composite "reinforced Aerogelbeton" when using reinforcing steel is not met: the requirement that the components used have the same thermal expansion. Conventional concrete has a thermal expansion coefficient of approximately 10 x 10 ^"6 1 / K, rebar also of 10 x ^{10" 6} 1 / K and Aerogelbeton about 5 x 10 ^"6 1 / K. The thermal expansion of reinforcing steel is thus about twice as large as that of airgel concrete, so that it will come at temperature stress to expansion differences between airgel concrete and reinforcing steel, which is associated with a loss of adhesion. In this case, the functionality of the "reinforced Aerogelbetons" irrevocably lost.

Another essential element of the invention is to replace the previously used reinforcement made of reinforcing steel by a reinforcement made of glass fiber reinforced plastic. This reinforcement is commercially available, but so far used only in normal or conventional lightweight concrete. Inventive investigations of the composite behavior between high-performance aerosol concrete and GRP reinforcement have shown that the composite stresses of up to fb = 3 MPa are considerably higher than those previously determined for airgel concrete with reinforcing steel reinforcement and, moreover, in the value range of conventional reinforced concrete. The high-performance aerosol concrete according to the invention thus makes it possible to produce FRP-reinforced airgel concrete components. Moreover, fiberglass reinforcement with a thermal expansion coefficient of 6 x 10 ^"6 1 / K considerably better suited for use in Aerogelbeton as concrete steel. Since Aerogelbetonbauteile is used almost exclusively in areas where high demands are made to the thermal protection, turns out to the The use of GFRP reinforcement is also particularly advantageous in this respect: the thermal conductivity of GFRP, at 0.7 W / (mK), is 85 times lower than the thermal conductivity of reinforcing steel, because GFRP reinforcement, unlike rebar, has no claim to alkaline environment, are smaller concrete covers and therefore better

Cross-sectional utilization possible.

In the manufacture of the thermal envelope of residential and non-residential buildings, penetrations of this envelope are unavoidable. Thus, for example, in the case of balconies made of reinforced concrete cantilevers, which, for structural reasons, must necessarily be connected to the floor slabs of the building, thermal bridges (case a) arise. Other geometric thermal bridges may occur at the base of solid walls and columns standing on uninsulated / unheated floor slabs or basement ceilings (case b)). The high performance aerated aerated concrete element of the invention serves to thermally separate such structures while maintaining stability.

So far, components are used for the thermal separation of reinforced concrete slabs, which consist of an insulating body, a tensile reinforcement and thrust bearings. The insulating body are made of rock wool or polystyrene foam and can not take on any supporting function alone. Reinforcement elements made of reinforcing steel, stainless steel or glass fibers are used to transmit tensile forces from bending moments and shear forces. The transmission of compressive forces from bending moments and shear forces via pressure bearings made of mild steel or high-strength mortars. The equivalent thermal conductivities (ie the thermal conductivities calculated from the thermal conductivities of the individual components) of such components are in the range 0.06 <λ <0.25 W / (mK). For the thermal separation of masonry walls with high bulk density (eg sand-lime brickwork), masonry blocks are used whose thermal conductivity is reduced by the use of lightweight aggregates against sand-lime bricks. Typical strengths of such "Kimmsteine" are, in connection with mortar group IIa, in the range 6.0 <= f <= 8.1 MPa, the thermal conductivity at about λ = 0.35 W / (mK). Lightweight concrete or brick) can not be used here due to the significantly lower compressive strengths.

For both types of components, the difficulty arises of simultaneously ensuring the negatively correlating properties "high pressure resistance" and "low thermal conductivity". In the case a), this applies in particular to the thrust bearings: While the insulating body has a thermal conductivity of approximately λ = 0.03 to 0.035 W / (mK), the thermal conductivity of the prior art pressure elements made of high-strength mortars is approximately λ = 0, 80 W / (m-K). These punctual thermal bridges are, in addition to the high thermal conductivity of the tension rods, the cause of the fact that the equivalent thermal conductivity of the component by a factor of 2 to 7 on the thermal conductivity of the insulating body. Technically, a reduction in the thermal conductivity of the printing elements by the use of airgel concrete due to the required compressive strengths was not possible. In case b) this applies to the entire component. In case a), moreover, the problem of fire protection, if combustible materials (polystyrene hard foam) are used as insulation material.

The high-performance aerosol concrete according to the invention has a significantly better ratio between compressive strength and thermal conductivity on (Λ <0.26 W / (mK) at an average compressive strength of f _cm = 25 MPa).

Another essential element of the invention is, in the case of a), to produce the pressure bearings or parts of the component or the entire component from airgel concrete and in case b) to produce the entire component from airgel concrete (FIG. 5). In this way, the thermal conductivity of the components is significantly reduced while ensuring the required compressive strengths (in case b) e.g. by a factor of 2). In case a) reinforcement steel, stainless steel or GRP reinforcement is used for the tensile reinforcement. By using GRP reinforcement, the equivalent thermal conductivity can be further reduced compared to other tensile reinforcements.

Claims

claims:

1. containing airgel concrete mixture

From 10 to 85% by volume / m ^{3 of} airgel granules having a particle size in the range from 0.01 to 4 mm,

100 to 900 kg / m ^{3 of} inorganic hydraulic binder,

From 10 to 40% by weight, based on the content of binder of at least one silica gel suspension,

1 to 5 wt .-% based on the content of binder at least one superplasticizer,

0.2 to 1 wt .-% based on the content of binder at least one stabilizer and

0 to 60% by volume / m ^{3 of} at least one light aggregate.

2. Aerogelbetonmischung according to claim 1, characterized in that it contains 60 to 65 vol.% Airgel granules.

3. Airgel concrete mixture according to claim 1 or 2, characterized in that the airgel granules have a particle size in the range of 1 to 4 mm.

4. Airgel concrete mixture according to one of claims 1 to 3, characterized in that it comprises 500 to 550 kg / m ^{3 of} inorganic hydraulic binder.

5. Airgel concrete mixture according to one of claims 1 to 4, characterized in that the inorganic hydraulic binder comprises cement, in particular Portland cement.

6. Aerogelbetonmischung according to any one of claims 1 to 5, characterized in that the silica gel suspension 1 to 60 vol .-%, in particular 50 vol .-% active substance (solids content).

7. Airgel concrete mixture according to one of claims 1 to 6, characterized in that it has a w / b value of 0.20 to 0.60, in particular from 0.28 to 0.35.

8th.

A process for the production of an airgel concrete with an airgel concrete mixture according to any one of claims 1 to 7, characterized in that initially mixed airgel and optionally light aggregates, then a water-silica mixture, a water-solvent mixture and the stabilizer, in a mixing break the inorganic binder and, after mixing again, the remaining water is added and mixed further.

9. The method according to claim 8, characterized in that after every 30 to 60 seconds of mixing time, a water-silica mixture, a water-solvent mixture and the stabilizer, in a mixing break, the inorganic binder and in particular after renewed 1-2- mixing, adding the remaining water and mixing for a further 2-10 minutes.

10. The method according to claim 8 or 9, characterized in that the addition water is cooled before mixing to a temperature of less than 10 ° C, in particular to less than 5 ° C.

11. Concretes reinforced with fiberglass reinforced plastic (GRP) reinforcement, in-situ concretes, precast concrete, screeds, precast concrete screeds, fire protection boards, structural elements for thermal separation of cantilevered (steel) concrete slabs and walls (thermal insulation elements for cantilevered components) or bricks A method according to any one of claims 8 to 10.

12. Graded in-situ concrete components or precast concrete parts according to claim 11, characterized in that they comprise a base layer and a viable thermal barrier coating.