CH658854A5 - ADDITIVES FOR CEMENT, CONCRETE OR MORTAR, METHOD FOR THE PRODUCTION THEREOF AND THE USE THEREOF. - Google Patents

Description

The present invention relates to an additive for cement, concrete or mortar, one in water and / or egg

ner organic liquid slurried mixture of solids. This mixture of solids contains micro-silica and furthermore at least one component from the group of water-reducing agents. In this context, it should be pointed out that in the present description, the term “water-reducing agents” is also to be understood as meaning those that are referred to in the literature as “strongly water-reducing agents”.

The additives for cement, concrete or mortar according to the invention can also contain further constituents, for example one or more accelerating agents to accelerate the hardening of the concrete or one or more retarding agents to prolong the hardening time of the concrete. Furthermore, the additives according to the invention can also contain air-introducing agents as a further component.

The additives according to the invention are intended to eliminate those disadvantages which have hitherto been caused by the use of water-reducing agents in concretes, while at the same time other known advantages of a concrete which contains water-reducing agents, such as, for example, advantages in terms of workability, strength and dimensional stability of the concrete should essentially be maintained.

British Patent No. 1,532,178 describes a method of making a cement composition in which cement with a low content of aluminum, sand, water and at least 10% by weight based on the weight of the cement is fine Distributed reactive silica is mixed until the reactive silica is uniformly distributed in this mixture (see claim 1 of this British patent). The reactive silica is preferably added in an amount of up to 30% by weight, for example 10-25% by weight, and particularly preferably 15-25% by weight, based in each case on the cement present. According to preferred embodiments of the processes described in this British patent specification, dry premixes which contain the finely divided reactive silica and further constituents are added during the preparation of the concrete. The dry premix added according to claim 13 of this patent contains the following components:

80-90% by weight of finely divided reactive silica,

0-10% by weight of cement with a low content of aluminate,

3-8 wt .-% of a condensation product of formaldehyde and sodium naphthalenesulfonate and

3-8% by weight in lignosulfonate.

Both the above-mentioned condensation products of formaldehyde and sodium naphthalenesulfonate and the lignosulfonates are typical examples of water-reducing agents which are used as additives for cement, concrete or mortar.

When using the dry additives for cement, concrete or mortar described in the above-mentioned British patent, difficulties arise with regard to a homogeneous distribution of the particles of micro-silica in the concrete batch. However, a homogeneous distribution of the micro-silica in the entire concrete batch is necessary so that the advantageous properties of the addition of the micro-silica are achieved.

It is also known that aqueous slurries of micro-silica and water are thixotropic mixtures and that such slurries often form gels during storage. However, gels are unsuitable as additives for cement, concrete or mortar because they cannot be mixed homogeneously with the other components.

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It has now surprisingly been found that a mixture of solids which is slurried in water and / or an organic liquid and which contains both silica and at least one constituent from the group of the water-reducing agents has no tendency to form gels on storage. For example, corresponding aqueous slurries can be stored for long periods and remain easily pumpable even after long periods of storage. Furthermore, it was found that when such slurried mixtures of solids in concrete or mortar are mixed in, a uniform distribution of the silica can be achieved in the entire concrete batch or mortar batch. The use of such mixtures of solids slurried in water and / or organic liquids thus avoids those disadvantages which are found in the dry premixes which have already been described in British Patent No. 1,532,178.

The present invention therefore relates to an additive for cement, concrete or mortar, which is characterized in that it is a mixture of solids slurried in water and / or an organic liquid which comprises 10% by weight to 80% by weight of microsilica , based on the dry weight of the slurry, and 0.5 wt .-% to 40 wt .-% of at least one component from the group of water-reducing agents, based on the dry weight of the slurry.

Investigations showed that in the slurries according to the invention the surface of the particles of microsilicic acid is coated with the at least one water-reducing agent.

Another object of the present invention is a method for producing the additive according to the invention for cement, concrete or mortar, this method being characterized in that at least one component from the group of water-reducing agents is mixed with the water and / or the organic liquid and Micro silica mixed to give a slurry mixture of solids and using the solids in such an amount that the slurry mixture of solids 10 wt .-% to 80 wt .-% micro silica, based on the dry weight of the Slurry and 0.5 wt .-% to 40 wt .-% of the at least one component from the group of water-reducing agents, based on the dry weight of the slurry.

Another object of the present invention is the use of the additive according to the invention for cement, concrete or mortar for the production of a concrete batch or mortar batch. This use is characterized in that the agent is mixed into a fresh concrete batch or mortar batch.

The additives according to the invention for cement, concrete or mortar can optionally contain, as a further component, one or more accelerating agents to accelerate the hardening of the concrete or one or more retarding agents to prolong the hardening time of the concrete.

The accelerating means or decelerating means are known and commonly used materials which are used very frequently in the production of zones of high strength, the compressive strengths of up to about 427.59-105 Pa to 855.18-105 Pa (422 kg / cm 2 -844 kg / cm2).

One of the greatest advances in concrete technology in recent decades has been the inclusion of air in the concrete to protect the concrete from damage caused by freezing

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Processes and thawing processes in the presence of deicing chemicals. The use of air pockets is generally recommended for concrete in almost all areas of application. Namely, tests have shown that concrete containing about 5 to 7.5% by volume ± 1% by volume of air can withstand up to about 1900 freeze-thaw cycles, in contrast to a maximum of about 150 such Cycles is when a concrete is used that contains no air pockets and is otherwise identical in all points to the concrete containing air pockets. In this context, reference is made to the publication entitled “Air-Entrained Concrete”, Portland Cement Association, Document ISO 45.02T, 1967.

There are many other benefits that can be achieved using air entrapped concrete, including improved workability, increased resistance to deicing agents such as calcium chloride, and increased resistance to sulfates, as well as improved water resistance.

A widespread method for the production of concrete with air inclusions is to carry out a work step in which an air-entrapping material is added during the mixing process of the concrete. Experience has shown that the mixing process is the most important factor in the production of concrete with air pockets and in this respect the uniform distribution of the enclosed air bubbles is essential for the production of a concrete that is resistant to temperature fluctuations. There is always the risk of non-uniform distribution if the air introduced is distributed unevenly during the mixing process. Such factors as the size of the concrete batch to be mixed, the condition of the mixer and the speed of the mixing process are also important. Too much mixing can even result in some loss of some of the air that is introduced or entrained, but the operations and preferred steps performed in connection with the mixing phase of a concrete with air pockets are now widely known and to those skilled in the art on hand. Therefore, it is not necessary for a person skilled in the art to discuss these well-known processes further here.

A number of air-entrapping materials, which are also referred to in the description as air-introducing agents, are commercially available today. Examples of such materials are thermoplastic resins which contain phenol groups, aldehyde groups and ether groups, and salts of these thermoplastic resins, which are also referred to as soaps of these resins, and also sulfonated fatty acid derivatives.

A thermoplastic resin derived from pine wood that contains phenol, aldehyde and ether groups is a product called "Vinsol resin". These Vinsol resins are undoubtedly the most commonly used airborne agents in the United States. The sodium soaps of such Vinsol resins are particularly effective air-entraining agents or air-enclosing materials and in general only about 0.15% by weight of this sodium soap, based on the weight of the cement, has to be used in order to enclose air in a concrete batch in the usual way.

The product with the brand name “DAREX AEA”, which is launched by Dewey and Almy Chemical Co., is another widely used means of air entrapment. This agent is a sulfonated derivative of hydrocarbon acids from fats and lard.

Concrete with air pockets, which is obtained by using the known air-entrapping products, contains a number of air bubbles of exceptionally small size. The average bubble diameter is typically in the range of 0.0762 to 0.152 mm (0.003 to 0.006 inches), and there may be up to 300 to 500 billion bubbles in 0.7464 m3 (one cubic yard) of air-entrapped concrete that has an air content in the range of 4-6% by volume and has an aggregate with a maximum size of 2.54 cm to 3.81 cm (1 to 1.5 inches). The bubbles are not connected to each other and they are well distributed over the cement / water phase. The gaps between the air bubbles are an important factor in the freeze and thaw resistance of the hardened concrete and a gap or interval of less than 0.203 mm (0.008 inches) when determined according to the ASTM C457 standard is considered to be essential for the inclusion of air to the the desired freeze-thaw resistance of the product.

One of the most important developments in the field of concrete production since the development of concrete with air pockets in the mid-1930s is the use of so-called water-reducing agents.

Water-reducing agents are chemical compounds which, when added to the concrete, fluidize or keep the concrete fluid for a period of time, so that:

(1) normal workability can be achieved on a concrete that has much lower water to cement ratios than those commonly used or

(2) you get extremely workable, so-called «flowing concretes», i.e. those that level themselves essentially without any undesirable side effects, such as segregation, low durability, low abrasion resistance or bleeding or

(3) A combination of the properties mentioned under (1) and (2) can also be achieved.

Water reducing agents are well known additives for concrete. Such commercially available materials belong to six different classes of materials, namely the following:

A. hydroxylated carboxylic acids and their salts,

B. derivatives of hydroxylated carboxylic acids and their salts,

C. Inorganic materials such as zinc salts, borates, phosphates and chlorides,

D. carbohydrates, polysaccharides and sugar acids and

E. Amines and their derivatives and polymer compounds, such as cellulose ethers and silicones.

Other water reducing agents commonly used as additives for concrete are those commonly referred to in the literature as "highly water reducing agents". Examples of such known water reducing agents are the following:

1. lignosulfonic acids and their salts, and derivatives thereof,

2. Melamine derivatives and

3. Naphthalene derivatives.

It is also known that the water-reducing agents mentioned here, including those which are referred to in the technical literature as “strongly water-reducing agents”, can be used individually or in the form of mixtures of several such water-reducing agents.

The above-mentioned groups 1, 2 and 3 water reducing agents include at least twelve products which are currently frequently used as concrete additives. Da4

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eight belong to the group of melamine derivatives and naphthalene derivatives.

The preferred materials from group (2) of the melamine derivatives mentioned above are customary sulfonated condensates of melamine and formaldehyde, which are sold under the brand name “Melment”.

The preferred materials from group (3) of the naphthalene derivatives mentioned above are sulfonated condensates of naphthalene and formaldehyde.

The water-reducing agents of groups 1, 2 and 3 have a considerably greater softening effect in conventional concrete batches than the water-reducing agents of the classes A, B, C, D and E mentioned above. This is the reason why the water-reducing agents of groups 1 , 2 and 3 in the specialist literature as "strongly water-reducing agents".

Concretes containing class i, 2 or 3 water reducing agents are mainly used where the concrete is poured in place, especially in those cases where extreme flow properties are required. This is the case when a high density is required, for example due to the introduction of reinforcements in the concrete, or when the concrete has to be pumped or when complicated shaped structures have to be produced from the concrete.

The advantages achieved by using the water reducing agents of groups 1, 2 and 3 (strong water reducing agents) with pre-cast concrete or pre-mixed concrete include the following:

(a) increased strength in all ages,

(b) improved resistance to sulfate damage,

(c) increased bond to steel reinforcements,

(d) improved processability and formability and

(e) reduced water permeability.

If a strong water-reducing agent of class 1-3 is added to a concrete mixture, the plasticizing or softening effects last for about 30 to 60 minutes, depending on the conditions prevailing during processing. Accordingly, these additives should be added at the processing site when used in ready mixed concrete.

Concretes containing one or more highly water-reducing agents of class 1-3 are described in the publication entitled "Super Plasticized Concrete" in the ACI Journal, May 1977, page N6 up to and including NI 1 and also in those mentioned in this publication older publications.

Although concretes, which can either be called concretes with air inclusions or concretes with water-reducing agents, have proven to be very useful in many fields of application, where it is only necessary that the concrete in question has the special properties of a concrete with air inclusion or a concrete with softening agents, difficulties have nevertheless been found when attempting to produce a concrete by using both an air-entraining agent and a strongly water-reducing agent of class 1-3 in order to plasticize the concrete.

In particular, it is generally assumed today that the system of air bubbles in a hardened concrete with air inclusion is very poor if both an air-inducing agent from the class of neutralized Vinsol resins and a strongly water-reducing agent of class 1- are used in the production of the concrete. 3 adds. In this case, the space between the individual air bubbles in the concrete was previously larger than 0.203 mm (0.008 inches) and there was therefore a risk of air escaping from the fresh concrete. As explained earlier, 5 the parameters of a concrete in connection with the enclosed air bubbles and in particular the distance between the individual air bubbles in the concrete in question are the main criteria by means of which the probable behavior of the concrete can be predicted if it repeated io Cycles of freezing and thawing is subjected. The problem that the industry faces is that of producing a concrete that has the desired freezing and thawing properties and related properties of a concrete with air inclusions while having excellent workability and increased strength that is typical for concretes that have been plasticized with the help of water-reducing agents.

If the additives according to the invention for cement, concrete or mortar, which, in slurried form in water and / or an organic liquid, contain the silica and at least one water-reducing agent, are added during the preparation of a concrete batch, then a corresponding plasticized concrete is obtained which has good resistance to freezing and thawing. Compared to a concrete that was produced without the addition of any water-reducing agent, it not only exhibits the desired plasticization, but also has the same or even greater resistance to freezing and thawing than this.

Preferred water-reducing agents which are contained in the additives for cement, concrete or mortar according to the invention are those which are selected from the following group of materials:

35 1. Lignosulfonic acids and their salts, as well as derivatives thereof,

2. melamine derivatives,

3. naphthalene derivatives,

4. hydroxylated carboxylic acids and their salts,

40 5. Derivatives of hydroxy-hard carboxylic acids and their salts,

6. inorganic materials, such as zinc salts, borates, phosphates and chlorides,

7. carbohydrates, polysaccharides and sugar acids, and 45 8. amines and their derivatives and

9. Polymer compounds such as cellulose ethers and silicones.

The additives according to the invention particularly preferably contain at least one water-reducing agent from the above-mentioned group 1, 2 or 3, or a mixture of two or more such water-reducing agents, optionally in a mixture with another water-reducing agent, for example one from the above-mentioned groups 4 -9. It should be pointed out that the water-reducing agents of the above-mentioned groups 1, 2 or 3 55 are also referred to in the specialist literature as “strongly water-reducing agents”.

It was found that a concrete which was produced using the additives according to the invention, but without using an air-introducing agent, becomes practically impermeable to the ingress of water and the ingress of liquids which damage the concrete. Since water entering could freeze, a concrete produced with the aid of the additives according to the invention also has a high resistance to freezing and thawing. This resistance to freezing and thawing of the concretes produced using the additives according to the invention is generally the same as or even better than that of a concrete which is under

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Use of suitable air-inducing agents was produced. Furthermore, the concretes which were produced using the additives according to the invention generally have a strength which is equal to or even higher than the strength of corresponding concretes which were produced without the use of the additives according to the invention.

It is also advantageous to use the additives according to the invention in the production of such concretes which contain an air-entraining agent.

Preferred additives according to the invention for cement, concrete or mortar accordingly contain at least one air-introducing agent as a further component.

Preferred air-entraining agents which can be contained in the mixtures according to the invention slurried in water and / or an organic liquid are those which have hitherto been used as air-entraining agents in the production of concretes, namely thermoplastic resins which contain phenol groups, aldehyde groups and ether groups , or salts of these resins or sulfonated fatty acid derivatives.

It was found that when the additives according to the invention were used in combination with an air-entraining agent, there was no deterioration in the system having air bubbles, which had previously been found when a water-reducing agent was added to a concrete which contained an air-entraining agent. The micro silicic acid contained in the additives according to the invention causes a fundamental change in the pore structure of the binder phase of the concrete. With the aid of the additives according to the invention, a more uniform dispersion of the binder phase is achieved and this has a significantly finer pore structure compared to corresponding binder phases which were obtained without adding the additives according to the invention. Accordingly, the use of the additives according to the invention in concretes which contain an air-introducing agent as a further component results in no loss of air and also no enlargement of the spaces between the air bubbles.

The mixture slurried in the water and / or the organic liquid in the additives according to the invention must contain a silica as a silica. This micro-silica is preferably an amorphous silica in which generally at least 90% by weight of the particles are smaller than 1 µm. An amorphous silica which has a specific surface area of 18-22 m 2 / g and preferably has a density of 2.20-2.25 g / cm 3 is particularly preferred as micro-silica.

Micro silica is a pozzuolan, or a pozzuolan earth, i.e. it combines with lime and moisture at ambient temperatures, forming compounds that have cement-like properties. The main constituent of the micro silicic acid used in the additives according to the invention is silicon dioxide of the formula SiO 2 and this is usually present in an amount of at least 60%. However, the best results are achieved with the additives according to the invention if the micro-silica contained therein has an SiO 2 content of at least about 85% by weight.

A preferred silicic acid contained in the additives according to the invention is an amorphous silicic acid which is obtained as a by-product in the production of ferrosilicon and elemental silicon. This microsilicic acid is generally obtained by separating the finely divided particles from the exhaust gases from arc furnaces which are used for the production of ferrosilicon and silicon metal.

Such amorphous silicas, which are obtained as a by-product in the production of elemental silicon or ferrosilicon in electric arc furnaces, are particularly suitable for use as microsilica in the additives according to the invention. When producing 5 elemental silicon or ferrosilicon in arc furnaces, quite large amounts of silica are formed as dust, which is separated in filters and other collecting devices. Such silica can be obtained from Eikern A / S, Norway.

io The values obtained in the chemical analysis and the physical properties of typical samples of this type of silica are summarized in the following tables:

i5 Table 1

Dust collected in the bag filter during the production of elemental silicon:

Component 20 SÌO2 SiC Fe203 Ti02 Al203 25 MgO CaO Na20 K20 Mn 30 Cu Zn Ni S C

35 P.

Loss on ignition at 1000 ° C density when removed from the silo

Bulk density in the compressed state, actual density specific surface

% By weight

94-98

0.2-0.7

0.05-0.15

0.01-0.02

0.1-0.3

0.2-0.8

0.1-0.3

0.3-0.5

0.2-0.6

0.003-0.01

0.002-0.005

0.005-0.01

0.001-0.002

0.1-0.3

0.2-1.0

0.03-0.06

0.8-1.5% by weight

200-300 g / 1

500-700 g / 1 2.20-2.25 g / cm3 18-22 m2 / g

The main particle size of this product, i.e. 45 the percentage of particles smaller than 1 µm is 90%.

Table 2

Dust that is obtained in the bag filter during the production of 75% 50 FeSi:

Component Si02 SiC 55 Fe203 Ti02 A1203 MgO CaO 60 Na20 K20 Mn Cu Zn 65 Ni s

C P

% By weight

86-90

0.1-0.4

0.3-0.9

0.02-0.06

0.2-0.6

2.5-3.5

0.2-0.5

0.9-1.8

2.5-3.5

0.2-0.4 0.8-2.0 0.03-0.08

Table 2 (continued)

component

Loss on ignition at 1000 ° C density when removed from the silo

Bulk density when compressed, actual density specific surface

% By weight

2.4-4.0

200-300 g / 1

500-700 g / 1 2.20-2.25 g / cm3 18-22 m2 / g

The main particle size of this product, i.e. the percentage of particles smaller than 1 µm is 90%.

Amorphous silica of the type described above can also be obtained, for example, from other fins that produce elemental silicon or ferrosilicon. In the manufacture of elemental silicon, a material containing silicon dioxide, generally coarse silicon dioxide, for example quartz, is reduced with carbon. Iron is added when the ferrosilicon alloy is to be produced. Part of the product obtained in this reduction process from silicon dioxide-containing materials, preferably silicon dioxide, can be oxidized again in the vapor phase, for example in the air, to form the fine, small-particle silicon-containing material that forms here Silica is called and which is advantageously used as a component in the additives according to the invention. Although the dust which is collected in an arc furnace with the aid of which ferrosilicon with a content of at least 75% silicon is produced is the preferred product, dust which is obtained in an arc furnace can also be used in the additives according to the invention , which is used to manufacture ferrosilicon with a silicon content of 50%.

It is possible to obtain amorphous silica not as a by-product but as the main product by adjusting the reaction conditions accordingly. Amorphous silica of this type can also be produced synthetically without reduction and re-oxidation.

A preferred amorphous silica which is used in the additives according to the invention consists essentially of spherical particles with a particle size of less than 1 [im. The spherical shape of these particles, in combination with their fineness with their effectiveness as pozzuolan, makes these particles particularly suitable as a component in the additives according to the invention.

For example, the amorphous silicon dioxide particles can consist of at least 60 to 90% by weight of SiO 2, have an actual density of 2.20-2.25 g / cm 3 and have a specific surface area of 18-22 m2 / g. Furthermore, these amorphous silica particles should be substantially spherical and at least 90% by weight of the main particles present should have a particle size of less than 1 µm (1 micron). Of course, deviations from these values are easily possible. For example, the silica can also have a lower silicon dioxide content than that mentioned above. In addition, the distribution of the particle size can be adjusted, i.e. it is possible to first separate the coarser particles from a less desirable product by means of sorting processes, for example sieving.

The amorphous silica can have a dark gray color due to its carbon content. However, this carbon can be burned off, for example at temperatures above 400 ° C. It's fer7 658 854

ner possible to modify the manufacturing process for elemental silicon and ferrosilicon so that the by-product silica is obtained in a relatively white form, but this product is practically identical in terms of its other properties to the gray silica that is normally obtained as a by-product. In essence, one modification of the manufacturing process for the production of relatively white amorphous silica is that the amount of coal in the feed is reduced, or that coal is left out of the feed at all. Another consequence of this modification is a change in the amount ratio of silica formed to the amount of elemental silicon or ferrosilicon formed. In other words, in the production process i5 modified in this way, the quantitative ratio of silicic acid formed to elemental silicon or ferrosilicon produced is higher than in the conventional production process.

In the present description, the expression “micro silicic acid” can be understood to mean an amorphous, particle-built silicic acid or a corresponding silicon dioxide material, which is obtained in a process in which a silicon dioxide-containing material, for example quartz or silicic acid, is reduced and the reduction product is oxidized in the vapor phase in air. The term "micro silica" as used herein can also include the same type of amorphous silica that is synthetically produced, i.e. without reduction and re-oxidation. The easiest way to obtain the micro-30 silicic acid used in the additives according to the invention is from waste gases which arise in the manufacture of elemental silicon or ferrosilicon in an arc opening.

In the admixtures for cement, concrete or mortar according to the invention, the mixture of solids slurried in water and / or an organic liquid must contain 10% by weight to 80% by weight, based on the dry weight of the slurry, of micro silica and furthermore 0. 5% by weight to 40% by weight of at least one constituent from the group of the water-reducing agents, based on the dry weight of the slurry. As already mentioned, investigations showed that in the slurries according to the invention the surface of the particles of the silica is coated with the water-reducing agent or several water-reducing agents.

In the production of the additives according to the invention for cement, concrete or mortar, at least one component from the group of water-reducing agents is mixed with the water and / or the organic liquid and the micro-50 silicic acid, 10% by weight to 80% by weight. % of silicic acid, based on the dry weight of the slurry and 0.5% by weight to 40% by weight, based on the dry weight of the slurry, of at least one component from the group of 55 water-reducing agents.

It is particularly preferred to use 40-60% by weight of the micro-silica and 0.1-20% by weight of the water-reducing agent or a mixture of water-reducing agents and the preferred liquid is water, 60 each of which accounts for the rest to 100% by weight .-% of the slurry. For example, an additive according to the invention can be prepared which contains 50 parts by weight, based on the dry weight, of micro silica and 5 parts by weight of a water-reducing agent from the group of 65 melamine derivatives, which contains a sulfonated condensate of melamine and formaldehyde which is bought under the brand name «Melment».

In another example, 20.43 kg (45

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Pound) micro silicic acid, 1.362 kg (3 pounds) of commercially available water is the cheapest liquid, the water-reducing agent obtainable in the manufacture, which contains a sulfo-like slurry-like composition according to the invention.

nated condensate of naphthalene and formaldehyde, and can be used. If desired, however, can also

1.362 kg (3 pounds) of a commercially available cellulose ether, an organic liquid, provided that it is also a water reducing agent, uniform that it is compatible with the concrete and that it is also in and homogeneous in 20.8 liters (5.5 Gallons) of water disper- not harmful in any other way.

greed, preferably using a Banbury mixer. The pH of this aqueous slurry can be adjusted using a conventional mineral acid or an alkaline. The relative viscosity of an additional reactive material according to the present invention, in the form of an aqueous slurry, has been used in the range of about 3.0 to about 7 , 5 and uses a Haake viscometer, the measurement of which is preferably in the range from about 5.0 to about 6.0. With solution an E.30 sensor was used and the standard help of this adjustment of the pH value is to be achieved, working procedures have been used that the manufacturer provides to obtain a paste that is written with the appropriate consistency. The sample was compared with a Verden Transport and for the admixture to a concrete batch 15 same sample, which was an aqueous slurry that has the same. Amount of micro silica contained as the sample of the invented

In addition, instead of adjusting the pH additive, which, however, does not use any of the slurry at all, use water-reducing agents. In each sample, such as phosphates, citric acid, polyacrylates, the slurry contained 65% by weight of the micro-silica.

or glycerin to achieve the desired consistency of the paste. The results obtained in these tests are obtained in the. following table:

Table 3 Sample reverse speed of sensor rotation

Torque determined after a seven

Hour days

28 days

Comparative

32

53

> 150

> 150

sample

16

56

> 150

> 150

8th

60

> 150

> 150

4th

64

> 150

> 150

2nd

69

> 150

> 150

1

78

> 150

> 150

Yield point

49

> 150

> 150

Sample A

32

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11

16

4th

11

16

8th

5

11

17th

4th

6

12

18th

2nd

7

14

23

1

9

16

23

Yield point

2nd

3.5

15.0

Sample B

32

18th

17th

26

16

20th

21st

27th

8th

25th

23

26

4th

27th

24th

25th

2nd

32

28

27th

1

39

34

33

Yield point

28

28

43

Sample C

32

21st

57

55

16

32

63

61

8th

33

68

64

4th

36

74

69

2nd

42

81

76

1

49

91

88

Yield point

32

63

72

The sample A and formaldehyde listed in the previous table 3, namely the product with the brand name, contained 2.5% by weight of the lignosulfonate with the brand name 65 "Mighty".

designation «Borresperse NA».

Sample B shown in Table 3 contained Sample C listed in Table 3 contained

2.5% by weight of a sulfonated condensate made from naphthalene 2.5% by weight of a sulfonated condensate made from melamine

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and formaldehyde, namely the product with the brand name "Rescon H P".

As can be seen from the results given in Table 3 above, the micro silica in water tends to form a thixotropic mixture which often results in gelation of the aqueous slurry. If the slurry solidifies into a gel, then it cannot be used satisfactorily, since it is extremely difficult to pump out a gel from a storage vessel when used in practice.

It has now been found, completely surprisingly and unexpectedly, that the water-reducing agents used in samples B and C above and the water-reducing agents used in sample A above were effective in the inclination of the aqueous slurry Gel to diminish. Gel formation is often found when micro silica is used alone in an aqueous slurry.

It is believed that during the mixing, the strong water reducing agent and the water reducing agent tend to coat the surface of the particles of the silica, effectively reducing the tendency of the slurry to form a gel. Experience has shown that when the flow limit in Table 3 above is in the vicinity of about 25, the aqueous slurry is extremely well suited to be used as an additive according to the invention. Furthermore, it was found that the aqueous slurry still has satisfactory properties up to a yield point of about 75. However, if the flow limit of the slurry rises above about 100, it becomes difficult to pump this slurry and the slurry is then considered unsatisfactory to be used as an additive according to the invention.

Additives according to the invention for cement, concrete or mortar, which contain water as a liquid, are stabilized against gel formation of the silica if, according to the invention, they contain 10% by weight to 80% by weight of microsilicic acid and 0.5% by weight to 40 % By weight of at least one component from the group of water-reducing agents, in each case based on the dry weight. Such aqueous slurries which have a significantly reduced or no tendency to form a gel can be prepared, for example, by adding 0.1% by weight to 10% by weight, preferably 2% by weight to 5% by weight. % of the water-reducing agent, calculated as the dry weight and based on the dry weight of the micro-silica in the finished additive, in which water is dispersed. One or more water-reducing agents, including those which are referred to in the technical literature as strongly water-reducing agents, can be used in the preparation of the additives according to the invention, and these agents stabilize the silica in corresponding aqueous slurry mixtures.

In the aqueous slurry mixtures according to the invention, the content of the water-reducing agent is preferably more than 10% by weight, based on the dry weight of the slurry, but the maximum value of 40% by weight, based on the dry weight of the slurry, is preferably an aqueous slurry mixture , must not be exceeded.

When using the additives according to the invention, the amount in which they are added to a freshly prepared concrete mixture or mortar generally depends on the intended use of the concrete mixture or mortar mixture. The amount of admixture to be added depends on the weight of cement present in the concrete batch or the mortar batch.

In general, a sufficient amount of the additive according to the invention is added and mixed in a fresh concrete batch or mortar batch, so that it is ensured that in the batch about 2% by weight to about 100% by weight, and preferably about 2% by weight to about 25% by weight of dry silicic acid, based on the weight of the cement, is present in the concrete batch and that, furthermore, about 0.1% by weight to about 5% by weight, based on the weight of the cement in the concrete batch or mortar batch of strongly water reducing agent or water reducing agent, either alone or in combination.

In accordance with the usual practice in this field, the optimal amount of ingredients in the admixture and the optimal amount of admixtures within the specified range added to the concrete are tested using those materials that are actually used and using of tests that simulate the environmental and working conditions encountered at the place of use where the concrete is used for construction purposes.

Common tests are used to determine the effect of the additive on the concrete, insofar as this is important at the place of use, with regard to the air content of the concrete, its consistency, its water bleeding and the possible loss of water Air from the fresh concrete, taking into account the hardening time, the compressive strength, the bending strength, the resistance of the concrete to freezing and thawing, the shrinkage of the concrete during drying and the permissible chloride content.

Adding strongly water-reducing agents or water-reducing agents to a concrete batch according to the previously customary working methods often leads to the concrete batch bleeding out very heavily and segregation taking place, as is the case when a thin, aqueous paste forms is no longer able to keep the coarse particles of the aggregate in suspension. Furthermore, it is also known that most water reducing agents tend to soften or plasticize the concrete mix by reducing the surface tension of the water component of the concrete mix. This can lead to a deposition of coarse aggregate particles and cause a low resistance to freezing and thawing and further to a loss of the pumpability of the batch, to a poor resistance to abrasion and to an aggravation of the surface treatment steps and furthermore to a poor texture the surface when using the concrete as a filling compound or when pouring the concrete into a formwork.

The micro silicic acid contained in the additives according to the invention has a high degree of fineness and, when the additives according to the invention are added, the surface of the solids per unit volume of water is increased, so that better separation and suspension of coarse aggregate parts is achieved and furthermore an increased softening or plasticity and a workability due to the change of mutual influence of the particles. The mixture of cement, water and additive according to the invention contains more solids per unit volume and therefore this paste-like material is less aqueous and has a low tendency for particles to separate from it. Because the micro-silica contained in the additives according to the invention retains the water in the paste, the tendency for

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bleeding reduced. Accordingly, you can use different additives. In addition, a homogeneous, capacities are saved by using the additives according to the invention, and the quality control is thereby obtained with a well-processable, pumpable mixture, which improves that a single manufacturer has all additives in the form of reduced tendency to bleed. of the additives according to the invention, the dispersions in

The compressive strength achieved with concrete which is the water or organic liquid and which contains additives according to the invention is generally avoided by problems with regard to contamination higher than the compressive strength that one would expect from storage tanks. A further advantage if the components of the inventive additives according to the invention were added in the form of an aqueous slurry composition in separate form. This consists in that a dust built up at the processing site for the reason why the mixture according to the invention has fine particles is avoided.

What properties are obtained is not entirely clear, it is believed that the ability of the according to the invention is believed, however, that the strong water-reducing agent, the additive in the concrete containing it, increases the water or the water-reducing agent for a better Resistance to sulfates and an increased curvature in the concrete mass, due to the resilience to an alkali-silicic acid reac- tion, which particles of micro-silicic acid and that give certain system, on the beneficial effect of Micro-energetic effects between the constituents of the inventic acid in the additive according to the invention and the additive according to the invention can be found. lead is.

The additive according to the invention is advantageously used in

Conventional fresh concrete mixes are used and it can be used in genes by which the hardening time in the concrete mass may be prolonged too much, using the usual working methods, it may be mixed in, which is currently being used lent in the additives according to the invention as further additives

Mix concrete approaches. For example, one can use some accelerator to provide optimal aqueous slurry that provides 20.43 kg (45 pounds) of micro-silica curing properties to quickly achieve acidity, 3.63 kg (8 pounds) of dry, strong water resistance . It may also be desirable to use reducing agents with the brand name "Lomar 25 to delay the hardening time of the fresh concrete, D", which is a sulfonated condensate from naphthalene and used, for example, in bridge building, so that hardening is instead of formaldehyde and 20.86 (5, 5 gallons) of water, after the work steps add to the appropriate fresh concrete batch, the 204.3 gk (450 pound) order and also the finishing steps are completely Portland I type cement without any other additions.

contains sets and mix after addition. 30 The additives according to the invention are very precisely adapted to the concrete mixture and have a weight-based adaptation to the respective requirements, the optimum water to cement ratio of 0.35 and it has good constituents and the optimal amounts of the constituents machinability and a suitable consistency occurs and it occurs for the concrete that is available at the construction-no separation in the fresh state. place is used. Any of the well-known

In the hardened state, the compressive strength after 28 days 35 position of concrete batches or mortar batches used is typically high, in the order of magnitude of additives, to the additives according to the invention of 855.18-IO5 Pa (844 kg / cm2). Resilience must be present as a further component.

compared to freezing and thawing is surprisingly high, accelerating agents, such as that for this when you consider that this concrete mix contains no calcium chloride used for the purpose, as well as quay closures. 40 citrate nitrate and calcium formate can be added to the

The concrete mixture contains 10% dry micro-pebble-like additives, together with acid and about 1.5% of the dry Lomar D, based on the essential constituents in such quantities, based on the weight of the cement present in the concrete mixture. that are commonly used in industry. The je-mentes. The reduced permeability of the resulting quantities is increased by standard tests, and their resistance to harmony is increased in order to ensure an optimal quantity of these accelerations of water and aggressive chemicals, which are suitable for the respective area of application Allows the concrete so produced to provide improved freeze-up. In general, one or more of the tau properties, compared to a like accelerator, are used in amounts that are about 5 clay mix or mortar mix that does not have this micro-% to about 20% by weight. based on the additive containing dry silica based on an aqueous so important the micro silica in the slurry. Contains porridge. Delay means, such as various additives

The additive according to the invention is a premixer, for example glucose or sucrose.

formation in optimal proportions, as determined by standardized industrial tests on the basis of concrete batches and mortar batches, and they and these delay agents can be a single dispersion system in the invention, and in contrast to the additives according to the invention, they can be contained in optimal amounts. sentence to the usual way of working, in which three or four again the optimal amounts are determined by standardized dispersion systems at the processing site of the concrete test method. One or more such or mortar are needed. The dispersing of all additives retarding agents can be carried out in amounts of about 5% by weight at the same time, using up to about 20% by weight according to the invention, based on the dry weight of the additives in which the silicic acid present in the slurry is present in the parts in the form of a uniform, homogeneous dispersion of additives according to the invention.

lie. This is in contrast to the previously usual work processes. If it is desired, air-introducing vehicles can also be used in which the separated components are successively added to the composition as a component in the additive according to the invention in order to avoid floc formation. May be included in the middle, for those particular aids of the additives according to the invention, for loading purposes, where a certain amount of insertion of the wagon is saved, and the risk of closed air for the properties of the error thus produced is also reduced because only an additive tones is desirable. Vinsol resin or Darex should be mentioned as examples of usable ones that must be added to the approach and not three or four air introduction agents,

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which is a sulfonated fatty acid derivative obtained from fats and lard types. One or more such air-introducing agents can be present in the additives according to the invention in an amount which is in the range from about 0.5% by weight to about 3% by weight, based on the dry weight of the micro-silica contained in the slurries.

One or more such additives, either alone or in combination with other additives, can be contained as essential components in the additives according to the invention. The compatibility and the consistency of the mixture obtained in this way can be determined by conventional standard tests and also the final effect which this formulated additive has on a particular concrete batch or mortar batch that is to be used on the construction site.

The additives according to the invention can have different proportions of the selected constituents, but in order to be able to fully achieve the advantages of the additives according to the invention, the amount of the mixture which is added to a conventional fresh concrete batch should be sufficiently large, so that about 2% by weight to about 100% by weight of micro silicic acid, based on the weight of the cement in the concrete mixture and about 0.1% by weight to about 5% by weight of the one or more water-reducing agents, either alone or in combination with one another, based on the weight of the cement in the final concrete mix.

A sufficient amount of water or an organic liquid which is compatible with fresh concrete is contained in the agents according to the invention so that a slurry is formed in which the essential components are uniformly and homogeneously distributed.

Accelerating agents, retarding agents, air-introducing agents and any other conventional additives can be contained in the additives according to the invention, in amounts sufficient to provide the desired concentration in the fresh concrete batch. In all cases, the optimal amounts of constituents which are contained in the additives according to the invention are determined by standard test methods which are carried out under the simulated environmental conditions of the construction site where the materials are to be used and taking into account the construction methods which 20 should be applied at the respective location.

It will be apparent to those skilled in the art that modifications and changes to the preferred embodiments of the present invention are possible at any time, and the examples given here serve only to illustrate the invention.

C.

Claims (23)

658 854 2nd PATENT CLAIMS 1. Additive for cement, concrete or mortar, characterized in that it is a mixture of solids which is slurried in water and / or an organic liquid and which comprises 10% by weight to 80% by weight of micro-silica, based on the dry weight of the slurry , and at least one component from the group of water-reducing agents, based on the dry weight of the slurry. 2. Additive according to claim 1, characterized in that it contains, as a further component, one or more accelerating agents for accelerating the hardening of the concrete, preferably calcium chloride, calcium nitrate or calcium formate, or that it is a further component, a delaying agent for extending the hardening time of the concrete contains, preferably a sugar, wherein the accelerating or retarding agent is contained in an amount of 5 wt .-% to 20 wt .-%, based on the weight of the micro-silica present in the mixture. 3. Additive according to claim 1 or 2, characterized in that it contains at least one air-introducing agent as a further component. 4. Additive according to one of the claims 1 to 3, characterized in that the micro-silica is an amorphous silica in which at least 90% by weight of the particles are smaller than 1 µm. 5. Additive according to claim 4, characterized in that the micro silica is an amorphous silica which has a specific surface area of 18-22 m2 / g and preferably has a density of 2.20-2.25 g / cm3. 6. Additive according to claim 1, characterized in that the slurried aqueous mixture of solids has a pH in the range of 3.0-7.5, preferably in the range of 5.0-6.0. . 7. Additive according to claim 1, characterized in that the micro-silica and the at least one water-reducing agent are dispersed uniformly and homogeneously in suspension in this slurry or slurry. 8. Additive according to claim 1, characterized in that it contains at least one water-reducing agent which is selected from the following group of materials: a. Lignosulfonic acids and their salts and derivatives thereof, b. Melamine derivatives, c. Naphthalene derivatives, d. hydroxylated carboxylic acids and their salts, e. Derivatives of hydroxylated carboxylic acids and their salts, f. inorganic materials, such as zinc salts, borates, phosphates and chlorides, G. Carbohydrates, polysaccharides and sugar acids, and h. Amines and their derivatives and i. Polymeric compounds such as cellulose ethers and silicones. 9. Additive according to claim 1, characterized in that it contains, as a further component, an agent for adjusting the pH of the slurry and / or at least one agent for adjusting the desired consistency of the slurry, preferably phosphates, citric acid, polyacrylates or glycerin. 10. Additive according to claim 1, characterized in that in the slurry the surface of the particles of micro silica is coated with the at least one water reducing agent. 11. Additive according to claim 3, characterized in that the slurry as an air-introducing agent contains thermoplastic resins which contain phenol groups, aldehyde groups and ether groups, or salts of these resins or sulfonated fatty acid derivatives. 12. Process for the preparation of the additive for 5 ment, concrete or mortar, according to claim 1, characterized in that at least one component from the group of water-reducing agents is mixed with the water and / or the organic liquid and the micro-silica, whereby a slurry mixture io of solids is obtained and wherein the solids are used in such an amount that the slurried mixture of solids 10 wt.% to 80 wt.% micro silica, based on the dry weight of the slurry and 0.5 wt.% to 40 wt contains at least one component from the group of water-reducing agents, based on the dry weight of the slurry. 13. The method according to claim 12, characterized in that an amorphous silica as micro silica 20 acid used, in which at least 90 wt .-% of the particles are smaller than 1 | xm, this micro silicic acid preferably originating from the exhaust gases of an electric furnace which is used for the production of ferrosilicon or elemental silicon. 14. The method according to claim 12 or 13, characterized in that an aqueous mixture is prepared and the pH is adjusted to 3.0 to 7.5 during the mixing process. 15. The method according to any one of claims 12 to 14, characterized in that one produces an aqueous slurry and that this method comprises a step in which the aqueous slurry is continuously mixed from the mixture of the components until the micro-silica and the at least a water-reducing agent 35 lent and homogeneous and dispersed in intimate contact in the mixture. 16. The method according to any one of claims 12 to 15, characterized in that it comprises a working step in which one or more additional additives of the 40 slurry can be added and mixed with it. 17. The method according to any one of claims 12 to 16, characterized in that a means for delaying the hardening of the concrete and an air-introducing agent is added as a further agent. 45 18. Use of the additive for cement, concrete or mortar, according to claim 1, for producing a concrete batch or mortar batch, characterized in that the agent is mixed into a fresh concrete batch or mortar batch. 19. Use according to claim 18, characterized in that the agent is mixed with a fresh concrete batch in such an amount that in the concrete batch 2 to 100% by weight, preferably 2 to 25% by weight, of micro-silica, calculated as Dry weight, based on 55 the dry weight of the cement in the concrete batch. 20. Use according to claim 18 or 19, characterized gekennzeichneat that the additive is added to a fresh concrete batch in such an amount that in 60 the concrete batch 0.1 wt .-% to 5 wt .-%, calculated as the dry weight of the at least one component from the group of water-reducing agents, based on the dry weight of the cement present in the concrete batch, is present. 65