CS231767B1 - Admixture into concrete - Google Patents

Description

1.54) Concrete additive

2

The purpose of the invention is to accelerate the hardening of the concrete, in particular in pre-ironing, and thus to accelerate the turnover of the molds and to save energy to accelerate the heat build-up. This is achieved by the addition of an additive consisting of a substance containing or providing hydrated aluminum oxide and water-soluble salts of inorganic and organic acids in a specified proportion. There are also other variants characterized by increased efficiency. The invention is intended for use in construction.

231787

The invention relates to an additive which accelerates the hardening of Portland cement clinker mortars and bephons.

In the current state, the hardening of concrete is accelerated most frequently by heating, which is energy intensive. Relatively long heating times are required to achieve handling strength, which also increases the cost of the molds being bound for a long time and therefore requires a large number of molds as well as a large space. Reducing the heating time by accelerating the strength is therefore of great economic importance.

Another known method of accelerating hardening is the use of chemically absorbent additives.

Of these, one group of substances are the flowability enhancers of concrete mixtures, which make it possible to reduce the content of the mixing water and, consequently, to increase the strength of the concrete. However, this is not achieved> in the first hours of hardening, respectively. heating, although these substances, such as sulfonated condensates of thtaleneTormaldehyde, femolformaldehyde, melamine formaldehyde, lignosulfonates and the like act more or less retarding.

The second group are some of the water-soluble metal salts of the third group - in particular sodium, potassium, calcium, aluminum and iron. Of these, chlorides are best known. The use of chlorides, however, limits the slight negative effect on corrosion of the reinforcement, which may be used in larger batches, which are, however, necessary to achieve a significant acceleration of hardening. This is similar to the salts of some other strong acids such as dusionelj.

Other known soluble salts such as sodium and potassium carbonates, aluminates and silicates, or the combined ingredients containing them, accelerate the considerable solidification of cemeint. This makes it virtually impossible to utilize such additives effectively in the conventional manufacture of both prefabricated and monolithic structures, since it is not possible to reliably ensure immediate processing of the produced mixture, which requires accelerated solidification. Acceleration of solidification results in worse workability, deteriorated compaction and consequently deteriorated final strength as well as resulting properties. The same negative effect is compensated by the effect of rapid solidification on the consistency by increasing the mixing water dose. Therefore, the use of such substances is limited to special cases and technologies such as water-tightening, spray-spraying and the like where rapid solidification is required.

Without undue acceleration of solidification, the growth of strength in the initial phase can be accelerated with sodium and potassium sulphate. They do not have a negative effect on the corrosion of the reinforcement. However, their usability is also limited, both by the maximum permissible SO ₃ content in the cement and by the formation of efflorescence. At low additions, however, their effectiveness for practical use is insufficient.

Thus, the use of the known water-soluble salts is limited by either accelerating the onset of solidification in an undesirable manner, or for other side effects, it is not possible to add these substances in an amount necessary for the practically useful accelerating effect (reinforcement, ultimate strength, efflorescence).

These drawbacks are overcome by the additive according to the invention. It was found that a significantly higher accelerating effect than the addition of the solubilized soluble salt, respectively. a high accelerating elfect, even with a relatively low solubility of salt, is achieved by adding, simultaneously with the addition of the water-soluble salt, a hydrous alumina and / or AlO (OH) hydrated aluminum oxide and / or aluminum oxihydroxide and / or aluminum hydroxide and / or hydroxoaluminates. Such substances occurring commonly in industry and nature - as described below - added alone have no or comparable effect on cemeint hardening at a similar dose. In combination with the addition of water-soluble salts, however, they provide an additive which, without undesirably accelerating the start of solidification, speeds up hardening at least in the first hours of heating, thus reducing heating up to half or lowering the heating temperature accordingly. for the production of prefabricated elements, or to accelerate construction work dependent on the rate of hardening of the concrete. It is also possible to shorten the delay time before starting the heating and the temperature increase can be faster.

The additive according to the invention consists essentially of two components. In principle, any fine or finely divided substance which contains or in admixture with a hydrated Portland clinker cement can be used as one component to provide hydrated alumina and / or aluminum oxyhydroxide A10 (0H) and / or aluminum hydroxide and / or hydroxyaluminates (see Remy). H. Inorganic Chemistry, Gázo J. General and Inorganic Chemistry). Such substances widely available in industry or nature are alumina, aluminum salts such as aluminum sulphate and double salts, aluminates and aluminosilicates or substances containing them such as high-aluminate metallurgical debris, high-throughput metal salts of the first to third groups - aluminum content or - if applicable - heat treatment - high aluminum minerals and soils such as bauxite, kaolinite, flakes, alunite and the like. The second component must be water-soluble, preferably sodium ^one inorganic and / or organic acid such as, for example, nitrous acid, nitric acid, sulfuric acid), SotN, oxalic acid, formic acid and the like or mixtures thereof.

Given the wide range of useful substances which differ in the content of the active ingredient, the ratio of the two components is applicable over a relatively wide range of 1: 200 to 200: 1 by weight. By changing the ratio of the components, the effect of the technological needs stage and the economic impact can be accentuated or reduced as shown in the examples below.

mixture

B

Converted example

Standard sand and Portland cement mortar were produced in a 2: 1 weight ratio and with water sinter at v / c = 0.4 without and with additives. Additions of additives are given in% by weight of the cement. The compressive strength was determined after 2 hours, possibly after three hours of heating of the samples stored immediately after production in a temperature of 80 ° C (air).

Compressive strength MPa after heating 2 hours 3 hours

Cement A without additives

4 - 0.5% Na ₂ SO ₄ + 0.5% Na 4 - 5% Al 2 O 3 + 0.5% Na ₂ SO ₄ + 5% kale. flake + 1% Na ₂ SO ₄ '+ 1% Na ₂ SO ₄ 4- 5'% A1 ₂ O ₃ + 1% Na ₂ SO ₄ 4- 3% C ₃ A + 1% Na ₂ SO ₄ 4- 3 % GA + 1% Na ₂ SO ₄ 4 · 5% C ₃ A + 1% Na ₂ SO ₄ + 5 '% CA.

Cement B without additives + 1% Na ₂ SO ₄ + 1 A1 ₃ O ₃ + 1 '% Na ₂ SO ₄ + 1% A1 ₃ (SO ₄ ) ₃

4- 1% Na ₂ SO ₄ 4- 1 ° / o bauxite

4- 1% Na ₂ SO ₄ + 3% bauxite + 1 ° / o Na ₂ SO ₄ 4- 1 ° / o | returnable dust + 1% Na ₂ SO ₄ + 2% returnable dust + 1% Na ₂ SO ₄ 4- 3% returnable dust

4- 1 '% Na ₂ SO ₄ + 4% returnable dust

4- 1% l Na ₂ SO ₄ 4- 2 ° / o slag

4- 1% Na ₂ SO ₄ 4- 3% slag

4- 1% Na ₂ SO ₄ 4- 4 ° / o slag

Note: C ₃ A means tricalcium aluminate, the returnable dust being an intermediate product of Al ₂ O _{3 production} , containing CA.

Execution example 2

In the same manner, tests were carried out with various water-soluble salts. Ingredients

No ingredients

4- 5% calcium aluminate dtto 4- 0,5 '% Na ₂ SO ₄ dtto 4- 0,5%! K ₂ SO ₄ dtto 4- 0,5% NaNO ₂ dtto 4- 1,0 '% NaNCl 3 dtto 4- 0,5% NaNO ₃ dtto 4- 1,0% Ca (NO ₃ ) ₂ dtto 4- 0,5 % NaCl dtto 4- 0,5% sodium oxalate dtto 4- 1,0% sodium oxalate dtto 4- 0,5% calcium formate dtto 4- 1,0% sodium formate

1.4 3.5 2.5 5.7 3.5 8.1 4.2 4.0 8.9 6.9 11.2 7.1 11.8 θ 8 11.2 9.0 14.2 8.9 11.6 2.7 8.3 9.1 10.9 11.5 7.6 8.2 9.5 8.3 8.2 9.1 9.6

CA means monocalcium aluminate, slag is ground metallurgical slag, and the admixture is understood as% by weight of the cement. Compressive strength was determined after heating at 80 ° C for 2 hours.

Compressive strength

Cement C Cement D

1.2 4.3 3.3 6.2 5.4 10.5 4.5 - 7.8 4.3 7.3 0.9 3.5 9.0 3.9 7.4 2.9 1.9 4.1 8.5

A further increase in efficiency in terms of cure speed is achieved surprisingly by adding simultaneously known otherwise cementitious mortars (mortars and concretes), which, in themselves, do not accelerate but slow down, such as salts of sulfonated formaldehyde condensates with naphthalene, melamine, phenol, ligninsulfoinanes and the like.

Third

Mixture Spilling cm

No additives 15.9 + 0.15% Na salt sulfonated naphthalemaldehyde condensate 18.5 dtto + 3% mix 5: 1 sodium sulphate and calcium aluminate 18.0

The acceleration effect is also obtained when industrial by-products or industrial wastes with a high content of Al 2 O 3 are used, as shown in the test results described in the embodiment no. 4th

Execution example no. 4

The tests were performed similarly as in the Premix

Spilling cm

The example converts ni and 3

Portland cement and standard sand cement mortars were produced in a ratio of 1: 2 by weight and s / c = 0.4. Samples of 4 x 4 x 16 cm were placed immediately after molding in an oven at 80 ° C. The strength was determined after two hours of heating. Additions are understood as% by weight of the cement.

MPA bending strength pressure

0.5 2.7 0.3 1.8 1.6 9.4

In the same case, the icon consistency was maintained by reducing the addition of the mixing water to the flowing action of the additive. The cement / sand ratio, the dimensions of the test specimens as well as the method of heating were the same as shown in the embodiment no. Third

Strength in MPa v / c bending pressure without additives 14.1 '+ 0.15% Na salt salt. naftalen formaldeh. condensate + 1 + 1% sodium sulfate 14.3 dto as 2 + 1% Al (OH) ₃ 14.4 dto as 2 + 2.5% high aluminate. slag with CA 13,5 dtto content as 2 + 5% high aluminate. slag containing CA 13,5

It is apparent from the foregoing examples that high acceleration efficiencies can be achieved over a wide range of additions of different alkaline salts from different aluminum components, which has not been known hitherto. Of the alkali, sodium is more effective than potassium for faster strength growth. Salts of caustic soils alone do not show a comparable beneficial effect with the same addition, but there is the possibility of combining them with alkaline salts for (specific technical conditions), while (alkali salts have always been effective - irrespective of the anion) sodium hydroxide alone has not been effective. without the retarding effect of the other retarding fluidiser, it allows a further increase in efficiency if:

0.40 0.5 2.6 0.38 1.0 4.3 0.38 1.24 5.9 0.37 2.1 8.7 0.37 2.3 9.7 liquefaction will use for content caching

mixed water.

The additive produced according to the invention accelerates hardening not only at elevated but also at normal temperature. This is shown in the example of embodiment no. 5th

Execution example 5

Standard sand / Portland cement mortar at a ratio of 2: 1 by weight was made of equal consistency without additive and with 6% by weight of additive cement consisting of 5 parts calcium aluminate, 1 part sodium sulfate and 0.15 parts sodium sulfonated naphthalemal formaldehyde condensate.

Mixture v / c spillage cm Strength MPa after 24 h at +20 ° C bending tension pressure

without additive 0.4 15.3 2.9 10.3 + 6% additive 0.37 15.4 5.3 19.8 Compressive strength MPa after machining ve at a temperature of 45 ° C for 3h 6 h

no additive 0,8 3,5 + 6% additive 2,1 11,1

MPa strength after 2 hours of heating in an environment of 80 ^C C bending tension pressure without additive 0,6 2,7 + 6 ° / o additive 2,4 10,6

A large acceleration of strength growth is achieved under the connection of work or even at temperatures close to 0 ° C, ie in low temperature difficulty.

Compressive strength MPa when stored in the environment 0 ⁰ to 5 ° C for h 3 days without additive + 5% additive

Other tests have shown that acceleration of hardening is achieved for all tested ceiments, which have been verified in total by 10 species. The absolute values of the strengths achieved after a certain heating depend on the type of cement, the composition of the mixture and the additive used. However, the addition of a certain composition always shows a similar relative increase in strength, regardless of the type of cement. This applies not only to. Portland as well as troscortland and pozzolanic cements.

panel

Strength MPa after heating 3h 4h 6h

0,8 17,5

4,5 29,5

The example converts ni and 6

With the same additive as in Example no. 5, the use in the manufacture of ceiling panels in a vertical battery has been verified. The concrete was composed of: 0 - 4 mm aggregate 925 kg, 8 - 16 mm 870 kg, SPC 400 troscortland cement dose 400 kgm ^-3 , water 200 1. The panels are produced without or with the addition of 6% by weight of cement. At a specified time, the hardness of the stiffness method was determined in a non-destructive manner by a 40-degree method of defect in various parts of the panel. Mean values are given.

MPa landfill strength in 7 days in 28 days without additive not determined with additive 18.90

In additive panels, the handling strength was achieved after less than half the heating time.

For practical implementation, the invention may be practiced by separately mixing the individual components or mixtures thereof at 18.02 17.65. 28.25

24.70 29.94 in the manufacture of concrete or mortar, or by adding the individual components of the additive or the mixture thereof in advance to the cement or already during the grinding of the clinker and any other additives.

Claims (2)

SUBJECT 1. Portland cement clinker mortar and concrete curing accelerating additive characterized in that it consists of at least one fine or finely divided material which contains or provides hydrated hydrated aluminum alumina and / or in the presence of water-based Portland clinker cement. or aluminum oxide and / or aluminum hydroxide and / or aluminum hydroxides, for example aluminum oxide, aluminum salts such as aluminum sulphate, aluminates and aluminosilicates or substances containing them, such as high-alumina metallurgical wastes - slags, clinkers with high aluminum where appropriate, the heat treatment of minerals and soils with a high aluminum content is bauxite, kaolyynthesis of thread, flake and the like, and in particular of one of the water-soluble, preferably sodium or potassium salts of inorganic and / or organic acids such as nitric, nitrous, sulfur, saline, ant, oxalic and the like or from a mixture of these salts, the ratio of the two components being 1: 200 to 200: 1 by weight. 2. An additive according to claim 1, characterized in that it contains at the same time a viscosity reducing agent of a cement-water mixture such as sulfated naphthalene-formaldehyde, melamine-formaldehyde, phenol-formaldehyde, lignin-sulphonates and the like or mixtures thereof, in an amount of 0.1 to 90 ¹⁰ / o. by weight of the resulting additive.