NL8702972A - MIXTURE FOR ACCELERATING THE OPEN GREEN STABILITY OF GAS CONCRETE OF LOW RAW THICKNESS. - Google Patents

Description

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Mixture for accelerated achievement of the open green stability of aerated concrete of low raw thickness.

The invention relates to a mixture for accelerated attainment of the open green stability of aerated concrete of low raw density. The invention is preferably applicable in aerated concrete works, in which different aerated concrete are produced on the same production line.

In the preparation of aerated concrete, the time span until reaching the open green stability is of particular importance. The green stability is here a mechanical key figure, which characterizes the development of stability of the aerated concrete block after the floating end.

The open green stability represents the area of the development of stability, which begins with the possible removal of the aerated concrete block and ends with the still possible cutting of this block.

In the preparation of low-density aerated concrete, the development of green stability is delayed due to the high water content determined by the formulation. Compared to mixtures for aerated concrete of higher raw densities, the open green stability is thereby achieved at a substantially later time. This leads to significant obstacles in the course of the process in the technological lines of the aerated concrete works.

Mixtures of chemical substances are known from the literature, with the aid of which the stability development of cement and cement mixtures can be accelerated.

In order to achieve this effect, for example, in accordance with DE-AS 2.114.081, IPK C 30 04 B 13/24, a mixture of an amine with up to 20 carbon atoms and a water-soluble salt of formic acid and further different limiting retarders used. With the use of this mixture, but with the exception of the setting retardant included in this mixture, which is not required in aerated concrete mix, the time period to achieve the open green stability cannot be decisively shortened.

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In accordance with DE-OS 2,819,483, IPK C 04 B, 13/22, the strength development of a cement concrete mixture is accelerated with the addition of a mixture of amorphous calcium aluminate and an inorganic sulfate. This mixture has the drawback that the usual sulphate contents of the aerated concrete mixture are largely exceeded and the excessively increased sulphate content strongly delays the calcination of lime in the binder of the aerated concrete mixture. Furthermore, when the mixture is used in aerated concrete mixtures, the sulphate component reduces the strength of the aerated concrete to be hardened and promotes shrinkage and cracking. It has thus been found that the chemical mixtures suitable for promoting the strength development of cement and cement-concrete mixtures cannot be used for shortening the time frames for achieving the open green stability in aerated concrete mixtures.

No means is known from the prior art to accelerate the development of the green stability in mixtures for aerated concrete of low crude density, such that the open green stability in the preparation of aerated concrete of different crude densities according to a uniform technological regime without negative effects due to technological breaks in the preceding or subsequent production and in the shortest measure times is achieved.

It is the object of the invention to rationally design the process for preparing aerated concrete of low raw thickness and to achieve a high quality. To this end, in particular, the time to achieve the open green stability of aerated concrete mixtures of low raw densities can be shortened and thereby increased labor productivity.

It is the task of the invention to reach the open green stability of at least 0.25 N / mm 2 in aerated concrete mixtures for low-density aerated concrete of the building material class DBk 300 resp. of at least 0.32 N / mm2 of the building material class GBK 500 so that its production 40 is problem-free in the technological process of aerated concrete

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-3- works can be integrated, in which different aerated concrete classes are prepared on the same production line.

According to the invention, the specification with a chemical mixture of the components 5 is 0.10 to 0.31% by weight of calcium formate 0.007 to 0.025% by weight of triethanolamine 0.22 to 0.57% by weight of sodium aluminate based on the cement content of the binder for the aerated concrete mixture. , solved.

This mixture is added to the aerated concrete mixture during the mixing process, exemplary embodiments.

In the preparation of low-density aerated concrete, for example aerated concrete of the DBk 300 insulation building material, the open green stability is only reached 7 hours after the pouring of the aerated concrete mixture. In many experiments, to reduce this time span to 3 hours, chemicals were added to the aerated concrete mixture, which accelerate the hardening and effect the development of strength in the case of cement and cement-concrete mixtures. The desired effects did not occur, or only slightly, in the aerated concrete mixture. The time between floating end and open green stability could not be shortened, or only insignificantly, whereby the known substances or mixtures were found to be unsuitable for solving the problem. See also examples I and II.

Example I.

Aerated concrete Mixture resp. substances for Time to class the solution of the task of reaching the open green stability ___ of 0.25 N / mm2. DBk 300 0.22 M% calcium formate 0.01 M% triethanolamine 3.6 hours 35 0.55 M-% sodium aluminate iv / - -4- * »

Example II.

Aerated concrete Mixture resp. substances Time to reach the open green stability of 0.25 5 _N / mm2_ DBk 300 0.62 M% sodium aluminate 4.5 hours

The mixtures according to examples I and II are not suitable to reach the minimum time of 3 hours required in accordance with the task. The use of sodium aluminate alone does not accomplish the achievement of open green stability in the required short time of 3 hours. Also with larger addition amounts of sodium aluminate, one could not stay below 4.5 hours. Surprisingly, however, it appeared that a mixture in hitherto unknown composition of certain substances, when used in small but different percentages, involved success in the cement content of the binder amount of an aerated concrete mixture of the insulation building class DBk 300, was successful. This, the task dissolving mixture, is further composed of the substances and percentages according to example III.

Example III.

25 Aerated concrete Mixture resp. substances Time to reach the open green stability of 0.25 N / mm2 DBk 300 0.30 M% calcium formate 0.02 M% triethanol 3.0 hours amine 0.55 M -% sodium aluminate 35

This mixture according to the invention was added to the aerated concrete mixture during the mixing process. When preparing the aerated concrete of building material class GBk 40 500 with a substantially higher solids input than 8702S7 i -5- $ with building material class DBk 300, an open green stability without use of additives was achieved after 3 hours. However, this time can be shortened for GBk 500.

Using 0.24 M% sodium aluminate, no reduction of the time span until reaching the open green stability could be achieved. A targeted influence of the technological regime of the preparation line was therefore unsuccessful. See example IV for this.

Example VI.

10 Aerated concrete mix or. substances Time to reach the open green stability of 0.32 'N / mm2 15 GBk 500 0.24 M% sodium aluminate 3.0 hours

In contrast, the mixture according to the invention demonstrated the required reduction of the time span to 20 to achieve open green stability, thereby providing the possibility of targeting the technological regime in the production of the richer GBk 500. See example V.

25 Example V.

Aerated concrete Mixture resp. substances Time to reach the open green stability of 0.32 N / mm2 30 __ GBk 500 0.13 M% calcium formate 0.0078 M% triethanolamine 2.5 hours 35 0.24 M -% sodium aluminate

The mixture percentages were also based on the cement content of the aerated concrete binder in Examples IV and V. By using the mixture according to the invention in the concentrations according to example III, it became possible to use aerated concrete of a lower raw density, for example of the building material class DBk 300, in the technological process of aerated concrete works, in which -5 different aerated concrete classes were prepared, rationally taken into account and prepared economically.

The use of the mixture according to the invention in the concentrations according to Example V in the continuous production of the aerated concrete class GBk 500 shortened the process of the aerated concrete prepared before the autoclave, thereby creating a condition for the production increase.

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Claims (1)

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