Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Patent
1996-01-24
1997-08-26
Green, Anthony
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
106819, 423556, C04B 2214
Patent
active
056606257
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns the use of basic aluminium sulphates of the general formula Al(OH).sub.a (SO.sub.4).sub.b, whereby the indices a and b fulfil the following conditions: in particular for cement.
TECHNOLOGY REVIEW
Cement is an essential constituent of concrete. Since most concreting work in the alpine countries, e.g. in tunnel construction, occur in the months with low temperatures, it is necessary to influence the setting, processing and hardening time by admixtures. These admixtures are used primarily to solve the following problems: temperatures
Especially for the production of fast setting gunite, no other alternative is available than using set accelerating admixtures.
A number of set accelerating admixtures are known in the current state of technology.
The admixtures are classified according to their function and there are also overlapping effects:
1. Set accelerating admixtures
These are such admixtures which shorten the period after mixing the concrete up to the transition into the solidified phase.
2. Hardening accelerating admixtures
These are such admixtures which accelerate the development of the early strength of concrete with or without influence on the setting time.
In the course of the present invention, compounds are presented here which preferably influence the processes named in Item 1, i.e. these are compounds which considerably shorten the period after mixing of the concrete up to the transition into the solidified phase. They are also named in the following briefly only as set accelerators (SA).
The following are known in the current state of technology as set accelerators:
Calcium chloride, sodium silicate, sodium hydrogen carbonate, sodium bicarbonate, sodium aluminate, aluminium sulphate, calcium formate, triethanolamine (TEA), soluble alkali fluorides and Seignette salt.
Aluminium hydroxides, which are used either alone or mixed with other compounds, are also known as SA.
Thus the use of aluminium hydroxide is described, for instance in the CA96:167570e and in the EP -0 026 262 B1.
An alkali-free and chloride-free set accelerator, which is characterized in that it contains amorphous aluminium hydroxide mixed with at least one water-soluble sulphate and/or nitrate and/or formate is described in the EP-0 076 927 B1. The set accelerating effect on cement is increased by mixing the amorphous aluminium hydroxide with water-soluble sulphates, nitrates and formates of the alkaline earth and transition metals. However, the disadvantage of this method is seen in that it contains water-soluble added substances of which it is known that they negatively influence the setting process of the cement.
Using aluminium sulphate alone or as mixing component for accelerated setting of cement is also known from the FR-2031950.
A cement mixture is known from the CS-257142 which, apart from cement, water and/or filler and/or admixture substances possibly contains calcined aluminium sulphate, here designated as additional substance C, column 6, 1st paragraph of the German translation. The additional substance C is obtained here by calcination at 600.degree. C. for 5 hours. It was determined by means of RTG phase analysis that this substance C is neither Al.sub.2 O.sub.3 nor Al(OH).sub.3. The additional substance C has a molar ratio of Al.sub.2 O.sub.3 : SO.sub.3 of 1:2.367, i.e. S/AL=1.184.
A disadvantage of this method is the fact that to obtain this product, calcination must be very long at high temperatures, which is unfavourable with regard to energy consumption. In addition a product which is inhomogeneous and does not deliver reproducible results in its effect as SA is produced by the calcination.
Using a calcined aluminium sulphate as set accelerator component is also already known from the DE-OS 21 22 710, in which case here as well it is already clear that calcination must last a very long time, namely 24 h at 450.degree.-490.degree. C. in order to obtain a suitable type of aluminum sulphate.
As already discussed above, SA known in the current state of tec
REFERENCES:
patent: 3114647 (1963-12-01), Mecham
patent: 4415367 (1983-11-01), Nelson
Chemical Abstracts, vol. 90, No. 26, Jun. 25, 1979, Columbus, Ohio, U.S.; abstract No. 206693v, Y. Fjihira et al "Transparent aqueous aluminum sulphate from alumina sludge", p. 162; JPA781462997 (Nippon Light Metal Co., Ltd.) Dec. 20, 1978.
Chemical Abstracts, vol. 111, No. 6, Sep. 18, 1989, Columbus, Ohio, U.S., abstract No. 102002e, S. Slanicka "Rapid-setting cement mixtures", p. 302; & CSA257,142 (S. Slanicka et al) Nov. 15, 1988.
Chemical Abstracts, vol. 96, No. 20, Nov. 25, 1981, Columbus, Ohio, U.S., abstract No. 167570e, K. Nakanishi "Setting Acceleration of Cement", & JP 56-049867, Nov. 25, 1981.
Breker Johannes
Helmboldt Otto
Potencsik Istvan
Roggenkamp Detlev
Sedelies Reinhold
Giulini Chemie GmbH
Green Anthony
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