Solidifying and hardening accelerator for hydraulic binders

Details Solidifying and hardening accelerator for hydraulic binders Solidifying and hardening accelerator for hydraulic binders

1999-08-20

2001-10-16

Marcantoni, Paul (Department: 1755)

Compositions: coating or plastic

Coating or plastic compositions

Inorganic settable ingredient containing

C106S819000, C106S823000

Reexamination Certificate

active

06302954

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to stable solidification and curing accelerators for hydraulic binders in dissolved form, and to their preparation and use.
2. Description of the Related Art
EP 0 76 927 B1 discloses an alkali metal-free setting accelerator based on aluminium hydroxide. The further constituents of this composition are, according to Claim 1, at least one water-soluble sulphate and/or nitrate and/or formate of alkaline earth metals and transition metals which are added to the main constituent by simple mixing. It is unambiguously stated on page 2, line 55, that this composition is a pulverulent mixture which is added in solid form to the hydraulic binder. Water-swellable compounds are added to the mixture only to avoid excessive dust formation.
DD 266 344 A1 describes cationic aluminium salts obtained by reacting a precipitated aluminium hydroxide with concentrated formic, acetic or nitric acid, which salts are mixed in the form of a powder into the hydraulically setting cement or mortar concerned. The compounds formed by reaction of the aluminium hydroxide with the appropriate acids can be described by a general formula, e.g. Al (OH)
2
R×H
2
O, Al (OH) R
2
×H
2
O or AlR
3
×H
2
O. These aluminium salts contain no sulphate or chloride ions.
FR 2 471 955 describes a process for the accelerated setting of cement which is characterized in that bisulphite-formaldehyde, calcium formate and calcium nitrate in the form of a solution are used as accelerating agent, e.g. see page 3, from line 19, Examples.
Finally, EP 0 657 398 A1 likewise discloses a process for accelerating the setting of hydraulic binders, which is characterized in that the accelerating agent is a mixture containing at least one water-soluble sulphate of a polyvalent cation, in particular of aluminium, and a further water-insoluble component, e.g. calcium sulphoaluminate, calcium aluminate, basic aluminium sulphate and at least one further component. This further component can, according to Claim 24, be a dispersant, an inorganic binder, a fluidizer or a deaerating agent.
The setting accelerators are of particular interest in industry if they can be used in liquid form. Compared with the solid accelerators, mention may be made of essentially their better meterability, the more rapid release of the active substance (s) and naturally the negligible dust or aerosol formation during handling.
The classical liquid, alkaline accelerators, e.g. sodium aluminate and water glass are not only corrosive because of their high pH but also lead to a sometimes drastic decrease in the final strength of concrete because of the high amounts of alkali metal which they introduce.
Newer, liquid accelerators comprise mainly aqueous suspensions of basic aluminium sulphates. However, they are generally not stable to freezing, tend to sediment and display, although they could be employed in liquid form in the wet spraying process, unsatisfactory early strength development and also have only a slight accelerating effect, depending on the type of cement. Other commercially available concentrated aluminium salt solutions, e.g. Al
2
(SO
4
)
3
containing about 8% of Al
2
O
3
or aluminium triformate solutions containing about 5% of Al
2
O
3
, are unsuitable, at least for the wet spraying process, since they result in an undesirably low compressive strength because of the increased amount of water introduced into the concrete composition and the associated increased water-cement factor.
It is therefore an object of the present invention to provide a concentrated solidification and curing accelerator in aqueous solution form for hydraulic binders, which accelerator does not have the disadvantages of the classical liquid accelerators such as sodium aluminate and water glass and is, in particular, well suited to the wet spraying process.
SUMMARY OF THE INVENTION
This object has surprisingly been able to be achieved by new liquid solidification and curing accelerators for hydraulic binders such as cement, which accelerators are obtainable by a process which is characterized in that the following components Component a: basic aluminium salts and/or aluminium hydroxide Component b: aluminium sulphate and/or sulphuric acid Component c: organic carboxylic acids or mixtures of at least two organic carboxylic acids Component d: aluminium salts of organic carboxylic acids Component e: organic and/or inorganic sulphates and/or hydrogensulphates and/or carbonates and/or hydrogen-carbonates and/or alkaline earth metal oxides and/or alkaline earth metal hydroxides are reacted in water at temperatures up to 150° C. to give a solution, where
1. all components or a selection of the components react with one another so that the molar rations of aluminium to sulphate in the final product are from 0.83 to 13.3 and the molar rations of aluminium to organic carboxylic acid are from 0.67 to 33.3 or
2. all components apart from component e or a selection of the components apart from component e react with one another so that the molar ratios of aluminium to sulphate in the final product are from 0.83 to 13.3 and the molar ratios of aluminium to organic carboxylic acid in the final product are from 0.67 to 33.3 or
3. the component e is subsequently dissolved in the reaction product from Point 2.
As basic aluminium salts, preference is given to using the basic sulphates, carbonates, carbonate sulphates and nitrates and mixtures of at least two of these components.
Suitable organic carboxylic acids are essentially monocarboxylic acids, hydroxycarboxylic acids and dicarboxylic acids, e.g. formic acid, acetic acid, glycolic acid, lactic acid and mixtures thereof.
As inorganic and organic sulphates or hydrogen-sulphates, use is made of the alkaline earth metal salts and/or triethanolamine salts and/or diethanol-amine salts of sulphuric acid. However, the alkali metal salts of sulphuric acid are also used as sulphate or hydrogensulphate.
As carbonates and/or hydrogencarbonates, it is possible to use the alkaline earth metal salts. Alkaline earth metal oxides or alkaline earth metal hydroxides may also be used.
The setting accelerators of the invention can, it required, be used together with other compounds such as setting retardants, fluidizers and rebound-reducing agents.


REFERENCES:
patent: 5560774 (1996-10-01), Bürge et al.
patent: 3233474 A1 (1984-03-01), None
patent: 266344 A1 (1989-03-01), None
patent: 0076927 A1 (1983-04-01), None
patent: 0657398 A1 (1995-06-01), None
patent: 0670292 A1 (1995-09-01), None
patent: 2471955 (1981-06-01), None
patent: 95/03257 (1995-02-01), None
Fouche, P.M., ZA 93/05,646A, Dec. 29, 1993, Derwent Abstract 94-083589.

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