DD233836A1 - METHOD FOR PRODUCING HIGH QUALITY TONER DEZEMENTS WITH ADVANTAGEOUS HYDRATION AND HIGH TEMPERATURE BEHAVIOR - Google Patents

Abstract

High Al 2 O 3 -containing alumina cements are preferably produced for stomping and torquing mixtures and for the production of precast parts which are used in pyrotechnic installations as a whole. According to the invention, a suitable cement is obtained if the preparation of the raw mixture takes place with simultaneous addition of small amounts of calcium sulfate. In the case of clinker firing, this leads to improved conversion of the raw material components and to the formation of the phase 3 CACs, which prevents the damaging hydrate phase transformation at elevated setting temperatures. This results in improved strength properties, especially after thermal stress of the concrete.

Description

Features of the invention

ie this object is achieved in that the group consisting of chalk and Calcined clay and n small amounts of carboxymethyl cellulose, and sulphite waste liquor produced with the addition) suspension, such as commonly found for the production of alumina cements use, up to 5% gypsum (CaSCU · V2 H ₂ O ) or another CaSO ₄ carrier, based on the solid, is added. The wet-mechanically treated suspension is dehydrated according to known per se, the dehydration product - possibly as Sprühkom - briquetted and then sintered at temperatures between 400 and 145O ⁰ C, sintered into clinker. With this procedure, a clinker is obtained, which differs from 3m obtained from the corresponding suspension without gypsum additive differs in that, due to the lineralizing effect of the gypsum or the resultant during the thermal treatment of SO ₂ and SO ₃ a Dllständiger expiry of the solid has occurred reactions between the CaO and Al ₂ O 3 formed correspondingly none 1 ₂ a ₇ content is detectable and is present a small fraction of 3 CA · Cs, where the bulk density increases significantly, accordingly it indicates from this clinker ermahlene cement favorable strength development when processing j concrete, a time delay of the conversion reaction of the low-lime into the lime-rich hydration products and, in particular, a favorable strength behavior under thermal stress.

usführungsbeispiele

The invention will be explained in more detail in the following examples.

Ice Pie 1

after the composition of 040 kg chalk

610 kg calz. aluminum oxide

2kg plaster

2kg carboxymethyl cellulose oil sulfite, d = 1.25g / cm ³

The raw materials are metered in terms of weight and volume and prepared in an agitator with the addition of water to form an uspension. The solids content of the suspension was 61.4%. This suspension was transferred to a wet drum mill where further homogenization and wet milling of the raw material components took place. After a grinding time of 3 hours, the Festoff the suspension was recovered by spray drying. The resulting Sprühkom had in Siebrückstand, based on the primary grain, of 12.6% at 40 μιπ clear width and a humidity of 14.5%. On ydraulischen processes the Sprühkom at a pressing pressure of approx. 40MPa pressed into blanks with the dimensions 50 χ 150 χ 65mm, which were then fired in the gas continuous furnace to the calcium aluminate clinker.

Already in the microstructure parameters, there are clear differences to the clinker without gypsum additive, such as from the

following overview.

Bulk density g / cm ³ Water absorption% Open porosity% Left with gypsum additive [left without gypsum additive 2.24 1.90 10.3 18.1 23 34 η of the phase composition are present. the two clinker are also marked changes, the following 'Hare ME Clinker with gypsum additive Clinker without gypsum additive

a%

: a ₂ %

; ₁₂ A ₇ %

5CA-Cs%

AI ₂ O ₃ (unreacted A)%

44.6 53.9 1.1

approached 0.4

The cement made from the clinker with gypsum additive was characterized by the following parameters.

Sieve residue 90 μ, ηη 2.2%

Sieve residue 63 μ 4.0%

Sieve residue 40 μ 10.6%

Compressive strength standard test, 25% cement WZF 0.5,

24 hour value 40.3MPa

7 days value 77.4MPa

The test of the strength after thermal stress on a corundum concrete at 1200 ° C gave a value of 35.5 MPa for the cement from the clinker with gypsum additive. This value and the delayed conversion of the hydrate phases formed during the hydration into the stable phase C ₃ AH ₆ are significant for this cement.

In the following overview, the delayed hydrate phase transformation is expressed. Time Cement from clinker with gypsum additive Clinker without gypsum additive

1d CAH ₁₀ , C ₂ AH ₈ CAH ₁₀ , C ₂ AH ₈

3d CAH ₁₀ , C ₂ AH ₈ CAH ₁₀₁ C ₂ AH ^ C ₃ AH ₆

8d CAH ₁₀₁ C ₂ AH ₈ C ₂ AH ₈₁ C ₃ AH ₆

28 d C ₂ AH ₈₁ C ₃ AH ₆ C ₂ AH ₃ C ₃ AH ₆

The advantageous use of such a cement, z. In a Fe-Cr slag concrete with the composition of 45 mass% Fe-Cr base material 3-6 mm

30% by weight Fe-Cr basic substance 0-3 mm 5% by weight Fe-Cr basic material 0-0.9 mm 20% by weight TZ70 is well-expressed in terms of compressive strength after 7 days and thermal stress.

TZ70 with plaster additive TZ70 without

additional plaster

after 7 d, 20 ⁰ C 52,7MPa 56,4MPa

after 7 d and pre-firing 600 ° C / 4h. 50.5MPa 44.7MPa

nach7dundVorbrand1000 ° C / 4h. 45.5MPa 34.5MPa

Example 2

Calcined alumina and chalk are as indicated in Example 1, dosed, homogenized by wet mechanical means and in particular the alumina content ground and then spray-dried. 2% gypsum is added to the dried sprayed grain with the addition of water until it has reached the consistency of a tough consistency. This plastic raw mixture is then converted into forms. After drying and curing of the blanks, the clinker firing takes place by a known method. As indicated in the exemplary embodiment 1, the increase in the gross density is remarkable here as well, as can be seen from the following information.

ME clinker with 2% gypsum additive clinker without

to the spray grain gypsum additive

Bulk density g / cm ³ 1.89 1.28

Water absorption% 18.2 27.5

Open porosity% 34 35

In the tests on the cement samples similar results could be found as in the embodiment 1.

Claims (3)

Invention claim: Process for the preparation of high-quality alumina cements with modified hydration and high-temperature behavior, characterized in that up to 5% of calcium sulfate in the form of gypsum or another CaSO ₄ carrier is added to the raw meal consisting of CaCO 3 and calcined clay in the crude mixture preparation and according to methods known per se sintered to clinker and ground in the presence of up to 0.5% sulphite powder in the batch cement grinding. Field of application of the invention The invention relates to a process for the production of high-grade alumina cements with advantageous hydration and high-temperature behavior, in particular in the processing and the use of precast concrete parts and mixtures for pyrotechnic systems. Characteristic of the known technical solutions There are various methods for the production of high-quality alumina cements, which consist practically only of the compounds of CaO and Al2O3, all of which can be attributed to the same basic principle, namely the raw material preparation of a mixture of CaCO ₃ and alumina, the burning of the raw melt at Temperatures around 1450 ⁰ C to the cement clinker and the grinding of the clinker to the cement. The commercial cements produced in this way are generally between 70 and 72% in total Al ₂ O ₃ content and have a theoretical phase composition of about 40-46% monocalzium aluminate (CA) and about 60-54% monocalzium dialuminate (CA ₂ ). This theoretical phase composition is in practice but only at increased cost - exact adherence of 1450 ° C in the clinker fire, which entails a high grinding costs for the resulting at these temperatures hard clinker-reaches, since the solid-state reaction of CaCO3 resulting CaO with the AI2O3 runs relatively slowly completely and is hindered even at a slight decrease in the specified firing temperature. Thus, in addition to CA and CA ₂ , the technical cements also frequently contain the lime-rich phase dodecacalzium heptaaluminate (C12A7) in relatively high amounts (up to 2%). CA / CA ₂ cement clinkers produced in this way have too low bulk density values, in particular if they contain the mentioned small proportions of Ci ₂ A ₇ , which has the disadvantage of high reactivity towards water, which inter alia results in a strong temperature development in the processing of cements to refractory precast concrete states, is indirectly related. Such a high reactivity further creates favorable conditions for the course of conversion reactions of the hydrate phase resulting from the hydration towards CaO.Al ₂ O ₃ .10H ₂ O (CAH ₁₀ ). 2 CaO.Al ₂ O ₃ .8H ₂ O (C ₂ AH ₈ ) - » 3 CaO Al ₂ O ₃ 6 H ₂ O (C ₃ AH ₆ ), which, in particular at elevated outside temperatures of more than 29 ^° C., run relatively fast and lead to strength losses of the component due to different specific volumes. These strength losses of the concrete have an adverse effect on the high-temperature properties of the material when used in pyrotechnic systems. In the literature, various substances are described which in small proportions - up to 5% - added to the pure calcium aluminate, to hinder the unwanted conversion reaction described above. As such compounds are known CaCO ₃ , Al (OH) ₃ and 3 (CaO · Al ₂ O ₃ ). CaSO ₄ (3 CA · Cs), without these having been used as additives in practice. Object of the invention The aim of the invention is to influence the solid state reaction between CaO and Al ₂ O ₃ by adding a material or mixture of substances acting as a mineralizer in such a way that it proceeds faster and possibly at reduced temperature to the final state, a Ci ₂ A ₇ Clinker formation is avoided and a higher apparent density of the clinker is achieved, reducing the reactivity of the cement and the conditions favoring undesirable conversion reactions of the hydrate phases. In order to achieve a further desirable side effect, the additive should be selected so that the clinker fire forms one of the compounds of which it is known that their addition to a calcium aluminate causes a hindrance of the conversion reaction. The technical problem to be solved by the invention The technical problem to be solved by the invention is to provide a process for the production of an alumina cement which is characterized by A completely expired solids reaction between the oxides formed from the raw material components, - the absence of a content of Ci ₂ A ₇ A comparatively high clinker density and - gff. Ainet; C-content of an additional phase formed during the clinker fire, the presence of which hinders unwanted conversion reactions of the hydration products and thus has an advantageous hydration and high-temperature behavior during processing and the use of precast concrete parts and mixtures for pyrotechnic systems.