DD158026A5 - BINDER BASED ON REINFORCED GUNS AND SYNTHETIC ANHYDRITES - Google Patents

Abstract

The invention relates to novel binders obtained by simple mixing of residual gypsum (phosphogypsum, gypsum from the desulphurisation of thermal power plants) with synthetic anhydrite (fluoroanhydrite, phosphoanhydrite) and water without purification or calcination.

Description

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58 867/13

Binders based on residual gypsum and synthetic anhydrite

Field of application of the invention. *

The invention relates to. new binders obtained by simple mixing of residual gypsum from the chemical industry or from thermal power stations with synthetic anhydrites;

the known technical solutions

To date, the gypsum produced in the chemical industry as a by-product, such as Ze Β * the phosphogypsum or remaining in the desulfurization of the flue gases from thermal power plasters. not really satisfactorily resolved. "

The processes by which a semi-hydrate calcium sulfate can be prepared from these waste products and used as binders in the construction industry have the disadvantage that they require on the same side a cleaning of the residual gypsum and a calcination (firing) process

Furthermore, it has been proposed in the European patent application 0 007, after dehydration of the flue gases from thermal power plants remaining gypsum after partial or complete dehydration with a dehydrated Katurgips to mix or dehydrate a mixture of residual gypsum and JTaturgipsen simultaneously «This method requires a more energy-consuming Dehydratisierungsschrit'U

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Object of the invention

The aim of the invention is to avoid the disadvantages of the prior art »

Explanation of the essence of the invention

The invention has for its object to provide a binder based on residual gypsum and synthetic anhydrites available.

It has now been found, completely surprisingly, that very good quality binders can be obtained simply by mixing residual gypsum, of chemical origin or desulphurisation of flue gases from thermal power plants, with a binder of synthetic anhydrite, without any purification or mixing a burning is necessary. As binding agent of synthetic anhydrite, a binder corresponding to German standard DIN 4208 is understood, which is obtained starting from fluoranhydride, a by-product in the production of hydrofluoric acid or starting from phosphoanhydrite, which is obtained, for example, according to the method described in French Patent FR-PS 2 423 463 produced by the Applicant. Natural anhydrite is not usable for the preparation of binders according to the invention.

Residual plasters from the chemical industry, such as the phosphogypsum, which can be used according to the invention contain at least 90 % and preferably at least 95 % calcium sulfate dihydrate (CaSO..2HpO). They are mixed with various impurities such as calcium fluoride, silica, iron oxides, alumina, phosphates, etc. Their maximum grain size is generally below 0.3 mm.

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mean granule size on the order of 30 to 40 / uu

Residual plasters of thermal power plants, which are likewise usable according to the invention, are obtained during the desulphurisation of the combustion gases of these thermal power plants by washing with an aqueous lime solution. First, a mixture of neutral and acidic calcium sulphite _{y is formed,} which is oxygenated by the atmospheric oxygen to form calcium sulphate dihydrate. This gypsum rock containing at least 90 percent by weight CaSO ♦ 2 H ₂ O * It is by numerous impurities such as sulfites _v CKLois.de, carbonates, silica, alumina, magnesia, iron oxides etc "ver" unreinigt * Its maximum Körnimg is generally below .0.2 mm, the mean grain size is in the order of 30 to 40 / Um,

The respective proportions of residual gypsum and of synthetic anhydrite in the mixtures according to the invention which form the novel binders can vary within fairly wide ranges of from 90 to 10 % and from 10 to 90 % . From an economic point of view, it is interesting to enter in mixes the largest possible quantity of inexpensive residual plaster; However, in terms of their technical properties, the blends with a large proportion of synthetic anhydrites are the most interesting. "The best compromise is achieved in blends with equal proportions by weight of residual gypsum and synthetic anhydrite."

According to the invention, it is also possible to use a plurality of residual plasters of different origin in admixture with the anhydritic binder.

The novel ₉ binders according to the invention can be described as pure.

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Gypsum slurry or they can be mixed with granules to obtain mortar or concrete. Additives may be added to the pure gypsum mastics, mortars or concrete to modify the properties of the batter before setting or to change the properties of the material after hardening,.

The application covers all building materials used in the construction industry. * In particular, self-leveling layers of pure gypsum slurry or mortar can be produced by liquefaction. It is also possible to produce porous material by expanding the pure gypsum slurry or mortar, for example by means of pulverized aluminum,

Execution example

In the two reproduced in the following to illustrate the invention examples pure gypsum puree have been prepared with the addition of so much mixing water that determined according to the German standard DIN 1164 certain slump at 150 - 5 mm, the beginning and end of setting are according to the same standard DIN 1164 has been determined. The flexural tensile strength and the compressive strength were determined on test pieces of 4 × 4 × 16 cm according to the standard NP P 15-451.

Example 1

The residual gypsum used is a phosphogypsum with the following properties:

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- 5 - ·

a) Granule size: is it between 0 _? 7 and 200 / Um; Mean value: 33 / Um ·

c) chemical analysis;

GaSO ₄ · 2H ₂ O · · 95.5%

2.0%:; 0.8 %

TTi-v f * \ - \ r \ c \ of

jj'e pU " _s ζ / o

Al ₂ O ₃ : 0.3 %

PpOf- water soluble 0.1%

PoO ^ insoluble in water 0 _s 5%

800 g of this phosphogypsum is mixed with 800 g of plutonium anhydride according to the German standard. DIlT 4208 and stirred with 176 g of water. The table reproduced after Example 2 gives the times for the beginning and the end of setting and also the mechanical strength values after 7 and after 28 days.

Example 2

Is a residue plaster from thermal power plants used, which has the following characteristics? ·.

a) Körncheoigröße * determined by sieving of the dry product at 100 ⁰ C (373 K):

Mesh size of the sieve residue

(/ um) '(in weight percentages)

37 74

90 · 100

88 Λ 10 1 _p 0

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b) Chemical analysis:

CaSO ₄ - 2 H ₂ O 95.5 %

SiO ₂ '. 0.5 %

SO ₂ 0.3 %

₃ 0.1 %

0.1 %

CO ₂ 0.1 %

H ₂ O "3.4 %

800 g of this desulfurization gypsum are mixed with 800 g of fluoroanhydrite according to the German standard DIH 4208 and 168 g of water. The table below summarizes the times for the beginning and end of setting and the mechanical strengths after 7 and 28 days have elapsed:

table

Beginning of end flexure

With- out Fade Strength (bar)

Game is' weight (bar)

dens dens (g / cm3)

7 28 7 28 7 days days days' days days days

1 > 6 h > 12 h 1 , 68 1 , 66 26 ' 52 115 220 2 65 min. 105 mini , 78 1 , 76 74 76 270 275

Claims (1)

10 ". 7. 1981 58 867 Γ 13 1 * Binders, characterized in that they are composed of mixtures of "residue gypsum and synthetic anhydrite", Binder according to item 1, characterized in that the backing plasters are phosphogypsum, 3 · Binder according to item 1, characterized in that the residual agglomerations derive from the desulphurisation of the combustion gases (flue gases) of thermal power plants ». Binder according to item 1, characterized in that the synthetic anhydrite is a pluroranhydrite, 5 "Binder according to item 1, characterized in that the synthetic anhydrite is a phosphoanhydrite" Ge binder according to one of the items 1 to 5 $ characterized in that the weight fraction of the residual plaster is 10 to 90 % , 7 ". Binder according to one of the items 1 _S 4 ₅ 5 or 6, characterized in that it has several residue plasters of different origin ,, Β * binder according to one of the points I ₉ 2, 3 _? 6 or 7? characterized in that it comprises several synthetic anhydrites of different origin * 9 * construction material, characterized by; that it is produced using the binding agents according to points 1 to 8 _β