SK12722001A3 - Hydraulic binder - Google Patents

Abstract

A hydraulic binder containing finely ground moderately latent hydraulic blast-furnace slag with a Blaine factor higher than 5000 cm2 g, as well as a sulphate activator and activating additives. The moderately latent hydraulic blast-furnace slag has the following analytic values: vitreousness above 93 %; content SiO2 34 - 40 %; CaO 34 - 37 %; Al2O5 above 9 % and preferably under 13 %; (CaO + MgO)/(Al2O5 + SiO2) 0.88 - 0.98. These values can be achieved by mixing different types of slag. The binder embodying the invention preferentially contains 0.5 - 5 % Portland cement clinker or Portland cement.

Description

BACKGROUND OF THE INVENTION

Blast furnace slag is formed as a by-product in the recovery of pig iron. In a blast furnace, iron ore is formed from clay, silicic acid and lime, as well as from limestone and coal impurities at 1900 ° C, a melt of iron melt, a so-called blast furnace slag. This slag is cooled with water at 1400 ° C. This rapid cooling produces a highly glassy granulate having latent hydraulic bonding forces. Therefore, the glassy blast furnace slag does not come as a separate binder to its curing energy can be activated by the addition. There are basically two additions of calcium hydroxide for this activation. or cement (alkaline activation) and the addition of calcium sulfate (sulfate activation). But each slag is not equally activated.

Activator considerations options:

The assessment of the latent hydraulic slag coupling force is based on the slag composition. So judge Dr.. Fritz Keil in Zement, Herstellung und Eigenschaften, SpringerVerlag, Berlin 1971 on page 116 slag quality according to the ratio (CaO + CaS + 0.5MgO + Al ₂ O ₃ ) / (SiO ₂ + MnO) (F value). If the F value is above 1.9, the slag is considered to be very good, below 1.5 as slightly hydraulic.

Another criterion for assessing slag activity is content

SiO ₂ . Thus, debris with less than 32% generally applies to highly hydraulic, with more than 37% to less hydraulic.

With regard to alkaline activation, the following requirement is laid down in EN-1971 for the preparation of cement for slag quality: the ratio (CaO + MgO) / (SiO ₂ ) must be greater than 1.0.

In a sulphate activation the literature with a suitable slag which have a Al2O3 content of at least 13%, and the ratio of (CaO + MgO + Al ₂ O 3) / (SiO ₂₎ is above 1.6. Several patents require a CaO content above 40% and an Al2O3 content above 14% (see, for example, CAPS 1,131,664).

CA-PS 1 131 664 discloses a binder having the following composition:

80-85% granulated blast furnace slag (with 40 - 50% CaO

- 20% Al2O3

- 35% SiO ₂

- 8% MgO),

- 17% CaSO ₄ (calculated as anhydrite),

1.5 - 2.5% of Portland cement,

0.1-0.5% organic carboxylic acid or a salt thereof, 0.03-0.6% methylcellulose, Na-stearate or Na-laurylbenzenesulfonate; and

0.6 - 2% sodium sulfate.

In accordance with what has been said above, blast furnace slag is used. For improvement, it is even recommended to add Al ₂ O ₃ and CaO to the slag and heat the mixture.

Unfortunately, on the basis of the above criteria, a large part of the falling blast furnace slag is labeled as slightly hydraulic. These less valuable blast furnace slags can be used as primers in the cement industry, up to a maximum of 65% of the cement content, as they further decrease rapidly. Also, the concrete industry can use these debris as additives only to a limited extent.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a binder of the kind initially mentioned, which uses less valuable slag and which, in particular, provides a high value product.

This problem is solved by the binder of the initially mentioned type according to the invention in that the slightly latent hydraulic blast furnace slag exhibits the following analytical values:

glassiness:> 93%;

SiO ₂ : 34-40%,

CaO: 34-37%

Al ₂ O ₃ :> 9% (CaO + MgO) / (Al ₂ O ₃ + SiO ₂ ): 0.88-0.98.

Surprisingly, it has been found that slags that meet these parameters provide good products, even if they are classified as slightly hydraulic according to the usual criteria. Slags with less than 13% Al ₂ O ₃ may be used. The F value may be below 1.5 and the (CaO + MgO + Al ₂ O ₃ ) / SiO ₂ ratio below 1.6.

However, the slag will rarely randomly exhibit all the desired properties according to the invention. However, since there are many less valuable debris, it is often possible to achieve all the desired properties by mixing at least two blast furnace debris. This has the further advantage that the degree of activation is much higher when the above mentioned assumptions are achieved by mixing debris of different origins.

Slag activation is accomplished by admixing or ground natural gypsum, desulfurized flue gas / gypsum (REA) or 12-20% anhydrite, 0.5-5% Portland cement and / or other CaO carriers such as hot meal, quicklime or 0.5%. - 3% Ca (OH) ₂ , 0-3% alkali sulphates or alkali carbonates and / or 0.5-3% calcium carboxylic acid salts. The use of hot meal has been shown to be advantageous here, thereby accelerating the slag hydration and increasing the compressive strength.

The hot meal is 70 - 90% deoxygenated raw meal, which is produced in the lowest cyclone stage of the heat exchanger furnace at 800 - 900 ° C in the production of Portland cement clinker. The meal is taken from the furnace system by bypass. It contains mainly CaO.

French fries made from this binder exhibit higher resistance to sulfate attack and provide strengths that correspond to strength classes ORMNORM B3310 and EN 197-1 and are comparable to or even better than normal Portland cement.

DETAILED DESCRIPTION OF THE INVENTION

By way of example, the present invention will be elucidated. A binder was prepared from the following components:

% slag (Blain value 5800 cm ² / g)% gypsum REA% Portland cement

0.5% hot meal

0.5% calcium acetate

The slag according to the invention is used once as a slag and another slag is used (comparative experiment). The data on slag and strength obtained are given in the following table:

analysis Mixture of debris suitable Mixture of debris unfit glassiness 94 94 SiO ₂ % 38.3 37.3 A1 ₂ O ₃ % 11.2 10,0 CaO% 35, 8 38.2 MgO% 9 10, 5 (CaO + MgO) / (Al ₂ O ₃ + SiO) 0.91 1, 03 BN B3310 EN 196-1 BN B3310 EN 196-1 Compressive strength N / mm ² after 2 days 7 9 after 3 days 10 11 after 7 days 26 30 15 18 after 28 days 46 49 22 24

In addition, the strengths can be substantially increased by concrete additives (as diluents to reduce the water / binder value from 0.6 to 0.30).

The binder according to the invention is characterized by a very low hydration heat. It is highly suitable for the production of clarifying devices, ducts, canals, tanks, catch tanks and construction objects that are exposed to a kraft attack.

Claims (9)

PATENT CLAIMS 1. Hydraulic binder of finely ground - above 5,000 cm ² / g Blaine - slightly latent hydraulic blast furnace slag containing sulphate activators and activating additives, characterized in that the slightly latent hydraulic blast furnace slag exhibits the following analytical values: glassiness:> 93%; SiO _2: 34-40%, CaO: 34-37% Al ₂ O ₃ :> 9% (CaO + MgO) / (Al ₂ O ₃ + SiO ₂ ): 0.88-0.98. Binder according to claim 1, characterized in that the proportion of Al ₂ O ₃ in the blast furnace slag is at most 13%. Binder according to claim 1 or 2, characterized in that the blast furnace slag is formed by a mixture of at least two blast furnace slags. Binder according to one of Claims 1 to 3, characterized in that the slightly hydraulic slag has a fineness of 5000 - 6500 cm ² / g (Blaine). A binder according to any one of claims 1 to 4, characterized in that it contains a proportion of 0.5 - 5% of Portland cement clinker and Portland cement, respectively. Binder according to any one of claims 1 to 5, characterized in that it contains as a carrier of sulphate 12-20% of gypsum waste from flue gas desulphurisation or semi-hydrate or anhydrite or natural gypsum or a mixture of these sulphate carriers. I A binder according to any one of claims 1 to 6, characterized in that it contains 0.5 - 3% hot meal or calcium hydroxide or quicklime. Binder according to one of claims 1 to 7, characterized in that it contains up to 3% of alkali sulphates and / or alkali carbonates, in particular K 2 SO ₄ , Na ₂ SO ₄ , Na ₂ CO ₃ , Li ₂ CO ₃ or K 2 CO 3. Binder according to one of Claims 1 to 8, characterized in that it contains 0.5 - 3% of a carboxylic acid calcium salt, in particular calcium acetate and / or formate