DE3124521A1 - Sulphate slag cement and ready-to-use mortar or ready-to-use concrete prepared therewith - Google Patents

Description

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Sulphate cement and ready-to-use mortar made with it or ready-to-use concrete.

In traditional cement production, including Portland cement, very large amounts of natural raw materials such as marl, limestone are used and sound, consumed. There is a growing awareness that an unlimited continuation via this route, viewed regionally, will ultimately take place leads to the exhaustion of natural raw materials and an undesired change in nature.

There is a growing need in the industrialized countries to a meaningful application of industrial waste products instead of polluting landfill on land or in water. Sometimes use can be made of industrial waste or by-products mean a lowering of the cement price, for example there. less energy is needed.

Therefore, in cement production to an increasing extent

By-products. other industries, such as granulated basic blast furnace slag, used. The latter has no cementing properties, but rather is supposed to be activated with an alkaline substance in order to be practical Application to obtain suitable cement. The well-known blast furnace cement can be produced using granulated basic blast furnace slag and Portland clinker to be finely ground together or separately and mixed intensively. Therefore But in practice you need a lot of Portland clinker, namely about 20-75% (all percentages reported herein are percentages by mass).

For another type of cement, the so-called sulphate slag cement, on the other hand Only 1-6% Portland clinker is required in addition to 78-85% basic blast furnace slag and 10-18% calcium sulfate. This calcium sulphate occurs as gypsum stone, but also falls as a by-product or waste product in the chemical industry Industry, such as the production of hydrogen fluoride and phosphoric acid or for flue gas desulphurisation from coal-fired electricity centers at.

By far the most important uses of cement are in concrete and mortar. However, sulphate cement has a number of important disadvantages, as a result of which its practical application has so far remained very limited. A first The disadvantage is that the outer skin of the hardening material becomes dusty or "sanded off" Concrete or the hardening mortar. A soft surface layer is created. This is a result of the action of carbon dioxide from the air, which causes the alkaline environment that is formed by the Portland clinker the finely ground slag is no longer activated and so is not hydrated remain. As a result, there is no or only an insufficient bond, with the sanding of the outer skin as a result. Sanding during hydration Cement can be stopped in concrete structures by the concrete in them To close off the period from the outside air for some time, e.g. by taking it under To hold water, while the formwork also complicates the supply of carbon dioxide will. However, it is not always possible to bring it under water and leaving it in the formwork for a long time is often not economically attractive. This last one This aspect also has to do with a second disadvantage of sulphate slag cement, namely that the hardening takes place slowly, especially at low temperatures.

It has now been found that the above-described secondary sulphate slag cement can be avoided to a considerable extent if the chemical composition of the blast furnace slag is 30-45% CaO, 10-20% Al ₂ O, 3-20% MgO and 25% -45% SiO-, where the slag composition is converted to Ca0 + Al ₂ 0_ + Mg0 + Si0 ₂ = 100%, answered, and has a ratio of hexavalent to tetravalent coordinated cations of 0.30-0.50 and- the specific surface of the ground slag is greater than 450 m / kg according to Blaine and / or the residue of the ground slag on a sieve with a mesh size of 15 / m is less than 60%.

According to the invention, it comes down to the macroscopic chemical Composition as well as the ratio of the hexavalent to tetravalent coordinated To choose cations of the blast furnace slag in the specified manner, and further the Grind slag relatively finely. Blast furnace slag with the same macroscopic chemical composition can have a vastly different hydraulic rate to have. It is therefore not enough just to have the macroscopic chemical composition define. That is found only through, a combined application of the above Measures the related effect, namely accelerated hydration the slag even at relatively low temperatures, which removes the carbon dioxide The air hardly has the potential to disrupt the process is reached. So will after A fairly high level of strength has already been achieved in a short time, so that the negative effect of carbonation remains limited.

The basic blast-furnace slag to d \ each have above-mentioned chemical composition and should also have a suitable glass structure, so that the ratio of hexavalent to tetravalent coordinated cations from 0.3 to 0.50. The basic blast furnace slag used may also contain small amounts of other constituents that often occur in slag, such as iron oxide, titanium dioxide and alkali metal oxides, without the desired effect being significantly impaired.

In practice, the preferred calcium sulphate source is anhydrite, that occurs in nature or in the production of hydrogen fluoride obtained from fluorspar, applied. Plaster of paris from natural or chemical sources can also be used. The calcium sulphate used may only Contain very small amounts of readily soluble phosphates and fluorides, as these cause the reaction of water with sulphate cement to a large extent can delay. The calcium sulphate must also not be used after grinding react sourly.

For the production of the present sulphate slag cement, the slag alone or together with one or both of the other components is ground to the required fineness in a suitable grinding device, for example a ball mill, preferably so fine that the specific surface of the slag is 500-550 m / kg. If the slag is ground separately, the gypsum and / or the anhydrite and the possibly ground or not ground clinker are then mixed with the ground slag and the resulting mixture is ground again if necessary. The specific surface of the gypsum and / or the anhydrite and the Portland clinker is less important. These will generally vary between 200 and 800 m / kg. However, the clinker will preferably have a specific surface area that is not greater than ^ 00 m / kg. The optimal amount of Portland clinker is ~ k%, because then the strength development of the hardening mortar or the hardening concrete proceeds fastest and the ultimate compressive strength is greatest. The optimum should be determined experimentally for each slag. In addition to blast furnace slag, calcium sulfate and Portland clinker, the cement can also contain the usual grinding additives, fly ash and pigments.

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The present sulphate slag cement is made with water and the usual Aggregates such as sand, gravel, etc., prepared and mixed into a ready-to-use Nortel or a ready-to-use concrete with the fur Processing suitable consistency. During the start-up, during transport or immediately before use, various additives, aggregates, Fiber like glass fiber, etc. can be added to achieve certain effects.

For example, water-reducing additives such as superplasticizers can be used when mixing be added. Examples thereof are sulfonated melamine-formaldehyde resins, sulfonated naphthalene-formaldehyde resins and refined lignin sulfonate. These substances are normally added from aqueous solution at a concentration of 0.1-51 active substance, calculated on sulphate cement. By Application of such substances can result in the same workability of the mortar or concrete with up to 40% less water, whereby the Hardening takes place faster and a higher mechanical strength can be achieved. This increases the risk of sand being silted up humiliated.

The processed. Mortar or the processed concrete with Substances, so-called "curing compounds", which prevent the water from evaporating too quickly from the hardening mixture, thereby increasing the strength would not increase further, and which would have a low permeability for carbon dioxide have to be post-treated. Such substances can e.g.

2 be epoxy resins and are preferably used in an amount of 5 "100 g / m .upraged. The application should rather. .Fabrics leads to obtaining a large Ultimate strength and an even higher hardness of the surface layer.

After the mortar or concrete is processed and hardened, a material is obtained with an excellent surface hardness and a high mechanical strength, both in compression and in bending.

The invention will now be explained in more detail with the aid of the following examples.

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Example I.

The mechanical strength test was in agreement carried out with the Dutch standard NEN 3072. Sand cement mortar (3: 1) - prisms of 4 χ 4 χ l6 cm were used for 1 day 20 ° C and covered with plastic film, stored, removed from the mold and then stored under water at 20 ° C. To reduce the influence of temperature during hardening, To follow up, tests were also carried out at 5 ° C.

For the determination of the thickness of the soft surface layer, one of T. Tanaka, T. Sakai and I. Yamane-designed method, which is described in the magazine Zement-Kaik-Gips 2 (1958), p 50-55, under the title "Composition of Japanese blast furnace slag for sulphate slag cements" is used. The test specimens for determining the surface hardness were produced as described for the mechanical strength test. In order to resemble the practical conditions as closely as possible, they were removed from the mold after 2 days and then stored in the air at 20 ° C or 5 ° C.

The cement types Blast Furnace A and Portland Cement A, which are widely used in the Netherlands, were used as comparison cements. These Cements are described in the Dutch standard NEN 3550. The values determined for these cements are given in Table A.

TABLE A.

Mechanical strength and penetration depth of blast furnace cement A. and Portland cement A.

Cement type

Temperature ° C

R.F.

Penetration depth mm

7 days

Compressive strength MPa

3T.

7T.

28T.

Blast furnace A Portland A Blast furnace A Portland A

20th

20th

100
100
100
100

0.60 0.25 0.95 0.35

17th

21st

10

27

31

20th

31 39

The sulphate cements examined all consisted of 83% basic blast furnace slag, 15% calcium sulphate and 2% Portland clinker. Slags with the composition given in Table B were used as blast furnace slag.

TABLE B.

Composition of basic blast furnace slag:. CaO + Al ₂ O + MgO + SiO = 100%

slag CaO Al ₂ O ₃ MgO SiO ₂ * £ Me ⁶⁺ / ^ Me ⁴⁺ Blast furnace slag 1 38 15th 12th 35 0.38 Blast furnace slag 2 45 14th 4th 37 0.25 Blast furnace slag 3 42 8th 9 4i 0.52 Blast furnace slag 4 38 14th 13th 35 0.60

* £ Me / iY \ & : ratio of hexavalent to tetravalent coordinated cations.

Slag T = -. Meets the requirements in relation to the chemical composition and coordination.

Slag 2 satisfies the requirement with regard to the chemical composition but not the one with regard to the coordination.

Slag 3 does not meet either of the two requirements.

From a chemical point of view, slag 4 is almost identical to slag 1, but does not meet the requirements in terms of coordination.

The values determined for these suI fattening cements are given in Table C given.

TABLE C

Mechanical strength and penetration depth of sulphate slag cement

with a specific surface area of the ground slag of 530

2
m / kg and a sieve residue of the ground slag on a sieve with a mesh size of 15> jm less than 60%.

slag . ■ T R.F. Penetration depth Compressive strength MPa 7 T 28 T ° c % mm i * 6 52 7 days 3 T 31 iti Slag 1 20th 100 0.20 31 ■ 15th 20th Slag 2 20th 100 0.55 18th 20th Slag 3 20th 100 1.05 11 16 59 Slag k 20th 100 1.20 7th 8th 35 Slag 1 5 100 0.80 3 k 35 Slag 2 5 100 W * 5 1 12th Slag 3 5 100 2.10 0 Slag k 5 100 2.40 0

The values in Tables A and C show that sulphate slag cement from blast furnace slag 1 has a higher compressive strength and surface hardness than sulphate slag cement from blast furnace slag 2-k and as blast furnace cement A and also has a higher final strength than Portland cement A.

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Example I I

The tests described in Example I were carried out with sulphate slag cements, produced from blast furnace slag I, which was ground to different values of the specific surface area, repeated. The determined Values are given in Table D.

TABLE D.

Blaine value τ - R.F. Depth of penetration Compressive strength 7 T MPa 28 T mVkg ⁰ C % mm 16 33 7 days " 3 T 30th 45 250 20th 100 1, 00 15th 46 52 400 20th 100 0.85 15th 8th 30th 530 20th 100 0.20 31 12th 40 250 5 100 2.10 0 16 59 400 5 100 1.50 0 530 5 100 0.30 3

From the values in Table D it can be seen that the compressive strength and the surface hardness are much lower if the specific surface area is below the set minimum limit.

Example 111

The tests described in Example I were carried out with sulphate slag cement, " made from blast furnace slag 1 up to a specific Surface of 530 m / kg was ground, and repeated with the comparison cements, but the setting was carried out at a lower relative humidity.

The values determined are given in Table E.

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TABLE E.

cement T
° C RF
% Penetration depth
mm Pressure resistant! Gkei 7 T t MPa Sulphate huts 20th 7 days 3 T 48 28 T Blast furnace A 20th 60 0.25 ' 33 20th 55 Port country A. 20th 60 0.75 12th 24 36 60 0.30 18th 40

From the values in Table E it can be seen that the favorable properties of the present sulphate slag cement in relation to the comparison cements stand out even more if the hardening is at a lower relative Moisture is carried out »

Example IV

The one in example! The tests described were carried out with sulphate cement,

made from blast furnace slag 1, which has a specific surface area

2
of 530 m / kg was ground, repeated, the effect of the addition of a water-reducing substance being investigated. As a water-reducing substance, Melment L 10 (20% ~ 5% solution of a sulfonated Me.lamine-Formaldehyde resin from SKW, Germany) was added in an amount of 0.6% active substance based on cement. With this addition, less water was needed to get the same consistency. The values found are given in Table F.

TABLE F.

cement T
OC RF
% E indring deep
mm Pressure resistance 1 7 T : MPa Slag I with.
Melment L 10
I slag without
Melment L 10 20th
20 χ -
"\: 100
100 7 days 3 T 55
46 28 T. 0.15
0.20 41
31 71
52

It is clear from the values in Table F that the addition of a water-reducing substance, the compressive strength and surface hardness improved even further.

CONCLUSIONS

1. Sulphate slag cement comprising a finely ground mixture of 78-85% basic blast furnace slag, 10-18% calcium sulphate, calculated as anhydrite, and 1-6% Portland clinker, with the characteristic that the blast furnace slag with the chemical composition 30-45% CaO, 10 -20% Al 0, 3-20% MgO, and 25-45% Si0_, where the slag _{composition is converted to Ca0 + Al 2} 0- + Mg0 + Si0 = 100%, and a ratio of hexavalent to tetravalent coordinated cations is sufficient of 0.30-0.50, and the specific surface area of the ground slag is greater than 450 m / kg according to Blaine and / or the sieve residue of the ground slag on a sieve with a mesh size of 15 μm is less than 60%.

2. Sulphate slag cement according to Corollary 1, with the indication that the Cement contains 1-4% Portland clinker.

3. Sulphate slag cement according to Corollary 1-2, marked that the

2 specific surface area of the ground slag is 500-550 m / kg.

4. · Ready-to-use mortar or ready-to-use concrete, with the mark that a sulphate cement according to conclusions 1-3 with water and the usual aggregates to a paste with a suitable consistency is turned on.

5. Ready-to-use mortar or ready-to-use concrete according to the inference with the label that water-reducing substances have also been added to it are.

6. Ready-to-use mortar or ready-to-use concrete according to conclusion 5

with the label that the water-reducing substances in a concentration of 0.1-5% active substance based on the sulphate cement.

7. Working method for processing mortar or concrete according to the inference 4-6 with the indication that after bringing the Mortar or concrete an aftertreatment with a substance of a low level Permeability for carbon dioxide is carried out.

8. Working method according to Corollary 7 with the indication that the substance

which has a low permeability to carbon dioxide, in an amount of

2
5-100 g / m 2 is applied.

Claims (8)

Expectations (1. Sulphate cement, which comprises a finely ground mixture of 78 - 85% basic blast furnace slag, 10 - 18% calcium sulphate, calculated as anhydrite, and 1 - 6% Portland clinker, characterized in that the chemical composition of the blast furnace slag is 30 - 45% CaO, 10-20% Al ₂ O ₃ , 3-20% MgO and 25-45% SiO ₂ in such a way that the respective percentages add up to 100%, and that the blast furnace slag has hexavalent and tetravalent coordinated cations which are in a ratio of 0.3-0.5 to each other, and that the specific surface area of the ground slag is greater than 450 m² / kg according to Blaine and / or the sieve residue of the ground slag on a sieve with a mesh size of 15 / µm is less than 60% is. 2. Sulphate slag cement according to claim 1, characterized in that that it contains 1 - 4% Portland clinker. 3. Sulphate slag cement according to claim 1 or 2, characterized in that the specific surface of the ground slag 500 -. 550 qm / kg. J / 2 4. Ready-to-use mortar or concrete, characterized in that a sulphate cement according to one or several of claims' 1 to 3 with water and the usual additives to a pulp with a suitable consistency. 5. mortar or concrete according to claim 4, characterized in that water-reducing substances are added to it. 6. mortar or concrete according to claim 5, characterized in that that the water-reducing substances in a concentration of 0.1 to 5% active substance related to the sulphate cement are added. 7. A method for processing mortar or concrete according to one or more of claims 4 to 6, characterized in that that especially after the molding of the mortar or concrete, a post-treatment with a substance, the one has low permeability to carbon dioxide. 8. The method according to claim 7, characterized in that the substance having a low permeability for carbon dioxide has to be applied in an amount of 5-100 g / m2. - Description -