NL8003818A - Sulphated cement and ready-to-use mortar or ready-to-use concrete. - Google Patents

Description

i *

• vo 'IOO

Sulphated cement and ready-to-use mortar or ready-to-use concrete.

Traditional cement manufacturing, including Portland cement, uses very large amounts of natural raw materials, such as marl, limestone and clay. There is a growing awareness that unlimited progress along this path, seen regionally, ultimately leads to depletion of natural resources and to an undesirable change in nature.

In industrialized countries, there is an increasing need to achieve a meaningful application of industrial waste products, rather than environmentally damaging land or water deposits.

10 Sometimes the use of industrial waste or by-products can mean a reduction in the cement cost price, for example because less energy is required.

For this reason, cement production increasingly uses by-products from other industries, such as granulated 13 blast furnace slag. The latter does not in itself have any cementing properties, but must be activated with an alkaline substance in order to obtain a cement suitable for practical application.

It is thus known to prepare blast furnace cement by grinding granulated basic blast furnace slag and Portland clinker together or separately and mixing intimately. However, this requires quite a lot of Portland clinker in practice, namely about 20-75 # (all percentages as mentioned herein are weight percentages).

In contrast, for another type of cement, the so-called sulfated cement, only 1-6 # of Portland clinker is required in addition to T8-853 basic blast furnace slag and 10-18 # of calcium sulfate. This calcium sulphate occurs as gypsum stone, but is also released as a by-product or waste product in the chemical industry, such as in the production of hydrofluoric acid and phosphoric acid or in the flue gas desulphurisation of coal-fired power plants.

By far the most important applications of cement are in concrete 30 and mortar. However, sulphated cement has a number of important drawbacks, so that its practical application has so far been very limited. A first drawback is the dusting or "sanding" of the outer skin of the hardening concrete or the hardening mortar. So a soft surface layer is created. This is due to the action of Q 8003818 -2-ft carbon dioxide from the air, which degrades the alkaline environment formed by the Portland clinker, resulting in the finely ground slag. is no longer activated and thus remains unhydrated. Consequently, no or only insufficient binding takes place, with the result that the outer skin is changed. Sanding during the hydration of cement can be prevented in concrete structures by closing off the concrete from the outside air during that period, for example by keeping it under water, while also formwork will impede the supply of carbon dioxide. However, it is not always possible to flood it and keeping it in form for a long time is often not economically attractive. The latter aspect also has to do with a second disadvantage of sulphated. cement, namely that the pavement proceeds slowly, especially at low temperature.

It has now been found that the disadvantages of sulphated cement described above can be substantially avoided if the blast furnace slag corresponds to the chemical composition 30-b ^% CaO, 10-201 AlgO ^, 3-20 $ MgO and 25- ^ 5 $ SiOg, where the slag composition is converted to CaO + AlgO ^ + MgO + SiOg = 100 $, and has a ratio of six-fold to four-fold coordinated cations of 0.30-0.50, and the specific surface of the ground slag is greater than ^ 50 m / kg according to Blaine and / or the screen residue of the ground slag on a sieve with a mesh width of 15 µm is less than 60%.

According to the invention, therefore, it is important to choose the macroscopic chemical composition as well as the ratio of the sixfold to fourfold coordinated cations of the blast furnace slag in the manner indicated, and further to grind the slag relatively finely. Blast furnace slag with the same macroscopic chemical composition can have a completely different hydraulic system. It is therefore insufficient to define only the macroscopic chemical composition. It has been found that the present effect is achieved only by a combined application of the above measures, namely accelerated hydration of the slag, even at relatively low temperatures, so that the carbon dioxide from the air has little chance of disturbing the process. Thus, after a short time, a fairly great mechanical strength is already achieved, whereby the negative effect of the carbonation remains limited.

O The basic blast furnace slag must have the above chemical composition and must also have a suitable glass structure 1 8003818 ------------------- -3-, so that the ratio of sixfold to quadruple coordinated cations is 0.3-0.50. The basic blast furnace slag used may additionally contain small amounts of other components which are often found in slag, such as iron oxide, titanium dioxide and alkali metal oxides, without this substantially affecting the intended effect.

As a calcium sulfate source, anhydrite is preferably used in practice, which naturally occurs or is released in the manufacture of fluoro-hydrogen from fluorspar. It is also possible to use plaster from a natural or chemical source. The calcium sulfate used should only contain very small amounts of highly soluble phosphates and fluorides, as these can seriously slow the reaction of water with sulfated cement. Also, the calcium sulfate should not react acidically after grinding.

To prepare the present sulfated cement, the slag is ground alone or together with one or both other components in a suitable mill, for example a ball mill, to the required fineness, preferably even so fine that the specific surface area of the slag is 500-550 m / kg. If the slag is ground separately, the gypsum and / or the anhydrite and the Portland clinker, whether or not ground, are subsequently mixed with the ground slag and the resulting mixture is optionally ground again. The specific surface of the gypsum and / or the anhydrite and of the Portland clinker is of less importance. This will generally range from 200 to 800 m / kg. Preferably, however, the clinker will have a specific surface area greater than

O

400 m / kg. The optimal amount of Portland clinker is 1-4 $, because then the strength development of the hardening mortar or the hardening concrete is the fastest and the ultimate compressive strength is the greatest. The optimum should be determined experimentally for each snail. In addition to blast furnace slag, calcium sulfate and Portland clinker, the cement may also contain the usual grinding aids, fly ash and pigments.

The present sulfated cement is prepared with water and the usual additives such as sand, gravel, etc. and mixed into a ready-to-use mortar or ready-to-use concrete of the consistency suitable for processing. During the preparation, during transport or just before use, all kinds of auxiliary substances, additives, fibers such as glass fiber, etc. can be introduced in order to achieve certain effects.

Thus, water reducing agents, such as super-Q plasticizers, can be added upon registration. Examples thereof are sulfonated melamine-formaldehyde resins, sulfonated naphthalene formaldehyde resins I and refined lignin sulfonate. These substances are

* 80Ö381S

♦ You

-4- usually added from aqueous solution at a concentration of 0.1-5 # active agent, based on the sulfated cement. By using such materials, the same commercialization of the mortar or concrete can be achieved with up to 50% less water, whereby the hardening takes place faster and a higher mechanical strength can be achieved. This reduces the risk of sanding even further.

The processed mortar or processed concrete can also be post-treated with substances, so-called "curing compounds", which prevent the water from evaporating too quickly from the hardening mixture, so that the strength would not further increase, and which also has a low permeability. for carbon dioxide. Such materials can be, for example, epoxy resins and are preferably applied in an amount of 5-100 g / m 2. The use of these materials results in a high final strength and an even higher hardness of the surface layer.

After the mortar or concrete has been processed and cured, a material with excellent surface hardness and high mechanical strength is obtained, as much in pressure as in bending.

The invention is now further elucidated by means of the following examples.

Example I

The mechanical strength test was carried out in accordance with the Dutch standard NEN 3072. Sand cement mortar (3: 1) - prisms of 4 x 4 x 16 cm - stored 1 day at 20 ° C and covered with plastic foil, stripped and then under water stored at 20 ° C. In addition, tests were carried out at 5 ° C to check the influence of the temperature during the curing.

To determine the thickness of the soft surface layer, a method designed by T. Tanaka, T. Sakai and I. Yamane was used, which is described in the journal Zement-Kalk-Gips 2 (1958), pp. 50-55, under the title "Zusammensetzung Japanischer Hochofenschlacken fur Sulfat-hüttenzemente." The surface hardness test specimens were prepared as described under the mechanical strength test.

In order to approximate the practical conditions as much as possible, they were removed from the mold after 35 days and then stored in the air at 20 or 5 ° C.

The reference cements used were the very widely used 800 3 8 18 i-* -5 cement types high-cement A and Portland cement A in the Netherlands. These cements are described in the Dutch standard NEN 3550.

The values found for these cements are shown in Table A.

TABLE A

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

cement type temperature R.V. penetration depth compressive strength MPa ° C% mm 7 days 3 d 7 d 28 d 10 blast furnace A 20 100 0.60 17 27 ^ 3 portland A 2Q 100 0.25 21 31 blast furnace A 5 IOO 0.95 2 1¾. 31 portland A 5 100 0.35 10 20 39

The sulphated cements examined all consisted of 83? basic 15 blast furnace slag, 15? calcium sulfate and 2? portland vowel. The blast furnace slag used was slag with the composition listed in Table B.

•

TABLE B

Basic blast furnace slag composition: Ca0 + Al203 + Mg0 + Si02 * 100? slag CaO JÜ.g03 MgO SiOg * £ Me6 + / ^ Me ^ + 20 blast furnace slag 1 38 ^ 12 35 0.38 blast furnace slag 2 b $ ^ 1 »37 0.25 blast furnace slag 3 U2 g 9 Onion 0.52 blast furnace slag k 38 ^ 13 0.60 é ^ Me ^ + / <£ Me ^ + ratio of six-fold to four-fold coordinated cations.

Snail 1 fulfills the specified conditions with regard to chemical composition and coordination

Snail 2 fulfills the stipulated condition with regard to the chemical composition 8003818-6 but does not meet that with regard to coordination Snail 3 does not meet either of the two stipulated conditions Snail 1 * is chemically virtually identical to snail 1, but satisfies not subject to the stipulated condition with regard to the. coordination.

The values found for these sulphated cements are shown in Table C.

TABLE C

Mechanical strength and depth of penetration of sulphated cement with a specific surface area of the ground slag «of 530 ar / kg and a screen residue of the ground slag on a screen of 15 µm less than 60%,

Snail T R.V. penetration depth compressive strength MPa ° C * _3 d- Td. 28 d. Snail 1 20 100 0.20 31 U6 52 15 snail 2 20 100 0.55 18 31 Ul snail 3 20 1Q0 1.05 11 15 20 snail k 20 100 1.20 7 lU 20 snail 1 5 100 0.80 3 16 59 snail 2 5 100 1.1 * 5 1 8 35 20 snail 3 5 100 2.10 0 k 35 snail 1 * 5 100 2, U0 0 1 * 12

The values in Tables A and C show that sulphated cement from blast furnace slag 1 has a higher compressive strength and surface hardness than sulphated cement from blast furnace slag 2-U and then blast furnace cement A 25 and also has a higher final compressive strength than Portland cement A. Example II

The tests described in Example I were repeated with sulfated waxed cements made from blast furnace slag 1 / ground to different values of the specific surface. The values found are spring-30 given in Table D.

8003818 * -τ-

TABLE D

Blaine sailed Γ H.V. Penetration depth compressive strength MPa 2 am 1 1 m / kg ° C * T days 3d. T d. 28 d.

250 20 100 1.00 15 16 33 400 20 100 0.85 15 30 45 5 530 20 100 0.20 31 46 52 250 5 100 2.10 0 8 30 400 5 100 1.50 0 12 40 530 5 100 0 , 80 3 16 §9

The values in table D show that the compressive strength and the surface hardness are considerably lower when the specific surface is below the set minimum limit.

Example III

The tests described in example I were repeated with nitrous furnace slag 1, which had been sulfated cement, / ground to

O

15 a specific surface area of 530 m '/ kg, and with the reference cements, but. the hardening was carried out at a lower relative humidity.

The values found are shown in table E.

TABLE E

cement T R.V. Penetration depth _ compressive strength MPa _ ° C? T days 3 d. ? d. 28 d.

20 sulphated 20 0.25 33 48 55 blast furnace A 20 0.75 12 20 36 portland A 20 0.30 13 24 40

The advantages in Table E show that the favorable properties of the present sulphated cement relative to the reference cements manifest themselves even more strongly when the hardening is carried out at a lower relative humidity.

80038 18% -8-

Example IV

The tests described in Example 1 required repeated freshly sulfated wax cement made from blast furnace slag 1 / ground to a specific surface area of 530 m2 / kg, investigating the effect of the addition of a water reducing agent. Melment L 10 (20% solution of a sulphonated melamine formaldehyde resin from S.K.W., Federal Republic of Germany) was added as water reducing agent in an amount of 0.6%, based on the cement. This addition required less water to be used to achieve the same consistency. The values found are shown in Table F.

TABLE F

cement T R.V. penetration depth compressive strength MPa

O-% IHTB

• 7 days 3 d. 7d. 28 d.

snail 1 with Melment L 10 20 100 0.15 ^ 1 55 71 snail 1 without Melment L 10 20 100 0.20 31 ^ 6 52

It is very clear from the values in Table F that the addition of a water-reducing agent further improves compressive strength and surface hardness. 800 3 8 18

Claims (6)

Sulfated cement comprising a finely ground mixture of 78-85% "basic blast furnace slag, 10-18 calcium sulfate," calculated as anhydrite, and 6% Portland clinker, characterized in that the blast furnace slag conforms to the chemical composition 30- 1 * 5 $ CaO, 10-20 $ AlgO ^, 3-20 $ MgO and 5 25-1 * 5 $ SiOg, with the slag composition converted to CaO + AlgO ^ t • MgO + SiOg = 100 $, and a ratio has six-fold to four-fold coordinated cations from 0.30-0.50, and the specific surface area 2 of the ground slag is greater than 1 * 50 m / kg according to Blaine and / or the screen residue of the ground slag on a sieve with a mesh size of 15 um less than 10 is βθ $. 2. Sulfated cement according to claim 1, characterized in that the cement contains 1-1 * Portland clinker. Sulphated cement according to claims 1-3, characterized in that 2 the specific surface area of the ground slag is 500-550 m / kg. 15 1 *. Ready-to-use mortar or ready-to-use concrete, characterized in that a sulphated cement according to claims 1-3 is mixed with water and the usual additives to a slurry of suitable consistency. . Ready-to-use mortar or ready-to-use concrete according to claim 1 *, characterized in that water-reducing substances are also added thereto. Ready-to-use mortar or ready-to-use concrete according to claim 5, characterized in that the water-reducing substances are added in a concentration of 0.1-5% active substance, based on the sulphated cement. Method for processing mortar or concrete according to claims 1 * -6, characterized in that after the morph or concrete has been brought into the desired shape, a post-treatment is carried out with a substance which has a low permeability to carbon dioxide. A method according to claim 7, characterized in that the material having a low permeability to carbon dioxide is applied in an amount of 5-100 g / m 2. o 80038 18 I