CS203964B2 - Concrete mixture for fair-face concrete - Google Patents

Description

CZECHOSLOVAK SOCIALIST REPUBLIC (18) DESCRIPTION OF THE INVENTION 203964 (11) (B2) (22) Registered 02 11 71 (21) (PV 7701-71) (51) Int. Cl? C 04 B 31/02 C 04 B 13/00 (32) (31) (33) Priority from 06 11 70 (P 20 54 569.1) Federal Republic of Germany 0tA0 FOR INVENTIONS AND OB1P / Y (40) Published 30 06 80 (45) Released 15 10 83 {72) (73)

Author of the Invention JAKLIN HANS, TRIER (NSR) and Patent Owner (54) Concrete Mixture for Concrete 1

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete concrete mix for prefabricated concrete and on-site concrete.

The term "concrete" is understood to mean a housing which remains visible after completion of construction. It does not matter whether the concrete surface is sufficiently machined or remains unworked. It is known that the production of exposed concrete should be taken into account more frequently than in the case of filling and construction concrete. So far, in the case of structural concrete, it is primarily the strength and impermeability of the water that must be visible, besides these properties, the surface, color and surface appearance of the aesthetic requirements must also be beautiful. formwork, porous surface, rough surface and the like. Even after finishing the concrete body, other defects such as efflorescence, rust stains, fine and later coarse cracks and other defects may appear.

The emergence of these defects can be partially prevented by the selection of used aggregates in terms of purification, shape and surface structure and their grain composition. The mixing ratio of aggregates and aggregates to cement and water ratios is of decisive importance for the workability of the mixture and the quality of the exposed concrete. Recently, various formulations have been developed for exposed concrete, for example, from rough or planed wood panels, smooth plywood panels, rubber-coated panels or plastic materials, metal plates, and the like. However, even the use of these special formwork does not preclude the occurrence of certain defects in the unprocessed visible surfaces of the finished concrete. It is not possible to make any concrete concrete bodies with a completely smooth surface and uniform color. Consequently, the visible surface of the sighting concrete requires almost always additional processing to improve their appearance. It is necessary to fill in the broken edges and corners and additionally fill the air bubble pores between the concrete and the formwork and the wells in the surface of the concrete. It is often necessary to apply a coating to achieve a uniform appearance of exposed concrete. Each coat must be preceded by a pre-treatment of the surface-coated concrete to keep the coatings firmly on the screeds occasionally needs to be renewed. The cost of these modifications is particularly high in high-rise buildings with a glazing facade, as scaffolding must be built.

These defects can be partially removed by exposing the aggregates on the surface of the visual concrete. However, the cost of producing such eroded concrete surfaces, in particular the cost of draining, spying, and grinding, and particularly for grinding and polishing the visible surface of concrete, is very high. The purpose of the invention is to improve the composition of the visible concrete to have a uniform, non-stained and uniform surface that does not require additional processing. In this case, the concrete according to the invention is also particularly suitable for the production of building bodies of complex construction made on site.

SUMMARY OF THE INVENTION The present invention is based on the fact that the concrete composition, which consists of sand, gravel, hydraulic binder and optionally other customary components, comprises fine-grained silicas or fine-grained silicates of aluminum, calcium, magnesium, bariane, and the like. zinc or mixtures thereof with a specific surface area of 15 to 300 m 2 / g, of which at least 75% of the particles are less than 40 µm, in an amount of 0.5 to 10 wt. % refers to the weight of the hydraulic binder, in particular to the cement.

For example, the concrete composition of the present invention may contain 1 to 6 wt. % of silicas and / or silicates. The added amount of this material depends largely on the surface area of the grain size of the fine aggregate. The more fine the aggregate, the less silicas or silicates needed to achieve the uniform surface of the visible concrete. For example, if 8 to 15% of sand with a grain size of less than 4.8 mm is replaced by quartz flour or fly ash from electrostatic filters having a grain size of 0-0.2 mm, silicic acid or silicates may be added according to the invention. down to 1-2 wt. % cement. Adding 4-6 wt. % of silicic acid or silicates has a particularly bright colored surface, which reduces the addition of white pigments. When using steel shuttering to convert pre-fabricated structural concrete components, it is not more than 4 wt. % of the metal surface of the shuttering should be painted. This also applies when the steel sheet formwork is severely scratched by repeated use.

For example, fine-grained silicas can be prepared in a known manner from sodium silicate by precipitation with sulfuric acid. Fine-grained silicates can be obtained, for example, by precipitation of aluminum, magnesium or calcium salts with a water glass. Numerical data of a specific surface, referred to in the description, relate to a BET methographic measurement called Brunauer,

Emmett and Teller (J. Amer. Chem. Soc. 60,309, 1938 J. The use of the composition of the invention does not depend too much on the upper specific surface area of the silica used. The separation of the silica-containing concrete mixture consumes however, the ratio of water to cement is somewhat higher than that of conventional concrete mixes to render visible concrete, but this has no harmful consequences. which usually causes difficulty, particularly in the preparation of narrow pillars of at least one-wall or extensively articulated components, and the stripping is facilitated since the sharp corners and edges cannot be so easily damaged. Acid-silicates added and silicates act on the concrete mix by a homogenizing effect, and a good distribution of cement paints and other additives is made, so that the concrete surfaces produced have a uniform appearance. Other compositions, for example lignin sulphonate-based plasticizers or hydroxyacid complexes, may be added to the concrete composition of the present invention to provide a particularly well formed concrete mixture for highly structured irregular structures. Further, concrete retarders can be added if a break is made between the preparation of the concrete mixture and its processing, for example forced by concrete. Polystyrene foam particles may also be added to the concrete mixture if the exposed concrete body is also to be used for thermal insulation or to reduce the weight of the finished building material. Of course, other conventional additives and aggregates, such as aggregates common in the manufacture of lightweight concrete, such as pumice gravel, can also be added to the concrete mixture according to the invention. The concrete compositions of the present invention can be used to produce viscous concrete bodies having a perfect surface that does not require further processing, such as coatings, plastering or grinding, and the like. The enclosed, homogeneous surface of the concrete prevents the ingress of water and also prevents dust and other impurities from sticking, so that it is washed by rain and retains its perfect appearance for a long time.

Comparative experiments with pyrogenic silicic acid

The experiments were carried out according to the test conditions given by the standard, only the degree of dissolution was set for all mixtures at 115—120 mm, because the mortar with the addition of 2% pyrogenic silica Cab — O — Silo spillage of 180 mm according to the standard should have a water factor of 0, 7 and higher, which almost always gives rise to cracks in the tests - 203964 of them samples, so testing the strength of the nonsense. All percentages are in%.

The pyrogenic silicic acid Cab-O-SilM5 used for comparison had a specific surface area of 200-210 m 2 / g, as measured by the BET method, which is still within the spe-

Pyrogenic silicic acidCab — O — Sil M5

Spec. surfaceBET 214 m 2 / g of the fine surface of precipitated silicas.

The material according to the invention was the SM 404 silicate and the wetted KS 300 precipitated wet silica:

Pore volume 0.53 ml / g (nitrogen) wet silicate SM 404 110 m2 / g 0.44 ml / g wet-precipitated silica KS 300 124 m2 / g 0.35 ml / g

Cement: Portland cement A Sand: A 2.4-1.2 mmB 1.2-0.5 mm0.5—0.075 mm

Ratio: cement: sand = 1: 3: letter A: B: C = 1: 1: 1

The following were found: solidification Multi-point tensile strength under compression compression The results are summarized in the following tables.

Table - Solidification test (Vicat needle) Additive in% Consumption relative to water cement in%

Solidification - Hour Start End - 25.2 4.1 5.3 2% SM-404 28.5 4.1 5.2 4% SM-404 31.5 3.1 4.2 2% Cab — O— Sil M5 35.0 3.4 4.7 4% Cab-O-Sil M5 44.8 3.2 4.6 203964

Table - Compression and tensile strength test: Additive in% Water Tensile strength MPa Compressive strength MPa related to cement Factor 3 days 7 days 28 days Change in% 3 days 7 days 28 days Change in% - 0.400 51.9 62.7 70.6 - 344.2 452 510.9 -

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Claims (1)

203964 With all additives, the amount of water added to the mortar increases with increasing amounts of additives. An additional 10% of water is required for the addition of the pyrogenic silicic acid Cab-O-Sil, while, on the other hand, only 3% of the water is added when the same amount of additives according to the invention is added than with the additive alone. There is a close relationship between the amount of water used for the preparation of mortar and concrete mix and strength; with increasing amounts of water the strength decreases. While the wet strength of silicates and silicates precipitated according to the invention is only about 7 to 11%, it is 26 to 30% when using fumed silica. Such a loss in strength can be greatly reduced and hence makes it impossible to use pyrogenic silicas from the improvement of the surface of the mortar and concrete. By adding substances according to the invention, the reduction of strength can be prevented by not adding additional water at all and preparing a somewhat stiffer concrete mixture. At the optimum value of the water coefficient, the strength can be increased. In the case of the use of fumed silicic acid, Cab-O-Sil cannot be carried out, because both these and other fumed silicas induce such thickening of the concrete mixture that additional water must always be added to reduce the strength of the concrete. Additives can adversely affect the use of solidification for concrete. Addition of 2% silicate or fine-grained silica precipitated does not affect the solidification at all and only accelerates solidification on a larger amount. In contrast, the addition of 2% pyrogenic silica-Cab-O-Sil accelerates the solidification of concrete. An article Concrete mix for exposed concrete proprefabricated concrete components and beons produced on site, consisting of sand, gravel, hydraulic binder and other conventional components, characterized in that it contains water-insoluble fine-grained silicas or fine-grained silica aluminum, calcium, magnesium, barium or zinc, or mixtures thereof with a specific surface area of 15 to 300 m 2 / g, of which at least 75 percent of the particles are less than 40 microns, in an amount of 0.5 to 10 percent by weight; % based on the weight of the hydraulic binder, especially cement. Soverografl », n. P., Z A vod 7, Most