METHOD FOR THE APPLICATION OF MINERAL BINDER COMPOSITIONS CONTAINING FIBRES

Abstract

A method for the application of hydrous mineral binder compositions which contain fibres. An aqueous accelerator is mixed with the aqueous binder composition in a mixer shortly before the application. The method is very robust and makes it possible to quickly produce even large moulded bodies having a uniform surface and very good strength development properties.

Claims

1. A method for applying a fiber-containing building material, comprising the steps of providing a hydrous mineral binder composition, at least one aqueous accelerator and fibers, feeding the hydrous mineral binder composition, to a continuous mixer comprising a drive, a mixing region comprising at least one inlet and at least one dynamic mixing element and a conveying region connected to the mixing region and comprising at least one conveying device and an outlet, the hydrous mineral binder composition being conveyed through the at least one inlet into the mixing region, feeding the fibers into the mixing region of the continuous mixer feeding the at least one aqueous accelerator for the setting of the hydrous mineral binder composition into the mixing region of the continuous mixer, mixing the at least one aqueous accelerator with the hydrous mineral binder composition and the fibers in the mixing region of the continuous mixer to give an accelerated fiber-containing mineral binder composition, conveying the accelerated fiber-containing mineral binder composition by means of the conveying device to the outlet, and applying the accelerated fiber-containing mineral binder composition.

2. The method as claimed in claim 1, wherein hydrous mineral binder composition comprises at least one hydraulic binder.

3. The method as claimed in claim 1, wherein the fibers are selected from the group consisting of metal fibers, mineral fibers, natural fibers, and polymeric fibers, and mixtures thereof.

4. The method as claimed in claim 1, wherein the fibers are flexible, having a flexural rigidity of not more than 20 N mm.sup.2, the flexural rigidity in the case of flat fibers being based on the flexural direction requiring the least force for flexure.

5. The method as claimed in claim 1, wherein the fibers a) are round and have a length of 5 mm to 100 mm, and a diameter of 5 m to 500 m to 200 m, or b) are flat and have a length of 5 mm to 100 mm, a width of 5 m to 2 mm, and a height of 5 m to 300 m.

6. The method as claimed in claim 1, wherein one cubic meter of the fiber-containing hydrous mineral binder composition contains 0.4 to 25 liters of fibers, calculated with the apparent density of the fibers.

7. The method as claimed in claim 1, wherein the fiber-containing hydrous mineral binder composition is a fresh mortar having a slump of at least 170 mm, determined according to DIN EN 1015-3 after the raising of the slump cone without lifts of the flow table.

8. The method as claimed in claim 1, wherein the aqueous accelerator comprises at least one compound selected from the group consisting of amino alcohols, alkali metal and alkaline earth metal nitrates, alkali metal and alkaline earth metal nitrites, alkali metal and alkaline earth metal thiocyanates, alkali metal and alkaline earth metal halides, alkali metal and alkaline earth metal carbonates, glycerol, glycerol derivatives, glycols, glycol derivatives, aluminum salts, aluminum hydroxides, alkali metal and alkaline earth metal hydroxides, alkali metal and alkaline earth metal silicates, alkali metal and alkaline earth metal oxides, crystallization nuclei, and mixtures thereof.

9. The method as claimed in claim 1, wherein the aqueous accelerator is metered in an amount in the range from 0.1 to 8 parts by weight, calculated as solid without water, based on 100 parts by weight of mineral binder.

10. The method as claimed in claim 1, wherein the continuous mixer is mounted on a movable printing head.

11. The method as claimed in claim 1, wherein the dynamic mixing element comprises a stirring shaft having stirring elements, the stirring elements taking the form of pegs, and a distance between adjacent stirring elements being at least 40% of the length of the longest fibers.

12. The method as claimed in claim 1, wherein the conveying device takes the form of a screw conveyor having turns, a distance between adjacent turns of the screw conveyor being at least 40% of the length of the longest fibers.

13. The method as claimed in claim 12, wherein the distances between adjacent turns of the screw conveyor are of substantially equal size and/or in that the conveying device comprises two to four turns.

14. The method as claimed in claim 1, wherein the fibers are provided in the hydrous mineral binder composition and/or in that the fibers are fed in the hydrous mineral binder composition to the mixer.

15. A shaped body produced with the method as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0215] Exemplary embodiments of the invention are elucidated in more detail below with reference to the drawing.

[0216] FIG. 1 shows: a schematic illustration of an exemplary mixer.

[0217] Only those elements essential to the direct understanding of the invention have been shown.

[0218] FIG. 1 illustrates an exemplary mixer 1. The mixer 1 has a drive 3 and a drum 2 with a mixing region 10 and a conveying region 11. In the mixing region there is a stirring shaft 4 and two inlets 6; in the conveying region 11 there is a conveying device 5 and an outlet 7.

[0219] In this case, the conveying device 5 is arranged directly adjoining the stirring shaft 4, such that the accelerated mineral binder composition mixed by the stirring shaft 4 can be captured directly by the conveying device 5 and can be conveyed out of the drum 2 through the outlet 7.

[0220] The conveying device 5 in this illustration is configured as a screw conveyor. The screw conveyor in this illustration has two complete turns. Depending on the desired conveying rate, the screw conveyor may have different dimensioning and/or a different configuration. The conveying device 5 and the stirring shaft 4 are arranged on one and the same axis in the drum 2. In this illustration, the stirring shaft 4 is equipped with pegs 8, so that the hydrous binder composition in the drum is moved by the pegs 8 on rotation of the stirring shaft.

[0221] In this illustration there are two inlets 6 arranged on the drum 2. In an alternative variant, not illustrated, however, the drum 2 has only one inlet. In that case, the components to be mixed may already be combined before they are conveyed via the inlet into the drum 2.

[0222] Preference is given to a mixer 1 for mixing the hydrous mineral binder composition with the aqueous accelerator, the mixing region 10 and the conveying region 11 being arranged in one and the same drum 2.

[0223] The stirring shaft 4 and the conveying device 5 are preferably arranged on one and the same axis.

[0224] The dynamic mixing element preferably comprises a stirring shaft 4 having stirring elements 8, the stirring elements 8 taking the form of pegs and a distance between adjacent stirring elements being at least 40%, preferably at least 60%, more preferably at least 80% of the length of the longest fibers. This is particularly advantageous for the mixing of the fibers, the mineral binder composition, and the aqueous accelerator.

[0225] The conveying device 5 takes the form preferably of a screw conveyor with turns, there being a distance 9 between adjacent turns of the screw conveyor that is at least 40%, preferably at least 60%, more preferably at least 80% of the length of the longest fibers.

[0226] This is especially advantageous for conveying the fiber-containing, accelerated, hydrous mineral binder composition.

[0227] It is advantageous, additionally, if the distance between the ends of the stirring elements 8 of the stirring shaft 4 and the inner wall of the drum 2 is at least the same size as the diameter of the largest particles of the filler.

[0228] It is particularly advantageous if the distances 9 between adjacent turns of the screw conveyor are of substantially the same size. The conveying device 5 preferably comprises two to four turns.

[0229] Such mixers are especially well suited to uniform and rapid mixing of the aqueous accelerator, the fibers, and the hydrous mineral binder composition, without the fibers forming lumps or leading to blockages.