QUICK-DRYING BUILDING MATERIAL COMPOSITION BASED ON A MINERAL HYBRID BINDER

Abstract

A quick-drying gypsum composition, in particular for use as gypsum filling compound and for the production of floor coverings, wherein the gypsum composition contains 20 to 70% of a mixture of calcium aluminate and calcium sulfate hemihydrate and/or anhydrite and/or calcium sulfate dihydrate as hydraulic binders and 30 to 80% by weight of fillers, and wherein the weight ratio of calcium aluminate to calcium sulfate hemihydrate and/or anhydrite and/or calcium sulfate dihydrate binders lies in the range from 1:1 to 1:5. Gypsum compositions of this type are characterized by a particularly beneficial shrinkage behavior, such that stresses and cracks in the dried composition can be avoided. At the same time, the gypsum compositions dry to readiness for covering in a time that is compatible with conventional cement filling compounds.

Claims

1. A gypsum composition comprising 20 to 70 wt % of a mixture of calcium aluminate and calcium sulfate hemihydrate and/or anhydrite and/or calcium sulfate dihydrate as hydraulic binders, where the weight ratio of calcium aluminate to calcium sulfate hemihydrate and/or anhydrite and/or calcium sulfate dihydrate binder is in the range from 1:1 to 1:5, and 30 to 80 wt % of fillers, the weight figures being based in each case on the dry weight of the gypsum composition.

2. The gypsum composition as claimed in claim 1, wherein the weight ratio of calcium aluminate to calcium sulfate hemihydrate and/or anhydrite and/or calcium sulfate dihydrate binder is in the range from 1:1.6 to 1:4.

3. The gypsum composition as claimed in claim 1, comprises 20 to 60 wt %, of the mixture of calcium aluminate and calcium sulfate hemihydrate and/or anhydrite and/or calcium sulfate dihydrate binder.

4. The gypsum composition as claimed in claim 1, comprises fillers in the form of sand and calcium carbonate and/or finely ground limestone.

5. The gypsum composition as claimed in claim 1, wherein it has a fillers content of 35 to 75 wt %.

6. The gypsum composition as claimed in claim 1, further comprises a lithium salt.

7. The gypsum composition as claimed in claim 6, comprises lithium salts.

8. The gypsum composition as claimed in claim 1, further comprises tartaric acid and/or a tartaric salt.

9. The gypsum composition as claimed in claim 8, comprises tartaric acid or and/or a tartaric salt in an amount of 0.15 to 0.005 wt %.

10. The gypsum composition as claimed in claim 1, wherein it comprises additional additives selected from plasticizers, thickeners, dyes and/or color pigments, defoamers, stabilizers, curing retarders, and flexibilizing agents.

11. The gypsum composition as claimed in claim 1, wherein on account of its curing it exhibits after 28 days a shrinkage of not more than +/0.5 mm/m when curing takes place at 25 C. and 50% relative humidity.

12. The gypsum composition as claimed in claim 1, wherein on account of its curing it exhibits after 3 hours a shrinkage of not more than +/0.5 mm/m when curing takes place at 25 C. and 50% relative humidity.

13. A method for applying a gypsum filling compound to a substrate, comprising: mixing a gypsum composition as in claim 1 with water to form a fluid or pastelike gypsum composition, applying the fluid of pastelike gypsum composition to a substrate, and curing the composition.

14. A gypsum composition as in claim 1 is applied as gypsum filling compound or screed.

15. A gypsum composition as in claim 1 for producing a floor covering or a floor covering constituent.

Description

EXAMPLES

[0077] The compositions of various formulations are specified in table 1:

TABLE-US-00001 TABLE 1 Constituent Example 1 Example 2 Example 3 Calcium aluminate 10 15 14 Calcium sulfate 26 39 33 hemihydrate Calcium sulfate 1 1 1 dihydrate Calcium carbonate 7 10 10 (2.5 m) Sand (0.1-0.3 mm) 21.54 33.54 27.54 Sand (0.2-0.8 mm) 33 Finely ground 13 limestone Vinnapas 5025 L 1 1 1 Superplasticizer 0.2 0.2 0.2 Lithium carbonate 0.01 0.01 0.01 K/Na tartrate 0.1 0.1 0.1 Foamstar PB 1922 0.1 0.1 0.1 Tylose H 20 P2 0.05 0.05 0.05

[0078] Example 1 here represents a thick-layer application, and examples 2 and 3 thin-layer applications. The examples differ in the binder content and also in the grading curve of the fillers used. All figures in table 1 are in parts by weight.

[0079] The compositions were investigated for their properties. Examinations were made of the compressive strength and flexural tensile strength in accordance with DIN EN 196 Part 1.

[0080] The shrinkage was determined in a method based on DIN EN 13872 on test specimens with dimensions of 1*4*16 cm. In deviation from the standard, which prescribes the deshuttering of the test specimens 24 h after the composition has been mixed with water, the specimens were deshuttered 3 hours after mixing. Thereafter the changes in dimension in the lengthwise direction over time, after curing for a period of between 3 h and 3 d, were ascertained. The curing for this purpose took place at 25 C., in one case at 50% relative humidity and in another case at 75% relative humidity. The values reported in table 2 below were determined as the difference between the maximum of the expansion and the minimum value after 28 days.

[0081] The residual moisture content for different composition was determined by the calcium carbide method with the aid of a CM instrument (manufacturer: Riedel-de-Haen) after one day (24 h) at 25 C. and 75% relative humidity. The determination was made in a method based on DIN 18560 Part 4. In deviation from the CM method described in DIN 18560-4, the measurement value was read off after 5 minutes.

[0082] Recruited additionally, as comparative compositions, were the cement-based compositions SCHNOX ZM Rapid and SCHNOX DE and also the gypsum-based composition SCHNOX AM PLUS. The results of the determination of these parameters are evident from table 2 below:

TABLE-US-00002 TABLE 2 SCHNOX SCHNOX SCHNOX DE ZM Rapid AM-Plus Ex. 1 Ex. 2 Ex. 3 Compressive 1 d 10.0 36.0 12.6 23.4 22.4 21.6 strength 7 d 19.0 46.2 22.0 37.7 34.2 47.9 [N/mm.sup.2] 28 d 24.4 55.6 40.2 49.2 45.1 58.2 Flexural tensile 1 d 3.2 7.0 2.5 4.1 3.9 3.9 strength [N/mm.sup.2] 7 d 6.5 9.7 6.8 8.8 6.1 5.2 28 d 7.6 8.8 12.3 12.3 10.1 10.5 Shrinkage [mm/m] 0.30 0.65 0.25 0.38 0.40 0.20 50% r.h. Shrinkage [mm/m] 0.23 0.45 0.45 0.15 0.09 0.12 75% r.h. Residual moisture content [CM-%] after 24 h at 25 C. and 75% r.h. 3 mm/1 d 5.3 2.4 4.5 3.1 3.9 4.0 10 mm/1 d 7.2 3.7 6.0 3.6 5.0 5.0 20 mm/1 d 8.9 6.7 3.9 40 mm/1 d 10.8 7.8 4.2

[0083] The results of the determination of the shrinkage characteristics over the period from 3 h to 28 d are evident from FIG. 1 (drying at 50% relative humidity) and from FIG. 2 (drying at 75% relative humidity).

[0084] From the data determined it is apparent that the compositions of the invention exhibit rapid drying by comparison with conventional gypsum compositions (SCHNOX AM PLUS) in conjunction with very low shrinkage behavior.

[0085] Relative to cementitious compositions, the compositions of the invention display more rapid drying with comparable shrinkage (SCHNOX DE), or lower shrinkage with comparable drying (SCHNOX ZM RAPID). The binder compositions of the invention are therefore suitable especially for substrate preparation in the floor sector, where the overall working time can be reduced significantly by virtue of the relatively quick curing and drying.