DE3040077C2 - Dry plaster mortar and its use - Google Patents

Description

The invention relates to a hydraulically setting, machine-applicable dry plastering mortar which, when mixed with water, serves to fix and externally cover insulation layers and insulation boards on building walls and building ceilings, whereby the insertion of a glass fibre fabric is omitted, and which contains a hydraulic binder, aggregate and conventional additives.

Plastering compounds made from a hydraulically setting binding agent with plastic components and pure plastic compounds for application to insulation boards are known. For example, DE-OS 25 16 916 refers to the state of the art for external wall insulation in which grooved rigid foam plastic boards are attached to a wall using mortar made from cement and plastic components and the outside of which is covered with a layer of plaster that also contains cement and plastic components. One problem with such a multi-layer wall covering is the different shrinkage characteristics of the insulation boards, which are preferably made from polystyrene or polyurethane rigid foam, compared to the plaster coating. The different shrinkage of the materials easily leads to cracking and detachment of the coating, which impairs the durability and thermal insulation properties of the wall covering. According to DE-OS 25 16 916, this disadvantage is to be eliminated by rigid foam boards with limited shrinkage characteristics and a reduced plastic content in the plaster layer. However, these measures alone do not lead to the desired result. It is therefore recommended to embed a glass fibre mesh in the plaster layer. However, this measure requires more work because the mesh must be fixed precisely.

DE-AS 27 03 342 refers to thermal insulation boards made of polystyrene or polyurethane base with a grid-reinforced filler or plaster mortar coating.

First, a plastic-modified mortar is spread onto the insulation board and then a mesh fabric is applied in a subsequent step. To improve the elastic properties of the mortar, the addition of plastic fibers, such as polyacrylonitrile, polyester, polyethylene, polyvinyl chloride or polyacrylate fibers, with a length of 0.8 mm to 2 mm is recommended.

Practical experience with the above-mentioned thermal insulation systems has shown that plastering thermal insulation panels without an inserted mesh does not lead to satisfactory, crack-free, non-detaching and durable thermal insulation. On the other hand, however, the use of a mesh has disadvantages for the thermal insulation systems. On the one hand, the insertion of a mesh requires an additional work step which, unlike plastering the thermal insulation panels themselves, cannot be carried out mechanically, and is therefore labor-intensive and costly. The mesh must be embedded in the plaster at a well-defined depth, the consistency of which must also be precisely adjusted at this point. Laying a mesh therefore requires the work of experienced specialists. In addition, a mesh in the finished plaster layer does not only have beneficial effects. A fine-mesh mesh, for example, acts as a mesh sieve on which coarse-grained aggregates and water collect when laying and applying further layers of plaster. This can prevent the formation of a homogeneous plaster layer and thus impair the durability and strength of the plaster.

On the other hand, a coarse-meshed mesh does not achieve the desired crack compensation. After all, only a limited layer thickness of up to 5 mm can be achieved with the known plastering compounds and systems, although larger layer thicknesses are practical and desirable in many cases.

In the magazine "Das Baugewerbe" (1971), issue 9, pages 787 to 790, and in the textbook Wendehorst, Baustoffkunde (1975), pages 327 to 337, various additives for plaster and masonry mortar are listed.

DE-OS 26 22 465 describes hydraulically setting compounds reinforced with glass fibers. According to DE-OS 29 14 410, it is known to mechanically provide rigid bodies, in particular pipes, with a corrosion and mechanical protection layer made of a hydraulically setting compound containing glass fibers. A coating on one or both sides of plastic panels, also mentioned in this context, has different adhesion and rapid hardening properties than a plaster used for insulation panels.

The object of the invention is to create a dry plaster mortar of the type mentioned at the outset which sets hydraulically with water and which achieves a strong internal cohesion of the set mass with a high level of tear-off resistance without the need for fabric inserts, whereby this property makes it possible to apply thicker coatings to insulation layers or insulation boards in one operation, i.e. in a labor-saving manner, by machine.

This task is solved with a dry plaster mortar of the type mentioned above in that it contains cut alkali-resistant glass fibers with a tex number of 20 to 200 g/km and a length of 5 to 33 mm in proportions of 0.3 to 3 vol.%.

The fibers can be uniform or different

lengths. They are used in particular in the form of chips with a minimum length, i.e. not shorter than 5 mm. A fibre length of more than 33 mm impairs processability and is therefore not recommended.

Sand and filler are preferably added with a true density of more than 0.1 g/cm3 in ratios to the hydraulic binder of 1:1 to 10:1 by volume.

The sand can consist of natural and/or synthetic products.

The dry plastering mortar can be mixed with water and used as a base coat, the latter optionally being provided with a surface structure.

The dry plaster mortar can also be mixed with water and used as a single-layer plaster.

The hydraulic binder of the dry plaster mortar can be modified with natural or synthetic materials.

To improve the processability in the mixed state, a proportion of air-entraining agents and/or liquefiers and/or cellulose ethers can be used.

To improve the adhesion, a proportion of polymeric compounds and/or cellulose ethers and/or polyvinyl acetate and/or polyvinyl alcohol and/or starch derivatives and/or protein derivatives is preferably provided.

To improve the extensibility, a proportion of polymeric compounds and/or rubber derivatives and/or air entraining agents and/or cellulose ethers and/or polyvinyl acetate and/or polyvinyl alcohol and/or starch derivatives and/or protein derivatives can be used.

Other ingredients can reduce the change in shape due to the effects of weather and moisture, namely sand and/or fillers and/or swelling components and/or polymeric compounds and/or hydrated lime.

Finally, the dry plastering mortar preferably contains a proportion of dry stabilizers, namely sand and/or fillers with a defined grading curve and/or polymeric compounds.

In addition to the components mentioned, the dry plaster mortar may also contain hardening accelerators and/or water-repellent and/or frost-resistance-increasing agents.

Hardening accelerators for Portland cement are, for example, high-alumina cement, CaCl[deep]2, C[deep]11A[deep]7 times point CaF[deep]2, C[deep]12A[deep]7, CA, sulfates and similar substances.

Examples of water-repellent substances include silicones, paraffins and other commercially available products.

Examples of agents that increase frost resistance include air pore depth, sealants and liquefiers.

The dry plaster mortar can also be coloured by adding pigments.

It was surprisingly found that an excellent coating can be produced using a dry plaster mortar of the composition mentioned, which can be optimally adapted to the respective requirements by appropriate selection of the components and their proportions. It has been shown that proportions of additives of up to 2% by weight to improve workability, up to 5% by weight to improve adhesion and up to 10% by weight to improve elasticity are particularly suitable.

The results achieved with the dry plaster mortar according to the invention are unexpected.

The mixture that forms the dry mortar is uniform and stable in its structure, so that it does not separate, even during transport, for example. But it is not only stable as a dry mass, but also when mixed with water and ready for processing. This means that the wet mass does not separate either, regardless of whether it is prepared for mechanical or manual processing. This advantageous property has an effect on the processing of the mass and ensures that after mixing with water a uniform plastering mass can be applied either mechanically or manually. The mixed mass is applied using pressure, and in the process fiber tips and with them also mass are pressed into the surface of the substrate to be plastered. It produces a hydraulically set, non-flammable, weather-resistant coating, the texture of which is characterized by an arrangement of fibers in all directions, whereby at least some of the fibers can dig into the insulation layer or insulation board serving as the substrate during application, thus further improving the cohesion of the layers.

After setting with water, the dry plaster mortar forms a closed, crack-free, flat and joint-covering shell, which not only makes fabric superfluous, but is superior to a fabric coating. The set plaster mass forms an integral bond with the insulation layer or insulation board, which can be further improved by structured interfaces if necessary. The rigid shell adheres in a practically springy manner to the yielding substrate, which may consist of a foamed plastic, for example. This kind of springy support reduces tension and reduces the risk of cracks forming.

Numerous experiments have confirmed the above results.

A particular advantage of the dry plaster mortar according to the invention is that it can be used to produce significantly thicker coatings than with conventional coating materials with mesh reinforcement. The fibers distributed over the entire cross-section and the greater layer thickness lead to higher impact resistance and greater fire safety.

It is also possible to anchor the plaster layer directly to the load-bearing substrate. To do this, anchors are used, for example made of steel, with the appropriate shear and buckling strength and length, which can protrude through the plaster layer and the insulation layer into the substrate.

The dry plastering mortar according to the invention can be adjusted without difficulty so that it can be applied in one operation after mixing with water using conventional plastering machines or by hand. It can be used as a base coat or as a single-layer plaster. It is not difficult to provide the mass with an ornamental or functional surface structure.

The invention is explained in more detail using three examples.

The quantities refer to 100 kg dry matter.

The specified ingredients were mixed together in conventional dry mixers. The ingredients that are added in less than 2% by weight can be mixed together in a premixing step if necessary. Fillers can be added to the premix if necessary. Mixing in batches is preferred.

example 1

The following ingredients were mixed together:

1. Plaster and masonry binder according to DIN 4211 30 kg

2. Filler 4 kg

3. Sand 62 kg

4. alkali-resistant glass fibres,

24 mm long 1 kg

12 mm long 1 kg

5. Polyvinyl acetate 2 kg

______

Dry mass 100 kg

The mixture was homogeneous and the mass did not separate during transport in the dry state or after the addition of water. It was easy to work with once mixed and the finished plaster was uniform.

The dry mass was mechanically mixed with 16 kg of water. This resulted in a bulk density of about 1.7 g/cm3 and an air void content of about 25%. After 28 days, the following strengths were achieved:

Compressive strength 10 N/mm[high]2

Bending tensile strength 6 N/mm[high]2

Example 2

The following ingredients were mixed together:

1. Portland cement 35[high]F according to DIN 1164 10 kg

2. Filler 20 kg

3. Sand 66 kg

4. alkali-resistant glass fibres,

18 mm long 1.50 kg

5. Casein 2.00 kg

6. Cellulose ether 0.40 kg

7. Air entraining agent 0.01 kg

8. Melamine resin powder 0.09kg

______

Dry mass 100.00 kg

The mixture was homogeneous and the mass did not separate during transport in the dry state or after the addition of water. It was easy to work with once mixed and the finished plaster was uniform.

The dry mass was mechanically mixed with 16 kg of water. This resulted in a bulk density of about 1.6 g/cm3 and an air void content of about 24%. After 28 days, the following strengths were achieved:

Compressive strength 6 N/mm[high]2

Bending tensile strength 4 N/mm[high]2

Example 3

The following ingredients were mixed together:

1. Plaster and masonry binder according to DIN 4211 18 kg

2. technical lime hydrate 8 kg

3. Sand 69 kg

4. alkali-resistant glass fibres,

12 mm long 1.50 kg

5. Polyvinyl alcohol 1.00 kg

6. Polyvinyl acetate 2.20 kg

7. Cellulose ether 0.27 kg

8. Air entraining agent 0.01 kg

9. Starch derivative 0.02 kg

______

Dry mass 100.00 kg

The mixture was homogeneous and the mass separated again during transport in the dry state even after water was added and the finished plaster was uniform. The dry mass was mixed mechanically with 15 kg of water. This resulted in a bulk density of about 1.5 g/cm3 and an air pore content of about 27%. After 28 days, the following strengths were achieved:

Compressive strength 4.5 N/mm[high]2

Bending tensile strength 2.5 N/mm[high]2

Claims (4)

1. Hydraulically setting, machine-applied dry plastering mortar which, when mixed with water, is used for fixing and externally covering insulation layers and insulation boards on building walls and ceilings, whereby the insertion of a glass fibre fabric is not necessary, and which contains a hydraulic binder, aggregate and conventional additives, characterized in that it contains cut alkali-resistant glass fibres with a tex number of 20 to 200 g/km and a length of 5 to 33 mm in proportions of 0.3 to 3 vol.%. 2. Dry plastering mortar according to claim 1, characterized in that it contains sand and filler with a pure density of more than 0.1 g/cm3 in ratios to the hydraulic binder of 1:1 to 1:10 by volume. 3. Use of a water-mixed dry plaster mortar according to claim 1 or 2 as a base coat, which is optionally provided with a surface structure. 4. Use of a water-mixed dry plaster mortar according to claim 1 or 2 as a single-layer plaster.