WO2003099467A1

WO2003099467A1 - Method for applying a material comprising a hydraulic binder to undersides of horizontal surfaces and vertical surfaces

Info

Publication number: WO2003099467A1
Application number: PCT/DK2003/000314
Authority: WO
Inventors: Finn Severin Jensen
Original assignee: Densit A/S
Priority date: 2002-05-29
Filing date: 2003-05-14
Publication date: 2003-12-04
Also published as: AU2003229533A1

Abstract

The present invention describes a method for applying cement based material to surfaces (vertical, horizontal and the underside of horizontal surfaces), on a surface structure/topology that normally is not suitable for applying cement based materials or substrates that provide only poor grip for cement based materials. A polymer based intermediate layer with good capability to stick to the substrate is applied on substrate revealing a new rougher surface with a surface structure/topology providing an improved grip for the cement based material layer.

Description

Method for applying a material comprising a hydraulic binder to undersides of horizontal surfaces and vertical surfaces

The present invention describes a method for applying a cement based material to surfaces, especially surfaces on the underside of horizontal objects or vertical surfaces.

When conveying materials in ducts, problems arise when the material has to change direction due to bends or turns in the duct. Here the material, whether it is a fluid or a gas having suspended particles, gets into abrasive and/or erosive contact with the interior surface of the duct in the outside of the bend or turn, whereby a wear situation arises on the inner surface of the duct. If the abrasive effect causes the bend, valve or whatever part in the duct to break or fail, the obvious solution is to replace the failing part with a new part. This means extended down-time for the duct and no improved characteristics of the duct after replacement.

An alternative way of repairing and protecting new constructions against the wear caused by the abrasive effect inside the duct can be by applying a very hard cement based material. For example materials chosen from the family of materials known as DSP technology (Densified Systems containing homogeneously arranged ultra fine Particles) materials to the worn surfaces.

Although these materials usually are used when arranging wear protective coatings inside the ducts, the method of applying a cement based material according to the invention is not limited to this type of material.

When applying cement based materials to smooth surfaces which are not normally suitable for application of cement based materials because of the surface structure or topology and which are horizontal, a problem of adhesion arises due to the fact that the material itself at the early stage, i.e. when the material is sprayable or trowable, does not have the necessary internal cohesion or adhesion properties. Therefore, when the mortar is applied to a surface, for example on the underside of horizontal surface or on a vertical surface, it will have a tendency to slip and fall down. In order to counter this lack of adhesion, reinforcement mesh or small studs/anchors are often provided on the surface. Hereby the applied cement based material will cling on to these studs/anchors or the reinforcement mesh long enough for the cement based material to obtain an interior strength, which will keep it in place.

Having to arrange studs or reinforcement mesh internally in a duct and around bends, where the three-dimensional contour of the duct is very hard to follow when having to fit in linear reinforcement mesh, makes this type of wear protection extremely costly.

Once the wear-protected lining is installed, it can also give rise to further problems in ducts where very warm materials are transported/conveyed, for example at temperatures from 200-800 C°. The difference in material characteristics, especially the differences in heat expansion coefficients between the mortar and the embedded reinforce- ments, can give rise to crack building, which will cause the wear protective layer to have a shortened use period.

In this application the emphasis as well as the examples are mainly concerned about cement based materials. It should, however, be understood that all materials having comparable internal structure, rehology and the like are incorporated within the inventive principle. The invention is therefore defined with respect to materials comprising hydraulic binders.

Consequently, there is a need for a method, whereby it is possible to apply a material to surfaces (vertical, horizontal and the underside of horizontal surfaces), especially surfaces on the underside of horizontal objects or vertical surfaces, which method is faster and cheaper and can be more easily achieved than with what is known from the prior art.

This is solved by the invention by a method for applying a material comprising a hydraulic binder and, in particular, a cement based material to surfaces, especially surfaces on the underside of horizontal objects or vertical surfaces, wherein a thin layer of a polymer based material is placed on the surface, where after the material comprising a hydraulic binder is arranged on the surface of the polymer based material.

According to the method a polymer based material is applied to the surface, for example by spraying, painting or other appropriate techniques. After hardening of this polymeric material the material comprising a hydraulic binder can be applied onto the thin polymer based layer. Surprisingly, it appears that the fresh trowable or sprayable material sticks to the polymer based material in such a way that the need for anchoring studs or reinforcement is alleviated.

Tests have shown that a method comprising applying the polymer based material to any surface and thereafter applying the material comprising a hydraulic binder to the polymer based material is sufficient in order to make the material stick to the surface.

In applications where this method is used in ducts where materials are conveyed, especially under conditions where wear can appear inside the duct due to abrasion between particles suspended in the material to be conveyed and the inside of the duct, materials from the Densit® family have shown extremely high resistance against wear and shown that they are also useable for application to the surface using the method according to the invention.

These Densit® materials are characterised by having an extremely dense matrix comprising cement particles in combination with ultra fine mineral particles and strong aggregate particles, which makes the material extremely hard and dense.

It is, therefore, in a further advantageous embodiment preferred to use a cement based material containing cement, water, micro silica and, optionally, fly ash and/or fibres. This type of material has a track record of proven wear characteristics and the fibre content gives it a certain ductility. This ductility is important because of the possible dimension changes caused by the changing temperature in the duct. All types of fibres are useable with the mortar matrix as described above, but especially preferred are steel fibres, polymer fibres, glass fibres and ceramic fibres. In one specific example where this method can be used advantageously is for ducts conveying hot gasses having suspended particles of fly ash or the like. These particles have a relatively high velocity inside the duct, which causes a huge abrasive impact on the sides of the duct whenever the gas needs to change direction inside the duct. This in combination with the elevated temperature, often 400-600 C°, makes the interior of the duct a very hostile environment. At these high temperatures the polymer based material will be burnt away and the applied cement based material will by then have attained sufficient interior strength to stand alone whereby the polymer material only has influence on the process during the application of the materials.

Another example where this method can be used advantageously is for bonding floor screeds to substrates with inadequate textures. This is often the case along walls and around pillars where mechanical equipment is incapable of reaching. These areas must be manually roughened, which is very time consuming and often poorly done. Instead the polymer can serve as bonding agent between the substrate and the screed in these areas. The polymer sticks to the substrate material leaving a polymer surface with a sufficient rough texture capable of offering an improved grip for the cement based top layer material.

For some applications it can be useful to have a reinforcement embedded in the mortar. Tests have shown that a coating of the reinforcement with a polymer based material, prior to applying a cement based material (castable, trowable, sprayable etc.), can be advantageous. Once the cement based material is hardened and the cement based material is in use, especially on wear protection at elevated temperatures, the polymer based layer will either become very soft or burn away due to the temperature. This allows the cement based material and the reinforcement to expand/contract without influencing each other. As these two materials have different temperature expansion coefficients, internal stresses in the cement based layer can be minimised.

Surface/Substrate

Tests with the method have shown that the requirements for the surface depend on the polymer used for the intermediate layer. In practise, all types of surfaces are suitable as long as they are firm, clean and dust free to a degree where the polymer based material will be able to adhere to the surface. Tests with wood, metal, concrete, ceramics, glass and plastic surfaces have all shown excellent characteristics and it has not been necessary to perform special cleaning or other surface treatments prior to the applica- tion of the polymer based intermediate layer. In respect of the duct application extensive tests were carried out with steel surfaces and excellent results were achieved.

The polymer based material

The polymer based material can be applied to the surface to be treated by for example spraying or brushing, but any technique for applying the polymer based material can, in principle, be used.

The amount of polymer based material to be used in order to be able to carry the desired thickness of the cement based material depends partly on the surface of the ob- ject to be treated. Another important factor influencing the requirement for the surface structure/topology of the polymer based material is the rheological characteristics of the cement based product. Among these characteristics is especially the viscosity as well as the internal cohesion of the cement based product to be used important.

It is not necessary that the polymer based material entirely covers the surface to be treated, but again depending on the material characteristics of the cement based product more or less of the surface to be treated can be covered with the polymer material.

For most dry firm surfaces, approximately 200 ml of polymer material was used per m². It is in this connection preferable to use a quantity of polymer based material from

30-500 ml per m² and more preferable 40-400 ml and most preferred for the widest range of applications 50-300 ml per m² used. The exact quantity will depend on the conditions as described above.

The cement based material

With prior art application techniques it is only possible to apply a cement based material layer of a few millimetres to the underside of horizontal surfaces as well as to ver- tical surfaces. On the top of horizontal surfaces (e.g. floors) there is a limit to the minimum thickness.

If full attachment can be achieved, the top layer thickness needs to be just a few mil- limetres. If no attachment can be achieved or when the substrate possesses low stiffness the top layer alone must carry the load on the floor (traffic, storage etc.) and will in general be at least 30 millimetre thick.

According to the invention using the inventive method whereby an intermediate poly- mer layer is applied before the cement based material, material thickness of more than

50 mm - regularly 50 mm was applied - both on vertical and the underside of horizontal surfaces can be achieved. This requires that the cement based material has a certain internal cohesion as well as a certain viscosity. Particularly preferred cement based products having these properties are in this connection a modified experimental Densit® WearSpray product and a modified experimental Densit® WearFlex product.

With prior art application techniques it is only possible to apply a cement based material top layers of at least 20 millimetre on top of horizontal old concrete surfaces if no preparation is done. According to the invention using the inventive method whereby an intermediate polymer layer is applied before the cement based material (the top layer), material thickness of only 5 millimetre can be achieved. This requires that the cement based material have certain strength and stiffness as well as a certain viscosity. Particularly preferred cement based products are in this connection a modified experimental Densitop^® product and a modified experimental Ducorit^® product.

The inventive method according to the invention thereby solves two related problems: a) how to in a very effective manner apply cement based materials in a sufficiently thick layer in one pass to vertical or undersides of horizontal surfaces, and b) how to make a thin layer adhere/attach to the top side of a horizontal surface. On horizontal surfaces as floors and the like, only a thin layer is necessary in order to achieve a wear resistant surface if the attachment of that layer is sufficient to the base. Whereas on vertical and the underside of horizontal surfaces a thicker layer is required as the layer itself must be able to be at least to a certain degree self supportive.

Above and below preferred embodiments of the invention have been listed with refer- ence to mainly cement based materials. It should be noted, however, that the invention is not limited to cement based materials, but to materials using any type of hydraulic binders and in particular cement is a preferred binder.

Examples In order to verify the effectiveness of the invention two series of experiments were carried out.

In the first series three types of surface materials/substrate (steel plate, plywood and a glass plate) were used in combination with one type of polymer (Berner® MS- Polymer sealer grey (Spraying/sealing compound)) and one type of cement based ma- terial (a modified experimental Densit® WearFlex product). Surprisingly it was possible to trowel a 30 mm thick layer of the modified experimental Densit® WearFlex product on the polymer surface, even when the polymer surface oriented horizontally on the underside of the substrate.

In the second series 10 types of polymer and one painting primer were tested on steel plates (3 mm x 300 mm x 400 mm) in combination with one type of cement based material. The polymer was used with different dosages and different methods of application. The tests were carried out in two steps.

First, the polymer was applied and it was judged how easy it was to obtain a surface structure suitable for carrying a 30 millimetre thick layer of trowable cement based material and one to five points was given. One point was given if it was impossible to obtain the wanted surface structure and five points when it was very easy to do. This first score is called A-score. Secondly, a 30 millimetre layer of cement based material was troweled at a vertical position on the substrate carrying the polymer.

The effect of the polymers was judged by comparing the ease of installation and the capability of carrying the cement based material in comparison with the conventional method of installing the actual cement based material, which conventionally is installed by troweling on an expanded steel mesh welded onto a steel casing. If troweling the cement based material on the polymer in the test was impossible 0 points were given, and if it was as easy as troweling on expanded steel mesh 5 points were given. The second score is referred to as B-score.

In all cases the applied cement based material was from the modified experimental Densit® WearFlex product family.

The modified experimental Densit® WearFlex product consist of Densit® Binder, quartz aggregate in the range 0-1 mm and corundum aggregate in the range 1-3 mm.

When mixing The modified experimental Densit® WearFlex product approximately 5,5% (by weight) water was added and approximately 4,4% (by weight) steel fibres (0 0,4 mm x 12,5 mm) were added.

The mortar flow was measured on an ASTM flow table to be 10,0 - 10,5 cm at zero stroke and 14,0-15,0 cm after 20 strokes. The air content was measured to 4,0 - 5,0 %.

The test sheets (3 mm thick steel plates 300 mm x 400 mm) were cleaned with a conventional soap and cold water and left over night for drying. Hereafter polymers were applied on the test sheets using several methods applicable for each type of polymer.

The methods in question were painting with a paint brush, painting with a paint roller and painting with a pneumatic paint gun using three different sizes of nozzles (normal, big, long).

The polymer based material was delivered in aerosol spraying cans and was used as such. The polymer types delivered in tubes containing approximately 300 ml was applied using a suitable tool driven by compressed air. The tubes were equipped with a 70 millimetre long plastic tube like nozzle. Used as it is the nozzle is called "long nozzle" and in a shorter version, where 3-4 mm was cut off, it is called "Short nozzle".

The polymer covered test sheets were left overnight for drying and hardening. De- pending on the actual polymer, according to the distributors of the polymers, the drying or hardening time is 4 - 10 hours at 20 °C.

Hereafter, if possible, the modified experimental Densit® WearFlex product was troweled onto the polymeric surface in a 30 millimetre thick layer.

Conclusions

From the above mentioned tests it can be concluded that the method used for applying the polymer on the test sheets has some influence on the hardened polymers capability to carry a 30 millimetre thick layer of the modified experimental Densit® WearFlex product installed in a vertical position.

The surface structure/topology created by a certain polymer seems to depend mostly on the polymer itself and polymers that create poor surface structures using one method will not create good surface structures using other methods.

It is not possible to select polymer types which are generally rated "poor" or "good" with respect to the surface structure.

It is not possible to select one applying method of the polymer based material to gen- erally be "poor" or "good" with respect to the surface structure.

For each polymer at least one applying method is preferred to give the best surface structure.

Combinations of polymers and applying methods with B-score equal 0 points do not work. Combination with B-score from 0 - 3 points do work, but the cement based material does not stick too well to the polymer and even minor hand made vibrations on the test sheet will cause the cement based material to slip off.

Combinations with B-score from 3 - 5 points do work. The more points the better the cement based material sticks to the polymer. Even minor hand made vibrations on the test sheets do not cause the cement based material to slip off.

In the following table the test results are indicated.

Although the invention has been explained with reference to applying a polymer based material to a base and thereafter applying a cement based material on the polymer, it should be recognised that further layers on the cement based material, as for example applying insulating materials, ceramic tiles, surface treatments as paint and the like, also lies within the scope of the present invention.

Claims

1. Method for applying a material comprising a hydraulic binder and in particular cement based material to surfaces, especially surfaces on the underside of horizontal objects or vertical surfaces, wherein a thin layer of a polymer based material is applied on the surface to be treated, whereupon the cement based material is arranged on the surface.

2. Method according to claim 1, wherein the cement based material contains cement, water, micro silica and, optionally, fly ash and/or fibres.

3. Method according to claim 1 or 2, wherein the surface onto which the material is to be applied is the inside and/or the outside of a hollow element, for example a cone or a duct element having a circular, oval, rectangular or square cross section.

4. Method according to claim 1 or 2, wherein the surface onto which the material is to be applied is a flat horizontal surface, for example a floor.

5. Method according to claim 1, wherein the polymer based material is applied to the surface by spraying techniques or by painting techniques.

6. Method according to any of the proceeding claims, wherein the cement based material layer is applied to the polymer based layer in a one-step application on vertical, horizontal and the underside of horizontal surfaces with a layer thickness of 5- 200 mm, preferably 10- 100 mm and most preferred 15- 50 mm.

7. Method according to any of the proceeding claims, wherein the cement based material layer is applied to the polymer based layer in a one-step application on horizontal surfaces with a layer thickness of up to 100 mm, preferably up to 50 mm and most preferred up to 25 mm.

8. Method according to any of claims 1-7, wherein the cement based material is applied in one or more layers wet-in-wet or wet in dry wherein each layer is 5- 200 mm, more preferable 10- 100 mm thick.

9. Method according to any of the proceeding claims, wherein the polymer base material comprises an intermediate layer connecting the substrate and the cement based material.

10. Method according to any of the proceeding claims, wherein the surface to be treated is steel, concrete or more general metals, ceramics, glass, plastic, wood.

11. Method according to any of the proceeding claims, wherein the polymer base material is used in a quantity of up to -500 ml per m², more preferred up to -400 ml per m² and most preferred less than 300 ml per m² surface to be treated.