FI78674B - Concrete product or construction whose surface is coated with a seamless ceramic or metal outer coating and a process for its manufacture - Google Patents

Abstract

The invention pertains to a concrete product or construction whose surface is coated with a thin, seamless ceramic or metal outer coating (1) and a process for its manufacture. In the thermal spray process, a heat-resistant type of concrete is applied as a thin layer to the surface (2) of the concrete construction to be coated with metal or ceramic, such that the concrete underneath is not damaged as a result of the high temperatures reached during the coating process.<IMAGE>

Description

78674

Concrete product or structure coated with a seamless ceramic or metal coating and method of making it

The invention relates to a concrete product or structure coated with a seamless ceramic or metallic coating and to a method for its production.

Coatings are used to improve and modify the surface properties of a material, such as wear, corrosion or oxidation resistance. Concrete structures, such as facade elements and sanitary facilities, are known to be coated with ceramic tiles during the casting phase of the structure or by tiling an already hardened concrete structure using a gluing technique. In this case, however, there are always joints between the tiles in the coating, which impairs the surface's resistance to weathering.

Seamless coatings can be made by a wide variety of thermal methods, such as welding, arc, flame and plasma spraying. The most versatile of these methods is the plasma spraying method, which can be used to make coatings on metals, alloys, ceramics, plastics, and combinations thereof. Almost all pulverized materials that melt without evaporation can be plasma sprayed.

The temperature of the gas or gas mixture introduced into the plasma space used in the plain injection equipment is about 10,000 to 28,000 ° C, which is sufficient to melt any material. The energy of the gas is used to melt the coating material in powder form, which is sprayed through a nozzle onto the surface of the substrate material to form a coating. The coating adheres to the base material mainly by non-short-acting forces of 2 78674. The temperature of the molten mass from the injection molding plant is about 1,500 to 3,000 C. The temperature of the body to be coated rises close to the surface to at least about 200 ° C and momentarily on the surface to about 1,000 ° C. As a result, the structure made of ordinary concrete to be coated undergoes harmful structural changes, because ordinary cements and aggregates cannot withstand the temperature.

The structure and the coating method according to the invention avoid the above-mentioned drawback. According to the invention, the surface part of the concrete structure to be coated by the thermal spraying method, preferably the plasma spraying method, is coated with heat-resistant concrete in a thin layer so that the underlying concrete surface below it is not damaged by high temperatures during coating work. The structure and the coating method are characterized by what is stated in the claims.

The main advantage of the invention is that it can be used to efficiently coat a concrete structure with a ceramic or metal coating by thermal spraying technology, preferably by plasma spraying technology, and thus to obtain a completely new and durable coating for concrete structures, such as weather-resistant and weather-resistant. . The surface structure is also freely formable.

The invention is based on the fact that in a thin surface part of the concrete structure to be coated, in a layer about 5-50 mm thick, preferably about 10 mm, special concrete, so-called refractory concrete, which enables the use of thermal spraying technology in the coating of concrete structures, for example by sergeants. In this refractory concrete, aluminate cement is used as a binder instead of ordinary cement. Thanks to the aluminate element, the hydraulic bonds normally present in concrete are therefore ceramic. This results in concrete o which is not damaged at high temperatures, even above 1 000 C, provided that the aggregate used for the concrete is a grade of stone which is also not damaged at this temperature; for example, ferrochrome slag and light gravel are suitable materials in this respect, as are low-cement LC castings. The layered structure consisting of refractory and ordinary concrete can be manufactured using known conventional methods for manufacturing concrete products.

Before spraying the ceramic or metallic coating, the concrete surface to be coated is still cleaned, for example by sandblasting. Just before coating, the concrete surface must be heated and dried with infrared radiation so that the water on the surface does not damage the coating if it evaporates. The coating is sprayed into a layer of concrete about 0.1 to 10 mm, preferably 0.5 mm thick. If surface layers about 1 mm thicker are desired, it is preferred to use more efficient thermal spraying methods than plasma spraying, such as flame or arc spraying. Spraying should be performed in a controlled manner as it greatly affects the quality of the coating. Optimum spraying values are obtained by test spraying.

Examples of plasma sprayable materials are given in "Welding Technology", No. 4 (1988), pp. 39-42.

In the following, the invention will be described with reference to the figures.

Figure 1 shows a cross-sectional view of a concrete structure coated with a seamless ceramic or metal coating 1. The sprayed coating 1 is attached in the structure to a thin concrete layer 2, which is refractory concrete. The frame 3 of the concrete structure is ordinary concrete.

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Figure 2 schematically shows the coating of a concrete product with a ceramic or metal coating using a thermal spraying method. In step 1, the coating material is in the form of a coating wire or powder. In step 2, the material melts, in step 3 the melt droplet accelerates, and in step 4, the surface of the material to be coated is impacted. In step 5, the final structure is shown.

Claims (6)

Method for fabricating a concrete product or structure surface coated with a seamless ceramic or metallic surface coating, characterized in that the pA body part (3) of ordinary concrete is cast on a layer of fire-resistant concrete <2>, after which the coating is applied using a thermal spray. process, preferably using a plasma spraying process, by spraying the coating on a fire-resistant concrete layer, the plain concrete layer not being exposed to high temperatures or aletrae during coating work. Process according to claim 1, characterized in that the surface of the concrete structure is clean, preheated and dry before the surface coating. 3. Concrete product or structure surface coated with a seamless ceramic or metallic surface coating, characterized in that it consists of a body part (3) of ordinary concrete surface coated with a layer of fire-resistant concrete (2) and the coating (1) is sprayed using a thermal spraying method, preferably a plasma spraying method, on the layer of fire-resistant concrete. 4. Concrete product or structure according to claim 3, characterized in that in the fire-resistant concrete there is an aluminate cement binder and a heat-resistant core material types and / or LC casts with a low cement content. 1 Concrete product or structure according to claim 3 or 4, characterized in that the thickness of the fire-resistant concrete layer is about 5-50 mm, preferably about 10 mm.