The present invention relates to a tube for chemical injection in concrete, comprising an injection material feed portion and a compressible, porous material attached thereto.

It is known that concrete structures subject to water pressure make heavy demands on the execution of concrete casting in general and on concrete joints in particular.

The ideal joint between two concrete moulds would be without fissures, cracks, interstices between the rocks, and the like. The problem of leakage may particularly arise when concrete walls are poured on a previously cast concrete base.

However, in practice ideal joints are nearly impossible to obtain because of a lack of homogeneity in the concrete and also, in particular, because of the shrinkage which neces¬ sarily occurs during the setting of the concrete.

An attempt must then be made after the casting to seal the cracks and fissures that have formed, and a great number of methods and devices are known in the art.

The oldest and previously most used method for sealing concrete cracks was point-by-point injection into the concrete joint. However, this method is unreliable and, importantly, very expensive.

Accordingly, the search for better methods of sealing concrete joints has continued, and the method generally used today is an injection system which is based on tubes perforated in various ways and run in the longitudinal direction of the concrete joint, and according to which a sealer, usually a two-component polyurethane material, is injected into the tubes and distributed in the joint by means

of the perforations, the material thereafter hardening and sealing the -joint.

As indicated, this arrangement is laid in advance, prior to the new subsequent casting, and the very time-consuming and expensive process of drilling through the concrete structure is therefore avoided.

As to the prior art in this field, reference is specially made to EP 0.125.696-A3 which comprises one central, regularly perforated feed tube outside which there is placed a tubular filter layer which, in turn, is sheathed by a tubular, mesh-like protective layer.

Reference is also made to NO Application P911086, which describes an injection tube for chemical injection in concrete, comprising a central, regularly perforated feed tube having a cover disposed on top of the perforations, said cover consisting of a compressible sleeve disposed around the periphery of the tube and having fine pores running therethrough.

The purpose of the sheathing is to prevent that the concrete mass during the pouring blocks the perforations in the sealer distribution tube. For this purpose a textile cloth has proved disadvantageous, the cloth itself being a surface element which during casting is sealed so that the injection mass is not let out from the perforated tube for sealing the fissures and cracks that have been formed.

Later development and research in the field has resulted in a system which is currently being marketed under the name "FUKO." This system comprises a tube core of a solid and strong material along which, in the longitudinal direction thereof, are disposed grooves, through the bottom of which there are, in turn, formed perforations. These grooves are

covered by loosely positioned slats so that the overall profile of the tube is almost circular.

The purpose of these slats is to prevent the concrete mass during casting from blocking the perforations of the tube, while at the same time ensuring that the injection material, even at low pressure, can be pressed out of the feed tube and into the surrounding fissures and cracks.

Finally, the "FUKO" system is provided with a circumferential woven, open plastic sleeve for holding the longitudinal slats in position.

This system is technically very reliable and very safe in operation, but is, in contrast with the device of the above mentioned NO P911086,, relatively complicated to produce and also very expensive.

This cost, inherent in the technically most sophisticated products, can only justify their use in those cases where the particular concrete structures are under permanent water pressure and therefore must be secured.

In a great many structures, the risk of water pressure outside the concrete structure would be only periodical and may even be expected relatively seldom, examples being spring tide areas and other, more or less periodically but very infrequently flooded regions. In such cases it would be appropriate to utilize technically simpler but nevertheless dependable systems which, by being simple and easy to produce, are reasonable in purchase and in operation, for example, the above mentioned NO P911086.

The the present invention aims at advancing the state of the art to the point where it is possible to inject simultane¬ ously at least two different components and, optionally, on a

later occasion to inject further components if this should prove necessary.

The invention is based on the discovery that only one injection duct may prove disadvantageous, and, further, on the consideration that the wider the area is across which the injection mass is sprayed, the better the seal will be secured, especially when the injection is made from an element further described below.

The present invention therefore relates to a tube of the kind mentioned by way of introduction, and this tube is charac¬ terized in that the feed portion comprises at least two moulded channels running side by side, preferably in one piece and in the form of strips, in the outer walls of which microscopic apertures are formed for emission from the interior to the outside, at a predetermined interior overpressure.

The compressible, porous material mentioned by way of introduction is preferably foamed plastic, but may be any material satisfying the requirements, for example, finely wired steel wool.

The invention shall be further illustrated with reference to the enclosed drawing, 'in which the feed portion (1) in the depicted case comprises three channels (2) running side by side, each provided with microscopic apertures (3), which, because of the arched configuration of the tube, will open for emission at high pressure in the channels (2) but which will be sealed at low pressure in the channels.

The surrounding cover (4), preferably of foamed plastic having pores running therethrough, is to ensure a further distribution of the injection material at the same time as it serves to to keep the microscopic apertures open.

The product according to the invention is simple and easy to produce compared with the most sophisticated embodiments of prior art, and can therefore be produced at a very low cost at the same time as the desired level of operational safety is maintained.

The subject matter of the invention thus meets the market's need for an inexpensive product to be used with reasonable safety in all places where protection against water is necessary because of sporadic risk of water pressure outside the concrete structure, the main object, however, being not so much to shut out the water completely, as to delay water seepage, to the extent that the protection is proportional to the actual risk.