Cracks or deformations can occur in buildings and structural works such as roads, bridges, viaducts and the like owing to uneven expansion and shrinkage, settling of the building or structural work, too high a load and so on. A good example in road-building is the forming of ruts in asphalt roads due to overloading.

Forming of cracks in buildings can for instance also occur in the finish thereof, such as in building materials applied therein such as gypsum plaster or cement plaster, or in floors, terraces, asphalt roofs, outside wall insulation systems and the like. In order to prevent this type of effect the building material used is generally strengthened by means of a strengthening material.

Known strengthening materials consist of open- mesh woven fabrics or webs, the fibres of which are generally protected against wear or the action of acids and/or bases by means of a resin. When used in building materials the strengthening material is then pressed into the preferably still wet base layer, whereafter a finishing layer is applied.

However, when the base layer is not or no longer wet, some form of fixing of the strengthening material to the base layer is still required. It is therefore known to apply a glue layer on one side after arranging and setting of the protective resin. This application of the glue layer generally takes place at the location of the works.

The drawback hereof, however, is that the applying of the glue layer requires an additional operation and extra material.

It is the object of the present invention to provide a new method for manufacturing a self-adhesive

strengthening material, and also to provide a new strengthening material.

This is achieved by the invention with a method comprising the steps of: a) providing a coarse-mesh net consisting at least partially of strengthening fibres; b) at least partly encapsulating or impregnating the strengthening fibres of the net with a coating layer of an adhesive resin; and c) making the resin non-adhering on one side of the net.

The above described method has a great number of advantages. Making the strengthening material self- adhesive as well as the encapsulation or impregnation of the strengthening fibres are carried out in one process.

For the manufacturer this means economizing on an additional process in the manufacture of the strengthening material. Because the coating layer and the glue are one product the binding strength of the strengthening fibres of the net with the resin is maximal. For the user the self-adhesive strengthening material according to the invention has the advantage that no extra glue has to be applied. This not only saves the glue but also the operation of applying the glue.

The invention further relates to the strengthening material which can be obtained by means of the method according to the invention. Such a self- adhesive strengthening material comprises for instance a coarse-mesh net consisting of strengthening fibres, which strengthening fibres are at least partially encapsulated or impregnated with an adhesive resin which is made non- adhering on one side of the net. The strengthening material according to the invention can optionally be combined with other strengthening materials, such as threads, non-wovens, membranes, rovings, mats and others.

The strengthening material according to the invention is particularly suitable as reinforcement for building

materials and in particular for use in road-building, for instance as reinforcement in asphalt.

When the strengthening material according to the invention is fixed to surfaces or walls, it remains lying or hanging in place. This facilitates the processing, whereby it can also be used overhead and against vertical or inclining surfaces. However, as long as no finishing layer of asphalt, cement, plaster, paint, stucco and the like has been applied thereover, the strengthening material can be removed without damage and then fixed once again. This is particularly effective when the surface is dry and dust-free.

Because the strengthening material is non- adhering on one side, it can be supplied for instance as a roll. Because it is non-adhering on one side the strengthening material is moreover not dirtied and does not adhere to machines, material, hands or feet during manufacture or when the finishing layers are applied.

The open net structure ensures that the subsequent finishing layers penetrate well through the strengthening material and anchor it firmly to the base and the subsequent layers. It hereby comes to form part of the whole and can absorb all pressure and tensile forces, shear stresses and the like. The occurrence of cracks as a result of the settling of the ground, for instance in the case of walls, floors, roads etc. is thereby reduced or even prevented. When the strengthening material according to the invention is used in asphalt roads it prevents the rut formation which occurs as a result of road traffic, in particular by trucks during the summer.

In the manufacture of the self-adhesive strengthening material according to the invention a resin is preferably used which can be made partially self- adhesive in one way or other. Particularly recommended is a resin which is sensitive to, or can be made sensitive to, r W light, wherein making the resin non-adhering on one side takes place by radiating the net, which is

encapsulated or impregnated with resin, on one side with UV light. Examples of such resins which are UV-sensitive or can be made W-sensitive are acrylate resins or a mixture of a plurality of acrylate resins with each other or with other types of resin.

The net is for instance a woven fabric or web, and can be manufactured by weaving, knitting, stitching together, tying together or mutually adhering strengthen- ing fibres. The strengthening fibres can have a random mutual angle. Angles between approximately 45" and 90" are recommended. The strengthening fibres forming the net can be threads or rovings, which are manufactured for instance from glass, carbon, aramid, polyester, acryl, polyvinyl alcohol or combinations thereof. The above mentioned materials and net-forming methods are of course only examples which have a particular preference but which can be replaced by the skilled person by equiva- lents which also fall within the scope of the present invention.

The invention further comprises a method for strengthening building materials, comprising the arrangement of the strengthening material on a base layer and applying thereover one or more finishing layers. The finishing layers can be plaster layers of gypsum or cement, layers of asphalt, concrete, paint, stucco and the like.

The present invention will be further elucidated with reference to the following examples, which are only given by way of illustration and are not intended to limit the invention in any way whatsoever.

EXAMPLE 1 Strensthenins woven fabric On a loom a roving of 1 x 600 Tex per centimetre is woven onto a warp consisting of two threads of 272 Tex per centimetre. An open-mesh or coarse-mesh woven fabric hereby results with a mesh size of 1 cm2.

This woven fabric is subsequently coated with a W-

sensitive self-adhesive acrylate dispersion and after drying irradiated on one side with W lamps in order to make this side non-adhering.

EXAMPLE 2 Self-adhesive strenqthenins web On a knitting machine warps of 2400 Tex are knitted to each other every two centimetres with a weft thread of 2400 Tex every centimetre. This open-mesh web is then treated as in example 1.