The present invention relates to means for use in sealing of casting joints against penetration of water. Moreover, the invention relates to the use of a film material for protection of a swellable material.

Background of the invention.

Sealing of casting joints in concrete structures is made below the level of the subsoil water, for instance in buildings, in cases when the external water pressure may cause seeping in of water. Casting joints occur when concrete is cast in stages (successively); i. e. when new concrete is cast upon hardened concrete. Thereby a perfectly sealed transition between the old and the new concrete will not be formed.

Prior art.

In order to achieve sealing i such cases it is known to use swelling "sausages", i. e. sausage-like strings of a material which swells upon addition of water. Such"sausages"are laid on the hardened concrete on which new concrete is to be cast, for instance when casting walls on an earlier cast floor below the ground level. When the walls have been cast and the area outside of the lower part of the walls has been filled with a mass, such as earth, sand or crushed rock, subsoil water will seep into the mass and in against the walls, whereby moisture is added to the"sausages"which swell and develop a pressure which causes sealing against continued penetration of water through the joint.

It is also known to use swellable mats between layers of concrete which are cast one upon another.

A problem in connection with such"sausages"and mats is that they may be exposed to moisture, even in a long time prior to being used, whereby they

swell before being put in place for use, and thereby they have lost at least some of the swelling ability when they are put in place. The effect with respect to sealing will then be largely reduced. The"sausages"or mats may for instance be brought to a construction site a reasonable time before they are to be used, and even if some precautions are taken in order to protect the "sausages"or mats against water, it frequently happens that they become wet prior to being laid in place, or after having been laid in place, which may occur some time prior to casting of new concrete. During work in rainy or snowy weather it is impossible to avoid that the"sausages"or mats become wet before or after they are put in place.

Norwegian Patent Application No. 1997 4729 discloses the use of common types of plastics in the film, such as PE and PVC. However, such materials will make the film rather resistant, and a considerable time will lapse until the film is sufficiently disintegrated to permit a substantial penetration of water into and swelling of the"sausage"or mat. This gives rise to the problem that the concrete is not sealed for a long time after the casting of new concrete on hardened concrete.

The present invention relates to a solution of this problem.

The invention comprises means for sealing joints between concrete elements which are cast successively one upon another, comprising -a swellable material to be placed on a first concrete element prior to casting of a second concrete element thereupon, and -a cover encapsulating the swellable material, said cover being constituted of a film which will degrade/disintegrate due to the influence from the chemical ingredients in the fresh concrete of the second concrete element, whereby the film consists of a rapidly degradable and in addition compostable material comprising polycaprolactone and corn starch.

The invention also comprises, for protection of a swellable material to be placed on a first concrete element prior to casting of a second concrete

element thereupon, the use of a cover for encapsulating the swellable material, said cover being constituted of a film which will degrade/disintegrate due to the influence from the chemical ingredients in the fresh concrete of the second concrete element, whereby the film consists of a rapidly degradable and compostable material comprising polycaprolactone and corn starch.

The relative amounts of polycaprolactone and corn starch may vary within wide limits, such as between 20 and 80% by weight of polycaprolactone and between 80 and 20% by weight of corn starch.

Such a material will completely dissolve in concrete in about 3 to 8 weeks, and the swelling of the"sausage"or mat will start shortly after the casting.

The material is in addition slightly permeable. Thus, the swelling will start sufficiently early to cause that the"sausage"penetrates into fissures in the concrete and prevents ingress of water between successively cast layers of concrete.

Thus, the swellable materials may be situated in a sealing cover, in the form of a film of the above specified material, both during storage at the manufacturer or dealer, during transportation to construction sites, during storage at construction sites and after having been put in place for casting of new concrete on already hardened concrete.

The cover has to be of a material which degrades (disintegrates) rather rapidly when being exposed to the concrete. This exposure will be highly alkaline, and the material will be disintegrated by the fresh concrete.

Thus, the disintegration of the cover will start when the new concrete has been cast, due to the influence from the fresh concrete on the material of the cover, and water which seeps into the casting joint from outside will be able to penetrate into the swellable material and cause swelling at an early stage after the casting. The penetration will start almost immediately, due to the permeability of the material.

The film material is non-toxic, and it is edible. Thus, the material can be used when casting basins or other reservoirs for drinking water, because the material will not cause any dangerous contamination.

The film material has a low melting point, approximately 60°C. The hardening of concrete may develop sufficiently heat to exceed this melting point, whereby the material will melt and water is given free access to the swellable material.

Because the film material is compostable, the composting process may start shortly after the deposition of the covered"sausage"or mat, due to bacteria in the water.

The film material will, however, seal against ingress of mainly pure water, for instance rain, for a substantial period, such as 10 to 15 days. If submersed in water, the film material will not become permeable until several days. In a dry condition the film material will remain impermeable for a long period.

The film material is elastic and stretchable, and deformations caused during handling and transportation will not cause fissures.

"Sausages"of swellable material may be stored without any cover if not exposed to water. The"sausages"may also be used without any cover, whereby the costs of the film cover are saved. However, if the uncovered "sausages"will probably be exposed to water prior to use, a film cover according to the present invention, in the form of a hose, can be pulled onto the"sausages". Another possibility is to store such film covers in the form of "rolled up"hoses, and to"roll"the film hoses onto the"sausages"if protection against water is necessary. Such"rolling up"and"rolling on"is possible due to the elasticity or stretchability of the film material.

Detailed description of an embodiment.

The invention will hereinafter be explained by means of an embodiment shown

on the accompanying drawing.

The drawing shows a means in accordance with the invention, for sealing joints between concrete elements which are cast successively one upon another. The drawing shows a cover 1 encapsulating a swellable material. In the embodiment shown the means is shaped like a"sausage", the ends of which being shown to be tied by strings 2. The ends may of course be closed by other means, such as by being welded or glued. The length may of course be adapted to the concrete elements, and the thickness and width (or diameter when the cross section is round) may be chosen so that the desired amount of swellable material per unit length is used.

The means comprising the swellable material is to be placed on a first concrete element prior to casting of a second concrete element thereupon, said cover 1 being constituted of a film will degrade/disintegrate due to the influence from the chemical ingredients in the fresh concrete of the second concrete element. Water from the surroundings will penetrate into the casting joint from outside and into the exposed swellable material and cause swelling thereof. The water may also start a composting process in the film material.

It will be understood that the means according to the invention may have other shapes than a"sausage", for instance webs or mats.

The invention makes it possible to store the swellable material in a safe manner, with little or no risk of wetting, all the time until being used, and to keep the swellable material dry until the cover is degraded by the constituents of the fresh concrete.

The invention may of course be used in all types of joints between concrete parts which are cast successively, when water should be prevented in penetrating through the joint between the concrete parts. The casting of walls on an earlier cast floor is merely mentioned as an example.