EP0297730A1

EP0297730A1 - Improved waterstops

Info

Publication number: EP0297730A1
Application number: EP88305036A
Authority: EP
Inventors: Timothy John Martin
Original assignee: WR Grace Ltd
Current assignee: GCP Products UK Ltd
Priority date: 1987-06-03
Filing date: 1988-06-02
Publication date: 1989-01-04
Also published as: DK301088D0; GB8712998D0; GB2205872A; DK301088A

Abstract

A waterstop having a body comprising an elongate web (10) with a keying formation (11) at or near each edge of the web (10) by which the waterstop may be secured in adjacent respective bodies of concrete so as to seal the gap between such bodies, and, on each side of the centre line, a strip of water swellable material (20) attached to the body and positioned so as to engage the concrete and effective in use to improve the seal between the waterstop and concrete in the event of water or moisture penetration.

Description

This invention relates to waterstops.
Waterstops are extruded or moulded sections of rubber or other flexible moisture proof materials, such as plastics material such as polyvinyl chloride, which are used to prevent the passage of moisture or water through the joints which are provided in concrete structures such as floors, bases and walls when such structures are formed in successively cast sections.
Waterstops of the so-called internal type are conventional structures having enlarged formations at or near both longitudinal edges, or having projections on both faces. These allow the waterstop to be anchored in the concrete so as to bridge the gap between adjacent bodies which are poured in situ, so that it is not pulled out when the concrete bodies move apart as they inevitably will in time and with the change of weather and seasons. The waterstops have to be of strong flexible material in order to withstand such movement without tearing out or rupturing. In practice about half the waterstop is first cast into and secured in the first formed body of concrete defining a joint, and subsequently the other half of the waterstop is cast in the adjacent, subsequently cast concrete body.
A second type of waterstop is the so called external type the subject inter alia British Patent No. 1008811 in which keying formations are provided on only one face of the waterstop so that the waterstop spans one longitudinal edge of a concrete joint. Single or double sets of keying formations are provided on respective sides of the longitudinal centre line of the waterstop. In the finished structure the waterstop is on the external face of the construction, spanning the gap between the adjacent concrete bodies.
Most waterstops are obscured from view once a building is completed so that their subsequent performance is not readily monitored. Most are thought to work adequately but occasional complaints of failure to prevent water or moisture penetration do arise. Possible causes are air collection under the waterstop section at the time of casting concrete around the section, leading to weakened porous concrete, and stretching and thinning of the waterstop on concrete shrinkage and building movement leading to the section drawing away from the concrete.
Accordingly an aim of the present invention is to provide improved waterstops.
We now propose to attach to a waterstop strips of water swellable material to provide improved sealing in the event of water penetration.
According to the present invention there is provided a waterstop having a body comprising an elongate web with a keying formation at or near each edge of the web by which the waterstop may be secured in adjacent respective bodies of concrete so as to seal the gap between such bodies, and on each side of the longitudinal centre line, a strip of water swellable material attached to the waterstop body and positioned so as to engage the concrete and effective in use to improve the seal between the waterstop and concrete in the event of water or moisture penetration.
The waterstop body will normally be an extruded or moulded section of rubber or other moisture and water resistant flexible plastics material, preferably plasticised polyvinylchloride.
The strips of water swellable material may be arranged so as themselves to expand to contact the concrete and provide the improved seal. Alternatively or in addition they may be arranged so that upon expansion they urge another part of the waterstop body to form an improved seal with the concrete.
The strips may be mechanically attached to the waterstop body being for instance received in a reentrant groove in the waterstop. Such strips can be attached in the web provided that the web is thick enough to accommodate a groove without being unduly weakened, or may be attached to a groove formed in the web area with an additional part of the cross section. Normally the mechanical attachment will be continuous and coextensive with the strips, though this is not always essential.
With a waterstop of the internal type, the strips may be provided on one of the keying formations, which take the form of enlargements such as rounded enlargements and in particular enlargements such that the waterstop takes the dumb-bell configuration. Where the waterstop is of the external type having keying formations upon only one face the strips of water swellable material can again be on the web or on the projections, for instance at the top of the projections or keying formations. Particularly where the water swellable strips are provided on the keying formations of either type of waterstop, they may be arranged such that upon swelling they cause adjacent parts of the waterstop to move into more close sealing engagement with surrounding concrete.
Where the water swellable strips are mechanically attached to the waterstop body it may be preferable for them to be removable and readily reattached to the web or keying formations. This is particularly advantageous where welding of sections of waterstop, either longitudinally or more commonly at an angle, is required. It will be appreciated that in most concrete constructions the walls meet each other at right angles or other angles and the corresponding waterstops need to be joined in a completely water tight network, normally by welding. A continuous or substantially continuous water swellable strip will also of course be desirable in such situations.
As an alternative to mechanical attachment the water swellable strips may be adhered to the web or keying formations of the waterstop body. As with mechanically attached strips, the water swellable strips can be on the keying formations, for instance the tops of the projections in external waterstops or the outsides of the enlarged keying formations in internal ones. Alternatively, location on the web may be appropriate, in which case it is preferably not close to the keying formations, particularly with internal waterstops, in case the pressure of the strip weakens the concrete near the critical area where the keying formations seal most firmly against the concrete.
In addition to waterstops as such, the present invention provides a concrete joint with such a waterstop embedded in the respective parts of the concrete.
Further, the invention provides a method of providing such a concrete joint in which the waterstop is first embedded in a first concrete body and subsequently in a second formed concrete body so as to span the joint or gap between the two parts of concrete. Further the invention provides such a method wherein the concrete joint is in parts which have corners between them. For this, the sections of waterstop are welded together, and where the waterstop is of the type with a water swellable strip which is detachable the welding takes place with such strip removed and the strip is subsequently reattached.
Plasticised polyvinylchloride is a preferred material for the bodies of waterstops of the invention, because welding is easily and effectively performed. Alternative materials include chlorinated polyethylene and rubber.
The swellable materials may be any of a variety of materials such as are commercially available. Such materials commonly comprise a rubber or flexible plastic component with a water swellable component, such as of bentonite or a water swellable plastic material such as polyacrylic acid. The strips could be preformed, for instance formed in a liquid system from hot melt or solution, or formed in situ.
The present invention thus provides, in a simple, cheap and easily controlled manner, a waterstop improved by a provision of a water swellable strip on each side to improve sealing in the event of moisture or water penetration.
Only relatively minor investment is needed to provide the addition of the water swellable strips to water stops of generally known design. Thus, the invention can be applied to a full range of waterstops with little investment and thus relatively small increase in price. Further the water swellable strips can be added off line, that is to say subsequent to the extrusion of the water stop body. This will allow better control and the economical production due to reduced rejection and scrap. Further, the adhesion or mechanical attachment proposals do not involve any restriction on the materials which can be selected for the water swellable material such as might arise were there possibility of interaction in the liquid state in a co-extrusion situation. The advantage of the water swellable strip being temporarily removable if mechanically attached has been mentioned, and this applies both to on site welding and to factory welded fabrications.
In order that the invention may be more clearly understood the following description is given by way of example only with reference to the accompanying drawings in which:-

Figures 1 to 7 are sections of waterstops according to the present invention in which the water swellable strips are attached mechanically
Figures 8 to 13 are detailed part sectional views of some possibilities for mechanical attachment of the water swellable strips
Figures 14 to 20 are sectional views of waterstops according to the invention where the water swellable strips are attached by an adhesive
Figures 21 to 23 are sectional views of further embodiments of waterstops according to the invention, and
Figure 24 shows a concrete joint including a waterstop for purposes of explanation.

In the accompanying drawings in each case the waterstop has a body comprising a web such as is indicated at 10 and enlargements or keying formations of one of two general types. The first type as shown for instance in Figure 1 is a swelling at the margin of the waterstop and is indicated by the numeral 11. Figures 1 to 3 and 14 to 16 thus show internal waterstops, to be buried away from the surface of the concrete bodies involved in a concrete joint.
Figures 4 to 7 and 17 to 20 show external waterstops, which have projecting keying formations such as 19 on one face only. These waterstops are for attachment to the surfaces of the two concrete bodies involved in the concrete joint, with the keying formations on each side of the longitudinal centre line of the waterstop being respectively gripped by the concrete in the two bodies.
Figures 1 to 7 and, for the adhesively applied strips Figures 14 to 20, show a non-exclusive selection of waterstop bodies the features of which will be briefly described.
Figures l and 14 show a simple dumb-bell waterstop merely having a bulb or enlargement 11 along each edge. The Figures l and 14 waterstops can be used for construction joints, where the two masses of concrete are encouraged to bind to each other, or in contraction joints where, although the masses are distinct they are close to each other and movement between them is expected.
Figures 2 and 15 show a modification, for an expansion joint. Such a joint occurs where the two concrete bodies are separate from each other, and the gap between them is filled with a joint filler of some description. The Figures 2 and 15 embodiment has a central flexible bulb 12 therefore to be at the centre of the joint at the gap between the bodies. The Figure 3 and 16 embodiment has a flange 13 outboard of the keying formation 11 which may be penetrated with means to hold the waterstop in place prior to pouring concrete.
One variation between the embodiments of Figures 4 to 7, and Figures 17 to 20, is a difference in the number of keying formations 9 on each side of the centre line of the waterstop. Generally, there are two such keying formations on each side of the centre line although as shown in Figure 5 it is possible, though perhaps less effective, to have only one. Figure 5 shows the provision of central flexible ribs 15 on the same side of the waterstop as the keying formations. This portion is adapted to have shuttering placed upon it while the first side of the waterstop is embedded in the concrete. The ribs prevent seepage of grout under the shuttering and across to the other side of the waterstop.
Figures 6 and 19 shows a flange 16 outwards of the outer keying formation 9 on each side. This can be used to fix the waterstop by nails against shuttering prior to the pouring of concrete, with the waterstop then being penetrated only at a point outside the keying formations. Figures 7 and 20 show an embodiment appropriate for an expansion joint, with a flexible central portion 17 to be received in the gap between the bodies of concrete.
The water swellable strips 20 as shown in Figures 1 and 14 these can be located on the outer sides of the keying formations.
Figures 2 and 15 show an alternative position involving two strips on each formation 11 and on opposite faces of the waterstop. Figures 3 and 15 show an embodiment where the strips of swellable material are on the web between the enlargements. In Figure 16 they are located relatively close to the centre line of the waterstop, and further from the keying formations for reasons described below. In Figure 3 they are offset to reduce the strength loss which may occur in the web when the water swellable strips 20 are received in grooves. Any of the suggested positionings for the water swellable material strips may be used with any of the various types of waterstop of the internal and the external types.
Other locations also may be contemplated. As shown in Figures 4 and 17 the strips of the water swellable material are at the top of at least one and perhaps both keys on each side of the centre line of the waterstop. Figures 5 and 18 show embodiments where the water swellable material is located at the part of the keying formations where these narrow down towards the web, and where normally close contact and sealing between the waterstop and the concrete bodies is expected. In Figures 6 and 19 the strips are placed on lower parts of the keying formations. In Figures 7 and 20 they are placed in the web and on particular between the keying formations on each side, although of course there may be only one keying formation on each side.
Regarding the external waterstops, it is presently thought that the arrangements of Figures 4 and 17 may show the most appropriate locations for the water swellable strip. In general, although the matter is not without doubt, it is thought that the waterstop to concrete seal is most effective at the sides of the keying formations, particularly where they broaden out from the base. It is thought that locating the potential additional sealing agent elsewhere might be most appropriate. A possible disadvantage in the Figures 7 and 20 construction may be that on swelling the strips will tend to push the waterstop away from the concrete bodies.
As to Figures 3 and 7, in both of which mechanical attachment to the web is proposed, care should generally be taken to avoid unduly reducing the thickness of the web which is after all designed to withstand considerable stress during relative movement between the concrete blocks.
It is probable with the known waterstops that any leakage will follow of a tortuous nature. Referring to Figure 24, it is normally expected that the best sealing occurs in the region of the enlargement, that is to say the area shown at 30. However, it may be that such seal is not effective throughout the length of the waterstop. Accordingly moisture penetrating the joint beneath the waterstop at one point may run parallel to the waterstop, between it and the concrete, for some distance before reaching what may be a small and isolated area where sealing in the region 30 is weak. Penetration there could lead to subsequent movement around and along the waterstop to the upper side. Thus there may be longitudinal transverses between weaknesses in the seals at each stage around the waterstop.
It can therefore be seen that provision of the water swellable strips almost anywhere may be of advantage. However a complication is that in use the web may well be stretched and thus narrowed. This narrowing will be greater in the central part of the web of the waterstop than elsewhere. This is a good reason why, as suggested in Figures 3 and in particular Figure 16 which relates to the adhered strip, the strip is actually placed closer to the centre of the waterstop rather than adjacent the enlargement or keying formation. Positioning relatively close to the enlargement or keying formation would, it is believed, be one of the less advantageous places to locate the water swellable strip particularly when it is adhered in place. It is possible that the pressure of the strip may weaken the adjacent concrete due to entrapment of air. It is particularly undesirable that this should happen near the enlargement or keying formation, where the most effective seal is generally thought to be.
Figures 8 to 11 show possible sections of water swellable material for mechanical attachment but by no means as exclusive disclosure. In Figure 8 the section is circular and is received in a recess slightly greater than semi-circular in size, so as to project above the surface of what in this case is shown as the upper part of a keying formation of the type used with an external waterstop. Clearly in this case, as with the other Figures, the particular sections and mode of attachment can be applied to the other positions proposed for the water swellable material.
In Figure 9 a section having a reentrant base received in a slot has a domed top offering ample material to be available to expand and create a seal. Figure 10 is a more simple section shown as being slightly reentrant on one side, but conceivably merely being rectangular provided that sufficient resistance to removal although not too much resistance is available.
In Figure 11 the material is designed particularly to cause sideways expansion of the base material of the waterstop . Thus, additional sealing will take place between the waterstop body and the concrete as well as between the water swellable material and the concrete. Figures 12 and 13 show alternative forms where the water swellable material is primarily designed to move a lip or flange of the main body of the waterstop so as to improve the sealing effect. Figure 13 shows how this could be employed in the web.
With any mechanical anchoring the water swellable material will tend to push the material of the web or keying formations outwardly and in that way create a better seal.
It is possible that a dual securing arrangement could be employed, that is to say a mechanical arrangement such as is illustrated in Figures 1 and 7 with the addition of continuous or occasional adhesive application. For that and the other embodiments nitrile adhesives are expected to the suitable.
The option of removing the mechanically fastened swellable materials may be particularly useful where such materials are not weldable, being for instance rubber based. Many water swellable materials currently available are of that type and thus have that disadvantage. Accordingly, to avoid material being burnt during the welding operation leading to weakness, it is best to remove them on welding. A continuous angled channel for the water swellable material should result and the water swellable material can then be reinserted, either in a continuous manner with an angle in it, or conceivably by the material being cut and a butt or mitre joint between sections provided. Welding is easier and more effective with the swellable material removed and out of the way. In the event of factory formed joints the water swellable material could be applied before or after the joint section has been created.
Normally the adhesive attachment is continuous and coextensive with the strips, though this is not always essential.
Figures 21 to 23 are further embodiments. In the embodiment of Figure 21, water swellable material is applied to both edges of one keying formation on each side. As with other embodiments having two keying formations on each side, such application could be to the other one, or to both, on each side, and this disposition of swellable material is also useful where there is one keying formation on each side.
In the embodiment of Figure 22, the water swellable material is applied at the roots of the keying formations. When located here, they will, on swelling, tend to tighten the keying formation in the concrete, by putting it under tension, thus improving the seal made at the top of the keying formation.
These embodiments lend themselves readily to thick layer application methods, i.e. the water swellable material is deposited as a layer onto the waterstop. Alternatively, pre-formed strips can be applied by adhesion.
A mechanical attachment in a similar place is shown in Figure 23. Here the keying formation is broadened at its root so as to permit formation of a re-entrant groove into which a key shaped end of a strip of water swellable material can be received.
Examples of water swellable materials suitable for all embodiments are: Adeka Ultra Seal, a water swellable rubber, Series KCH sold by Asahi Denka Kogyo KK of Tokyo, and Sumikagel GRC-VCL-3B sold by Sumitomo Chemical Co Ltd of Osaka, Japan.
To protect the system from premature expansion the water swellable material may be covered with a known water or alkali penetrable or soluble coating.

Claims

1. A waterstop having a body comprising an elongate web with a keying formation at or near each edge of the web by which the waterstop may be secured in adjacent respective bodies of concrete so as to seal the gap between such bodies, and, on each side of the longitudinal centre line, a strip of water swellable material attached to the waterstop body and positioned so as to engage the concrete and effective in use to improve the seal between the waterstop and concrete in the event of water or moisture penetration.

2. A waterstop according to claim 1, wherein the strips of water swellable material are arranged so that, in use, upon expansion, they urge another part of the waterstop body to form an improved seal with the concrete.

3. A waterstop according to claim 1 or 2, wherein the strips are mechanically attached to the waterstop body.

4. A waterstop according to claim 3, wherein the strips are attached to the body between the keying formations.

5. A waterstop according to claim 3 or 4, wherein the strips are of circular cross section received in a groove of greater than semi-circular cross section.

6. A waterstop according to claim 3 or 4, having a strip received in a reentrant groove and a head above and wider than such groove.

7. A waterstop according to any one of claims 3 to 6, wherein the water swellable strips are removable from and reattachable to the waterstop body.

8. A waterstop according to claim 1 or 2, wherein the water swellable strips are adhered to the waterstop body.

9. A waterstop according to claim 10, wherein the strips are located on the web and preferably to nearer the centre of the waterstop than to the keying formations.

10. A waterstop according to any one of claims 1 to 8, which is of the internal type with the strips attached to the outer edges or to opposite sides of the keying formations.

11. A waterstop according to any one of claims 1 to 8, which is of the external type with the strips attached to top or sides of the key formations.

12. A method of providing a concrete joint in which a waterstop according to any one of claims 1 to 11, is embedded in a first concrete body and subsequently in a second concrete body so as to seal the joint or gap between the two concrete bodies.

13. A method of forming a concrete joint according to claim 12, wherein angles are formed between the concrete bodies and the waterstop includes sections welded to one another, the weld having been performed with the water swellable strip removed and the water swellable strip being subsequently reattached to provide a substantially continuous seal.