GB2256445A - Waterstops. - Google Patents

Abstract

A waterstop for a joint between adjacent concrete blocks including first and second elongate sheet-like members (10) each comprising a substrate with an adhesive layer (12) on one side, the sheet-like members being continuously joined to one another along a longitudinal line (11) and arranged such that they overlap one another, and the adhesive layers being on the sides of the substrate remote from each other, such that the sheet-like members can be adhered to the respective faces of the concrete blocks at the joint to provide a seal therebetween. <IMAGE>

Description

WATERS TOPS The present invention relates to waterstops of the type used to provide a seal in a gap between adjacent blocks of concrete.

The joints between separately poured masses of concrete are of three types; contraction, construction and expansion joints. In contraction and construction joints the two masses of concrete are contiguous. In contraction joints the two masses of concrete are maintained distinct from each other, for instance by placing a very thin separating layer on the first mass of concrete before the second mass is poured. This type of joint is used when it is expected that the masses of concrete will move relative to each other in a direction at right angles to the plane of a joint. In construction joints the two masses of concrete are encouraged to bind to each other and such a joint is used when it is not expected that the masses of concrete will move relative to each other.

In expansion joints on the other hand, the two masses of concrete are not contiguous, but are separate from each other, for instance, by a distance of a few centimeters. The gap between them is filled by a joint filler of some description. Expansion joints are used when it is expected that the two masses of concrete will move relative to one another in a direction along the plane of a joint and possibly also in a direction at right angles'to the plane of a joint. This movement may take place, of course, with changes in the seasons and changes in temperature occurring during the course of a day.

All three types of joint need to be sealed with the aid of a waterstop. A waterstop spans the joint, being embedded or attached to both masses of concrete. There is an important difference between the waterstops employed for contraction and construction joints on the one hand, and expansion joints on the other because a waterstop for an expansion joint must have an enlarged central section which will be generally as wide as the gap between the concrete masses and is flexible so that it will accommodate the expected movement.

Originally waterstops were located centrally of joints, between the faces of the concrete masses, so that they had ends located in and entirely surrounded by the concrete of the adjacent masses. These became known as internal waterstops. A dumb-bell type of cross-section was typical.

In the 1960's so-called "external" waterstops were developed, to be located on the outside of the two adjacent masses of concrete. Waterstops of this type are for instance the subject of British Patent Specifications 1008811 and 1300811 and have on one face only keying formations which are so shaped as to be gripped by the concrete masses when the concrete sets in order to hold the waterstop in place. These external waterstops are easier to locate than internal ones.

The present invention represents a radical departure from prior water stops. Instead of being mechanically engaged with the poured concrete of the concrete masses, with the present invention the waterstop is to adhere to the concrete on both sides of the joint.

According to the present invention there is provided a waterstop for a joint between adjacent concrete blocks including first and second elongate sheet-like members each comprising a substrate with an adhesive layer on one side, the sheet-like members being continuously joined to one another along a longitudinal line and arranged such that they overlap one another, and the adhesive layers being on the sides of the substrate remote from each other, such that the sheet-like members can be adhered to the respective faces of the concrete blocks at the joint to provide a seal therebetween.

Preferably the two sheet-like members are joined to each other along a line between their longitudinal edges, normally the centre line. With this arrangement, the sheet-like members need not be the same. For instance, one may be thicker than the other, while for expansion joints it is convenient that one should be more like a board, having considerable thickness.

On the other hand, a single sheet folded for instance along its centre line and with adhesive on the outside of the fold can alternatively be used in accordance with the invention.

When a waterstop according to this invention is in place between adjacent bodies of concrete in a joint, water pressure applied to the joint in a direction between the sheet-like members towards the point where they are joined to each other is prevented from penetrating the joint by the provision of the members, and the adhesive between them and the concrete. Further, the increasing pressure causes the waterstop more securely to be adhered to the adjacent faces of concrete. Thus, the waterstops of the invention act in a positive way when pressure is applied.

Normally, an arrangement with a substantially central line of join between the two sheet-like members is to be preferred. It allows the waterstop to be installed either way round in a joint with equal effect, which will be particularly important if it is not clear from which direction water pressure is likely to arise. It also provides protection against water pressure from both directions through the joint. There are instances in construction work where passage of water may take place in both directions, e.g. swimming pools and water tanks. The joint will preferably be central although it need not be, and will typically be a weld.

For use in contraction and construction joints, both the sheet-like members of the waterstop will usually be relatively thin and flexible so that the overall waterstop is not particularly thick. For expansion joints on the other hand, one of the sheets will normally be in the form of a board with the adhesive on one face. This may be an expanded cellular board.

In the thin waterstops of the invention there are preferably provided at intervals transverse welds. These are to prevent longitudinal passage of moisture along the waterstop and are particularly important at overlaps or the ends of waterstops. One form of waterstop of the invention for expansion joints can comprise a board, typically of expanded plastics material, and two plastics sheets, welded to one another, centrally perhaps of the waterstop. One sheet is approximately the same width as the board, the other is considerably larger and is folded so as substantially entirely to envelope the board, whereupon adhesive can be applied to both exterior faces of the construction. Such waterstops can be butt jointed.

The adhesives useful in waterstops of the invention may be waterproof pressure-sensitive adhesives such as a bitumen rubber mixture.

Alternatively a synthetic adhesive coating may be used, which may have a protection layer thereon. Such an adhesive coating may be of a type particularly effective in adhering to post-poured concrete.

The invention will be better understood from the following description which is given by way of example only, with reference to the accompanying drawings in which: Figures lA to 1D show sectional views of four waterstops according to the invention; Figure 2 is a perspective view of a waterstop of the invention of the type shown in Figure lB; Figure 3 is a perspective view showing the use of a waterstop of the invention in a vertical wall and Figure 4 is a perspective view showing the use of different types of waterstop of the invention in a concrete construction having a horizontal slab with a vertical wall extending from one edge thereof.

The waterstops shown in Figures 1A and 1B are for clarity shown out of proportion. They comprise two plastics sheets 10 welded together at their centres at 11 and with adhesive layers 12 provided on the exterior faces of the two-sheets.

The only difference between the embodiments of Figures 1A and 1B is in their width. They may typically be 50 or 100 millimeters in width. The different waterstop widths are envisaged in order to accommodate a variety of expected hydrostatic pressures. The consequence of a greater width is an increased contact area between adhesive and concrete. The waterstops of Figures 1C and 1D are of an alternative type wherein one sheet-like member includes a board 13 surrounded by a plastic sheet 14 which is welded centrally to a second plastic sheet 15. Again on the exterior faces are adhesive layers 12.

Figures 1C and 1D show two different embodiments of these waterstops having different thicknesses, typically 12 or 25 millimeters thickness and with a width typically of 100 millimeters.

Figure 2 shows a perspective view of a waterstop such as is shown in Figure 1B indicating at 20 transverse welds in additional to the longitudinal weld shown at 11.

Typically the transverse welds are spaced apart 50 millimeters or perhaps as much as 100 millimeters, for instance the same spacing as the width of the waterstop, in order to stop water passage at junctions or overlaps of waterstops or for instance at positions where some corner piece may be provided. Longitudinal movement of moisture is prevented by these transverse welds.

In the waterstops of Figures 1C and 1D the board 13 which may typically be of a low compression non-absorbent plastics material preferably with good recovery properties. Expanded polyethylene or polystyrene may be useful for this purpose.

This board is enveloped by the plastic sheet 14.

The plastics sheets 14 and 15, Figures 1C and 1D, and 10 in Figures 1A and 1B may be of heavy duty or alternatively high or low density polyethylene or PVC or some other thermoplastic or plastic sheet material. A thickness of between 0.1 and 1 millimetre can be considered, depending on the tensile strength required, the conformability and of course the cost.

A non-degradable board is most appropriate for the boards 13 in Figures 1C and 1D. Provision of adhesive mastic to seal the ends and prevent water entry is also advisable.

Waterstops of the invention can provide a reliable seal between the two sides of a concrete structure within joints of civil engineering and building constructions. The great advantage is that they are more economical in cost than conventional waterstops and they also facilitate and simplify the method of installation.

Further, increasing water pressure has the effect of increasing the sealing effect, due to the pressure applying the adhesive more firmly against the concrete surface. This function of self-sealing under positive pressure is also new in the waterstop field. Flexibility of the waterstop remains permanent thanks to the provision of relatively thin plastics sheet which is also resistant to aggressive soils and corrosive ground water. No special tools are required for installation and at joints simple overlapping in the case of the thin waterstops (Figures 1A and 1B) is sufficient, while butt jointing of waterstops of the type shown in Figures 1C and 1D can be performed by cutting back one end of the board, say by 100 mm, and simply overlapping the plastics sheets remaining with the plastics sheets of the adjacent section.

Therefore no special junction pieces are needed.

So far as the adhesive material is concerned this may be a pressure-sensitive adhesive, typically a bitumen rubber mixture preferably at least 0.025 cm thick and for instance up to 0.5 cm thick if desired. The adhesive will generally be such that the waterstop will stick to the required surface, without the use of heat or additional bonding agents. The thicker the layer of the adhesive the better the water proofing effect, but in general 0.063 to 0.4 cm thickness is satisfactory. For a bituminous adhesive it is preferable to use a natural or synthetic rubber, virgin or reclaimed, blended into bitumen to provide a smooth mix. The ratio by weight of bitumen to rubber is 80:20 up to 95:5 especially about 90:10.Generally, suitable compositions have softening temperatures measured by the Ring and Ball method of 60 to 140 C and penetration values of about 30 to 150 at 250C (Institute of Petroleum Method).

The above adhesive materials may suffer from the draw back that exposure prior to casting concrete may lead to adverse weathering. Further, they may pick up unwanted dirt and dust and their tenacious tack may prove a problem to workers.

Alternatively, therefore, synthetic adhesives may be used, preferably covered by a protection layer.

As used herein, the term "synthetic adhesive" refers to non-bituminous and non-asphaltic adhesives. The adhesive layers can be selected from butyl rubber based adhesives, polyisobutylene based adhesives, polyisobutyl based adhesives, acrylic based adhesives, vinyl ether based adhesives, styrene-isoprene-styrene based (SIS) adhesives, styrene-ethylene-butylene-styrene based (STUBS) adhesives, styrene-butadiene-styrene based (SBS) adhesives, and combinations thereof.

Pressure sensitive adhesives are preferred. Preferably, the synthetic adhesive is a pressure sensitive hot melt adhesive block copolymer of SIS, SBS or SEBS. Most preferably, the synthetic pressure sensitive hot melt adhesive is based on an SIS block copolymer. For a more detailed description of pressure sensitive adhesives, see Satan Handbook of Pressure Sensitive Adhesive Technology by Van Nostrand Reinhold Company, Inc. (1982), incorporated herein by reference.

The synthetic adhesive layer can optionally contain typical additives, such as, light absorbers (i.e. carbon black, benzotriazoles, etc), light stabilizers (i;e. hindered amines, benzophenones), antioxidants (i.e. hindered phenols), fillers (i.e. calcium carbonate, silica, titanium dioxide, etc), plasticizers, rheological additives, and mixtures thereof. Preferred synthetic adhesive layers contain light absorbers, light stabilizers and antioxidants.

It has been discovered that the adhesion to post cast concrete is improved when the synthetic adhesive layer has a penetration greater than about 30 decimillimeters (dmm) (150 g. 5 sec., 700F) as measured according to ASTM D 5-73, incorporated herein by reference.

The "adhesive" nature of the synthetic pressure sensitive adhesive has the added benefit in that side laps and end laps of the membrane are easily formed. The thickness of the synthetic adhesive layer is from about 0.005 inches to about 0.080 inches, preferably greater than about 0.020 inches.

The use of a protective coating gives the waterstops minimal tack and protects the synthetic adhesive from dust, dirt and the elements (particularly sunlight). At the same time, the protective coating does not hinder the ability of the waterstops to form a fully adhered strong bond to the post cast concrete and the resulting structure.

The protective coating can be selected from the group consisting of styrene butadiene rubber based (SBR) coatings, carboxylated SBR based coatings, acrylic based coatings, polyvinylidene chloride based (PVDC) coatings, polyvinyl chloride based (PVC) coatings, ethylene vinyl acetate copolymer based (EVA) coatings, ethylene ethyl acetate copolymer based (EEA) coatings, polychloroprene based coatings, polyester based coatings, polyurethane based coatings, styrene-isoprene-styrene based (SIS) coatings, styrene-butadiene-styrene based (SBS) coatings, and combinations thereof. Preferred protective coatings are acrylic based coatings. Most preferred are styrene butylacrylate based coatings.

Elastomeric protective coatings are preferred. As used herein, the term elastomer means an elastic polymer having properties, similar to those of vulcanized natural rubber; namely the ability to be stretched to at least twice its original length and to retract very rapidly to approximately its original length when released. Elastomeric acrylic based coatings are preferred and elastomeric styrene butylacrylate based coatings are most preferred.

The protective coating may optionally contain typical additives, such as, light absorbers (i.e. carbon black, benzotriazoles, etc), light stabilizers (i.e. hindered amines, benzophenones), antioxidants (i.e. hindered phenols), fillers (i.e. calcium carbonate, silica, titanium dioxide, etc) plasticizers, rheological additives and mixtures thereof. Preferred synthetic adhesive layers contain light absorbers, light stabilizers and antioxidants.

The adhesion to post cast concrete is greatly improved when the protective coating has a penetration greater than about 30 dmm (150 g. 5 sec. 70-F) as measured according to ASTM D 5-73, incorporated herein by reference.

The thickness of the protective coating can be from about 0.001 inches (0.0025 cms) to about 0.020 inches (0.05 cms), preferably about 0.005 inches (0.0125 cms).

Further advantages of the present invention are that there will be no complication in form work when a waterstop is to be used, in contrast to the situation at present where, for instance, to allow location of an internal waterstop a corresponding gap in the form work is needed.

Figure 3 is a perspective view showing a hardened concrete wall 30 from which moulding and formers have been removed and which contains sets of reinforcements 31, 32 in respective planes. Around the adjoining narrow faces of this wall has been positioned a waterstop of the type shown in Figures 1A and 1B, that is the thin type comprising adjacent flexible sheets welded together, this being shown at 32 on both faces.

The next step in construction, of course, will be the pouring of an adjacent wall using the reinforcement indicated on the right side of the Figure.

It can be noted that viewed from its right edge this Figure can be seen to represent the same situation in a horizontal slab rather than the vertical wall. At 33 there is a lap joint between adjacent sections of waterstop. The simplicity of application can readily be appreciated, it being merely a question of applying the waterstop onto the formwork prior to pouring of the concrete, or alternatively applying the waterstop to set concrete and pressing it into place. Subsequent pouring of concrete to complete the joint leads to automatic adhesion of the waterstop to the freshly poured second section of the joint.

It may be noted that, as provided, the waterstops may have release sheets or non-adhesive coatings on one or both sides to prevent premature adhesion to other members or other parts of the same waterstop.

Figure 4 shows a horizontal slab 40 of concrete separated by an expansion joint 41 from a corner section 42. There is then a construction joint between this and a vertical wall 43, this being a "kicker" construction joint. The exposed faces illustrated are all in the same plane. They are covered by flexible waterstops 47 of the present invention, located centrally of these vertical faces and forming lap joints between adjacent lengths and where corner sections are required, for instance, where the horizontal meets the vertical, and also a lap joint between these thin sections and an expansion joint type of waterstop of the invention shown at 44.

The expansion joint 41 contains a waterstop 44 of the invention generally located at its midheight. It is then completely filled by poured or other joint filler 45, such as are conventionally used at the present time in expansion joints. The waterstop 44 can be seen to have its board on the adjacent side and it extends out of the joint shown so as to be ready for abutting to the next poured section and to receive at the lap joint 46, the thin waterstop 47 already referred to.

At the kicker construction joint a thin waterstop 48 of the present invention is provided, this also being shown extending out of the joint horizontally.

Claims (14)

1. A waterstop for a joint between adjacent concrete blocks including first and second elongate sheet-like members each comprising a substrate with an adhesive layer on one side, the sheet-like members being continuously joined to one another along a longitudinal line and arranged such that they overlap one another, and the adhesive layers being on the sides of the substrate remote from each other, such that the sheet-like members can be adhered to the respective faces of the concrete blocks at the joint to provide a seal therebetween.

2. A waterstop according to claim 1, wherein the two sheet-like members are joined to each other along a line between the longitudinal edges.

3. A waterstop according to claim 2, wherein the line is the centre line.

4. A waterstop according to claim 1, 2 or 3, wherein both sheet-like members are plastics sheets.

5. A waterstop according to claim 4, wherein the sheets are joined additionally with a plurality of transverse joins spaced along its length.

6. A waterstop according to any one of claims 1 to 4, wherein one of the sheet-like members is or includes a boardlike member.

7. A waterstop according to claim 6, wherein the board-like member is made of expanded plastics material.

8. A water stop according to any one of claims 6 or 7, wherein the board-like member is surrounded by a plastics sheet member attached to the other sheet-like member.

9. A waterstop according to any preceding claim wherein the adhesive is a synthetic adhesive.

10. A waterstop according to claim 9 including a protective layer coated on the synthetic adhesive.

11. Waterstops constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

12. A joint between adjacent blocks of concrete, including a waterstop according to any preceding claim.

13. A method of providing a seal between adjacent blocks of concrete by adhering to a first block after pouring a waterstop according to any one of claims 1 to 11, and subsequently pouring an adjacent block so that it adheres to the other side of the waterstop.

14. A concrete construction including waterstops according to any one of claims 1 to 11.