AU2006200869A1 - Waterproof Cladding - Google Patents

Description

o WATERPROOF CLADING This invention relates to the cladding of partially-overhanging substrates.

By "partially-overhanging substrates" is meant simply a substrate part of which overhangs.

One example is a tunnel bored in rock, which has an overhanging roof and non- 0 0 arch of concrete, brick, stone or other material.

Cl 10 The exposed rock surfaces of tunnels often require cladding, this cladding generally being concrete, which may be sprayed (so-called "shoterete"), cast in formnwork or placed in prefabricated sections which are then grouted. One of the problems frequently encountered is water corning through and running down the substrate during the construction. The standard way of dealing'-with this problem is the application to the substrate of a drainage means. This is simply something which provides on the substrate a plurality of drainage channels, so that the water is directed away from the substrate to provided drainage outlets.

The sequence therefore is usually as follows; apply a drainage means, followed by a waterproof membrane, followed by a final layer of concrete.

The drainage means known to the art can take various physical forms. One popular type comprises an open mesh made of plastics material, this being generally supplemented by an at least partially waterproof covering sheet to help direct the water to the provided drainage outlets and prevent it, in the case of high water flow, from runining straight through. Another common type is a sheet of plastics material (typically of PVC or PB) which provides drainage channels. In one such material, the sheet comprises grooves through which water can In another variant, there is formed on the sheet a series of depressions which appear as protrusions on the other side of the sheet .These protrusions hold the sheet off the substrate and allow water drainage. Such drainage means are fixed to the substrate by any convenient means (adhesive, nails, rock anchors).

To this drainage means is -usually attached a waterproof membrane. This is generally'a series of oyerlappin 4g sheets of thermoplastic material which is applied to the drainage -2- IND means and secured in place by melting the sheet round bolts previously applied through 0 the drainage means into the rock for this purpose, the sheets then being joi'ned by welding ci to form a single waterproof sheet. A final layer of concrete is applied to them by any of the methods hereinabove described.

0 In practice, this method suffers from a variety of drawbacks. Jt is difficult to weld the thermoplastic sheets together with complete success, so that there can be imperfect joins 00 where water can come through. Moreover, such sheets may be damaged in handling and 0 0 application and consequently suffer from leaks. In any case, the work of applying such IND 10 sheets is time-consuming and difficult in a tunnel, as is the work of erecting the drainage mueans itefIn all cases, where other fixtures such as railway catenary supports are required, either these have to be driven through the drainage means into the rock (thereby providing a potential point of water entry), or the final concrete layer must itself be strong enough to support them, which usually means using a thickness of concrete not otherwise required.

It has now been found that such water problems can be substanti 'ally or even. completely overcome by a particular structure. This invention therefore provides a cladding on a partially-overhanging substrate which comprises, in sequence starting from the substrate;a drainage means; (ii) a waterproofing membrane which has been applied thereto by spraying; and (iii) a layer of concrete.

The invention further provides a method of providing a waterproof cladd ing on a partiallyoverhanging substrate, comprising the application to the substrate of the following elements in sequence; a drainage means; (ii) a waterproofing membrane, applied by spraying; and (iii) a layer of concrete.

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0 In a preferred embodiment of the invention, the substrate is given an initial layer of concrete. This is especially important when the substrate is rough, for example, as a result Sof blasting, and it preferably applied by means of spraying. Although it can also be done by casting or placing of prefabricated sections, shotcreting has the advantage that it conforms more exactly to the wall while providing a desirable smoother surface for the fixing of o0 drainage means. This makes the final cladding essentially a single unit with the wall, 00 enhancing its strength and making possible a cladding with substantially less material than Sformerly used.

o 10 The drainage means may be selected from any of the means of this type known to the art. A typical example is a plastics mesh to which is applied (to that side remote from the substrate) an at least partially waterproof layer. A particularly good variety of this type is a mesh to which is fixed a thin plastics impermeable sheet, on the other side of which sheet is a fibrous layer which assists in the bonding of the waterproofing membrane hereinunder described. However, there are many other types possible, and any of the art-recognised types are acceptable.

A preferred drainage means consists of two layers of"geotextile", fibrous materials of the type hereinabove described, between which is a waterproof film. Preferably the geotextile against the rock is hydrophobic and that further removed from the rock is hydrophilic. The hydrophobic layer helps repel water and the hydrophilic layer allows a water-based sprayable membrane to penetrate well and bond thoroughly as further described hereinunder, thus helping create a composite structure. This means is supplied as a single material, a so-called "drainage fleece". Any kind of sprayable membrane is useful in the working of this invention.

One particularly useful type of sprayable membrane is the membrane described in International Application WO 97/25484 the contents of which are incorporated herein by reference. In this case, it is a plastics material applied by spraying (a thermosetting polyurethane is described), the surface of this layer being configured in order to provide anchoring means for subsequently applied layers. This is done typically by mechanically -4- ND deforming the surface before it hardens fully, or by embedding therein solid material such 0 as stone chips.

CtI SAnother particularly useful type of sprayable membrane is described in International Application WO 98/24738, the contents of which are incorporated herein be reference. In this case, the membrane is formed from a layer of coalesced particles of thermoplastic Spolymer laid down form an aqueous dispersion. Polyurethanes, polyesters ahd vinyls may N be used, but the preferred materials are addition polymers of ethylenically-unsaturated Smonomers, more preferably, those having a glass transition temperature (Tg) of below ID 10 15 0 C, even more preferably below 0 The weight solids contents of the aqueous dispersions from which the membranes are formed typically lie within the range of 30-60%. Specific examples of suitable materials include polyurethanes, styrene-butadiene copolymers, ABS (acrylonitrile-butadienestyrene) polymers, acrylonitrile-butadiene copolymers, styrene-acrylic copolymers, polsulphide dispersions, polyurethane-acrylic dispersions, polyisoprene and PVC latexes and copolymers of vinyl chloride and/or vinyl acetate with acrylic monomers such as (meth)acrylic acid and esters thereof. Materials such as bitumen emulsions may be used in conjunction with these materials, but as such materials do not coalesce, they should not comprise more than 50% by weight solids of the binder. This list is not exhaustive, and the skilled person equipped within the concept of this invention will readily be able to identify other suitable materials. Many such materials are available commercially and examples of suitable commercial materials include those sold by BASF AG under the mark "Acronal" and those sold by Synthomer under the trade mark "Synthomer".

In addition to the aqueous dispersion, the composition may include other ingredients. One especially useful ingredient is filler. This not only "extends" the composition, but also roughens the surface, thus providing a "key" for a subsequently applied cementitious composition. Its presence is preferred. Typical examples of suitable fillers include quartz sand and quartz flour of average diameters in the range of from 0.04-1.5 mm, as well as dolomite, talc, mica, barytes, iron oxide, titanium dioxide, rubber and plastics granules, lightweighted aggregates and glassy furnace residues such as "holospheres". Fibres of

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C steel, glass or polymeric material can also be used, preferred examples of polymeric fibre t being those of thermoplastic material, especially polyethylene and polyacrylonitrile, preferably with lengths of from 0.2-12 mm and surface area of from 6-8 m 2 /g.

o Sprayable membranes confer good waterproofness, but cannot be used on a substrate on IND which there is running water. The combination of drainage means and waterproofing membranes overcomes this difficulty and gives an especially versatile and high-performing system. This is largely because the two components, drainage means and sprayable o 10 membrane, become in effect a single composite entity. The invention therefore also provides a composite waterproofing system for application to surfaces, consisting of a drainage means as hereinabove defined and a sprayed waterproof membrane. In addition, fixtures can be added before the membrane spraying and the subsequent membrane spraying will ensure that the penetration of the fixture through the drainage means remains watertight. This means that a subsequent layer of concrete need not be load-bearing and therefore can be much thinner than would otherwise be the case.

To the surface of the membrane is applied a layer of concrete. This can be done by any convenient means, but ideally by spraying. Spraying brings many advantages. For example, the layer conforms with the membrane and forms with it, the drainage means, the substrate and, if applied, any initial concrete layer a single composite entity, thus enhancing the benefits of the composite waterproofing system hereinabove described. This is very strong and reduces substantially the quantities of concrete needed. For example, using prior art-recognised methods, a final concrete layer would need to be typically cm. thick. When this invention is used, a layer may be as low as 5 cm. thick, representing a significant saving in time, money and material. In addition, application methods such as casting require not only complex formwork, but also reinforcing grids. The sprayed concrete does not need this, it being possible, if desired, to provide fibre reinforcement in the concrete mix itself by the inclusion of fibres.

-6- IND A futher important characteristic is that the continuous bond between the sprayed membrane and the final shotcrete layer prevents what often happens on sheet-based systems, namely the movement of water along the membrane-shotorete interface from the Ct point of actual leakage and its eventual appearance tens of metres from that point. In the system of the present invention, any leakage will take place at the point of leakage itself, o and canl be easily repaired.

NO The invention is useful primarily in tunnelling, but it may also be used in free-standing 00 0 completely artificial structures which comprise partial overhangs of the type hereinabove described, for example, arches of concrete, brick, stone or other such material. In comparison wihthe art-recognised methods, it is simpler to use, it provides better results and it requires less material and time.

In a further, broad, form of the present invention there is provided a composite waterproofing system for application to surfaces, consisting of a drainage means and a sprayed waterproof membrane. The drainage means and sprayed waterproof membrane for use in this further, broad, embodiment of the invention may be as described above.

The invention will now be described with reference to the accompanying drawing which depicts a schematic cross-sectional view of a preferred embodiment. In this drawing, the dimensions of some elements have been exaggerated to make clear the nature of the construction.

In the drawing, the invention has been applied to a rock wall 1 of a bored tunnel. To this rock wall is applied an initial layer of shoterete 2. To this is then applied a drainage fleece, generally designated as 3. This drainage means consists of three elements, a fibrous, hydrophobic sheet 4, a waterproof film 5 and a fibrous hydrophilic sheet 6, the three being combined in a single sheet and secured to the shotcrete layer 2 by means o f nails 7 whose heads protrude slightly from the drainage means. The nails additionally comprise fleece retaining means 8, preferably of plastics material, which comprise shanks which are a tight O fit on the nails 7 and comparatively large roundels which press the fleece against shoterete layer 2. The fibrous sheet 6 and the nail heads help a subsequent sprayed membrane 9 to Cbond more securely to the drainage means.

To the drainage means is applied by spraying a waterproofing membrane 9, the composition of which is

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SPolymer dispersion' 30 parts by weight barytes 27 calcium carbonate 42.5" titanium dioxide Istyrene-acry~lic ester copolymer emulsion 50% solids by Weight ("Acronal') (Wrade mark) 8361 (ex BASF)) 0S Thi s corresponds to Example 1 of WO 98/2473 8.

IND 10 Finally, a layer of reinforcing fibre-containing shoterete 10 is applied.

The shoterete formnulation useful in this application may be any such formulation useful in such an application. in addition, the skilled person will readily appreciate that there are possible many variations in bath materials and methods which fall within the scope of the invention. For example, should enhanced load-bearing strength be needed, the nails 7, depicted in the drawing as being covered by the sprayed membrane 9, may protrude through it and -into the shotcrete layer 10. Thec nail heads provide a "key" which supplements the excellent bonding of the shotcrete to the membrane.

In another embodiment, the hydrophobic fibrous sheet may be replaced by a plastics grid which has the forn of two parallel sets of elongate intersecting elements, one set resting on the surface of shotcrete layer 2 and spacing the other set from it, thus defining a plurality of drainage channels. The waterproof plastics sheet 5 is advantageously of the same plastics material.

Claims (12)

1. A cladding on a partially-overhanging substrate which comprises, in sequence Sstarting from the substrate; o a drainage means; (ii) a waterproofing membrane which has been applied thereto by spraying; and 00 0 (iii) a layer of concrete. o 10

2. A cladding accotding to claim 1, wherein the substrate is given an initial layer of concrete.

3. A cladding according to claim 1 or claim 2 wherein the drainage means is a plastic mesh which plastic mesh includes an at least partially waterproof layer applied to that side of the plastic mesh which is remote from the substrate.

4. A cladding according to any one of claims 1-3, wherein thewaterproofing membrane is a plastics material applied by spraying and whose surface is configured so that anchoring means for subsequently-applied layers is provided.

A cladding according to any one of claims 1-4 wherein the waterproofing membrane is a layer of coalesced particles of thermoplastic polymer formed from a sprayed aqueous dispersion.

6. A cladding according to any one of claims 1-5, wherein the layer of concrete is applied by spraying.

7. A cladding according to claim 6, wherein the sprayed concrete comprises reinforcing fibres. I

8. A method of providing a waterproof cladding on a partially-overhanging substrate, 0 Scomprising the application to the substrate of the following elements in sequence; S(i) a drainage means; (ii) a waterproofing membrane, applied by spraying; and (iii) a layer of concrete. 00

9. A composite waterproofing system for application to surfaces, consisting of a Sdrainage means and a sprayed waterproof membrane. IND) "I

10. A cladding on a partially overhanging substrate substantially as hereinabove described with reference to the examples and/or drawings.

11. A method of providing a waterproof cladding on a partially overhanging substrate substantially as hereinabove described with reference to the examples and/or drawings.

12. A composite waterproofing system substantially as hereinabove described with reference to the examples and/or drawings. DATED this first day of March 2006 Construction Research Technology GmbH By their Patent Attorneys CULLEN CO.