EP0190250A1 - Shuttering unit - Google Patents

Abstract

Formwork unit for the formation of permanent formwork, having two panels with concrete sides (2, 3) interconnected and kept apart by diagonal braces (6) fixed to anchoring elements (7) embedded in the concrete of the panels (2, 3). The formwork unit (1) can be assembled on site using prefabricated panels (2, 3) and cross braces (6).

Description

Shuttering Unit The present invention relates to shuttering units, that is, units for use in the erection of permanent shuttering or formwork for the pouring of concrete or ot.:.er infilling, or for the erection of walls or barriers.

Mois particularly, the invention is concerned with shuttering units of the type comprising two four-siαe panels of concrete interconnected in a parallel, spaced-apart relationship by rigid ties. Units of this type are disclosed, for example, in GB-A-1188066 and GB-A-1549859.

Shuttering units of the aforesaid type are used in the erection of walls, embankments, culverts and the like to provide a self-supporting permanent shuttering or formwork having a cavity which can be filled, for example, by concrete. The shuttering or formwork so formed can be erected quickly and accurately, without the need for mortar joints or external bracing. Once erected, the units remain in place during the pouring and subsequent curing of the infilling concrete.

Such shuttering units can also be used to erect temporary walls or barriers, in which case the cavity between the panels of the erected units may be filled with ballast, rubble or other loose fill material, or left empty to form a cavity wall. The terms "shuttering" and "shuttering unit" as used herein are intended to comprehend walls having internal cavities whether or not these walls are in practice filled with concrete or other fill material. In the shuttering units of the prior art, the panels are interconnected by rigid ties which are embedded at each end in a respective panel during casting, as described in GB-B-2050920. In this way the spacing between the panels is set during manufacture of the units and, if units with a greater or lesser spacing are required during construction of the shuttering or formwork, units with ties of a length corresponding to the new spacing have to be cast specially.

Furthermore, these previous shuttering units are often manufactured away from the site of their use and the shape of the finished units is such as to give rise to difficulties or inconveniences of transport to the site. The transport costs are often prohibitively high over longer distances, given the number of units making a load.

The object of the present invention is to provide a concrete shuttering unit of the type referred to above, which "'can be assembled simply and accurately on site, if necessary with different spacings between the panels, avoiding the drawbacks mentioned above of the prior art.

Accordingly, the present invention provides in one aspect a concrete shuttering unit of the aforesaid type, wherein the rigid ties are separate from the panels, and wherein each panel is cast with tie anchoring means engageable by the ties upon assembly of the unit such that the ties extend diagonally between the panels to cross-brace them.

The anchoring means can be of any suitable form capable of being located precisely in the panels during casting, and capable of cooperating with the ties to produce a stress-bearing interconnection of the panels.

The anchoring means may comprise anchor elements of metal or plastics which are embedded in or bonded to the concrete of the panels at or near the corners of the panels. Each anchor element,- in a preferred embodiment of the invention, comprises a three-sided base in the form of a corner cube enclosing the respective corner of each panel. The anchor elements may include U-shaped loops of metal rod engageable by the hooked ends of respective ties, metal plates having T- or dovetail-sectioned channels which are closed at one end and are engageable with complementary terminal portions of respective ties, or plates or blocks having lugs or sockets engageable by cooperatingly shaped ends of respective ties.

The tie anchoring means may alternatively comprise pins or rods which project into recesses adjacent the corners of the panels and are engageable by respective ends of the ties. In each of the aforesaid cases, the engagement between the ties and the anchoring means may be locked by conventional means, such as locking pins, locking nuts, wedges or friction fitting.

For ease and accuracy of casting of the panels, the anchoring means may comprise anchor rods or dowels a pair of which are embedded in each panel to extend parallel to each other between the aforesaid opposing edges. The anchor rods may have shaped (for example square or triangular) end sections onto which respective ends of the ties are keyed by means of complementary eyes, or, as stated above, the ends of the anchor rods may be formed with eyes into which hooked ends of the ties are fitted. In one embodiment, to facilitate casting, at least the ends of the anchor rods are of circular section and are engaged by complementary eyes at the ends of the ties; this avoids the need to ensure a particular angular orientation-of the anchor rods during casting of the panels.

The panels may have two adjoining longitudinally tongued edges, its remaining two edges being complementarily grooved so that the panels of neighbouring units can be interlocked when the units are erected into shuttering. The tie anchoring means project perpendicularly from opposing edges of each panel and may be recessed relative . to the tongue on one edge of the panel and project into the groove in the opposing edge of the panel, the tongue and groove having, in correspondence with the anchoring means, respective lateral notches through which the ties extend, whereby the ties are retained on the respective anchoring means by the interlocking of the tongues and grooves of neighbouring units upon erection. In practice, abutment or near-abutment of the ends of the anchoring means of neighbouring units may also serve to retain the ties.

Alternatively, each panel may have complementary rebates extending along their parallel upper and lower edges so that when the shuttering unit is superimposed upon another its lower edge interlocks with the upper edge of the shuttering unit below.

In a preferred embodiment sockets are formed in the upper and lower edges of each panel, the sockets of adjoining units being aligned with each other in pairs upon correct erection of shuttering from a plurality of the units, and locking pins engageable in the aligned pairs of sockets to lock the panels of neighbouring units against relative movement.

The ties may be made conventionally from concrete reinforced by metal rods having end portions projecting from the ties and hooked or so shaped as to cooperate with the loops, channels, lugs or sockets of the anchoring means. Alternatively, the ties may be made from angle irons or metal X-shaped elements with ends appropriately shaped for engagement with the anchoring means. Preferably, however, the ties are constituted by rods or flat bars of metal or plastics. These ties may be formed intermediate their ends with off-set portions which allow adjacent ties to "nest" together at their cross-over zone and thus be in a common plane at their ends,_, or they may be straight and simply overlap each other at their cross-over zone and be relatively off-set at their ends.

In the preferred orientation of erection of the units into shuttering or formwork, the units are arranged so that the ties lie in planes perpendicular to the courses of erected units and so do not present an obstruction to the flow of the infilling concrete or foam. It is possible by means of suitable additional ties to effect a strong lattice-like interconnection between units of superjacent and subjacent courses in the shuttering or formwork by, for example, interconnecting one edge of one panel of one unit with the corresponding edge of the opposing panel of the subjacent unit and/or the corresponding edge of the opposing panel of the superjacent unit. In any event, as the infill is poured into the mould cavity between the panels of the erected units, the ties are put under tension by the outwardly-directed foreces exerted on the panels by the infill and the panels are held firmly in position.

The surfaces of the panels which face inwardly of the assembled unit may .be formed with recesses or depressions. These recesses or depressions allow a reduction in the amount of concrete necessary for casting the panels and, more importantly, enable a positive "keying" between the units and the infill.

The shuttering unit of the present invention represents a considerable improvement over the prior art in that the panels, with their incorporated tie anchoring means, can be prefabricated off-site in economic quantities and packed flat for transport to a site. The units themselves can be assembled accurately on site by unskilled labour as the formwork or shuttering is being erected, simply by engaging the ties on the anchoring means to cross-brace the two panels of each unit. Different spacings between the panels of each unit can be accommodated by ties of different lengths or of adjustable lengths.

In another aspect the invention comprehends shuttering formed by the erection of a number of shuttering units as aforesaid with the panels of neighbouring units abutting each other in a number of superimposed horizontal courses, the ties of the units being so arranged that they lie in vertical.planes and do not present a substantial obstruction to the flow of concrete or infill material with the cavity defined between the panels. Preferably additional ties interconnect the shuttering units of superjacent and subjacent courses of the shuttering, the additional ties extending between panels of different shuttering units on opposite sides of the cavity defined between the panels.

_aferably the opposite vertical edges of: each panel of the assembled shuttering units are bevelled towards the inter-panel cavity to define inwardly divergent gaps between the bevelled vertical edges of neighbouring panels. Some of the shuttering units may be arranged with their neighbouring panels at an angle to each other, these panels being interconnected by corner brackets secured by fixings to tie anchoring 'means at the abutting edges of the neighbouring panels.

The invention will now b described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a concrete shuttering unit according to one embodiment of the present invention;

Figure 2 is a scrap perspective view of a first detail of the unit of Figure 1, on an enlarged scale;

Figure 3 is a partially-sectioned scrap view in a horizontal plane of the joint between two panels of neighbouring units of the invention;

Figure 4 is a perspective view of a shuttering unit according to another embodiment of the invention; Figure 5 is a scrap cross sectional view of adjoining panels of two tiers of shuttering units according to the invention;

Figure 6 is a plan view of shuttering erected from shuttering units according to the invention;

E'igure 7 is a scrap plan view illustrating the possibility of ^' bending the shuttering formed from shuttering units of the invention;

Figure 8 is a plan view of shuttering according to the invention showing a corner therein, and

Figures 9 and 10 are diagrammatic elevational views showing two of the many ways in which shuttering units according to the invention can be assembled to form a wall or shuttering.

Referring first to Figures 1 to 3, there is shown a shuttering unit, generally indicated 1, comprising two rectangular precast concrete panels 2, 3. Each panel 2, 3 has two adjoining edges with longitudinal tongues 4 and two adjoining edges with grooves 5 complementary to the tongues 4, so that the panels of neighbouring units 1 can be interlocked during the construction of the shuttering or formwork, in the manner shown in Figure 3. The panels 2, 3 are interconnected in a parallel spaced-apart relationship by respective pairs of rigid ties 6 at opposite ends of the unit 1.

These ties 6 extend diagonally between opposing ends of adjacent edges of the panels 2, 3, lying in planes substantially perpendicular to the planes of the panels 2, 3, to cross-brace them. The ties 6 may, however, be engaged with the anchoring means 7 in such a way that each tie 6 extends from a respective end of one edge of one panel 2, 3 to the opposite end of the opposing edge of the other panel 2, 3 to form a lattice. The ties 6 comprise flat bars, for example of stainless steel or suitable plastics having respective terminal eyes for engagement with respective tie anchoring means 7 which prcject from the aforesaid edges of the panels 2, 3. The ties 6 simply overlap each other at their cross-over zone and thus lie in relatively off-set planes at their ends (Figure 1) .

The anchoring means 7 comprise circular-sectioned rods, for example of stainless steel, a pair of which is embedded in each panel 2, 3 during casting thereof so as to be mutually parallel and accurately parallel with the adjacent non-tied edges of the panel 2, 3. The projecting ends of the rods 7, which provide the anchorages for the respective ties 6, are recessed relative to the tongue 4 on one edge of the respective panel 2, 3 and project into the groove 5 in the opposite edge of the panel. In correspondence with these projecting ends, the tongues 4 and grooves 5 have respective lateral notches 8, 9 which open into the space between the panels 2, 3 of the assembled unit 1 and through which the respective ties 6 extend.

In use, each shuttering unit 1 may be assembled on site immediately prior to its incorporation in the shuttering or formwork under construction simply by engaging respective ties 6 with the anchoring means 7 at opposing edges of the panels 2, 3. The ties 6 are retained on their anchoring means 7 by the interlocking of the tongues 4 and grooves 5 of neighbouring units 1 and by the abutment of the ends of the corresponding anchoring means 7, as shown in Figure 3. The shuttering or formwork is erected with the ties 6 lying in vertical planes perpendicular to the courses of the units (that is, in the orientation of Figure 1).

Once the shuttering has been erected concrete may be poured into the mould cavity defined between the panels 2, 3 of the units or other infill material may be introduced. By exerting outwardly-directed forces against the panels 2, 3, the concrete or other infill material puts the ties 6 under tension so that the panels are braced firmly in position.

The panels 2, 3 are cast with recesses or depressions 10 in their surfaces which face inwardly of the assembled unit 1. In addition to allowing a reduction in the concrete used in the casting of the panels 2, 3, these recesses or depressions 10 enable a positive "keying" between the units 1 of the shuttering or formwork and the infilling concrete.

The panels 2, 3 and ties 6 will usually be prefrabricated off-site, the precise orientation of the anchoring means 7 in the panels 2, 3, and the accuracy of the ties 6, ensuring that the panels of the assembled units 1 are accurately parallel with each other and that the neighbouring units 1 in the shuttering or formwork fit together evenly. The shuttering units 1 can be assembled and erected by unskilled site labour, although, in some cases, transport costs or user requirements may necessitate the on-site manufacture of the panels and ties. The tongued and grooved panels of the shuttering units 1 shown in Figures 1 to 3 require precision casting and may be vulnerable to damage in transit. An alternative form of shuttering unit according to the invention is illustrated in Figure 4, in which the same reference numerals have been used to identify parts corresponding to those of the Figure 1 embodiment.

The two precast concrete panels 2, 3 of the shuttering unit 1 shown in Figure 4 are formed with complementary rebates 11, 12 extending along their parallel upper and lower edges, so that when the shuttering unit 1 is superimposed upon another, its lower edge interlocks with the upper edge of the shuttering unit below, as shown in Figure 5, the rebates 11, 12 forming horizontal joints between the superimposed units which are inclined outwardly and downwardly for drainage. In this embodiment the vertical edge surfaces of each panel 2,_ 3 are plain.

In the shuttering unit' 1 of Figure 4 the' tie anchoring means comprise respective anchor elements 7 of metal or plastics material bonded to or embedded in the concrete of the panels 2, 3 and located at each of the four corners of each panel. Each anchor element 7 comprises a three-sided base in the form of a corner cube enclosing the respective corner of each panel 2, 3. Each corner cube anchor element 7 may be recessed in the concrete of each panel 2, 3 so that its surfaces lie flush with the surrounding concrete.

The anchor elements 7 are located in the concrete panels 2, 3 during casting of the latter. The flat surfaces of each anchor element 7 which lie on the horizontal upper and lower surfaces of the panels 2, 3 in the normal erected position thereof (Figure 1) have central holes 13, the underlying concrete of the panels 2, 3 being formed with blind sockets 14 (Figure 5) in register with the holes 13.

Two further vertically extending blind sockets 15 are formed in each of the upper and lower edges of the panels 2, 3, in positions located symmetrically between the end sockets 14.

Each of the tie anchor elements 7 is formed with a lug 16 on its inwardly facing surface, that is, the surface which, in the assembled shuttering unit 1, faces the cavity between the panels 2, 3, so that the lugs 16 project into this cavity. Each lug 16 has a hole which, in the assembled unit 1, is aligned with a corresponding hole at the end of one of the ties 6, the ties 6 being secured to the lugs 16 by fixing pins 17 passing through the aligned holes in the lugs 16 and the ties 6.

The fixing pins 17 may be force-fitted in the aligned holes of the lugs 16 and the ties 6, or alternatively may be secured by lock nuts engaging threaded ends of the pins 17.

The corner lugs 16, as well as acting as anchorages for the diagonal ties 6 of each shuttering unit 1, may also serve as anchorages for cross-bracing ties (not shown) extending between shuttering units 1 of adjacent courses in an erected shuttering structure, as previously described with reference to Figures 1 to 3.

When the shuttering units 1 are erected on site sealing strips 18 are inserted between the mating horizontal and vertical surfaces of adjacent panels 2, 3, as shown in Figures 5 and 6. The sealing strips 18 may comprise compressible cord, plastics or neoprene, the purpose of these strips being to seal the cavity between the panels 2, 3 against leakage of wet concrete.

The corner lugs 16 of each shuttering unit 1. are co eniently located for the. attachment of cavi_y end walls or connector pieces. Figure 6 shows a cavity end stop wall 19 which seals the end of the cavity in the erected shuttering and is attached to adjacent lugs 16 of the end shuttering units 1 by means of bolts 20.

Figure 8 shows part of shuttering erected using shuttering units 1 according to the invention in order to form a right angled corner. The outside of the corner includes two stop end walls 19 attached to the shuttering units and to each other by means of bolts 20 engaged in the lugs 16. The adjacent panels 4 of the shuttering units 1 on the inside of the corner are attached to each other by a corner bracket 21 which extends vertically and is attached to the lugs 16 of the superimposed panels 4 by means of further bolts 20, these bolts 20 also anchoring the ends of the respective cross-bracing ties 6 between the panels 3, 4 of the shuttering units 1.

The plain vertical edges of each panel 2, 3 in the shuttering unit 1 of Figure 4 are bevelled inwardly so that the length of each panel 2, 3 on its inside face is less than that on its outside face. When shuttering units 1 are erected to form shuttering the abutting vertical edges of the panels 2, 3 define inwardly divergent gaps in which respective sealing strips 18 are located, as shown in Figure 6. The divergence of these gaps not only facilitates the placement of the sealing elements 18, but also permits slight inclination of the panels of adjacent shuttering units 1 when laying a horizontal course, in order to form a shuttering wall with a slight curvature. Such an inclination between adjacent panels 3 in an erected shuttering - is illustrated in Figure 7. It will be seen that such an arrangement allows minor changes in direction or alignment to be accommodated during the erection of shuttering using the shuttering units 1.

The shuttering units 1 of Figure 4 may be erected to form a shuttering wall with staggered vertical joints between the panels 2, 3 of successive horizontal courses, as shown in Figure 9. In this case the sockets 15 of each panel 2, 3 will be aligned in registration with the holes 13 and sockets 14 at the ends of the underlying and overlying panels of adjacent courses, and locking pins or dowels 22, indicated in broken outline, will be inserted in these aligned sockets as each course is- erected.

Alternatively, successive courses may be arranged with their vertical joints aligned vertically in a "straight bond" configuration, as shown in Figure 10. In this case the sockets 15 in adjacent courses will be in registration with each other, as will the sockets 14 at the ends of each panel 2, 3, and the*locking pins or dowels 22 will be located in the aligned sockets 14; additional locking pins may be located in the aligned sockets 15, although this is not essential.

One or more vertical ties (not shown) may extend within the cavity of the erected shuttering from the top course thereof to clamp the courses together, putting the panel elements under compression vertically.

The accurate location of the corner anchor elements 7 in the embodiment of Figure 4 ensures the precision interlocking and erection of a shuttering wall without the necessity for high precision forming of the concrete panels 2, 3 themselves. The anchor elements 7, as well as affording secure fixings for the ties 6, also protect and reinforce the corners of the panels 2, 3.

In both the illustrated embodiments of the invention the panels 2, 3 may be of plain concrete or .concrete reinforced with steel, fibres or plastics, and with or without chemical additives. The outer surfaces of one or both of the panels may be formed with a decorative and/or anti-vandal finish, for example, a fluted or textured surface.

The shuttering units described and illustrated are intended for use as permanent formwork, for the pouring of concrete. An alternative use envisaged for the units is the erection of walls, for example as temporary barriers, in which case the cavity of the erected shuttering may be filled with loose infill material, or simply left void.

A further alternative use of the shuttering units is in the erection of cavity walls in building construction. In this application the cavity of the erected shuttering may be filled with insulating material, for example insulating foam introduced into the cavity on site after erection. One or both of the panels of each shuttering unit may alternatively be provided with a thermally insulating layer bonded to the inside surface of the panel or panels.

Claims

1. A concrete shuttering unit (1) of the type comprising two four-sided panels (2, 3) of concrete interconnected in a parallel, spaced-apart relationship by rigid ties (6) characterised in that the rigid ties (6) are separate from the panels (2, 3), each panel being cast with tie anchoring means (7) engageable by the ties (6) upon assembly of the unit (1) such that the ties (6) extend diagonally between the panels (2, 3) to cross-brace them in the assembled unit (1).

2. A shuttering unit according to Claim 1, characterised in that the tie anchoring means (7) are located at or near the corners of each panel (2, 3).

•3. A shuttering unit according to Claim 2, characterised in that the tie anchoring .means (7) comprise-anchor elements embedded in the concrete panels and provided with projections (16) from the surfaces of the panels (2,

3) which face inwardly of the assembled unit (1), the projections (16) being engageable by the ends of respective ties (6).

4. A shuttering unit according to Claim 3, characterised in that the projections (16) on the anchor elements (7) comprise eyes, loops or lugs engageable by the ends of respective ties (6) directly or by means of releasable connectors (17).

5. A shuttering unit according to any one of Claims 1 to 4, characterised in that the diagonal ties (6) are arranged in pairs at opposite ends of the two panels (2, 3), the ties (6) of each pair being inclined to each other and crossing over in planes perpendicular to the planes of the panels (2, 3).

6. A shuttering unit according to any one of the preceding claims, characterised in that the panels (2, 3) are disposed vertically in use of -the unit and have complementary rebates (11, 12) extending along their parallel upper and lower edges so that when the shuttering unit (1) is superimposed upon another its lower edge interlocks with the upper edge of the shuttering unit below.

7. A shuttering unit according to any one of Claims 1 to 5, characterised in that each panel (2, 3) has two adjoining longitudinally tongued edges (4), its remaining two edges being complementarily grooved (5) so that the panels (2, 3) of neighbouring units' (1) can be interlocked when the units are erected into shuttering.

8. A shuttering unit according to any one of the claims 1- to 6, characterised in that sockets^" (13, 15) are formed in the upper and lower edges of each panel (2, 3), the sockets (13, 15) of adjoining units (1) being aligned with each other in pairs upon correct erection of shuttering from a plurality of the units, and locking pins (23) are provided for engagement in the aligned pairs of sockets (13, 15) to lock the panels of neighbouring units against relative movement.

9. A shuttering unit according to Claim 3 or Claim 4, characterised in that the anchor elements (7) are of metal or plastics material and are bonded to or embedded in the concrete of the panels (2, 3).

10. A shuttering unit according to Claim 9, characterised in that each anchor element (7) comprises a three-sided base in the form of a corner cube enclosing the respective corner of each panel (2, 3).

11. A shuttering unit according to Claim 3, characterised in that the anchor elements comprise metal plates having T- or dovetail-sectioned channels which are closed at one end and are engageable with complementary terminal portions of respective ties (6).

12. A shuttering unit according to Claim 3, characterised in that the anchor elements comprise plates or blocks having lugs or sockets engageable by cooperatingly shaped ends of respective ties (6).

13. A shuttering unit according to Claim 1, characterised in that the anchoring means comprise pins or rods (7) which project into recesses adjacent the corners of the panels (2, 3) and are engageable by respective ends of the ties (6) .

14. A shuttering unit according to Claim 13, characterised in that the anchoring pins or rods (7) project perpendicularly from opposing edges of each pane1 (2, 3).

15. A shuttering unit according to Claim 7 and Claim 14, characterised in that the anchoring means (7) are recessed relative to the tongue (4) on one edge of the panel (2, 3) and project into the groove (5) in the opposite edge of the panel, the said tongue (4) and the said groove (5) being formed with respective lateral notches (8, 9) in correspondence with the anchoring means (7), through which the ties (6) extend, whereby the ties are retained on the anchoring means by the interlocking of the' tongues and grooves of neighbouring units upon erection.

16. A shuttering unit according to Claim 10 or Claim 15- characterised in that the anchoring means comprise a pair of rods or dowels (7) embedded in and projecting from each panel (2, 3) and extending parallel to each other between the said opposing edges, the rods or dowels (7) being engageable by complementary eyes at the ends of the ties (6).

17. A shuttering unit according to any one of the preceding claims, characterised in that the ties (6) comprise rods or bars of metal or plastics.

18. Shuttering formed by the erection of a number of shuttering units (1) according to ^" any one of the preceding claims, characterised in that the panels (2, 3) of neighbouring units (1) abut each other In a number of superimposed horizontal courses, the ties (6) of the units being so arranged that they lie in vertical planes and do not present a substantial obstruction to the .flow of concrete or infill material into the cavity defined between the panels.

19. Shuttering according to Claim 18, characterised in that -additional ties (6) interconnect the shuttering units (1) of superjacent and subjacent courses of the shuttering,, the additional ties extending between panels (2, 3) of different shuttering units (1) on opposite sides of the cavity defined between the panels. - 21 -

20. Shuttering according to Claim 19, characterised in that additional ties (6) are connected at opposite ends to respective tie anchor means (7) of the interconnected panels.

21. Shuttering according to any one of Claims 18-20, characterised in that the opposite vertical edges of each panel (2, 3) of the assembled shuttering units (1) xs bevelled towards the inter-panel cavity to define inwardly divergent gaps between the bevelled vertical edges of neighbouring panels (2, 3).

22. Shuttering units according to Claim 21, characterised in that a sealing element (18) is interposed between the abutting edges of adjacent panels (2, 3) of neighbouring shuttering units (1).

23. Shuttering according to Claim 18, characterised by end walls (19) connected to the vertical edges of the panels (2, 3) of the end shuttering units (1), by fixings (20) attached to the tie anchoring means (7), in order to close the end of the cavity between the panels (2, 3).

24. Shuttering according to Claim 22 or Claim 23, characterised in that some of the shuttering units (1) are arranged with their neighbouring panels (2, 3) at an angle to each other, these panels being interconnected by corner brackets (21) secured by fixings (20) to tie anchoring means (7) at the abutting edges of the neighbouring panels (2, 3).

25. Shuttering according to any one of Claims 18-24, characterised in that the surfaces of the panels (2, 3) which face the 'inter-panel cavity are formed with recesses or depressions (10) to effect keying with concrete or infill material poured into the cavity.