Method of installing a concrete structure

Abstract

The invention relates to a method of installing a concrete structure having an aesthetic surface, the method comprising: installing an imprint former raised from a base surface; applying concrete to the base surface around and beneath the imprint former to form the concrete structure; and removing the imprint former to leave an imprint in the surface of the concrete structure.

Description

METHOD OF INSTALLING A CONCRETE STRUCTUREFIELD

[0001] The present invention is directed to a method of installing a concrete structure having an aesthetic surface.BACKGROUND

[0002] Shotcreting is a construction technique used to apply a layer of concrete or mortar onto a surface through a high-pressure spraying process. The sprayed concrete is generally formulated to be sticky and resist flowing when at rest to allow the concrete to be applied to and otherwise form complex shapes.

[0003] Shotcreting can be used for a variety of applications, including: reinforcing and repairing existing structures to strengthen old or damaged concrete surfaces, like bridges or tunnels; building new structures by creating elements like retaining walls, underground facilities, or complex shapes that might be difficult to form using traditional concreting methods; and stabilising rock faces in tunnelling or mining, or in highway construction, to prevent collapses.

[0004] Shotcrete offers several advantages in construction and repair, making it a popular choice for various applications, due to its: versatility, strength and durability, reduced formwork requirements, enhanced bonding, speed of application, effectiveness for repairs, reduced waste, flexibility in thickness, and enhanced safety.

[0005] Shotcreting is commonly conducted using either a ‘dry-mix’ method or a ‘wet-mix’ method. In the dry-mix method, dry components are conveyed pneumatically through a hose and water is added at the nozzle. Mixture of the dry and wet components is completed as the mixture hits the application surface. In the wet-mix method, a pre-mixed concrete composition is pumped through a hose and compressed air is added at the nozzle to accelerate the wet mixture onto the intended surface.

[0006] Whether a dry-mix method or a wet-mix method is utilised, shotcreting will typically involve the following steps: the base surface or application surface is firstly cleaned, prepared, and wet; a formwork to support the application of concrete to the application surface is established (if required);the shotcrete is then applied to the application surface in a high-pressure stream in layers. The thickness of each layer is typically between 1 to 2 inches, where multiple layers may be needed to achieve the desired thickness and strength. Each layer should be applied while the previous layer is still wet to ensure good bonding; once the shotcrete has achieved the desired thickness, the shotcrete surface may be finished. Finishing can involve smoothing the surface using tools like trowels or brushes, depending on the desired texture and aesthetic appearance of the finished surface; and the applied shotcrete should then be allowed to cure to achieve its full strength. During curing the surface is kept moist for a specified period (typically 7 days, depending on the air temperature during curing, concrete grade and exposure classification) to prevent it from drying out too quickly, which can cause cracking. Optionally, a curing compound may be applied to the freshly concreted surface to form an impervious film over the concrete to prevent it from evaporating and maintaining the correct cement hydration.

[0007] From an architectural perspective, it is commonly desirable to incorporate an aesthetic surface into concrete surfaces, including shotcrete-formed surfaces. For example, it may be desirable to provide a concrete construction element having patterned imprints within its surface. In this way, a retaining wall established alongside a highway may provide an aesthetically pleasing patterned surface for viewing by passing road users.

[0008] There are currently a number of ways to provide an aesthetic surface, such as a patterned aesthetic surface, on a construction element that has been produced through shotcreting. These include: covering over the relevant surface of the shotcrete construction element with further precast concrete panels, each precast concrete panel incorporating a precast aesthetic surface. This method is time consuming and expensive, noting that the shotcrete construction element is typically cured before any precast concrete panel may be applied and the precast concrete panels require additional concrete and are expensive to produce; and bolting imprint formers to the cured shotcrete construction element, applying a further layer of shotcrete over the cured construction element between adjacent imprint formers, and thereafter removing the imprint formers to provide a pattern of imprints within the resulting shotcrete surface. However, applying a thin shotcrete layer to an existing cured shotcrete construction element can create bonding issues whereby the cured thin shotcrete layer can commonly crack and fall off the concrete element. This process is also time consuming involving two application steps separated by a curing step.

[0009] In view of the above, it may be desirable to provide a method of installing a concrete structure such as shotcrete, which overcomes one or more of the above disadvantages, or at least offers a viable alternative.

[0010] The above discussion of background art is included to explain the context of the present invention. It is not to be taken as an admission that the background art was known or part of the common general knowledge at the priority date of any one of the claims of the specification.SUMMARY

[0011] According to a first aspect of the invention, there is provided a method of installing a concrete structure having an aesthetic surface, the method comprising: installing an imprint former raised from a base surface; applying concrete to the base surface around and beneath the imprint former to form the concrete structure; and removing the imprint former to leave an imprint in the surface of the concrete structure, wherein the base surface is at least partially non-horizontal, and the step of applying concrete comprises pneumatically projecting concrete onto the base surface around and beneath the imprint former.

[0012] In an embodiment, the step of installing an imprint former raised from a base surface comprises removably connecting the imprint former to a support such that the imprint former is raised by the support from the base surface.

[0013] In an embodiment, the method further comprises providing a framework, wherein the step of applying the concrete to the base surface comprises applying concrete within the framework.

[0014] In an embodiment, the method further comprising smoothing the surface of the applied concrete around the imprint former prior to removing the imprint former. In an embodiment, the step of smoothing the surface of the applied concrete comprises trowelling the surface.

[0015] In an embodiment, the method comprises installing one or more reinforcing elements for reinforcing the concrete element between the base surface and the imprint former prior to the step of applying the concrete. In an embodiment, the one or more reinforcing elements comprise reinforcement steel. In an embodiment, the reinforcement steel comprises one or more of wire mesh, loose bar, chain mesh or a combination thereof.

[0016] In an embodiment, wherein the imprint former is removably connected to a reinforcing element. In an embodiment, the imprint former is removably connected to the reinforcing element via a threaded fastener arrangement. In an embodiment, the step of removing the imprint former comprises unscrewing a threaded component of the threaded fastener arrangement and removing a threaded fastener component along with the imprint former.

[0017] In an embodiment, a hole in the concrete structure remains following removal of the threaded fastener component and the method further comprises filling the hole left by the threaded fastener component. In an embodiment, the step of filling the hole comprises filling the hole with a patching product.

[0018] In an embodiment, the imprint former comprises specific design features or aesthetics to imprint into the surface of the concrete structure, such design features including one or more of: a textured surface feature, a pattern, an image, a number or a letter.

[0019] In an embodiment, the method further comprises substantially curing the applied concrete and the step of removing the imprint former occurs after the applied concrete has been substantially cured. In an embodiment, the method further comprises finishing the concrete surface around the imprint after the imprint former has been removed. In an embodiment, the method further comprises painting the finished concrete surface.

[0020] In an embodiment, the base surface is formed of a substrate comprising one or more of, rock, soil, earth, or formwork.

[0021] In an embodiment, the method comprises inserting bolts into the base surface to increase the stability of the base surface or the concrete structure prior to the step of applying the concrete. In an embodiment, the imprint former is located above the bolts.

[0022] In an embodiment, the method comprises: installing a plurality of imprint formers raised from a base surface; applying concrete to the base surface around and beneath each of the imprint formers to form a concrete structure; and removing each of the imprint formers to leave a plurality of imprints in the surface of the concrete structure.

[0023] In an embodiment, the step of installing a plurality of imprint formers raised from the base surface comprises installing the imprint formers at regular intervals to provide a patterned effect in the surface of the concrete structure.

[0024] According to a second aspect of the invention, there is provided a concrete structure having an aesthetic surface produced in accordance with the first aspect of the invention.

[0025] Throughout this specification and the claims which follow, unless the context requires otherwise: reference to like numbers denotes reference to like features; the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps; the use of '(s)' following a noun means the plural and / or singular form of that noun. Further, as used herein the term 'and / or' means 'and' or 'or', or where the context allows both; the word “concrete” is not intended to be limited to a composite material formed with a Portland cement binder, but rather is intended to include composite materials formed with a number of different binders including geopolymer cements, Roman cements, hydraulic cements, and asphalt. According to preferred embodiments, the concrete may be a form of shotcrete; reference to “a” or “one” thing, includes a reference to “one or more” of that thing; terms such as "side," "end," "top," "bottom," “on”, “onto”, “under” “above”, “below”, beside”, “beneath” and the like are only used to describe elements as they relate to one another but are in no way meant to recite specific orientations of the device, to indicate or imply necessary or required orientations of the device, or to specify how the invention described herein will be used, mounted, displayed, or positioned in use; and the reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.BRIEF DESCRIPTION OF THE FIGURES

[0026] The present invention is described by way of non-limiting examples within the following description and figures. To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the present invention will suggest themselves without departing from the scope of the present invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting. Where specific integers are mentioned herein, which have known equivalents in the art to which this invention relates; such known equivalents are deemed to be incorporated herein as if individually set forth.

[0027] FIGURE 1 shows a line drawing of shotcrete application according to the prior art.

[0028] FIGURE 2 shows an example of the formwork, according to an embodiment of the invention.

[0029] FIGURE 3 shows an example of the formwork and imprint former assembly, according to an embodiment of the invention.

[0030] FIGURE 4 shows a close-up view of the threaded fastener arrangement of the embodiment of FIGURE 3.

[0031] FIGURE 5 shows a concrete structure with an imprint formed via the method according to an embodiment of the invention.List of Parts1 concrete structure2 base surface3 form work4 rock bolts5 concrete6 reinforcing element7 imprint former8 threaded fastener9 imprint10 nozzleDETAILED DESCRIPTION

[0032] In broad terms, the present invention provides a method of installing a concrete structure having an aesthetic surface. Within the broader inventive concept, various embodiments of the method are described in further detail below with reference to FIGURES 1 to 5.

[0033] FIGURE 1 shows a concrete structure 1 being installed according to the prior art against a substantially vertical base surface 2, such as a rock surface. In the prior art example shown, the area is prepared for installation of concrete 5 by installing formwork 3 against the base surface 2, and concrete 5 is sprayed onto the base surface 2 into a cavity defined by the formwork 3 in a sweeping motion through nozzle 10. The concrete 5 is applied in layers, often in thicknesses ranging from 1 to 2 inches per pass, with the nozzle 10 being adjusted to control the application rate to achieve the desired texture and finish. Once the concrete 5 has cured,the formwork 3 may be removed to leave the resulting concrete structure 1 installed on the base surface 2.

[0034] The person skilled in the art would appreciate that use of a formwork is not necessarily required. That is, concrete may be applied directly to a base surface such as to a rock face, an earthen face, or a previously existing building face, without use of any formwork. In these instances, the concrete would more simply still be sprayed in a sweeping motion in layers, often in thicknesses ranging from 1 to 2 inches per pass, onto the intended base surface.

[0035] FIGURE 2 nevertheless shows an example of formwork 3 according to an embodiment of the invention. The formwork 3 may define a cavity or mould providing the basic shape of the resulting concrete structure, while supporting the applied concrete as it cures. In the embodiment shown, the base surface 2 is provided as a wall panel specifically installed to enable construction of a concrete element. In other embodiments, a formwork may for example be built directly onto a natural substrate (such as a rock face, or earthen surface) where the substrate forms the base surface on which concrete may be applied. Alternatively, a base surface may for example be formed of a coating or a plastic film layer atop a preexisting substrate or similar. In some embodiments, a mould structure may be created incorporating an integral base surface and that would for example enable production of prefabricated concrete elements.

[0036] In the embodiment shown in FIGURE 2, the formwork 3 has a regular, rectangular shape. The precise shape, size and nature of any formwork used may be designed based on requirements such as dimensions, shape, finish, reinforcement, and load-bearing needs, and may for example be made of materials such as plywood or metal sheeting. In the embodiment shown in FIGURE 2, the formwork 3 is configured generally vertically so that the concrete structure is installed generally vertically (such as through shotcrete application) to provide a generally vertical concrete structure. However, it is also envisaged to for example apply the invention in respect of substantially horizontal base surfaces, such as to create floors in constructions, swimming pools, parking structures and roof decks; or alternatively a sloped base surface such as lining tunnels and underground mines.

[0037] Returning to FIGURE 2, one or more reinforcing elements 6, in this case rebar, are shown installed between the base surface 2 and the imprint former 9. In use more generally, reinforcing elements may for example be connected to a formwork or directly to a base surface. Reinforcing elements 6 may be arranged in a grid like pattern, with specific horizontal and vertical spacing. According to certain embodiments, it may be preferable for the reinforcing elements to be generally spaced from any formwork, the base surface and / oradjacent reinforcing elements to enable sufficient bonding between the reinforcing elements and the concrete. As exemplified in FIGURES 2 to 4 (best shown in FIGURE 4), rebar 6 is spaced above the base surface 2. According to certain embodiments, 12mm or 16mm bar wire may for example be used to secure adjacent reinforcing elements 6. The wire may be twisted tightly around the reinforcing elements 6 using existing tools such as pliers, end nippers, or a twisting tool, ensuring that the ties are snug but not too tight.

[0038] Those skilled in the art would appreciate that there are various manners in which to prepare an area or surface for application of concrete, whether using formwork, reinforcing elements, or otherwise. Such deviations are contemplated within the scope of the invention.

[0039] According to embodiments of the invention, imprint formers are provided above a base surface on which concrete is to be applied to create specific design features or aesthetics within the surface of the resulting concrete structure. By having the imprint former raised from the base surface, concrete may be applied beneath the imprint former, between the imprint former and the wall surface, such that a single continuous concrete element may be formed around and beneath the imprint former. This will not necessarily prevent supporting elements forming part of the imprint formers from being in contact with the base surface, though configuration of the supporting elements should enable concrete to be applied beneath the supporting elements, between the supporting element and the base surface.

[0040] As exemplified in FIGURES 3 and 4, imprint formers 7 may be fitted onto a cavity formed by formwork 3. In FIGURES 3 and 4 the imprint formers 7 are formed of metal in a generally straight rectangular shape to leave straight vertical line imprints within the resulting concrete structure. More generally, imprint formers could for example leave a textured surface feature, a pattern, an image, a number, lettering, or intricate designs, and could be made of custom components or flexible materials.

[0041] As exemplified in FIGURES 3 and 4, the imprint formers 7 may be removably connected to reinforcing elements 6 via a threaded fastener 8 arrangement acting as a support for the imprint formers 7 to raise the imprint formers 7 above the base surface 2, such as a nut and threaded rod arrangement. In certain embodiments, a first nut may be welded onto a rear surface of a reinforcing element 6 (in the embodiment shown via a plate welded to the reinforcing element 6). A threaded rod 8 may then be threaded into the first nut. The imprint former 7 is then located over the threaded rod 8 such that the threaded rod 8 passes through a hole in the imprint former 7. A second nut may then be threaded onto the threaded rod 8 over the imprint former 7 to fix the imprint former 7 in place. As an alternative support mechanism to threaded fasteners, bolts and nuts, a user may for example weld an unthreadedrod onto the reinforcing element 6, the rod incorporating holes which enable locking pins to pass through the rod at set heights. In this way, the imprint former 7 may be positioned on the unthreaded rod using locking pins and the locking pins can be removed later to enable the imprint former 7 to be removed. Further alternatively, the imprint former 7 may be connected to the reinforcing element 6 or the base surface 2 via a frangible connector acting as a support for the imprint former 7 that is designed to break upon a predetermined force being applied to remove the imprint former 7 after curing of the concrete. This could for example be a rod glued to the base surface 2 or the reinforcing elements 6, whereby the glue is configured to fail upon a predetermined force being applied to enable removal of the imprint former 7 and the rod after the concrete 5 has been applied. More generally, imprint formers 7 could for example be raised from the base surface 2 by for example a connector removably connected to the base surface 2, formwork 3 (if any), or by any other object which allows imprint formers 7 to be supported above the base surface 2 during application of the concrete 5; and thereafter be removed to leave an imprint in the resulting concrete structure 1.

[0042] As best shown in FIGURES 3 and 4 and in accordance with the above, imprint formers 7 are positioned to allow concrete 5 to be applied around them, such that when the imprint formers 7 are removed, an imprint 9 in the shape of the imprint former 7 remains in the surface of the resulting concrete structure 1 . As shown in FIGURE 5, if a plurality of imprint formers 7 are installed, they may for example be installed at regular intervals to provide a regular patterned effect of imprints 9 within the surface of the concrete structure 1 .

[0043] If installing a concrete structure 1 directly onto a rock face, rock bolts may be inserted into the rock face to increase stability, similar to the rock bolt 4 that is shown in FIGURE 1 . Prior to applying the concrete, the base surface may be moistened to enhance bond strength of the concrete. The concrete may then be projected onto the base surface around and beneath the imprint former(s). The concrete may be applied in one pass or multiple passes, ensuring required thickness and full coverage is met. While according to certain embodiments, the concrete may be projected pneumatically onto the base surface (by for example using shotcrete), any means in which concrete may be applied onto a base surface is contemplated. Once sufficient concrete is applied to form the concrete element, the surface of the applied concrete may then be smoothed around the imprint former(s), such as via trowelling the surface of the concrete element.

[0044] The concrete element may then be cured to ensure its strength, durability, and overall performance. During curing, the concrete surface may be kept moist to avoid drying out. Curing, over a period of for example seven days, may for example be used to allow theconcrete element to hydrate and gain strength effectively while also minimising surface cracking, improving durability, and achieving the desired structural integrity.

[0045] Once the concrete element is substantially cured the imprint former(s) 7 may be removed. It is noted that the imprint former(s) 7 may be removed prior to substantially complete curing, though this may risk the shape of the resulting imprint being altered if the concrete moves before it is set. According to embodiments where a threaded fastener arrangement 8 is used to connect and position the imprint former(s) 7 (see again for example FIGURES 3 and 4), removal of the imprint former(s) 7 may involve unscrewing and removing a threaded fastener component (e.g. a nut or a screw) to enable the imprint former(s) 7 to be removed from the concrete structure 1 , leaving an imprint in the surface of the concrete structure 1 corresponding to the shape of the imprint former 7 (see for example FIGURE 5). In certain embodiments, removal of the threaded fastener 8 may involve first unthreading a second nut on a front surface of the imprint former 7, then unthreading the threaded fastener 8 from a first nut located behind the reinforcing element 6.

[0046] According to certain embodiments, removal of a threaded fastener component may result in a hole remaining in the concrete structure corresponding to the shape of the threaded fastener component. This hole may be filled with a patching product such as but not limited to an epoxy resin, to provide an even surface.

[0047] The cured concrete structure may then be finished to achieve a smooth, aesthetically pleasing surface. An edging tool may be used to refine the edges, giving the edges a clean and finished look, and / or the concrete structure may be painted to a desired colour. A sealant may separately or additionally be applied to protect the surface of the concrete element from environmental factors, and to enhance the colour and finish of the concrete structure.

[0048] It will be understood to persons skilled in the art of the invention that modifications may be made without departing from the spirit and scope of the invention. The embodiments and / or examples as described herein are therefore to be considered as illustrative and not restrictive.

Claims

CLAIMS1. A method of installing a concrete structure having an aesthetic surface, the method comprising: installing an imprint former raised from a base surface; applying concrete to the base surface around and beneath the imprint former to form the concrete structure; and removing the imprint former to leave an imprint in the surface of the concrete structure, wherein the base surface is at least partially non-horizontal, and the step of applying concrete comprises pneumatically projecting concrete onto the base surface around and beneath the imprint former.

2. A method according to claim 1 , wherein the step of installing an imprint former raised from a base surface comprises removably connecting the imprint former to a support such that the imprint former is raised by the support from the base surface.

3. A method of installing a concrete structure according to claim 1 or claim 2, the method further comprising providing a framework, wherein the step of applying the concrete to the base surface comprises applying concrete within the framework.

4. A method of installing a concrete structure according to any one of the previous claims, the method further comprising smoothing the surface of the applied concrete around the imprint former prior to removing the imprint former.

5. A method of installing a concrete structure according to claim 4, wherein the step of smoothing the surface of the applied concrete comprises trowelling the surface.

6. A method of installing a concrete structure according to any one of the previous claims, wherein the method comprises installing one or more reinforcing elements for reinforcing the concrete element between the base surface and the imprint former prior to the step of applying the concrete.

7. A method of installing a concrete structure according to claim 6, wherein the one or more reinforcing elements comprise reinforcement steel.

8. A method of installing a concrete structure according to claim 7, wherein the reinforcement steel comprises one or more of wire mesh, loose bar, chain mesh or a combination thereof.

9. A method of installing a concrete structure according to any one of claims 6 to claim 8, wherein the imprint former is removably connected to a reinforcing element.

10. A method of installing a concrete structure according to claim 9, wherein the imprint former is removably connected to the reinforcing element via a threaded fastener arrangement.

11. A method of installing a concrete structure according to either one of claim 10, wherein the step of removing the imprint former comprises unscrewing a threaded component of the threaded fastener arrangement and removing the threaded fastener component along with the imprint former.

12. A method of installing a concrete structure according to claim 11 , wherein a hole in the concrete structure remains following removal of the threaded fastener component and the method further comprises filling the hole left by the threaded fastener component.

13. A method of installing a concrete structure according to claim 12, wherein the step of filling the hole comprises filling the hole with a patching product.

14. A method according to any one of the previous claims, wherein the imprint former comprises specific design features or aesthetics to imprint into the surface of the concrete structure, such design features including one or more of: a textured surface feature, a pattern, an image, a number or a letter.

15. A method according to any one of the previous claims, the method further comprising substantially curing the applied concrete and the step of removing the imprint former occurs after the applied concrete has been substantially cured.

16. A method according to any one of the previous claims, the method further comprising finishing the concrete surface around the imprint after the imprint former has been removed.

17. A method according to claim 16, the method further comprising painting the finished concrete surface.

18. A method according to any one of the previous claims, wherein the base surface is formed of a substrate comprising one or more of, rock, soil, earth, or formwork.

19. A method of installing a concrete structure according to any one of the previous claims, the method comprising: installing a plurality of imprint formers raised from a base surface;applying concrete to the base surface around and beneath the imprint formers to form a concrete structure; and removing each of the imprint formers to leave a plurality of imprints in the surface of the concrete structure.

20. A method installing a concrete structure according to claim 19, wherein the step of installing a plurality of imprint formers raised from the base surface comprises installing the imprint formers at regular intervals to provide a patterned effect in the surface of the concrete structure.21 . A concrete structure having an aesthetic surface produced by the method of any one of claims 1 to claim 20.

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