Patent Application
20200263416
This invention relates to a fixing for connecting an insulation layer to a precast concrete panel and to a precast concrete panel system made up of the concrete panel and the fixing. The invention also relates to a method for forming an insulated precast concrete panel.
Precast concrete panels for walls, floors, ceilings and the like are increasingly used in the construction of industrial, commercial and residential buildings. Most commonly, the precast concrete panel is formed off-site and then delivered to a construction site for assembly.
Precast concrete wall panels are generally manufactured on the flat in wooden concrete decks or forms sized to define the perimeter of the concrete panel.
A grid of steel rebar can be constructed and tied in-place within the form to reinforce the panel. Embeds for attaching the structural panel to footings, other panels, columns, slabs, roof systems, or for receiving building accessories and inserts which serve as attachment points for lifting hardware and temporary braces can also be provided in the form. Anchor-like fixings can also be employed to secure insulation to the concrete.
Concrete is then poured into the form in the same manner as floor slabs and is then finished as required e.g. a trowel finish or other types of architectural finishes and patterns.
Precast concrete panels offer a number benefits for construction. Whilst enjoying the benefits of being formed from concrete, the panels can be manufactured consistently and reproducibly with the high degree of accuracy required in modern construction. The pre-cast panels can then be rapidly assembled at building sites facilitating rapid builds.
Generally, precast concrete wall panels fall into three basic categories: sandwich, thin-shell and solid while the wall panels can be designed as non- loadbearing or loadbearing, carrying floor and roof loads, as well as lateral loads.
As indicated above, precast concrete panels are typically manufactured off-site, although the panels can be manufactured on-site, and the necessary external finishes, such as plaster boarding and plastering, and services, such as electrics and plumbing, fitted following installation of the panels on-site.
The precast panels must also be insulated when used for domestic, institutional and commercial buildings. In sandwich panels, rigid insulation is sandwiched between two layers of concrete. The insulation thickness can vary to create the desired thermal insulating property (“U” value, or known as ‘IR’ value in the United States) for the wall. However, sandwich panels are relatively expensive and more time consuming to manufacture due to the multiple layers of concrete required. Moreover, as the insulation is placed between two layers of concrete, a significant risk exists that undesirable levels of thermal bridging can occur across the pre-cast panel.
Thin-shell wall panels consist of a thin outer-layer of concrete connected to a back-up system typically constructed of steel framing or concrete which connects the wall panel to the building structure. A layer of rigid insulation is generally placed between the exterior layer of concrete and the back-up system. However, thin-shell wall panels can also be expensive and slow to produce due to the relatively complex nature of the required back-up system and multiple layers required.
Solid precast concrete wall panels are typically formed from a single solid concrete layer and as such are quicker and less expensive to produce than sandwich or thin shell precast panels. Insulation can be fixed to the pre-cast panel wall insulation anchors following removal of the precast panel from its form. However, the manual fixing of insulation to the precast panel following removal from the form introduces another step to the manufacturing process can slow down manufacture and increase the risk of thermal bridging. Alternatively, as described in Specification U.S. Pat. No. 8,555,584, an insulation layer provided with rigid anchors which also serve to support the steel rebar can be included in the form during casting of the panel. However, due to the rigid nature of the anchor, the anchor can fail during expansion/contraction of the concrete during curing while contact of the anchor with the steel rebar can result in thermal bridging across the panel. European Patent Specification No. 3,106,579, German Patent Specification No. 101 18 678, Specification U.S. Pat. No. 5,660,015 and PCT Patent Specification No. WO 2017/116237 all describe similar fixing methods in which fixings can be retrofitted to existing concrete substrates in a manner requiring the use of labour-intensive pre-drilling steps, nail guns, fastening guns and the like.
In short, conventional block on flat construction methods are slow while known precast panels suffer from a number of disadvantages—e.g. structural insulated panels (SIP's) require a cavity and outer layer of blockwork and insulated structural panels (ISP's) require an inner layer of concrete coupled with an outer layer of concrete and insulated core. Moreover, all of the above construction methods are labour intensive and require skilled on-site construction while all suffer from excessive thermal bridging.
According to the invention there is provided a fixing, as set out in the appended claims, for connecting an insulation layer to a precast concrete panel comprising:
Suitably, the insulation layer penetrating portion further comprises a tension head attachable to the flexible tie. The tension head can have one or two pawls depending on pull off requirements and wind loads on larger residential buildings.
Preferably, the flexible tie comprises a ratchet attachable to the tension head at a pawl. Advantageously, the ratchet comprises through holes in the tie.
Preferably, the pawl comprises a slot in the tension head. Suitably, the tension head comprises a collar surrounding the slot.
Preferably, the tension head comprises indents to define finger grips in the tension head.
Suitably, the concrete penetrating portion comprises a wall plug.
Preferably, the wall plug comprises a substantially cylindrical head. More preferably, the substantially cylindrical head comprises at least one laterally extending fin for maximizing grip of the wall plug on concrete. Advantageously, the substantially cylindrical head comprises at least one notch for maximizing grip of the wall plug on concrete. Alternatively, the wall plug comprises a substantially T-shaped head.
Preferably, the concrete penetrating portion comprises a flange for stabilising the fixing in position during concrete pouring. More preferably, the flange extends laterally outwards from the concrete penetrating portion.
In one embodiment, the fixing comprises at least one rib for strengthening the fixing. Preferably, the at least one rib is provided on the insulation layer penetrating portion. Alternatively or in addition, the at least one rib is provided on the concrete penetrating portion.
The invention also extends to a precast concrete panel system comprising a fixing as hereinbefore defined.
Preferably, the precast concrete panel system comprises a precast concrete panel reinforced with rebar and insulation fixed to the precast concrete panel by the fixing wherein the rebar and the fixing are spatially separate within the system.
More preferably, the insulation layer comprises insulation board. Most preferably, the insulation board comprises expanded polystyrene.
In a further embodiment, the invention also extends to a method for forming an insulated precast concrete panel system comprising fixing an insulation layer to a concrete panel with fixings as hereinbefore defined.
Preferably, the method comprises fitting the fixings to the insulation layer via the insulation layer penetrating portion, laying the insulation layer in a deck and pouring concrete into the deck to encapsulate the concrete penetrating portion of the fixings.
Suitably, the method further comprises the step of constructing a rebar in the deck before pouring the concrete.
Preferably, the rebar is spatially separated from the fixings to prevent thermal bridging.
The invention meets and exceeds modern building regulation requirements for both domestic and commercial projects by enabling a fast, energy efficient/thermal bridge free construction. The fixing and associated precast panel system of the invention eliminate the need for the majority of skilled on- site labour thus providing a faster construction method.
The fixing and precast concrete panel system of the invention formed with the fixing exhibit minimal thermal bridging as compared with the fixings and insulated precast concrete panels of the prior art. In particular, the flexibility of the tie of the insulation penetrating portion of the ratchet fixing of the invention offers room for expansion and contraction during concrete curing thereby preserving the structural integrity of the system and eliminating the risk of thermal bridging caused by damage to ties and/or insulation during curing. Moreover, as the ratchet tie is structurally and spatially separated from and independent of any steel rebar employed in the precast concrete panel, the method for forming a precast concrete panel system eliminates the likelihood of thermal bridging through fixings and rebars. The ratcheting action of the ratchet tie also allows the tie to adapt to insulation of varying thicknesses whilst also enabling secure attachment of the insulation to the solid concrete panel.
Moreover, the solid precast concrete panel system and associated method for forming the system of the invention do not require the use of sandwiched layers of insulation resulting in an insulated concrete panel that is easier to form and manufacture to a high degree of accuracy with optimal thermal characteristics. The solid precast concrete panel of the invention is also relatively inexpensive to manufacture compared with sandwich and thin shell concrete panels.
The insulated precast panel systems of the invention can be formed off-site regardless of weather conditions and can then be rapidly assembled on site with significantly reduced skilled labour requirements. Accordingly, construction projects can be completed sooner and faster than with conventional construction methods.
In summary, the fixing of the invention can be installed, pre-pouring of concrete with minimal effort. Moreover, as insulation can be provided with suitable perforations to receive the fixings, no drilling or steel nail fastening is required when employing the fixing. Accordingly, the fixing of the invention dramatically reduces the need for onsite labour and allows for the delivery of a factory made fully structural insulated concrete panel that is of monolithic construction. The flexible plastics fixings of the invention, being separate from the structural steel and the like, minimise the risk of thermal bridging compared with the fixings and methods of the prior art. The fixing of the invention is also suitable for use with all concrete types.
The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:-
As shown in the drawings, a precast concrete panel system of the invention is generally indicated by the reference numeral 1 and (when viewed on the flat as shown in
As shall be explained more fully below, the ratchet fixing 5 securely attaches the insulation layer 4 to the concrete layer 3 and is independent of the grid of steel rebar i.e. does not contact the grid of steel rebar thereby minimising thermal bridging across the panel system of the invention whilst, being flexible, the ratchet fixing 5 offers room for expansion and contraction of concrete during curing.
The precast panel 2 is shaped to define scarf joints 11 for interconnecting individual precast panels 2 during the construction of a building.
As shown particularly in
The insulation layer penetrating portion 18 is also made up of a substantially rectangular elongate flexible tie 24 which extends between the tension head 20 and the concrete penetrating portion 19. More particularly, the flexible tie 24 is insertable in the central slot 21 of the tension head 20 and is securely attachable to the pawl 22 in the central slot 21 via a ratchet 25 formed in the flexible tie 24. In the present embodiment, the ratchet 25 is defined by through holes or notches 26 in the flexible tie 24. However, as will be appreciated by those skilled in the art, the ratchet 25 can be defined by teeth or similar structures on the tie 24 if desired.
The concrete penetrating portion 19 is made up of a circular stabilising flange 27 extending laterally outwards from the concrete penetrating portion 19 for stabilising the ratchet fixing 5 in position during concrete pouring. The circular stabilising flange 27 has a diameter smaller than that of the tension head 20. A wall plug 28 is mounted on the stabilising flange 27 for anchoring and embedding the concrete penetrating portion 19 in the concrete layer 3 of the precast panel 2. As shall be explained more fully below, the concrete penetrating portion 19, and in particular the wall plug 28, is encapsulated in the concrete layer 3 during manufacture of the precast panel system 1 of the invention.
In order to provide a highly effective anchor in the concrete layer 3, the wall plug 28 is made up of a substantially cylindrical head 29 having a pointed tip 30 and first and second pairs of laterally extending fins 31, 32 respectively for maximising grip in the concrete layer 3. The cylindrical head 29 is also provided with a first and second pair of notches 33, 34 respectively between the fins 31, 32 to further enhance the grip of the wall plug 24 in the concrete layer 3.
If desired, additional or alternatively positioned strengthening ribs 36 can be provided on the insulation penetrating portion 18.
In the present embodiment, the circular tension head 20 of the ratchet fixing 5 is provided with peripheral indents 37 to define finger grips 38 for gripping and positioning the tension head 20 in use. The tension head 20 is also provided with a central collar 39 surrounding the central slot 21. The central collar 39 serves to assist in supporting the elongate tie 24 in the toothed pawl 22 of the rectangular central slot 21 in use.
As shown particularly in
The ratchet fixing 5 of the present embodiment can be easily and simply manufactured using injection moulding techniques.
The precast concrete panel system 1 of the invention can be manufactured by first constructing a form or deck on the flat in accordance with the shape and size of precast panel 2 required. The deck is made up of supporting sides having a depth greater than the final depth required in the precast concrete panel 2. By way of example for a precast panel system 1 as shown in
In particular, elongate ties 24 of the ratchet fixing 5 with the tension head 20 removed as shown in
The insulation boards 4 are then laid face down in the deck i.e. with the tension heads 20 disposed downwards and the wall plugs 28 disposed upwards in the deck. Upon completion of the above steps, concrete is then poured into the deck to encapsulate the wall plugs 28 of the ratchet fixings 5 and the steel rebar structural support. The resultant precast concrete panel system 1 is a structurally sound, highly insulated structure which exhibits minimal thermal bridging characteristics of about 0.002 W/m2K or greater and which is suitable for delivery to a construction site for building construction.
If desired, a rebar can be constructed in the deck before pouring concrete e.g. in the present example a grid of steel rebar made up 50×6 mm iron ribs placed around the edges of the deck and at centres that do not interfere with the ratchet fixings 5 during manufacturing can be incorporated into the deck.
The ratchet fixing 5 can be formed from any suitable material such as plastics, nylon and the like and can be sized as required. For example, for the precast concrete panel system described above in
In an embodiment there is provided a conical flange positioned near the inside of the tension head, whose function is to hold a second or a stronger pawl depending on kN/mm required.
In the specification the terms “comprise, comprises, comprised and comprising” or any variation thereof and the terms include, includes, included and including” or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation and vice versa.
The invention is not limited to the embodiments herein described which may be varied in construction and detail without departing from the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1711987.6 | Jul 2017 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/070181 | 7/25/2018 | WO | 00 |
