Concrete balcony with low carbon footprint

Abstract

The present disclosure relates to a balcony (1) comprising: a concrete slab (10) having: an attachment portion (2) configured to ensure attachment of the balcony (1) to a building fagade (5), a loading portion (4) extending from the attachment portion (2) away from and in a direction perpendicular to the building fagade (5), reinforcing fibres (8) embedded within the loading portion (4), and at least one anchoring member (6) extending through a proximal portion of attachment portion (2) and being configured to extend through the building fagade (5) along a length direction (Y) perpendicular to the building fagade (5), wherein the loading portion (4) has a thickness (E4) in a height direction (X) of the building greater than a thickness (E2) of the attachment portion (2) in the height direction (X), and wherein a compressive strength at 28 days of the concrete within the concrete slab (10) is inferior or equal to 50 MPa

Description

[0001] Concrete balcony with low carbon footprint

[0002] TECHNICAL FIELD

[0003] The present subject matter relates generally to concrete structures, and more particularly to balconies made of precast concrete.

[0004] BACKGROUND

[0005] Balconies provide outdoor space within a building, allowing the residents or users of the building to enjoy the outdoor environment without having to leave their building. Some balconies only consist of a balustrade on the outside of the building, such that a user can open a window and enjoy the outdoors without risk of falling. Other balconies also include a loading portion which extends from the building surface, allowing the user to walk or perform other outdoor activities on the balcony.

[0006] It is common to manufacture a balcony out of concrete, by pre-casting the concrete into the shape wanted for the loading portion at a fabrication site, generally in the form of a slab, before moving the pre-cast slab thus obtained to a building site. Such structures are durable and able to withstand very high compressive loads, making them suitable for uses whereby a high number of people, furniture or other items need to be accommodated on the loading portion once in use.

[0007] In the 1980’s, high-strength and high-performance concrete materials with a particularly high compressive strength, better durability or better workability were developed. Some of these concretes also have the advantage of better wear resistance and overall resistance to adverse environmental conditions. However, the manufacture of slabs of pre-cast high performance concrete induces a high carbon footprint which adversely affects the overall environmental sustainability of a building project.

[0008] SUMMARY

[0009] A solution which provides a balcony capable of withstanding high loads with a lower carbon footprint is therefore needed.

[0010] To that end, the present disclosure relates to a balcony comprising: a concrete slab having: an attachment portion configured to ensure attachment of the balcony to a building fagade, a loading portion extending from the attachment portion away from and in a direction perpendicular to the building fagade, reinforcing fibres embedded within the loading portion, and at least one anchoring member extending through a proximal portion of attachment portion and being configured to extend through the building fagade along a length direction perpendicular to the building fagade, wherein the attachment portion has a thickness in a height direction of the building greater than a thickness of the loading portion in the height direction, and wherein a compressive strength at 28 days of the concrete within the concrete slab is inferior or equal to 50 MPa.

[0011] The decreased thickness of the loading portion in comparison with that of the attachment portion, together with the presence of reinforcing fibres, allows for a balcony with a satisfactory mechanical strength without the need to resort to high-performance concrete, thereby significantly decreasing the carbon footprint associated with the manufacture of the balcony.

[0012] According to one embodiment, the compressive strength at 28 days of the concrete within the concrete slab is superior to or equal to 25 MPa and inferior or equal to 35 MPa.

[0013] According to one embodiment, the reinforcing fibres are made of a plastic material, in particular of polypropylene, and / or wherein the anchoring members are made of structural steel.

[0014] According to one embodiment, the concrete slab further comprises a connecting portion located between the attachment portion and the loading portion, a thickness of the connecting portion varying between: the thickness of the attachment portion at a first junction between the attachment portion and the connecting portion, and the thickness of the loading portion at a second junction between the connecting portion and the loading portion.

[0015] According to one embodiment, the concrete within the concrete slab is based on a cement composition having a water- to-cem ent ratio inferior or equal to 45%.

[0016] According to one embodiment, an aggregate forming the concrete of the concrete slab has a maximum particle dimension of less than a third of a thickness of the concrete slab.

[0017] According to one embodiment, the concrete within the concrete slab is a low carbon concrete. According to one embodiment, a spacing is provided between the attachment portion and the building surface and the anchoring members extend through a proximal portion of the attachment portion, through the spacing and through the building surface.

[0018] According to one embodiment, the anchoring members extend throughout the attachment portion and at least partially through the loading portion along length direction.

[0019] According to one embodiment, the thickness of the loading portion is superior or equal to 5 cm and inferior or equal to 15 cm, preferably substantially equal to 10 cm and / or the thickness of the attachment portion is superior or equal to 7 cm and inferior or equal to 20 cm.

[0020] BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Further features, purposes and advantages will be apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the drawings in which:

[0022] Figure 1 is a schematic view of a balcony according to the present disclosure, according to a first embodiment;

[0023] Figure 2 is a schematic view of a balcony according to the present disclosure, according to a second embodiment;

[0024] Figure 3 is a schematic view of a loading portion of a balcony viewed from section cut AA’ represented on Figures 1 and 2.

[0025] On all figures, similar elements are designated with the same reference numerals.

[0026] DETAILED DESCRIPTION

[0027] In reference to figure 1 , a pre-cast concrete balcony 1 is shown. A building has a lateral fagade 5, not part of balcony 1. Balcony 1 is connected to building fagade 5. In some embodiments, balcony 1 is connected to the fagade via a floor slab 7 so that balcony 1 is sensibly flush with floor slab 7. In this way, a user stepping onto balcony 1 from indoors will not experience a height difference between the floor on the indoor side of fagade 5 and the balcony 1.

[0028] Balcony 1 comprises a concrete slab 10 made of concrete which is not high- performance concrete, i.e with a compressive strength at 28 days of less than 50 MPa, thereby significantly reducing the carbon footprint of its manufacture. In some embodiments, the compressive strength at 28 days of the concrete is superior or equal to 25 MPa and inferior or equal to 35 MPa. In the following, a height direction X of the building is defined, which corresponds to a thickness direction of balcony 1. A length direction Y of the balcony is defined as extending perpendicular to the building fagade 5.

[0029] Concrete slab 10 has an attachment portion 2, which is attached to building fagade 5, and a loading portion 4 extending from attachment portion 2, away from building fagade 5 in length direction Y. In a preferred embodiment, loading portion 4 has a length superior to that of attachment portion 2.

[0030] A thickness E2 of attachment portion 2 is superior to a thickness E4 of loading portion 4. Indeed, the thickness E2 of attachment portion 2 must be sufficient to ensure an adequate fixation of the balcony 1 to the building fagade 5, while the thickness E4 of loading portion 4 can be reduced to a value necessary to accommodate the load imposed on balcony 1 by people and / or objects placed on it during its use. This optimal distribution of thickness allows balcony 1 to have adequate mechanical properties despite the use of non-high-performance concrete.

[0031] The thickness E4 of loading portion 4 can be superior or equal to 5 cm and inferior or equal to 15 cm. The thickness E2 of attachment portion 2 can be superior or equal to 7 cm and inferior or equal to 20 cm. In some embodiments, the thickness E4 of loading portion 4 is substantially equal to 10 cm.

[0032] According to some embodiments, attachment portion 2 does not directly touch building fagade 5, and a spacing 9 is provided therebetween. At least one anchoring member 6 ensures attachment of the balcony 1 to the building fagade 5, the anchoring members 6 extending at least within a proximal portion of loading portion 4 located closest to building fagade 5, through the spacing 9 and into the building fagade 5 - for example into floor slab 7. Anchoring members 6 can also extend further through all of attachment portion 2, or even into loading portion 4. The absence of a direct contact between building fagade 5 and balcony 1 thanks to spacing 9 minimises thermal conduction between them and therefore allows for optimal thermal insulation within the building.

[0033] In other embodiments, anchoring members 6 as described above may be present even in the absence of a spacing 9 between building fagade 5 and balcony 1 .

[0034] The fact that anchoring members 6 can extend, at least partially, through loading portion 4 along length direction 4 provides a framework for loading portion 4, adding tensile, compressive, and flexural strength to balcony 1. Anchoring members may have a thickness superior or equal to 0.5 cm and inferior or equal to 3 cm. According to some embodiments, loading portion 4 is continuous with attachment portion 2 and the thickness of concrete slab 10 evolves suddenly, at the junction between loading portion 4 and attachment portion 2.

[0035] According to other embodiments, a connecting portion 3 of concrete slab 10 extends between attachment portion 2 and loading portion 4 in the length direction. Within connecting portion 3, the thickness evolves gradually, to match the thickness of attachment portion 2 at a first junction between attachment portion 2 and connecting portion 3, and to match the thickness of loading portion 4 at a second junction between connecting portion 3 and loading portion 4. The evolution of thickness within connecting portion 3 can be linear, as represented on figure 1. Alternately, as represented on figure 2, the thickness within connecting portion 3 can evolve so that a lower face of connecting portion 3 along the thickness direction X forms a portion of a circle extending into connecting portion 3 from the first junction to the second junction. Any other gradual evolution of thickness within connecting portion 3, from the first junction to the second junction, falls within the scope of the present disclosure.

[0036] In reference to figure 3, which shows the view of loading portion 4 according to section cut AA’ represented on figures 1 and 2, reinforcing fibres 8 are embedded within the concrete of loading portion 4. These fibres do not present a uniform orientation but can extend along different directions within concrete slab 10. Reinforcing fibres 8 provide added flexural strength to loading portion 4, which contributes to allowing the reduction in thickness at loading portion 4 in comparison with attachment portion 2.

[0037] According to an embodiment, reinforcing fibres 8 are made of a plastic material, such as polypropene, which has good resistance to crack propagation, and therefore increase the toughness of loading portion 4. Some reinforcing fibres 8 may protrude from upper surface 12. If reinforcing fibres 8 were made of metal, they would risk damaging the shoes of a user walking on upper surface 12 of balcony 1 or injuring a user walking barefoot on upper surface 12. In contrast, plastic fibres are blunter by nature and could therefore not injure a user in the same way.

[0038] The concrete slab 10 is based on a cement composition.

[0039] A cement is a hydraulic binder comprising a proportion of at least 50 % by weight of calcium oxide (CaO) and silicon dioxide (SiO2). The cement is preferably a Portland cement as defined in the standard NF-EN-197-1 of April 2012 and can be a cement of CEM I, CEM II, CEM III, CEM IV or CEM V type according to the “Ciment” [Cement] Standard NF EN 197-1. In some embodiments, the water-to-cement ratio of the cement composition used for the concrete slab 10 is inferior or equal to 45% by weight. This allows for a more durable balcony, by reducing the porosity of the concrete, thereby slowing down diffusion of damaging particles to anchoring members 6, as well as ensuring protection of anchoring members 6 from their surrounding environment. Indeed, the low thickness E4 of loading portion 4 means that anchoring members 6 are not covered by a large amount of concrete, and a low porosity allows for maximum protection of anchoring members from corrosion due to the surrounding environment.

[0040] The concrete within concrete slab 10 can be such that aggregates within the concrete have a maximum dimension of less than a third of the thickness of concrete slab 10, at any position along length direction Y.

[0041] The concrete within concrete slab 10 can be a low carbon concrete. To this end, the cement composition can further comprise at least one mineral addition.

[0042] By adding mineral addition, such as, e.g., granulated blast-furnace slag, fly ash, natural pozzolans, calcined clays or ground limestone to Portland cement, the carbon dioxide footprint of the cement can be reduced by substituting Portland clinker by the cited mineral addition.

[0043] The mineral addition can be slag (for example, as defined in the European NF EN 197-1 Standard of April 2012, paragraph 5.2.2), pozzolanic materials (for example as defined in the European NF EN 197-1 Standard of April 2012, paragraph 5.2.3), fly ash (for example, as described in the European NF EN 197-1 Standard of April 2012, paragraph 5.2.4), calcined schists (for example, as described in the European NF EN 197-1 Standard of April 2012, paragraph 5.2.5), material containing calcium carbonate, for example limestone (for example, as defined in the European NF EN 197-1 Standard paragraph 5.2.6), limestone components (for example, as defined in the "Concrete" NF P 18-508 Standard), silica fume (for example, as defined in the European NF EN 197-1 Standard of April 2012, paragraph 5.2.7), siliceous components (for example, as defined in the "Concrete" NF P 18-509 Standard), metakaolin or mixtures thereof . The mineral component may also be ground construction demolition waste.

[0044] Examples of siliceous components are ground glass, solid or hollow glass beads, glass granules, expanded glass powder.

[0045] The mineral additions, typically between 10 and 70% by weight of the total weight of the weight of cement + mineral addition, are more preferably ground granulated blast furnace slag, fly ash, or mixtures thereof. Balcony 1 according to the above disclosure can be up to 40% thinner than comparable state of the art balconies with otherwise similar dimensions. It can be manufactured using 35% less raw materials (notably concrete and steel, as well as other accessory materials), thereby reducing carbon emissions for manufacture alone by up to 61.5 kg CO2 per square meter of upper surface 12 and reducing cost by up to 15%. In addition, the associated reduction in weight of concrete slab 10 significantly reduces carbon emissions attributable to transport, by up to 50%, and allows for the use of smaller cranes on the building site. For all these reasons, balcony 1 is much more environmentally sustainable than comparable state of the art balconies. The smaller cross-section of balcony 1 is also advantageous from an aesthetic and architectural perspective.

Claims

CLAIMS1. Balcony (1) comprising: a concrete slab (10) having: an attachment portion (2) configured to ensure attachment of the balcony (1) to a building fagade (5), a loading portion (4) extending from the attachment portion (2) away from and in a direction perpendicular to the building fagade (5), and at least one anchoring member (6) extending through a proximal portion of attachment portion (2) and being configured to extend through the building fagade (5) along a length direction (Y) perpendicular to the building fagade (5), characterised in that reinforcing fibres (8) are embedded within the loading portion (4) and in that the attachment portion (2) has a thickness (E2) in a height direction (X) of the building greater than a thickness (E4) of the loading portion (4) in the height direction (X), and in that a compressive strength at 28 days of the concrete within the concrete slab (10) is inferior or equal to 50 MPa.

2. Balcony according to claim 1 , wherein the compressive strength at 28 days of the concrete within the concrete slab (10) is superior to or equal to 25 MPa and inferior or equal to 35 MPa.

3. Balcony according to one of claims 1 and 2, wherein the reinforcing fibres (8) are made of a plastic material, in particular of polypropylene, and / or wherein the anchoring members (6) are made of structural steel.

4. Balcony according to one of claims 1 to 3, wherein the concrete slab (10) further comprises a connecting portion (3) located between the attachment portion (2) and the loading portion (4), a thickness of the connecting portion (3) varying between: the thickness of the attachment portion (2) at a first junction between the attachment portion (2) and the connecting portion (3), and the thickness of the loading portion (4) at a second junction between the connecting portion (2) and the loading portion (4).

5. Balcony according to one of claims 1 to 4, wherein the concrete within the concrete slab (10) is based on a cement composition having a water-to- cement ratio inferior or equal to 45%.

6. Balcony according to one of claims 1 to 5, wherein an aggregate forming the concrete of the concrete slab (10) has a maximum particle dimension of less than a third of a thickness of the concrete slab (10).

7. Balcony according to one of claims 1 to 6, wherein the concrete within the concrete slab (10) is a low carbon concrete.

8. Balcony according to one of claims 1 to 7, wherein a spacing (9) is provided between the attachment portion (2) and the building surface (5) and wherein the anchoring members (6) extend through a proximal portion of the attachment portion (2), through the spacing (9) and through the building surface (5).

9. Balcony according to claim 8, wherein the anchoring members (6) extend throughout the attachment portion (2) and at least partially through the loading portion (4) along length direction (Y).

10. Balcony according to one of claims 1 to 9, wherein the thickness (E4) of the loading portion (4) is superior or equal to 5 cm and inferior or equal to 15 cm, preferably substantially equal to 10 cm and / or the thickness (E2) of the attachment portion (2) is superior or equal to 7 cm and inferior or equal to 20 cm.

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