ARCHITECTURAL STRUCTURE FEATURING A UNIQUE FIBER GEOMETRY FORMING SHIELDING AGAINST ELECTROMAGNETIC RADIATION

Abstract

The invention relates to an architectural assembly comprising: - at least one concrete panel reinforced with conductive fibers, and lacking a conductive mesh for electromagnetic shielding, - at least one conductive mesh arranged on at least one face of the at least one concrete panel, forming a shield against electromagnetic radiation, characterized in that the concrete panel comprises concrete comprising at least a portion of conductive fibers having a length between 30 and 80 millimeters and a slenderness ratio between 80 and 200. Figure to be published with the abstract: Fig. 5

Description

Title of the invention: ARCHITECTURE ENSEMBLE WITH A PARTICULAR GEOMETRY OF FIBERS FORMING SHIELDING AGAINST RADIATION ELECTROMAGNETIC TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of construction of premises which need to be protected against electromagnetic radiation or waves, in particular the frequency spectrum for the proposed solution being between 1 megahertz (MHz) and 1 gigahertz (GHz).

[0002] It relates more particularly to electromagnetic shielding solutions consisting totally or partially of a concrete containing conductive fibers. STATE OF THE ART

[0003] The construction or renovation of buildings or premises, such as computing or data storage centers, businesses, offices, hospitals, housing in which people and / or equipment are located may require protection against electromagnetic waves. The outer shell of these buildings is mainly made of concrete, with a treatment limiting the transmission of electromagnetic waves and forming Electromagnetic Protection (EMP). This protection can take two forms and be of two kinds:

[0004] - Protection against the entry of electromagnetic waves into a room;

[0005] - Protection against the emission of electromagnetic waves, from the premises to the outside.

[0006] Various solutions for shielding against electromagnetic radiation based on concrete loaded with conductive particles or fibers have been proposed in recent years. The different dosages and fibers used, in particular the geometry of the fibers, are diverse.

[0007] It is desirable to propose one or more fiber geometries making it possible to cover a frequency spectrum in order to improve electromagnetic attenuation. OBJECT OF THE INVENTION

[0008] To this end, and according to a first aspect, the invention proposes an architectural assembly comprising: - at least one concrete panel loaded with conductive fibers, and being free of conductive electromagnetic shielding mesh, - at least one conductive mesh arranged on at least one of the faces of the at least one concrete panel, the assembly forming a shield against electromagnetic radiation, characterized in that the concrete comprises at least a portion of conductive fibers having a length of between 30 and 100 millimeters and a slenderness of between 50 and 200.

[0009] Thus, the solution proposes an optimal fiber geometry to achieve better electromagnetic attenuation performance. Preferably, the solution is proposed by reasoning with fixed dosage, fixed fiber concrete wall thickness, associated with a conductive coating, and fixed concrete formulation (the concrete matrix housing the fibers). This geometry is a compromise between the workability of the fiber concrete (its ability to be mixed) and its electromagnetic performance. In addition, the solution makes it possible to attenuate electromagnetic waves or radiation in a very wide frequency range, in particular low frequencies, for example the frequency spectrum between 1 MHz and 10 GHz, preferably between 1 MHz and 1 GHz.

[0010] The subject of the invention is the construction of a building limiting the propagation of electromagnetic waves in a wide frequency band, from the inside to the outside and / or from the outside to the inside. For example, an attenuation of at least 60 decibels is possible for a so-called low frequency of 1 MHz. The calculation of the electromagnetic attenuation, in particular concerning a conductive flat wall, is known to the person skilled in the art.

[0011] For the above and for the remainder of the description, the following terms are understood to mean:

[0012] - fiber or particle, a part which may be metallic or non-metallic but being conductive; preferably it has a cylindrical shape, preferably perfectly cylindrical, preferably circular, preferably cylindrical or circular along the entire length of the fiber; preferably having at least one fold at one or both ends of a fiber or particle;

[0013] - lattice, a two-dimensional set of conductors with electrical continuity conduction at the intersections of the crossed conductors. This mesh can also be made up of a metal mesh attached by riveting or stapling to the concrete panel loaded with conductive particles;

[0014] - slenderness, the length of a fiber divided by its diameter.

[0015] According to different variants of embodiment of the architectural assembly which may or may not be combinable:

[0016] - at least a portion of the conductive fibers represent between 0.2 and 3% in volume of concrete (volume of fibers divided by the volume of fiber-reinforced concrete, also called volume fraction of fibers), preferably less than 1.5%, preferably less than 1%;

[0017] - preferably all the conductive fibers represent between 0.2 and 2% by volume concrete, preferably less than 1.5%, preferably less than 1%;

[0018] - at least a portion of the conductive fibers, preferably all of them, represent between 0.2 and 2% by weight of the concrete;

[0019] - according to one embodiment, the concrete has a volume fraction of fibers in lower than the ratio 1 / slenderness;

[0020] The volume fraction indicated above is chosen to allow the workability of the fiber-reinforced concrete. Indeed, the greater the slenderness, the more difficult the mixture becomes because a percolation phenomenon (formation of a network of fibers) occurs.

[0021] There are different classes of concrete consistency ranging from SI to S5.

[0022] According to one embodiment, the volume fraction of fibers is equal to a / slenderness with:

[0023] - for a concrete of consistency class less than or equal to S2, a is preferably between 0.1 and 0.75, preferably between 0.2 and 0.75, preferably greater than 0.1, preferably greater than 0.2, preferably greater than 0.3, preferably greater than 0.4, preferably greater than 0.5, preferably greater than 0.6, preferably less than 0.75, preferably less than 0.7, preferably less than 0.6, preferably less than 0.5, preferably less than 0.4, preferably less than 0.3, preferably less than 0.2;

[0024] - for a concrete of consistency class between S3 and S4, a is preferably included between 0.1 and 1, preferably between 0.2 and 1, preferably greater than 0.1, preferably greater than 0.2, preferably greater than 0.3, preferably greater than 0.4, preferably greater than 0.5, preferably greater than 0.6, preferably greater than 0.7, preferably greater than 0.8, preferably greater than 0.9, preferably less than 1, preferably less than 0.9, preferably less than 0.8, preferably less than 0.75, preferably less than 0.7, preferably less than 0.6, preferably less than 0.5, preferably less than 0.4, preferably less than 0.3, preferably less than 0.2;

[0025] - for a concrete of consistency class S5, a is preferably between 0.1 and 1.5, of preferably between 0.2 and 1.5, preferably greater than 0.1, preferably greater than 0.2, preferably greater than 0.3, preferably greater than 0.4, preferably greater than 0.5, preferably greater than 0.6, preferably greater than 0.7, preferably greater than 0.8, preferably greater than 0.9, preferably greater than 1, preferably greater than 1.1, preferably greater than 1.2, preferably greater than 1.3, preferably greater than 1.4, preferably less than 1.5, preferably less than 1.4, preferably less than 1.3, preferably less than 1.2, preferably less than 1.1, preferably less than 1, preferably less than 0.9, preferably less than 0.8, preferably less than 0.75, preferably less than 0.7, preferably less than 0.6, preferably less than 0.5, preferably less than 0.4, of preferably less than 0.3, preferably less than 0.2;

[0026] - preferably the length of at least one part of the fibers has a length between 60 and 80 millimeters,

[0027] - preferably the length of at least one part of the fibers has a length greater than 30 millimeters, preferably greater than 40 millimeters, preferably greater than 50 millimeters, preferably greater than 60 millimeters, preferably greater than 70 millimeters, preferably greater than 80 millimeters, preferably greater than 90 millimeters, preferably less than 100 millimeters, preferably less than 90 millimeters, preferably less than 80 millimeters, preferably less than 70 millimeters, preferably less than 60 millimeters, preferably less than 50 millimeters, preferably less than 40 millimeters;

[0028] - preferably, all fibers have the length or a range of values ​​of aforementioned length;

[0029] - preferably the slenderness of at least one part of the fibers is between 80 and 100;

[0030] - preferably the slenderness of at least one part of the fibers is greater than 50, preferably greater than 60, preferably greater than 70, preferably greater than 80, preferably greater than 90, preferably less than 100, preferably greater than 110, preferably greater than 120, preferably greater than 130, preferably greater than 140, preferably greater than 150, preferably greater than 160, preferably greater than 170, preferably greater than 180, preferably greater than 190, preferably less than 200, preferably less than 190, preferably less than 180, preferably less than 170, preferably less than 160, preferably less than 150, preferably less than 140, preferably less than 130, preferably less than 120, preferably less than 110, preferably less than 100, preferably less than 90, preferably less than 80, preferably less than 70, preferably less than 60;

[0031] - preferably all the fibers have a aforementioned slenderness or a range of aforementioned slenderness values;

[0032] - preferably the thickness of the concrete or concrete panel between 15 and 50 centigrade timers;

[0033] - the concrete can have different external shapes so as to form a wall or walls or a wall element or wall elements, for example in the form of a panel;

[0034] - according to one embodiment, at least one part of the conductive fibers is by example in steel;

[0035] - the architectural assembly may further comprise a finishing material arranged on at least one of the faces of the at least one concrete panel, and the at least one trellis electromagnetic shielding conductor is embedded or not in said finishing material;

[0036] - according to one embodiment, the at least one conductive mesh is fixed on at least one of the faces of at least one concrete panel;

[0037] - the at least one conductive mesh may comprise meshes having di dimensions between 3x3 millimeters and 10 x 10 millimeters, preferably less than 30 x 30 millimeters, preferably less than 20 x 20 millimeters, preferably less than 10 x 10 millimeters, preferably equal to 5 x 5 millimeters, preferably equal to 3 x 3 millimeters, preferably greater than 3 x 3 millimeters, preferably greater than 5 x 5 millimeters;

[0038] - the at least one conductive mesh may comprise meshes having at least a dimension less than 30 millimeters, preferably less than 20 millimeters, preferably less than 10 millimeters, preferably less than 5 millimeters, preferably equal to 5 millimeters, preferably equal to 3 millimeters, preferably greater than 3 millimeters, preferably greater than 5 millimeters, preferably greater than 10 millimeters;

[0039] - the meshes can have a polygonal shape, for example rectangular, tri angular;

[0040] - the at least one concrete panel loaded with conductive fibers is devoid of conductive mesh for electromagnetic shielding, but this does not exclude the presence of metal reinforcement or reinforcing bars for the production of concrete;

[0041] - the architectural assembly may comprise at least one concrete panel loaded with conductive fibers and at least two conductive meshes, a first mesh being arranged on a first face of the panel, called the inner face, and a second mesh being arranged on a second face of the panel, called the outer face, opposite the first face of the panel;

[0042] - preferably the architectural assembly may comprise a concrete panel and two lattices embedded or not in a finishing material arranged on either side of the concrete panel so as to form a wall element;

[0043] According to another aspect, the invention also provides a method of manufacturing an assembly structured according to one or more of the characteristics of the first aspect, the method comprising: - manufacturing at least one concrete panel loaded with conductive fibers according to one or more of the characteristics of the first aspect, in particular comprising at least one portion of conductive fibers having a length of between 30 and 100 millimeters and a slenderness of between 50 and 200, - place at least one conductive mesh on at least one of the faces of the at least one concrete panel. BRIEF DESCRIPTION OF THE FIGURES

[0044] Other characteristics and advantages of the invention will emerge from the detailed description of the invention which follows with reference to the appended figures and in which:

[0045] [Fig.l] [Fig.l] shows three electromagnetic attenuation curves as a function of frequency for a concrete comprising 60 kilograms of fibers per cubic meter but having three different slendernesses;

[0046] [Fig.2] [Fig.2] shows three electromagnetic attenuation curves as a function of the frequency for the same concrete comprising 20 kilograms of fibers per cubic meter but presenting three different slendernesses;

[0047] [Fig.3] [Fig.3] shows two electromagnetic attenuation curves as a function of frequency for a concrete comprising 20 kilograms of fibers per cubic meter but having two different fiber lengths;

[0048] [Fig.4] [Fig.4] shows two electromagnetic attenuation curves as a function of the frequency for a concrete comprising 40 kilograms of fibers per cubic meter but having two different fiber lengths;

[0049] [Fig.5] [Fig.5] shows two electromagnetic attenuation curves as a function of frequency for concrete comprising 40 kilograms of fibers per cubic meter, the lower curve having a slenderness of 65 and a fiber length of 35 millimeters, the upper curve having a slenderness of 80 and a fiber length of 60 millimeters;

[0050] [Fig.6] [Fig.6] shows two examples of the outer shape of a conductive fiber;

[0051] [Fig.7] [Fig.7] shows another example of the outer shape of a conductive fiber.

[0052] For clarity, identical or similar elements of the different embodiments are identified by identical reference signs throughout the figures. DETAILED DESCRIPTION OF THE INVENTION

[0053] In relation to figures 1 to 5, there are illustrated electromagnetic attenuation measurements of concrete panels comprising conductive fibers, the concretes considered being identical, in particular with a thickness of 25 centimeters and a section of 1.2 x 1.2 meters in a Faraday cage.

[0054] In particular, the following attenuation formula was used:

[0055] SE=A+R+B

[0056] With

[0057] [Math.l] 20 i ki 10 6' — 20 lûg 20 41 / 3 / 4 S - 20 log î£} 1 - / e 2 / fet ' I Üfe +

[0058] where:

[0059] t: the thickness of the fiber-reinforced concrete wall,

[0060] f: the frequency,

[0061] co = 2irf: the pulsation,

[0062] q: the magnetic permeability of the material constituting the wall,

[0063] e: its permittivity,

[0064] o: its conductivity,

[0065] j: the imaginary number such that y2 = - ],

[0066] a+j[3: the complex number of the positive real part such that

[0067] [Math.2]

[0068]

[0069] [Math.3]

[0070] [Math.4] _ “O” r 2 a®

[0071] [Math.5] 2a

[0072] skin thickness,

[0073] [Math.6] a+

[0074] the complex impedance of the material constituting the wall,

[0075] [Math.7] = 376.73 Q * u

[0076] the vacuum impedance,

[0077] [Math. 8] k = + jfl)

[0078] the complex wave number of the material constituting the wall,

[0079] The magnetic permeability of fiber-reinforced concrete was taken equal to that of the vacuum.

[0080] The conductivity of fiber-reinforced concrete was taken to be equal to:

[0081] = ob + a. <p.(Th

[0082] The permittivity of fiber-reinforced concrete was taken to be equal to:

[0083] e hf = e h +p.(pe h

[0084] Where:

[0085] ^ / is the conductivity of fiber-reinforced concrete,

[0086] the conductivity of non-fibered concrete,

[0087] ^bf is the permittivity of fiber-reinforced concrete,

[0088] is the permittivity of non-fibered concrete,

[0089] a depends on the frequency and the geometry of the fibers, a increases with the slenderness, with the frequency and with the length of fibers,

[0090] [3 depends on the frequency and geometry of the fibers, and [3 increases with the slenderness,

[0091] q> is the volume fraction (volume of fibers divided by volume of fiber-reinforced concrete).

[0092] For example, the conductive fibers used are of one or both or all three types illustrated by figures 6 and 7.

[0093] With reference to [Fig. 1], the effect of varying the slenderness is illustrated by three curves with a slenderness of 45, 65 and 80 and a nearly identical fibre length: 30 mm, 35 mm and 30 mm. In this test, the dosage of conductive fibres is 60 kilograms per cubic metre. It can be seen that the electromagnetic attenuation performance is significantly better when the slenderness is large.

[0094] Similarly, when the dosage of conductive fibers is modified as illustrated by [Fig.2] with a dosage of 20 kilograms per cubic meter, the electromagnetic attenuation performance is significantly better when the slenderness is large.

[0095] Figures 3 and 4 illustrate another type of test in which the slenderness is fixed at a value of 80. The effect of varying the length of the fibers with two curves: a length of 30 millimeters and a length of 60 millimeters.

[0096] [Fig. 3] shows measurements for a conductive fiber dosage of 20 kilograms per cubic meter. The performance is clearly better for the longer fiber.

[0097] [Fig.4] shows measurements for a conductive fiber dosage of 40 kilograms per cubic meter. The performance is clearly better for the longer fiber.

[0098] [Fig.5] shows the synergistic effect of the two chosen parameters of length and slenderness combined. The two curves in [Fig.5] show that the choice of parameters makes it possible to obtain sometimes very different performances for the same dosage, in particular performances 3 to 5 times greater between 200 MHz and 700 MHz for the best performing concrete, for this example. It deals with the attenuations obtained with two samples of fiber-reinforced concrete, whose concrete (without fibers) is the same, one using fibers of length 35 mm and slenderness 65, the other using fibers of length 60 mm and slenderness 80. The two samples are dosed at 40 kilograms per cubic meter.

[0099] These tests were carried out as follows:

[0100] - the attenuation measurements are made in a Faraday cage, the cage having a square opening, a sample, for example a concrete panel, being placed in the opening or the frame of the opening;

[0101] - preferably the concrete is poured into a metal frame so as to form a concrete panel, the metal frame being fixed to the opening, by bolting means, and a conductive gasket is inserted between the metal frame and the opening, to ensure electrical continuity;

[0102] - antennas are arranged on either side of the opening comprising the sample to be tested, preferably so-called “bi-log” antennas, preferably located at a distance of one meter on either side of the sample.

Claims

Claims

1. Architectural assembly comprising: - at least one concrete panel loaded with conductive fibers, and being devoid of conductive electromagnetic shielding mesh, - at least one conductive mesh arranged on at least one of the faces of the at least one concrete panel, forming a shield against electromagnetic radiation characterized in that the concrete comprises at least a portion of conductive fibers having a length of between 30 and 100 millimeters and a slenderness of between 50 and 200.

2. Architectural assembly according to claim 1 in which at least some of the conductive fibers, preferably all of them, represent between 0.2 and 2% by weight of the concrete.

3. An architectural assembly according to claim 1 or 2, wherein the length of at least one portion of the fibers has a length of between 60 and 80 millimeters.

4. Architectural assembly according to one of the preceding claims, further comprising a finishing material arranged on at least one of the faces of the at least one concrete panel, and the at least one conductive electromagnetic shielding mesh is embedded or not in said finishing material.

5. Architectural assembly according to one of claims 1 to 3, in which the at least one conductive mesh is fixed on at least one of the faces of the at least one concrete panel.

6. Architectural assembly according to one of the preceding claims, in which the at least one conductive mesh comprises meshes having dimensions less than 30 x 30 millimeters.

7. Method for manufacturing an architectural assembly according to one of the preceding claims, the method comprising: - manufacturing at least one concrete panel loaded with conductive fibers comprising at least one portion of conductive fibers having a length of between 30 and 100 millimeters and a slenderness of between 50 and 200, - depositing at least one conductive mesh on at least one of the faces of the at least one concrete panel.

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