WO2004065322A1 - Construction material - Google Patents

Abstract

The invention relates to a construction material, such as an electrically-conductive plaster. The inventive material comprises a mixture of graphite, amorphous carbon and gypsum, which is used to produce electromagnetic radiation screens and which can also be used for heating. It has been shown that the aforementioned mixture provides an excellent screen in frequencies of between 1 MHz and 18 MHz owing to the properties thereof. The material is very easy to use and can be used as a coating or moulded in the form of plasterboards, partitions or tiles. Moreover, said material has flame-retardant and shock-resistant properties

Description

Construction material

The present invention relates to an electrically conductive building material, in particular plaster, comprising a binder and a mixture of graphite particles whose size is less than or equal to 12 microns, and amorphous carbon.

The use of carbons to produce electrically conductive building materials based on cement is known. US Patent 5,908,584 t (Bennett) discloses an electrically conductive cement comprising a mixture of graphite, amorphous carbon and sand to produce a plaster or mortar, a construction panel caught between two layers of different materials and bricks of construction .

WO00 / 69789 (MANTLE & LLAY LTD et al), presents a product based on cement or concrete which contains one or more forms of carbon dispersed in the mass in order to reduce the thermal conductance through the product. The carbon form or forms are preferably dispersed in the mass in small conglomerates and / or agglomerates which are completely or substantially isolated from each other.

The chemical reaction involved in making and setting the cement is extremely complex and, moreover, the particles are polymorphic in nature. This requires very meticulous monitoring of the mixture to ensure that the sand is evenly covered with carbon. To reduce the effect of the lack of homogeneity of conductivity in a cement-based mortar caused by incomplete mixing, the product can be applied in greater quantity to thicken it, but this increases the weight per covered area and results in support problems in construction.

A high percentage of carbon in a cement mixture reduces the resistance of the product, making it brittle, fragile and prone to fractures, which interrupts the conductivity and makes the screen effect unreliable. This problem can be overcome to some extent by subjecting the mixture to pressure during setting, or by using additives, which in both cases results in additional costs.

Cement products take many years to dry completely. Whether it is mortar, building blocks, or poured concrete, cement retains free aqueous radicals even when it is solidified and apparently dry. Many substances, and in particular steel and other metals, in contact with the material are subjected to chemical and electrolytic reactions which cause long-term corrosion and chemical modifications.

Cement and cement-based products have very long stabilization times, making mortar and plaster difficult to apply without additives, which adds to the cost of construction. This can cause significant delays when it comes to outdoor surfaces and therefore, exposed to extreme cold.

The complex chemical reaction and crystal formation involved in the manufacture of cement and concrete make the product rigid. Cements, mortars and plasters are subject to micro fractures, and the products must be thickened to reach their strength.

The object of the present invention is

1. to provide an electrically conductive material, in particular plaster, which is easy to use, reliable, economical in application, to provide a screen against electromagnetic interference accessible to those who use computers and data storage and which cannot bear the costs of the protections currently available.

2. to offer an electrically conductive plaster which can be used in the construction of prefabricated premises and buildings. 3. To offer an electrically conductive plaster which does not disintegrate in the event of impact, and which delays the flames.

4. To propose an electrically conductive plaster which will heat when an electric current crosses it.

The material corresponding to the present invention is characterized in that the binder is gypsum. The gypsum can be either calcium sulphate dihydrate, or hemihydrate in its α- or β- form or anhydrite III or II, or finally, depending on the applications, a mixture of these substances.

Gypsum has properties that are not present in cement or cement-based binders which gives it unique electrical, chemical and physical characteristics. As previously mentioned, cement-based products have drawbacks which make them impractical to use in many applications.

The material corresponding to the present invention produces inexpensive electrically conductive plasters, easy to use and which do not have the disadvantages of cement-based products. It provides a protective shield within the reach of many computer and other data storage facilities, which due to the high cost of existing technologies are commonly vulnerable to interference from intentional or unintentional magnetic radiation.

When water is added to the gypsum, whether in the form of hemihydrate or anhydrate (calcined), (CaSO ₄ V ₂ H ₂ O or CaS0 ₄ ) ₅ the calcined gypsum hydrates to form a dihydrate ( CaSO ^" 2H O). If we add just the amount of water necessary to produce a homogeneous, stable, fluid and non-sedimentary liquid mixture, the hydration is uniform throughout the mixture. As a result, the electrical conductivity through the mixing is not disturbed by non-homogeneous mixing. In the hydration mechanism of the hemihydrate gypsum mentioned above, the addition of water and the kneading of the hemihydrate powder, which causes the disintegration of the hemihydrate particles, is followed by a short induction period. , after which nuclei are formed from the super saturated solution. The hemihydrate is converted directly to the dihydrate, while ranhydrite is converted directly to the dihydrate. As hydration continues, the liquid mixture solidifies, the dihydrate crystals develop, crisscross and cling to each other (U. Ludwig, JK Kuhlmann, Tonind, Ztg. Keram. Rundsch. 98 ( 1974) 1- 4). The advantage of the material according to the present invention is the fact that the graphite becomes bonded to the mesh, the plaster is solid, and is not subject to fractures. A higher percentage of carbons can be incorporated into the mixture, which provides good reliability of the screen effect with thinner layers of plaster.

In addition, gypsum, (CaSO ₄ 2H ₂ O), is chemically stable. When the hydration reaction is complete, all the excess water evaporates. As the plaster is completely dry and chemically stable, there is no metallic corrosion or chemical reaction with other substances. This simplifies the connections between plaster and other electrically conductive components such as doors, vents and windows in the case of a screen protecting a given space.

Hydration of the gypsum produces heat, and the reaction time is short.

Gypsum hydration

CaSO ₄ V ₂ H ₂ O + ³ / _{2H 2} 0> CaSO ₄ 2H ₂ 0 + heat

CaSO ₄ + 2H ₂ O> CaSO ₄ 2H ₂ O + heat

There is another advantage of the material according to the present invention; it is on the one hand, the fact that the heat produced during hydration avoids the delays due to freezing of the water during the setting in cold weather, and on the other hand, that the duration of the reaction, which keeps the setting time to a minimum, allows to apply the plaster easily.

Setting time (min) initial setting final setting Projection plaster 60 - 120 170 - 220

Bonding plaster 50 - 90 80 - 200

Light plaster 50 - 90 100 - 170

Cement-based plasters have a rough surface, and the addition of carbon gives it a dark gray color. The color of the material of the present invention is also gray, but the application of a thin layer of pure gypsum plaster which, for its part, is opaque, will give a white finish surface which may be covered with paint or a coating. wall that will give an aesthetically pleasing finish.

The material corresponding to the present invention also acts as a flame retardant. When exposed to heat, gypsum dihydrate turns into hemihydrate or anhydrite by returning some of its water.

Dehydration of gypsum temperature required

CaSO ₄ 2H ₂ O -Chaleur-> V CaSO _{4 2H 2} O + ³ / _{2H 2} O> 130 ° C

CaSO ₄ 2H ₂ O - Heat> CaSO ₄ + 2H ₂ O> 600 ° C

CaSO. V ₂ H ₂ O - Heat> CaSO ₄ + V ₂ H ₂ O> 600 ° C

The water that is released on the surface of the material inhibits the transfer of heat to the lower plaster layers and this delays the destruction of the electromagnetic screen. In the event of a fire or an attack by incendiary projectiles, this delay allows the occupants of a protected room to have time to save or take away sensitive data before evacuating the premises. An additional advantage of the material corresponding to the present invention is the fact that the crystal and chemical structures of gypsum are simpler than those of cement. The chemical reactions consist of dehydration and hydration of the components of the gypsum, as described above, and the crystals are uniformly monoclinic with three axes, a pair that is not at right angles, and a direction of perfect cleavage. This allows sliding along the cleavage line, where the ions are bound by water, when the material is subjected to stresses or shocks. The basic structure is firmly maintained by the interwoven and interwoven growth of the crystals described above.

O o

Structure of CaS04 gypsum. The dotted line shows the cleavage line which breaks only the hydrogen bonds.

The material corresponding to the present invention is very malleable and can be manufactured in the form of wall panels, partitions, tiles for floors or ceilings, fiber reinforced plates, and pre-molded panels. Thanks to the plasticity described above, these products are resistant to shocks and do not disintegrate when attacked. The use of an ingredient such as β-hemihydrate as a starting gypsum makes it possible to obtain a mortar which adheres to any masonry surface, including gypsum, which does not crack, which slightly increases in volume when set, and which sets quickly. This mortar can be used to connect electrically conductive components together, for the rapid construction of prefabricated Faraday cages or of premises, buildings, military command posts and any other sensitive electronic installation.

The material according to the invention can be used mainly in the following ways:

1 As plaster or mortar

2 As plasterboard 3, As tiles for floors or ceilings 4 As ultra-light plasterboard reinforced with fibers 5, As partition 6 As structural building panels.

One or other of these six forms of the material corresponding to the invention can be used to produce an electrically conductive doubling of a room or a building, which attenuates radiation and constitutes a screen against electromagnetic interference. .

According to another application of the invention, the mixture contains barium sulphate, thus the doubling of a room or a building will attenuate the X-rays and γ rays (gamma) which will provide a screen against these radiations in hospitals, laboratories and will protect installations vulnerable to these rays from unintentional bombardment by such radiation.

In another application, the panels made from the material can be used as reflectors to create a screen protecting schools or any other building from radiation from cell phone transmitting stations which, it is feared, could be a health threat. According to another application, the coating produced from the material of the invention could be applied to damaged masonry surfaces.

According to another application, the coverings of roofs, ceilings and walls made from the material of the invention could be used to protect the occupants of buildings against bombardment by weapons of mental destabilization (REM).

According to another application, the material according to the invention could be used to provide a flame retardant material, electrically conductive, capable of producing a screen against electromagnetic interference for premises or buildings and giving the occupants more time in fire or attack.

According to another application, the material according to the invention could be used to provide an impact-resistant material, conductive of electricity, capable of producing a screen against electromagnetic interference for premises or buildings to protect the occupants and the contents of damage caused by cracking or disintegration of walls or wall surfaces in the event of an earthquake or bombardment.

The attenuation provided by the material of the invention can be greater than 40 dB in a frequency range from 1 MHz to 18 GHz. The attenuation varies according to the proportions of the carbons and the gypsum in the mixture. The fact that the gypsum can tolerate a high proportion of carbons before weakening makes it possible to obtain an attenuation of up to 60db on most of the frequencies in this band. By adding barium sulfate to the mixture, the attenuation frequency band can include x-rays and y-rays (gamma).

When an electric current is passed through the material corresponding to the invention, it produces heat. If, to pass the electric current, only two electrical contact points are used on each side of a tile or a panel made with the material of the invention, the heat produced will be uneven and some places will be warmer than others. To use the material as a heating element, the electric current must pass through it equally. To do this, a metal strip, or a metal bar must be fixed on each side of the tile or panel, then in turn connected to the electrical supply terminals. The chemically active nature of cement and cement-based products, as well as the fact that they retain water, make electrical connection very difficult. The current triggers an electrolytic reaction with the metals, which leads to their corrosion. This makes efficient connection of the element difficult, and the cables used for the connection cannot pass through the cement without protection.

As previously mentioned, the products and elements produced with the material of the invention do not experience the problems of connection of the cement because they are dry and chemically inert. We can easily fix metal on the edges of products and elements and connect them together with a connection bar taken in the mass of gypsum plaster without carbon or mortar, without fear of corrosion, thus avoiding having to use many connection cables that should be protected.

The heating properties of the material according to the invention are characterized by the fact that it acts as a semiconductor. Its resistivity increases with temperature, which makes it more effective in low temperatures (<40 ° C), there is only one temperature exchange, and no metallic heating element or hot water pipe, this which reduces energy consumption.

As mentioned earlier, gypsum sticks to any masonry surface. Carbonless gypsum is also dielectric, which allows its use as an insulator when connecting cables and elements made from the material.

One of the applications of the invention uses carbon-free gypsum plaster to cover the products and components made from the material corresponding to the invention, in order to electrically insulate them. Another application of the invention drowns the cables or connection bars, which connect the products or the components made from the material, in the mass of a gypsum without carbon to insulate them electrically.

Another application of the invention uses a layer of the material corresponding to the invention in the form of a wall panel to produce invisible wall heating.

The hot air rises, and therefore, the lower the heating source, the more it will be optimized in terms of energy. Another application of the invention uses sub basements made from the material of the invention to produce a heating by the walls at the level of the ground.

Another application of the invention uses the floor tiles made from the material corresponding to the invention to produce underfloor heating.

Another application of the invention uses thick bricks to store heat energy in order to take advantage of the off-peak tariff hours of the electricity company.

Another application of the invention uses floor tiles thick to achieve ^a floor heating heaters.

Another application of the invention uses roof tiles made from the material corresponding to the invention to defrost the roof to prevent the accumulation or the formation of ice on roofs in cold regions, in particular in ski resorts or wherever heavy snowfall and their accumulation on the roofs can be dangerous.

Underfloor heating and snow prevention generally only use temperatures <40 ° C which can be generated by currents low-voltage electrical devices, controlled by transformers, which reduces the risk of electric shock and lowers operating costs.

Claims

claims 1. Electrically conductive building material, in particular plaster, containing a binder and a mixture of graphite particles whose size is less than or equal to 12 microns, and amorphous carbon, characterized in that the binder is gypsum . 2. Electrically conductive building material according to claim 1, characterized in that the gypsum is calcium sulfate dihydrate, hemihydrate in the form α- or β-, or anhydrite III or IL 3. Electrically conductive building material according to claim 1 or 2, characterized in that the weight of the mixture of graphite and amorphous carbon represents between 25% and 75% of the total weight of said material. 4. Electrically conductive building material according to one of claims 1 to 3, characterized in that the weight of the amorphous carbon represents between 10% and 95% of the total weight of the mixture of graphite and amorphous carbon. 5. Electrically conductive building material according to one of the claims 1 to 4, characterized in that the amorphous carbon comprises at least one of the substances selected from the group consisting of calcined coke and ashes containing amorphous carbon produced by combustion of an organic component. 6. Electrically conductive building material according to one of the claims 2 to 5, characterized in that the mixture comprises one or more forms of gypsum in any proportion whatsoever. 7. Electrically conductive building material according to one of claims 1 to 6, characterized in that said material comprises glass fiber or any other fiber. 8. Electrically conductive building material according to one of claims 2 to 7, wherein said material, while the gypsum is in its form of β-hemihydrate contains small amounts of glass fibers to produce ceiling plates. i 9. Electrically conductive building material according to one of claims 1 to 7, characterized in that the material comprises one or more forms of calcium sulphate (dihydrate, hemihydrate α- or β-, or anhydrite II or III) for get multi phase plasters. 10. Electrically conductive building material according to one of claims 1 to 9, characterized in that the material contains just enough water to produce a homogeneous, stable, fluid and non-sedimentary liquid mixture. 11. Electrically conductive building material according to one of claims 1 to 10, characterized in that said material comprises magnetic or magnetizable molecules. 12. Electrically conductive building material according to claim 11, characterized in that said molecules are magnetic salts. 13. Electrically conductive building material according to claim 11, characterized in that said molecules are ferrites. 14. Electrically conductive building material according to one of claims 1 to 13, characterized in that the material, while the gypsum is in its form of β- hemihydrate, contains certain additives to produce gypsum plaster hemihydrate delayed and very light pre-mixed gypsum plaster. 15. Electrically conductive building material according to one of claims 1 to 14, characterized in that the material is between two layers of paper or other coverings to make wall panels. 16. Electrically conductive building material according to one of claims 1 to 14, characterized in that the material is between two support plates to make building panels. 17. Electrically conductive building material according to one of claims 1 to 10, characterized in that the mixture contains between 10% and 50% of Barium Sulfate to obtain attenuation of X-rays and γ rays (gamma). 18. A method of producing the material according to one of claims 1 to 17, characterized in that the material is mixed with certain hydrophilic colloidal additives which retain water to make it compatible with continuous application in machine. 19. A process for producing the material according to one of claims 1 to 17, characterized in that the gypsum is first mixed with carbons before adding water to it.