According to the International patent classification (MKP), labels are: E04 B 1/80, E04 C2/24 and B32 B13/00.

TECHNICAL PROBLEM The technical problem, which could be solved with this invention, consists of the following: how to find a structural solution and how to produce a thermo-insulation plate that could fulfill many requests, such as: low density, satisfactory mechanical strengths, good thermo-insulation properties, low water absorption, good steam and gas conductivity, frost resistance and fire resistance, chemical and biological stability, non-toxic, and all the above stated should be achieved with lower price of the product. The solution is in the application of the rebated three-layered plates and flat three-layered plates, consisting of a styrofoam plate in the middle, whose upper and lower surfaces are coated with polystyrene concrete layers.

TECHNICAL STATE-OF-THE-ART Introduction of various thermo-insulation systems in the contemporary civil engineering practice is caused by the major expansion of energy resource prices at the world market. As a result, there is a growing need for significant heat-loss reduction during exploitation of civil engineering structures, which as a rule could be realized using more or less effective building systems to prevent heat loss through external structures (outer walls). Thereby, the fact that the total heat-loss of a building consists of many particular heat-losses (through each of the structural elements) is often being neglected. For a non-insulated building, which could be situated in different climate conditions, these particular heat-losses can vary between 10-20% (through floors), 25-30% (through outer walls), 25-30% (through attic slabs and roof plates) and 30-40% (through windows) of the total heat-loss.

Solving the problem of heat-loss partially-by isolating only facade walls depending on given climate conditions, brings in every case less energy saving than possible.

Therefore, the thorough and professional selection of an optimal building thermo- insulation system represents one of the most important technical and economical goals for both the Designer and the Investor.

In contemporary civil engineering practice, the thermo-insulation of buildings is mostly reduced to facade walls"temperating" (together with replacement of single- layer glass windows with new double-or triple-layer"thermopan"glass windows which also have better sealing performance). In relation to that, there is an increase in application of two-layer and three-layer facade structures consisting of bearing elements (concrete walls, brick walls) and thermo-insulation layers made of materials with the heat conductivity coefficient smaller than 0,10 W/m°C (mineral wool, styrofoam panels or similar insulating materials), which are plastered or additionally coated with facade bricks or simple bricks laid sideways and then plastered. However, the solutions including multi-layered facade walls built at the construction site also mean more working tacts, more specialists for each working <BR> <BR> position, additional expense for connections (anchors, plugs, substructures, etc. ) and for various base-layers and technological mediators (such as special plastering over a special reinforcement mesh, using of glass or plastic fiber nets together with glue application, etc.).

All the above stated facts, together with construction complexity and working speed aspects, as well as the entire cost of the applied materials are the main reasons that the price of the facade structure plus the roof structure as"the fifth facade"has reached (depending on the climate conditions) between 15-25% of the total cost of the structure.

Also, there is usually not enough attention paid to the fact that multi-layered facade structures are made as composite sections of heterogeneous materials with different physical-mechanical properties, such as: different expansion and shrinkage coefficients, different compressive and tensile strengths, adhesion properties, behavior under different types of wind load (sucking, drying or abrasion effect), ultraviolet ray exposure effect, difference between strain values in adjacent walls with significant temperature variation due to different sun exposure and color of the final facade coating, different aging properties of each composite during exploitation, and finally different air and steam permeability values.

It is important to underline the fact that air and steam permeability represent not just physical-mechanical properties but also quality conditions essential for durability of facade structures as well as significant factors for energy saving and comfortable living. Facade structures must have sufficient air and steam permeability, especially if the closed areas of the building are not equipped with an adequate ventilation system. Namely, every man spends between 25-30 m3 of air and exhales 20-30 liters of carbon monoxide. Therefore, in every case of application of airtight and steam tight facade insulation, especially when combined with contemporary good quality facade carpentry, it is necessary to provide continuous ventilation in order to supply enough fresh air. However, frequent ventilation inevitably implies significant heat- loss from the building.

Today, there are many thermo-insulation systems at the world market but they are mostly intended for facade walls'insulation. These systems can be classified into one of the following categories.

The application of facade layers in order to insulate facade walls implies installation of multi-layered thermo insulating plates, which are fastened to the outer walls using glue or mechanical means (anchors, plugs or substructures). After that, plastering over special mesh reinforcement or skimming takes place, followed by the finishing facade layer, which has not only esthetic function, but also serves as a strengthening layer-at the same time protecting the thermo-insulation from the environmental influences, ultraviolet rays, etc. Generally, multi-layered plates are just glued to the wall in case when its height doesn't exceed 8 m, otherwise the use of mechanical fastening means is required. There are two different fastening systems available, depending on the thickness of the finishing layer: with rigid or with elastic (mobile or jointed) fastening elements (supports, consoles or anchors).

The first system (with rigid connections) is used in case of thin finishing layers application (8-12 mm). In such a case, the temperature-humidity deformations are not able to cause the appearance of cracks and the self-weight load of the layer is transferred to the thermo-insulated wall by means of rigid fastening elements. These elements are also"taking on"transversal deflections and strains induced by the sucking wind load. When the plaster layers are thicker (20-30 mm), the elastic connections are recommended. These connections allow the temperature-humidity deformations of the plaster layer and accept only tensile stresses, at the same time providing the self-weight load of the thick plaster layer to be transferred over the thermo-insulation plates to the walls of the building.

Thermo-insulating systems combined with masonry involve building of special layers using facade bricks, ordinary bricks or other elements (stone, gypsum <BR> <BR> plasterboards, etc. ), in cases when there is no requirement for ventilated air layer in the design. However, special attention should be paid that the height of the brickwork must be limited to the maximum of two stories, because of the difference in mechanical and thermo-hygrometric properties between the facade wall and the masonry layer.

Thermo-insulating systems based on protective-decorative screens (ventilated facade) involve coating of the facade walls with granite plates, aluminums boards, glass panels and similar materials. Generally speaking, these materials usually have insufficient steam permeability, which is the reason why there has to be a ventilated space between the thermo-insulation material and the screen (therefore, this facade system is called the"ventilated facade"). Such insulation and facade finishing systems allow the maintaining of a constant heat-exchange regime in the winter as well as in the summer period, making the living conditions comfortable and the heating energy expenses under the standard values. The outer finishing layer of the system is safely connected to the outer walls'bearing structure by means of a substructure usually made of aluminums or zinc-coated sheets. Various materials in the form of panels or sheets, such as natural stone, granite, marble, granite-ceramic plates, colored polymer materials or aluminums and other metal sheets coated with plastic are used as the finishing decorative facade layers.

One must be especially careful when choosing the type of the mineral wool suitable for the ventilated facade, because there are a lot of different factors influencing both the quality of the material and its exploitation performance in the system. While the factors influencing the material's quality (such as the sourness module, water tightness, medium diameter of the fiber, the applied bonding agents, etc. ) could be determined and checked in the laboratory, the behavior of the mineral wool as a part of the ventilated facade system during exploitation could not be uniformly established.

Namely, there are mineral wool panels having one side covered with a glass-fiber sheet already available on the market. This is necessary because of the possible local turbulent air currents appearing inside the ventilated facade and causing the emission of mineral wool fibers. This effect may take place under certain combinations of temperature regime, atmospheric pressure, air-space clearance and other factors, regardless to the relatively small air-stream velocity inside the ventilated space (around 0.3 m/sec). The additional glass-fiber sheets represent a way to"fight"with this phenomenon. However, cladding the mineral wool panels with glass-fiber sheets reduces the steam permeability of the system, which means that a part of the steam stays within the mineral wool layer. This could have a lot of negative consequences and the basic idea of the ventilated facade becomes senseless.

According to the research results of Dr. M. Y. Bikbey-member of the New York Academy of Civil Engineering and the Russian Academy of Natural Sciences-the only way to radically reduce the costs of the facade structure (and consequently the total building costs) is to use one-layer facade walls, which means abandoning all types of multi-layered polymer thermo-insulation materials and technologies.

Speaking at the Second International Conference on Roof Structures and Building Insulation held in Moscow (2002) he declares: "Ideally speaking, facade structures of residential and business buildings are facing following demands: the ability to function as bearing or self-bearing walls, possession of high thermo-insulation properties, good soundproofing characteristics, humidity resistance, frost resistance, air permeability, steam permeability, sufficient light-weightiness, ecological cleanliness, satisfactory fireproofing, durability, and finally, they must not obstruct the ability of architectural free expression.

Regretfully, there is no building material present which could be used for wall construction and fulfill the whole list of the above stated demands" (End of quote).

THE ESSENCE OF THE INVENTION The invention is related to the three-layered thermo-insulation plate and its production procedure. The plate consists of two composite materials: styrofoam in the middle layer and polystyrene concrete in two outer layers. Polystyrene concrete is made as a mixture of expanded polystyrene grains, Portland cement, water and special admixtures (in the following text :"SIMPROLIT", which is the commercial name of the product).

There are two types of this plate. The first type is a rebated three-layered plate and the second type is a flat three-layered plate. In both cases, the middle layer is made of styrofoam with a density varying from 12 to 15 kg/m3, depending on the production method. The three-layered rebated thermo-insulation plate is produced with rebates on both sides, one of them being on the lower and the other on the upper side of the plate. The height of the rebate is equal to the half of the plate's thickness and its width varies between 10-50 mm.

The rebated three-layered plate is produced using special molds and special procedure. First, the styrofoam plate with required dimensions is put in the middle of the mold and after that the outer layers are casted using fresh polystyrene concrete-"SIMPROLIT". The structural details and the production procedure for both types of thermo-insulation plates will be explained in the paragraph"Detailed description of the invention".

SHORT DESCRIPTION OF THE DRAFT PICTURES The invention will be described in detail using an example which is shown in the draft. The pictures shown in the draft represent: Picture 1-The three-layered thermo-insulation plate presented in axonometry, Picture 2-The cross-section A-A as shown on the picture 1, Picture 3-The longitudinal section B-B as shown on the picture 1, Picture 4-The cross-section of the flat three-layered plate.

DETAILED DESCRIPTION OF THE INVENTION The three-layered rebated plate (as shown on pictures 1,2 and 3) consists of two composite materials: styrofoam plate as the middle layer (1) and polystyrene concrete casted in two outer layers (2). Polystyrene concrete is made as a mixture of expanded polystyrene grains, Portland cement, water and special admixtures (in the following text :"SIMPROLIT", which is the commercial name of the product). The styrofoam plate (1) with required dimensions has a density between 12-15 kg/m3.

Rebates (3,4) are placed on both sides of the styrofoam plate (1), one of them being on the lower and the other on the upper side of the plate. The height of the rebate is equal to the half of the styrofoam plate's thickness and its width varies between 10- 50 mm.

The styrofoam plate (1) has a longitudinal rebate (3) and a transversal rebate (4) on the upper surface, and on the lower surface there are also a longitudinal rebate (3) and a transversal rebate (4) but they are cut in the opposite direction. Rebates (3 and 4) will not become covered with"Simprolit"polystyrene concrete, because of the specific mold construction, which covers the rebates at all four sides of the plate.

The rebated three-layered thermo-insulation plate's production procedure consists of several steps. First, the prefabricated styrofoam plate (1) with required dimensions is put in the middle of the mold (which is not presented) and after that, fresh polystyrene concrete-"SIMPROLIT" (2) is casted over the upper surface of the plate (1) as a half-dry mixture, forming a 10-30 mm thick layer. After that, the styrofoam plate (1) having its upper surface covered with"SIMPROLIT" polystyrene concrete is taken out of the mold and left to dry on the shelf for the next 12-24 hours, with the temperature of the environment ranging from 12-36°C (depending on the average regional temperature). After the drying and the hardening of the upper plate's surface, the plate is rotated for 180° and again put into the mold.

Then, the same procedure repeats-in order to cover the other-lower surface of the styrofoam plate (1) with"SIMPROLIT"polystyrene concrete (2), forming the second layer of the same thickness as the first one. In the next phase, the whole three-layered rebated plate is taken out of the mold and left on the shelf to dry for the next 12-24 hours, with the air temperature ranging from 12-36°C. Finally, the plate is moved to the storage where it ripens for minimum seven days, at a temperature that should be larger than 12°C.

It is very important to underline the fact that"SIMF'ROLIT"polystyrene concrete (2) is not casted over the longitudinal rebates (3), nor over the transversal rebates (4), but only over the upper and lower rectangular surface of the styrofoam plate (1).

The second type of the thermo-insulation plate, according to the invention, is the three-layered flat plate produced in the shape of parallelogram, without rebates. This plate consists of a styrofoam plate (5), which is a middle layer and two layers (upper and lower) of"SIMPROLIT"polystyrene concrete (2). The styrofoam plate (5) is ordered in required dimensions and has a density between 12-15 kg/m3.

The flat three-layered thermo-insulation plate's production procedure also consists of several steps. First, the prefabricated styrofoam plate (5) is put in the special mold (which is not presented) and after that, fresh polystyrene concrete- "SIMPROLIT" (2) is casted over the upper surface of the plate (5) as a half-dry mixture, forming a 10-30 mm thick layer. After that, the styrofoam plate (5) having its upper surface covered wii"SIMPROLIIq'polystyrene concrete is taken out of the mold and left to dry on the shelf for the next 12-24 hours, with the temperature of the environment ranging from 12-36°C (depending on the average regional temperature). After the drying and the hardening of the upper plate's surface, the plate is rotated for 180° and again put into the mold Then, the same procedure repeats-in order to cover the other-lower surface of the styrofoam plate (5) with "SIMPROLIT'polystyrene concrete (2), forming the second layer of the same thickness as the first one. In the next phase, the whole three-layered flat plate is taken out of the mold and left on the shelf to dry for the next 12-24 hours, with the air temperature ranging from 12-36°C. Finally, the plate is moved to the storage where it ripens for minimum seven days, at a temperature that should be larger than 12°C.

The half-dry mixture of polystyrene concrete, which is used for production of thermo-insulation plates is prepared using the following procedure: expanded polystyrene grains with diameter 1-3 mm in quantity of 3-6% (by mass) are put into the horizontal anti-current mixer; then, 1/3 of the total mass of water (24-32, 5%) already mixed with necessary 0,5-1% of various admixtures (for coating of polystyrene grains, for better adhesion, for plasticization of the mixture, for water absorption prevention, for frost resistance, for air-entrainment and pore creation, for faster strength increase and higher total strength of the material) is added and all ingredients have to be mixed for 1-2 minutes; finally, Portland cement (64-69% by mass) and the remaining quantity (2/3) of water is added and the complete mixture has to be mixed for another 3-4 minutes with the temperature of the ambient ranging between 12-36°C. The obtained composition is a half-dry polystyrene concrete mixture (with commercial name"SIMPltOLlT), which is applied in the production of three-layered rebated or flat thermo-insulation plates.

The three-layered thermo-insulation plate is produced in following dimensions : its standard length is 1000 mm, standard width is 750mm and standard thicknesses are 30,50, 80, 100 and 120 mm. The difference in the total thickness of the plate is achieved by variation of the middle styrofoam layer's thickness, whereas the outer layers made of"Simprolit"polystyrene concrete remain always the same-both layers are 10 mm thick. The heat conductivity coefficient varies between 0, 041- 0,061 W/m-°C. The mass per surface unit amounts to 11,5-12, 6 kg/m2. The adhesion between different layers varies from 0,066 to 0,085 MPa. These physical- mechanical properties have been certified by the lab tests of the plates conducted at the Institute for materials and structures-Faculty of Civil engineering in Belgrade.

The testing of fire resistance was performed at the Research Centre"Opitnoe"26 CNIII of the Russian Ministry of Defense. According to the testing results, the conclusion has been derived that during 90 minutes of fire-resistance testing (using standard fire curve with maximum temperature of 1000°C) of three-layered Simprolit plates according to GOST 30247. 1 limit state of integrity loss (E) and thermo-insulation ability loss (1) did not occur. Also, the tested samples of the plate did not burn and during fire simulation there were no smoldering or blazing effects.

The main advantage of these plates comes from the basically same raw material, which is used for production of all layers (SIMPROLlTErofoam+SlWROLIlO- styrofoam with density of 15 kgfni. From the physical-chemical aspect, it means that the whole plate has relatively homogenous mass with almost the same expansion/contraction coefficient, which also means increased durability and prevention of micro-cracks appearance on the surface of the plates. Other advantages are : better thermical properties for the same thickness of the finished plate ; existence of rebates, which are protecting the layers from freezing ; there are no organic components (such as wood fibers) that are susceptible to decay, the plates can be plastered or just skimmed using ordinary or cement-based glue. Two S1MPROLIT layers are not glued to the styrofoam layer (which is the case with other similar multi-layered plates present at the market), but they are connected during the production process by means of a special adhesion admixture added to the polystyrene concrete. As a result, excellent adhesion between the different layers is achieved, so that the majority of shear tests made in laboratory showed failure of the styrofoam layer (in more than 50% of tests) and only a few samples broke over the contact surface between the layers.

According to this invention, the three-layered plates may be put on facades or<BR> between the rafters (for thermo-insulation of attics), almost without any waste of material. Combining the plates and putting them lengthways or sideways, they can and columns, as floor plates for thermal and sound isolation or as suspended thermo-insulated ceilings. In addition to the fact that SIMPROLIT plates have exceptional physical, chemical and biological properties, they are also cost- competitive.

The production procedure of three-layered plates, according to the invention, will be presented as an example.

EXAMPLE 1 The three-layered rebated or flat SIMPROLIT thermo-insulation plates with 100mm thickness are made using styrofoam plates (density: 15 kg/m3), which dimensions are 750x1000 mm and thickness 80 mm. During the first phase, the half-dry polystyrene concrete mixture (SIMPROLIT) is casted over the upper surface of the styrofoam plate in a 10 mm thick layer. This mixture consists of Portland cement (64% by mass), water (32,5%), expanded polystyrene grains with diameter 1-3 mm (3%) and various admixtures (0,5%). The admixtures are used for: coating of polystyrene grains, better adhesion, plasticization of the mixture, water absorption prevention, frost resistance, air-entrainment and pore creation, faster strength increase and higher total strength of the material. The described procedure is used for both rebated and flat thermo-insulation plates. The surface of styrofoam which is coated with polystyrene concrete amounts to 725x975 mm for rebated plates (the rebates are not coated) and 750x1000 mm for flat thermo-insulation plates.