Patent EA-005049-B1 (EA)
Title: Method for making building elements
Inventor: SERRAS EDOUARD
IPC: C04B40/02
Filed: 2002-03-07
Abstract: 1. A method for making a building element based on gypsum plaster, which consists in filling a mould (10) in the form of an element to be obtained with at least gypsum plaster and water, compressing a mixture of gypsum plaster and water in the mould and taking a building element out, characterized in that a pressure is applied on said mixture in the mould, said pressure is not less than a threshold value as from which the gypsum plaster is prevented from being crystallised by increasing its water-solubility, then in causing it to be rapidly crystallised by decreasing the compression of the mixture. 2. The method according to claim 1, characterized in that the amount of water is practically equals the double amount of water necessary for crystallization of the gypsum plaster at an atmospheric pressure and is from 35 to 40 parts per 100 parts of gypsum plaster when the compression threshold value is about 150 bars. 3. The method according to claim 1 or 2, characterized in that includes forced crystallization of gypsum plaster in the mixture by stopping the compression of the mixture. 4. The method according to one of claims 1-3, characterized in that includes forced crystallization of gypsum plaster in the mixture by taking the element out of the mould resulted compression the mixture in the mould (10). 5. The method according to one of claims 1-4, characterized in that includes natural crystallization of gypsum plaster in the element outside the mould (10). 6. The method according to one of claims 1-5, characterized in that initially the mixture is compressed in the mould to reduce cavities in the mixture to the minimum or near the minimum value, and then gradually increase applied pressure at least to predetermined maximum value. 7. The method according to one of claims 1-6, characterized in that the mixture in the mould comprises a granular filler. 8. The method according to claim 7, characterized in that the filler is a chemically inert filler relative to gypsum plaster. 9. The method according to claim 7, characterized in that the filler is not a chemically inert filler relative to gypsum plaster. 10. The method according to one of claims 1-9, characterized in that the mixture in the mould comprises a diluent. 11. The method according to claim 10, characterized in that the diluent is a deflocculant, such as melamine. 12. The method according to one of claims 1-11, characterized in that said threshold pressure value increases with a temperature and ranges between from about 100 to 150 bars, when the temperature changes from about 15 to 20 degree C. 13. The method according to one of claims 1-12, characterized in that the pressure is applied on the mixture in the mould with an effort equal to at least said maximum value by immersing into the mixture inside the mould one element having a cross-section which is less than the corresponding cross-section of the mould cavity, said element is made, for example, as a cylindrical stem driven through a hole in the mould wall by applying a pushing axial effort thereon for immersing in the mixture.