Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Patent
1988-07-21
1991-03-19
Dixon, Jr., William R.
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
106778, 106783, 52257, 52258, E04C 110, E04C 106, B25B 300, E04B 254
Patent
active
050007939
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of manufacturing a building element based on a hydraulic binder, and in particular on plaster, to elements obtained by performing the method, and also to a building method using such elements.
Prefabricated building elements are already known which are made of plaster and which are used, in general, for lining walls and for making lightweight partitions. The drawback of these elements is their low mechanical strength.
Attempts have already been made to mix an inert fill, e.g. sand or fibers, with the plaster in order to increase the strength of such elements, however it has not been possible to increase strength sufficiently for such elements to be usable as elements in a load-carrying wall.
Further, elements based on plaster and made by prior manufacturing methods require a long drying time before they can be handled.
A particular object of the invention is to mitigate these drawbacks by proposing a plaster-based element whose mechanical strength is equivalent to that of ordinary grade concrete and whose hardness is equivalent to that of stone.
Another object of the invention is to provide a plasterbased building element which is capable of being handled and used immediately after it has been manufactured, without requiring prior drying.
Another object of the invention is to provide a plasterbased building element capable of being made from any type of plaster, including raw plaster or plaster of very ordinary quality.
The invention thus provides a method of manufacturing a building element based on a hydraulic binder, in particular plaster, characterized in that it consists in dry mixing plaster and an inert granular fill such as sand, in dampening said mixture by adding a quantity of water thereto which is substantially equal to or slightly greater than the quantity of water necessary for hydrating the plaster, or which is sufficient for obtaining maximum compactness of the mixture for a given compression energy, in immediately placing the damp mixture in a mold, and in compressing it in the mold for a predetermined period of time during which the plaster hydrates and the crystal lattice resulting from its hydrating densifies, then in extracting the element obtained in this way from the mold.
This method makes it possible to use: firstly plaster requiring no special precautions to be taken with respect to quality, grain size, setting speed, or expansion factor, although it is preferable for the expansion factor to be relatively high, and secondly a granular fill such as windblown sand, sea sand, laterite, etc. having a grain size appropriate to the final product which is to be obtained.
Because the quantity of water added to the mixture of plaster and sand or the like is low and corresponds substantially to the quantity required for hydrating the plaster, or as a function of the plaster content in the mixture to the quantity of water required for obtaining maximum compactness of the mixture for a given compression energy, a final product is obtained on unmolding which can be handled and used without requiring prior drying.
Further, since the plaster hydrates essentially while the damp mixture is being compressed in the mold, the expansion of the mixture due to the plaster hydrating is opposed by the compression applied thereto, thereby giving rise to considerable-e densification and to preferential orientations in the crystal lattice of the plaster. This characteristic makes it possible to obtain a building element whose compression strength is about 150 kg/cm.sup.2, for example. i.e. equivalent to that of concrete, while its hardness is equivalent to that of facing stone.
According to a characteristic of the method of the invention, the damp mixture is compressed in the mold in two opposite directions.
This provides an element which is more uniform, and whose compression strength is substantially constant over its entire height.
According to another characteristic of the method, the dry mixture comprises about 15% to about 40% by weight of plaster, with the plaster con
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Bonner Carol
Dixon Jr. William R.
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