Classifications

• • C—CHEMISTRY; METALLURGY
  • C05—FERTILISERS; MANUFACTURE THEREOF
  • C05D—INORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C; FERTILISERS PRODUCING CARBON DIOXIDE
  • C05D3/00—Calcareous fertilisers
  • C05D3/02—Calcareous fertilisers from limestone, calcium carbonate, calcium hydrate, slaked lime, calcium oxide, waste calcium products
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B11/00—Calcium sulfate cements
  • C04B11/02—Methods and apparatus for dehydrating gypsum
  • C04B11/022—Simultaneous dehydrating of gypsum and slaking of lime
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B11/00—Calcium sulfate cements
  • C04B11/02—Methods and apparatus for dehydrating gypsum
  • C04B11/024—Ingredients added before, or during, the calcining process, e.g. calcination modifiers
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/14—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
  • C04B40/0028—Aspects relating to the mixing step of the mortar preparation
  • C04B40/0039—Premixtures of ingredients
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
  • C04B2103/10—Accelerators; Activators
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/00732—Uses not provided for elsewhere in C04B2111/00 for soil stabilisation

Definitions

• the invention relates to a material, in particular a building material, its use for the manufacture of building elements and its manufacturing method.
• European patent 0 290 571 discloses building blocks made of a material essentially consisting of plaster and an inert filler such as sand, having very good resistance to compression due to their molding in a closed mold. during hydration of the plaster which counteracts the natural expansion of the plaster and causes a densification of its crystal lattice. According to this known process, a mixture of plaster, water and an inert filler such as sand is compressed and then kept in a closed mold and is therefore subjected to a high internal pressure resulting from the hydration of the plaster, the duration of this can vary quite widely depending on the temperature and the type of plaster used, so that the molding operation generally lasts a few minutes.
• the plasters available on the market are complex products of good quality, relatively expensive and almost all containing setting retarders which facilitate the practical use of plaster in conventional processes but which lengthen the time during which the mixture of plaster, water and inert filler should be kept in a closed mold in the counter expansion process described above.
• the extension of this duration reduces the production rate of the construction elements and has a significant impact on their cost price.
• the amounts of quicklime added to the gypsum are relatively high and determined to allow a complete transformation of the gypsum into plaster, that is to say double hydrate of calcium sulphate into semi-hydrate. Furthermore, the reaction takes place in an enclosed space to avoid any loss of heat and so that the water released by the gypsum is captured by quicklime, the reaction continuing until complete transformation of the gypsum into plaster, which is the goal.
• the subject of the invention is modifications to this known technique, with a view to obtaining a new construction material intended in particular for use in the process known as "thwarted expansion" with performances clearly superior to those obtained so far.
• the invention therefore provides, for this purpose, a material, in particular of construction, characterized in that it consists essentially of calcium sulphate hemihydrate, gypsum and slaked lime, the amount of gypsum in this material being between 0.5 and 5% by weight approximately.
• calcium sulphate hemihydrate is the main component of plaster
• such a material can be used as a conventional plaster or a mixture of conventional plaster and an inert filler for the manufacture of building elements according to the expansion process described in European Patent 0 290 571, but with the advantage that the gypsum it contains, being a setting accelerator, allows to significantly increase the rate of manufacture of construction elements, reducing the duration of their molding.
• the lime contained in this material has the long-term effect of increasing the surface hardness of the building elements and their resistance to water, ambient humidity, air and alkaline products.
• the material according to the invention is obtained by mixing wet gypsum and quicklime and partial cooking of the mixture.
• the wet gypsum can be, at least in part, residual gypsum and in particular a by-product of the chemical industry such as for example phosphogypsum (by-product of processes for the preparation of phosphoric acid), borogypsum (by- produces processes for the production of boron and borates) or sulfogypsum (by-product of smoke desulfurization, in particular smoke from thermal power plants), which are products naturally containing moisture and which the prior art does not allow to use without prior drying. It is also possible to use crushed rubble from constructions comprising plaster.
• phosphogypsum by-product of processes for the preparation of phosphoric acid
• borogypsum by- produces processes for the production of boron and borates
• sulfogypsum by-product of smoke desulfurization, in particular smoke from thermal power plants
• the new material according to the invention comprises by weight from 3 to 15% approximately of slaked lime for 97 to 85% approximately of calcium sulphate hemihydrate and gypsum.
• the invention also provides a process for manufacturing this new material, characterized in that it consists in mixing quicklime and wet gypsum and in subjecting this mixture to partial cooking in order to obtain a material consisting essentially of hemihydrate of calcium sulfate, slaked lime and gypsum, the amount of gypsum in the material being about 0.5 to 5% by weight.
• This process makes it possible to use wet gypsum without it being necessary to dry them completely beforehand, which saves energy, and to obtain a building material by partial firing of gypsum, hence another energy saving.
• This partial cooking is carried out at a relatively low temperature, for example of the order of 90 to 120 ° C.
• the product obtained by mixing wet gypsum and quicklime (a mixture of gypsum and slaked lime) can be used (before or after the above-mentioned partial cooking) for various purposes.
• soil improvement locculation of clay soil, liming and gypsum, the slaked lime of this mixture being assimilated by plants
• suifocalcic activation of road binders based on dairy or hydraulic or pozzolanic binders in general can be used (before or after the above-mentioned partial cooking) for various purposes.
• soil improvement locculation of clay soil, liming and gypsum, the slaked lime of this mixture being assimilated by plants
• suifocalcic activation of road binders based on dairy or hydraulic or pozzolanic binders in general in general.
• the first stage of this process is a mixing of quicklime 12 and wet gypsum 14, the latter advantageously being made up partly or entirely of residual gypsum such as phosphogypsum, borogypsum or sulfogypsum for example, which are naturally wet byproducts of the chemical industry.
• this gypsum or the gypsum-lime mixture can be subjected to partial drying.
• wet gypsum can contain about 5 to 10 percent by weight of free water and about 3 to 15 percent by weight of quicklime is added to it.
• quicklime hydrates quench
• free water from the wet gypsum and becomes very fine, its fineness being much greater than that of quicklime obtained by grinding (it passes from 3,000 to 10,000 on Blaine surfaces, for example).
• This hydration is accompanied by a release of heat causing a rise in temperature which may be sufficient for the production of semi-hydrate emerging from calcium sulphate.
• the mixture of gypsum and slaked lime is then subjected to partial firing 18, at a temperature which can be of the order of approximately 90 to 120 ° C.
• the gypsum transforming into a mixture of calcium sulphate hemihydrate and incuits which are accelerators for setting calcium sulphate hemihydrate.
• Mixing 10 and partial cooking 18 can be carried out using materials which are traditionally used for the manufacture of road mixes based on gravel and bitumen, these materials being robust, safe and well known in the art.
• the material leaving the partial cooking 18 is at a temperature in the region of 100 ° C. or higher and must be cooled, the cooling possibly natural (heat exchange with the surrounding environment) or may occur or continue during mixing 26 with an inert load which is cold and possibly wet. Mixing with the inert charge is in principle sufficient to cool the material to a temperature where water can be added to it without vaporization.
• the amount of water added to the material is slightly greater than the optimum Proctor to obtain the best possible compactness of the construction elements, and the inert load can be sand or any other load depending on the intended use of the construction elements .
• water can be added at the end of kneading of the material and of the inert filler, the mixture being for example at a temperature of the order of 60-80 ° C.
• the final temperature of the mixture can be determined to regulate the setting speed and promote the phenomenon of thwarted expansion.
• the mixture of material, water and filler is placed in a mold which is closed and which is placed under a press, and is kept in the closed mold for almost the entire duration of l hydration of plaster, as described in detail in European Patent 290,571 as well as in European Patent Application 619,773 to which a person skilled in the art can refer if necessary, the duration of this retention in the mold being previously a few minutes (typically two to four minutes) in these previous documents, whereas it can here be reduced to a much shorter duration, for example from ten to thirty seconds approximately, depending on the rate of incuits in the material according to the invention .
• the construction elements which are thus obtained can be used as soon as they are removed from the mold and they have a very high dimensional accuracy (of the order of 0.1 mm) due to the hindered expansion of the hemihydrate during their molding, so that they can be used without a joint.
• the lime contained in these elements carbonates slowly (within a few months) on contact with the carbon dioxide naturally present in the surrounding air and forms a surface layer of cullet which has the effect of improving resistance to air, to rain and to the surrounding humidity, as well as to alkaline products (washing or leaching products for example), and to increase the surface hardness of these elements, which allows them to be used under even more severe conditions and for example like good cut stone.
• the present invention has the essential advantage of using as is, in the wet state and very economically, by-products of the industry which are mixed with a small amount of quicklime to manufacture at low cost a new material itself usable in a particularly advantageous way for the manufacture of building elements according to the process of contrarian expansion, or to obtain a product usable for the amendment of soils and for the sulfo-calcium activation of binders.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Inorganic Chemistry (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1996
  • 1996-09-27 FR FR9611791A patent/FR2753964B1/fr not_active Expired - Fee Related
• 1997
  • 1997-09-26 WO PCT/FR1997/001697 patent/WO1998013309A1/fr not_active Application Discontinuation
  • 1997-09-26 AU AU44640/97A patent/AU4464097A/en not_active Abandoned
  • 1997-09-26 EP EP97943005A patent/EP0946445A1/de not_active Withdrawn

Non-Patent Citations (1)

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