Classifications

• • 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
  • C04B28/24—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 alkyl, ammonium or metal silicates; containing silica sols
  • C04B28/26—Silicates of the alkali metals
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

• This invention relates to a process for the preparation of shaped articles such as construction materials, pavers and the like, in particular to a process that utilises waste and other materials such as fly ash in amounts that may constitute a major proportion of the shaped articles.
• the invention also relates to a process for the disposal of particulate waste materials such as fly ash whereby these materials are converted into a solid aggregate.
• a construction 20 material is formed from a mixture of a soil that has been heated in a manner such that the property of the soil to swell with changing levels of moisture is destroyed without melting any of the soil constituents, with iron oxide which is added either before or after heating and 5 into which a solution of sodium silicate is added.
• the sodium silicate solution may be formed by admixing fly ash and sodium hydroxide. This use is of course indirect as the fly ash is merely used to form sodium silicate.
• the present invention consists in a process for the preparation of a solid aggregate material comprising: a) preparing a mixture of an aluminosilicate containing non-soil or waste material to contain, iron oxide, an alkali, a water soluble silicate, water and optional additives excluding binders; b) forming the mixture into a cohesive mass; and c) curing the mass whereby a solid aggregate material is formed.
• this invention consists in a solid aggregate material made by a process according to the present invention.
• the solid aggregate material may comprise a shaped article.
• This process requires that the step of forming the mixture into a cohesive mass comprise formation of the mixture into a shaped article.
• the subsequent curing step will be carried out in a manner such that the shaped article will attain a requisite strength.
• the solid aggregate may have a minimal compressive strength in which case the curing step will generally comprise air drying until a solid aggregate is formed.
• the curing step will generally comprise air drying until a solid aggregate is formed.
• Such a process is particularly useful for the disposal of particulate aluminosilicate containing waste materials.
• Australian patent 535130 has as an essential feature the use of a particularly prepared soil which is not essential in the present invention, and there is no suggestion or teaching to include fly ash per se or more particularly a water soluble silicate and fly ash, it is evident that the present invention represents a fundamentally different process.
• the present inventor believes that, without being bound by theory, in the process of the present invention an iron aluminosilicate crystal structure is formed which imparts relatively high strength to the resultant shaped articles.
• the aluminosilicate containing non-soil or waste material may comprise a variety of materials including fly ash, metropolitan waste ash, sewerage ash, other flue ashes, coal wash tailings, mineral tailings, scoria, obsidian, other pozzolanic materials and neutral to slightly acidic slags.
• the material will be in particulate form, usually relatively fine particles.
• an amount of up to about 95% by weight of the aluminosilicate material may be included in the mixture thereby providing for the possibility of both disposing of and utilising substantial amounts of fly ash.
• the amount of iron oxide used may be as low as about 1% by weight with respect to the aluminosilicate containing material. At levels up to about 7% compressive strength increases but above that level compressive strength remains substantially constant.
• the aluminosilicate containing material may comprise a material such as a flue dust high in iron oxide without being detrimental to the strength of shaped articles formed from such materials.
• aluminosilicate materials may inherently contain sufficient iron oxide to circumvent the need to add iron oxide when preparing the mixture.
• An example of such materials are particular ashes.
• a similar minimum level of water soluble silicate may be used as to iron oxide. In this case levels above about 10% do not result in further increases in compressive strength.
• the amount of alkali used is not critical in that levels as low as 0.9% by weight with respect to the aluminosilicate containing material have yielded shaped articles of acceptable compressive strength.
• the alkali will be a strong alkali such as sodium or potassium hydroxide.
• silicate used relative to the aluminosilicate containing material is an important factor in determining compressive strength.
• a minimum of at least about 5% by weight of silicate will generally be required.
• the amount of water incorporated in the mixture will depend upon the manner in which the shaped article is to be formed. An amount of water equivalent to at least about 10% by weight of the aluminosilicate containing material will usually be sufficient in forming the majority of shaped articles.
• a variety of additives, excluding binders, may be included in the mixture in amounts up to about three times the weight of aluminosilicate containing material. These additives including appropriately graded gravel, sand, pigments and calcined soils. Usually such additives will be included to produce a shaped article having a particularly desired texture, colour or appearance.
• the mixture of the aluminosilicate containing material, iron oxide, alkali, water and optional additives may be formed into a variety of shaped articles by compaction, moulding, extruding or slip forming.
• the method of formation will be largely determined by the composition of the mixture and the nature of the finished shaped article.
• a variety of shaped articles may be formed using this invention including tiles, pavers and construction materials such as bricks, blocks and the like.
• the shaped article may be allowed to cure in ambient air at a temperature of about 20-40 C. Under these conditions, curing will normally be completed in about 7 days.
• the energy requirements of the invention are quite low, thereby contributing to the relatively low cost of these shaped articles. It has, however, been found that it is possible to substantially accelerate the curing time by increasing the curing temperature, for example, by curing at 100°C in a confined environment.
• the present invention comprises shaped articles in the form of bricks which comply with Australian Standard AS1226-1984 for clay bricks or AS2733-1984 for concrete masonry units.

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Publications (2)

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Citations (4)

• 1992
  • 1992-06-12 EP EP19920911888 patent/EP0588872A4/de not_active Withdrawn
  • 1992-06-12 WO PCT/AU1992/000283 patent/WO1992022514A1/en not_active Application Discontinuation

Patent Citations (4)

Non-Patent Citations (4)

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