WO2020037349A1 - Procédé de préparation de compositions de mousses de géopolymères - Google Patents

Procédé de préparation de compositions de mousses de géopolymères Download PDF

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Publication number
WO2020037349A1
WO2020037349A1 PCT/AU2018/050894 AU2018050894W WO2020037349A1 WO 2020037349 A1 WO2020037349 A1 WO 2020037349A1 AU 2018050894 W AU2018050894 W AU 2018050894W WO 2020037349 A1 WO2020037349 A1 WO 2020037349A1
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Prior art keywords
geopolymer
foam
gum
aqueous composition
paste
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PCT/AU2018/050894
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English (en)
Inventor
Alireza KASHANI
Duc Ngo TUAN
Priyan MENDIS
Ailar HAJIMOHAMMADI
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The University Of Melbourne
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Priority to PCT/AU2018/050894 priority Critical patent/WO2020037349A1/fr
Publication of WO2020037349A1 publication Critical patent/WO2020037349A1/fr

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    • 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
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/04—Waste materials; Refuse
    • C04B18/06—Combustion residues, e.g. purification products of smoke, fumes or exhaust gases
    • C04B18/067—Slags
    • 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
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/04—Waste materials; Refuse
    • C04B18/06—Combustion residues, e.g. purification products of smoke, fumes or exhaust gases
    • C04B18/08—Flue dust, i.e. fly ash
    • 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
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/04—Waste materials; Refuse
    • C04B18/06—Combustion residues, e.g. purification products of smoke, fumes or exhaust gases
    • C04B18/08—Flue dust, i.e. fly ash
    • C04B18/081—Flue dust, i.e. fly ash from brown coal or lignite
    • 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
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/04—Waste materials; Refuse
    • C04B18/14—Waste materials; Refuse from metallurgical processes
    • C04B18/146—Silica fume
    • 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
    • C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
    • C04B24/24—Macromolecular compounds
    • C04B24/38—Polysaccharides or derivatives thereof
    • 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
    • C04B28/006—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 mineral polymers, e.g. geopolymers of the Davidovits type
    • 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
    • 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
    • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
    • C04B38/10—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by using foaming agents or by using mechanical means, e.g. adding preformed foam
    • 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
    • C04B2103/48—Foam stabilisers
    • 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
    • C04B2111/20—Resistance against chemical, physical or biological attack
    • 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
    • C04B2111/20—Resistance against chemical, physical or biological attack
    • C04B2111/28—Fire resistance, i.e. materials resistant to accidental fires or high temperatures
    • 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
    • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/05—Materials having an early high strength, e.g. allowing fast demoulding or formless casting
    • 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
    • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/20—Mortars, concrete or artificial stone characterised by specific physical values for the density
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding
    • 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

  • the invention relates to a process for preparation of geopolymer foam composition and to a geopolymer foam concrete.
  • Geopolymers are an environmentally friendly alternative to Portland cement. They have desirable properties such as high early strength, excellent fire resistance and high resistance to aggressive chemicals such as acids.
  • Geopolymer foamed concrete may be prepared by a range of methods include generating gas in situ by chemical foaming.
  • Chemical foaming agents include hydrogen peroxide, sodium perborate and aluminium metal which react with the alkaline activating agent such as sodium hydroxide. Air can also be entrained in the geopolymer concrete paste during the mixing process.
  • a process for preparing a geopolymer foam concrete comprising: preparing a geopolymer paste comprising mixing a composition comprising water, fly ash, blast furnace slag, and an alkaline activator;
  • foaming an aqueous composition comprising surfactant and polysaccharide thickener by entraining air, optionally under pressure, into the aqueous composition; blending the foamed aqueous composition with the geopolymer paste to form a geopolymer foam;
  • the foamed aqueous composition prior to blending with the geopolymer paste, has a drainage rate of the aqueous composition from the foamed aqueous composition of no more than 20% of the aqueous composition volume over 20 minutes (preferably no more than 15% of the aqueous composition volume over 20 minutes) from foaming.
  • the polysaccharide thickener may be present in an amount which is sufficient to provide a Brookfield viscosity (using spindle No. LV3(63) at 20 rpm and 20°C) in water of at least 200cp (such as 200 cp to 3000 cp), preferably at least 300 cp, more preferably 300 to 3000 cp, still more preferably 400 to 2000 cp.
  • a Brookfield viscosity using spindle No. LV3(63) at 20 rpm and 20°C
  • water of at least 200cp such as 200 cp to 3000 cp
  • preferably at least 300 cp, more preferably 300 to 3000 cp, still more preferably 400 to 2000 cp such as 200 cp to 3000 cp
  • an amount of the polysaccharide thickener which provides a Brookfield viscosity in water of at least 200cp, preferably 300 to 3000 cp, more preferably 400 to 2000 cp results in
  • the surfactant may comprise a mixture of anionic surfactant and a non ionic surfactant and in particular such a blend where the HLB of the non-ionic surfactant is at least 12.
  • the presence of the blend provides improved foam stability in both the pre-formed foam and the foam when blended with the geopolymer paste.
  • Figure 1 is a graph showing the influence of polysaccharide gum thickener (XG) on the amount of drainage of liquid from foam prepared by air entrainment, over time
  • Figure 2 is a graph showing the influence of polysaccharide gum thickener (XG) on the amount of drainage of liquid from foam prepared by chemical foaming, over time.
  • XG polysaccharide gum thickener
  • Figure 3 is a three dimensional graph showing the frequency of pore sizes in each of the ranges 0-0.005, 0..5-0.02, 0.02-0.4 and 0.4-1.47 for the foamed concrete compositions formed with foams CS1 , A1 , A2 and A3 in Example 1.
  • Figure 4 is a column chart showing the compressive strength of
  • Example 1 geopolymer foam concretes prepared with air entrained foams CS1 , A1 , A2 and A3 at 7 days, 14 days and 28 days (columns from left to right respectively, for each foam) referred to in Example 1 .
  • Figure 5 is a column chart showing the compressive strength of
  • comparative geopolymer foam concretes prepared with chemically prepared foams CS2 and B at 7 days, 14 days and 28 days (columns from left to right respectively, for each foam) as discussed in Example 1 .
  • FIG. 6 is a column chart showing the Ultrasound Pulse Velocity (UPV) test results for each geopolymer foam concrete prepare using foams CS1 , A1 , A2 and A3 formed by mechanical air entrainment and CS2 and B formed by chemical foaming as discussed in Example 1 .
  • UUV Ultrasound Pulse Velocity
  • Figure 7 is a graph of viscosity measurements with different spindle speeds for aqueous solutions containing different concentrations of xanthan gum from 0.18 wt% to 0.65 wt% as discussed in Example 2.
  • Figure 8 is a column chart showing the compressive strength of
  • geopolymer foam concrete prepared with no aggregate (control group), with sand aggregate and glass aggregate each shown at 7,14,28 and 56 days in successive columns in each group as discussed in Example 3.
  • Figure 9 is a column chart showing the strength development of
  • Figure 10 is a column chart showing the strength development of geopolymer with density of about 1000 Kg/m 3 for each of the control, sand aggregate group and glass aggregate group at 7,14, 28 and 56 days as discussed in Example 3.
  • Figure 11 is a column chart showing the strength development of geopolymer with density of about 800 Kg/m 3 for each of the control, sand aggregate group and glass aggregate group at 7,14, 28 and 56 days as discussed in Example 3.
  • Figure 12 is a column chart showing the strength development of geopolymer with density of about 600 Kg/m 3 for each of the control, sand aggregate group and glass aggregate group at 7,14, 28 and 56 days as discussed in Example 3.
  • Figure 13 is a graph showing the strength at different densities of the control group (no aggregate), sand aggregate group and glass aggregate group as discussed in Example 3.
  • wt% and %wt are used to refer to the percent by weight of a component based on the weight of the relevant composition.
  • the geopolymer paste composition used in the process of the present invention includes a binder composition comprising a mineral mixture comprising powder fly ash, blast furnace slag and optionally silica fume.
  • Fly ash is by product that is formed from the combustion of coal.
  • electric power plant utility furnaces can burn pulverized coal and produce fly ash.
  • the structure, composition, and other properties of fly ash can depend upon the composition of the coal and the combustion process by which fly ash is formed.
  • Class C fly ash can be produced from burning lignite or sub-bituminous coal.
  • Class F fly ash can be produced from burning anthracite or bituminous coal.
  • the fly ash can be selected from the group consisting of Class F fly ash, Class C fly ash, and combinations thereof. Typically the fly ash contains up to 30 wt% calcium oxide.
  • BFS Blast furnace slag
  • Other blast furnace slag materials are granulated blast furnace slag (GBFS) and ground granulated blast furnace slag (GGBFS), which is granulated blast furnace slag that has been finely pulverized.
  • Ground granulated blast furnace slag varies in terms of grinding fineness and grain size distribution, which depend on origin and treatment method, and grinding fineness influences reactivity here.
  • the Blaine value is used as a parameter for grinding fineness, and typically has an order of magnitude of from 200 to 1000 m 2 kg 1 , preferably from 300 to 500 m 2 kg 1 . Finer milling gives higher reactivity.
  • blast furnace slag is however intended to comprise materials resulting from all of the levels of treatment, milling, and quality mentioned (i.e. BFS, GBFS and GGBFS).
  • Blast furnace slag generally comprises from 30 to 45% by weight of CaO, about 4 to 17% by weight of MgO, about 30 to 45% by weight of S1O2 and about 5 to 15% by weight of AI2O3, typically about 40% by weight of CaO, about 10% by weight of MgO, about 35% by weight of Si0 2 and about 12% by weight of Al 2 0 3 .
  • the preferred binder for use in the process comprises a mixture of fly ash and blast furnace slag.
  • the weight ratio of fly ash to blast furnace slag is generally 1 :5 to 5:1 but significant advantages in the process of preparing the foamed geopolymer are provided in using a weight ratio of fly ash to blast furnace slag of 40:60 to 60:40 and generally it has been found that a weight ratio of about 1 :1 confers good results.
  • the binder component of the geopolymer paste may also comprise silica fume.
  • Silica fume is an amorphous silica by-product of the manufacture of ferro-silicon and also silicon metals produced by capturing the finely divided particles from stack gases of electric arc furnaces. Silica fume is a pozzolan and when present forms part of the binder composition of the geopolymer paste.
  • the main constituent is silicon dioxide (Si0 2 ) and it is usually present in at least about 60% but very good results are achieved in the present invention when the Si0 2 content is at least about 85% by weight of the silica fume.
  • Amorphous silica is preferably an X-ray-amorphous silica, i.e. a silica for which the powder diffraction method reveals no crystallinity.
  • Precipitated silica may be obtained on an industrial scale by way of precipitating processes starting from water glass. Precipitated silica from some production processes is also called silica gel.
  • Fumed silica may form part of the binder in an amount such as 1 wt% to 10wt% of the binder. It may be produced via reaction of chlorosilanes, for example silicon tetrachloride, in a hydrogen/oxygen flame. Fumed silica is an amorphous Si0 2 powder of particle diameter from 5 to 50 nm with specific surface area of from 50 to 600 m 2 g 1 . While its use is not excluded fumed silica is generally much more expensive than the other optional binder components and is not required in order to obtain excellent geopolymer concrete properties.
  • Microsilica may if desired, be used as an additional binder component in an amount of up to 10 wt%. It is a by-product of silicon production or ferrosilicon production, and likewise consists mostly of amorphous Si0 2 powder. The particles have diameters of the order of magnitude of 0.1 microns. Specific surface area is of the order of magnitude of from 15 to 30 m 2 g 1 .
  • quartz sand is crystalline and has comparatively large particles and comparatively small specific surface area. It serves as inert filler in the invention.
  • the preferred quantity present of the alkaline activator in the invention, based on the geopolymer foam mixture, is from 1 to 55% by weight and in particular from 2 to 50% by weight, based on the solids contents of the alkaline activator.
  • alkaline activator as used herein is intended to include an alkaline bicarbonate activator, an alkaline silicate activator, e.g. sodium silicate and/or potassium silicate and/or an alkaline hydroxide activator, e.g. sodium hydroxide, potassium hydroxide and/or other earth metal hydroxide or alkaline solutions.
  • the alkaline activators suitable for use in the present invention are those alkaline activators commonly used in the field of geopolymer concrete production.
  • the alkaline activator comprises a mixture of alkali metal hydroxides and of alkali metal silicates.
  • the amount of alkaline activator is typically 3 wt% to 15wt% (such as 3wt% to 10 wt%) of the dry weight of the geopolymer composition.
  • the alkaline activator is used in an amount of 3 wt% to 15 wt% based on the weight of the total of fly ash and blast furnace slag components
  • Polysaccharide thickeners are, generally speaking, thickening polymers for aqueous systems bearing sugar units, that is, units derived from a carbohydrate of formula C n (H 2 0)n-i or (CH 2 0) n , which may be optionally modified by substitution and/or by oxidation and/or by dehydration.
  • the sugar units that may be included in the composition of the thickening polymers of the invention are preferably derived from the following sugars: glucose, galactose, arabinose, rhamnose, mannose, xylose, fucose, anhydrogalactose, galacturonic acid, glucuronic acid, mannuronic acid, galactose sulfate,
  • Polysaccharide thickeners that may especially be mentioned include those of native gums such as: a) tree or shrub exudates, including:
  • gum arabic branched polymer of galactose, arabinose, rhamnose and glucuronic acid
  • ⁇ ghatti gum polymer derived from arabinose, galactose, mannose, xylose and glucuronic acid
  • ⁇ karaya gum (polymer derived from galacturonic acid, galactose, rhamnose and glucuronic acid);
  • gum tragacanth (or tragacanth) (polymer of galacturonic acid, galactose, fucose, xylose and arabinose);
  • gums derived from algae including:
  • ⁇ agar (polymer derived from galactose and anhydrogalactose);
  • alginates polymers of mannuronic acid and of glucuronic acid
  • gums derived from seeds or tubers including:
  • ⁇ guar gum (polymer of mannose and galactose);
  • locust bean gum polymer of mannose and galactose
  • ⁇ fenugreek gum polymer of mannose and galactose
  • ⁇ tamarind gum polymer of galactose, xylose and glucose
  • ⁇ konjac gum polymer of glucose and mannose
  • microbial gums including:
  • ⁇ xanthan gum polymer of glucose, mannose acetate, mannose/pyruvic acid and glucuronic acid
  • ⁇ gellan gum polymer of partially acylated glucose, rhamnose and glucuronic acid
  • ⁇ scleroglucan gum (glucose polymer); e) plant extracts, including:
  • These polymers may be physically or chemically modified.
  • a physical treatment that may especially be mentioned is the temperature.
  • Chemical treatments that may be mentioned include esterification, etherification, amidation or oxidation reactions. These treatments can lead to polymers that may especially be nonionic, anionic or amphoteric.
  • nonionic guar gums that may be used according to the invention may be modified with CrC 6 (poly)hydroxyalkyl groups.
  • C1-C6 (poly)hydroxyalkyl groups that may be mentioned, for example, are hydroxymethyl, hydroxyethyl, hydroxypropyl and hydroxybutyl groups.
  • the invention provides a process for preparing a geopolymer foam concrete comprising: preparing a geopolymer paste comprising water, fly ash, blast furnace slag, an alkaline activator and optionally silica fume; foaming an aqueous composition comprising surfactant and thickening agent by entraining air, optionally under pressure, into the aqueous composition; blending the foamed aqueous composition with the geopolymer paste to form a geopolymer foam; and curing the geopolymer foam to form the geopolymer foam concrete.
  • the process of the invention allows stable preformed foam to be formed by air entrainment of an aqueous composition comprising thickener and surfactant, preferably containing an anionic and non-ionic surfactant. Stability of the pre-formed foam has a significant bearing on the paste incorporating the foam.
  • the foam components, in accordance with the invention may readily be combined to provide formation of a stable foam which may be prepared, incorporated into the geopolymer paste composition and the resulting geopolymer foam set without substantial drainage of the foam, to produce a set geopolymer foam concrete of relatively uniform pore size.
  • the pre-formed foam will typically be formulated to provide a drainage rate of aqueous composition from the foamed aqueous composition of no more than 20% of the aqueous composition volume over 20 minutes, preferably no more than 15% over 20 minutes from foaming.
  • the balance of components and amounts used in the composition may be determined based on this drainage test and viscosity test as herein described without undue experimentation.
  • the stability of the foam is a result of the use of the thickener, particularly a polysaccharide thickener and the surfactant component which preferably comprises a mixture of ionic and non-ionic surfactant.
  • the amount of thickener to be used may be determined by examining the effect of the quantity of thickener in pure water, without other components such as the gaseous phase or surfactants.
  • the preferred amount of amount of polysaccharide thickener will generally provide a Brookfield viscosity in water of at least 200 cp (such as 200 cp to 3000 cp) preferably 300cp, more preferably 300 to 3000 cp, still more preferably 400 to 2000 cp.
  • the Brookfield viscosity is determined using spindle No. LV3(63) at 20 rpm and at 20°C.
  • the polysaccharide thickener may, for example comprise at least one selected from the group consisting of agar; alginates, carrageenan, gum Arabic, gum ghatti, gum tragacanth, karaya gum, guar gum, locust bean gum, beta-glucan, chicle gum, dammar gum, glucomannan, mastic gum, psyllium seed husks, spruce gum, tara gum, gellan gum, xanthan gum, pullulan, soybean polysaccharides, pectin, cellulose, carboxymethylcellulose (CMC).
  • agar alginates, carrageenan, gum Arabic, gum ghatti, gum tragacanth, karaya gum, guar gum, locust bean gum, beta-glucan, chicle gum, dammar gum, glucomannan, mastic gum, psyllium seed husks, spruce gum, tara gum, gellan gum, xanthan gum, pullul
  • the thickener is preferably selected from xanthan gum and galactomannan gums such as fenugreek gum, guar gum, tara gum locust bean gum and cassia gum. More preferably the thickener is guar gum, xanthan gum or mixture thereof and most preferably the thickener is xanthan gum. [0054]
  • the optimal amount of thickener will depend on the specific polysaccharide and its effect on viscosity.
  • the thickener in one embodiment is present in an amount of 0.1 wt % to 3 wt % (more preferably 0.1 wt% to 1 wt%) of the aqueous composition in which the foam is prepared by air entrainment.
  • the preferred thickener for use in these amounts is xanthan gum, guar gum or mixture thereof.
  • the thickener is xanthan gum present in an amount of 0.15 wt % to 0.65 wt % of the aqueous composition.
  • the preformed foam composition comprises surfactant preferably including an anionic surfactant and a non-ionic surfactant.
  • an anionic surfactant is particularly suitable for stabilising the pre-formed foam.
  • there is commonly a problem in maintaining stability of the foam on combining the pre-formed foam with the geopolymer paste. While such a process may be carried out using an anionic surfactant without a non-ionic co-surfactant we have found that the resulting stability of the foamed geopolymer concrete derived from mixing of the pre-formed foam and geopolymer paste is significantly enhanced in the presence of a non-ionic surfactant.
  • the non-ionic surfactant has been found to significantly enhance the stability of the foam on mixing of the pre-formed foam with the paste providing a more consistent result and more uniform pore and pore size distribution.
  • the hydrophilic-lipophilic balance (HLB) of the non-ionic surfactant plays a role in the effectiveness of the non-ionic surfactant in stabilising the foam composition and the resulting product. It is preferred that the HLB of the non-ionic surfactant is at least 12, such as from 12 to 16. [0058] Examples of suitable classes of non-ionic surfactant include surfactants of HLB is at least 12, such as from 12 to 16. The surfactants may be selected from alkyl polyglucosides, alcohol ethoxylates including primary and secondary alkyl
  • alkylphenol ethoxylates such as nonylphenol ethoxylates and
  • octylphenol ethoxylates and particularly surfactants of these types in which the HLB is at least 12, such as from 12 to 16.
  • the HLB of a range of surfactants may readily be determined and are reported in texts such as McCutcheon’s Emulsifiers and
  • nonylphenol ethoxylates and octylphenol ethoxylates of HLB at least 12 and preferably 12 to 16 have been found to be useful.
  • examples of commercially available surfactants of this type include octyl phenol ethoxylates having about 8 to about 12 moles of EO and HLB at least 12 such as TRITONTM X-100 (TRITON is a trademark of the Dow Chemical Company) which has an HLB of about 13.4 and about 9.4 moles of EO.
  • the surfactant preferably comprises an anionic surfactant.
  • Suitable anionic surfactants may be selected from the group consisting of C 8 to Ci 8 aliphatic sulfates (particularly C 8 to Ci 8 - alpha-olefin sulfates), C 8 to Ci 8 alkyl ether sulfates, fluorinated alkyl sulfonates such as C 4 to C10 perfluoroalkylsulfonates, C 8 to Ci 8 alkylsarcosinates.
  • the more preferred anionic surfactants are selected from sodium dodecyl sulfate and sodium lauryl ether sulfate.
  • Gemini surfactants a family of synthetic surfactants which possess, in sequence, a long hydrocarbon chain an anionic group, a spacer, a second anionic group and a further hydrocarbon tail. Examples of Gemini surfactants are discussed by Menger et al,“Gemini Surfactants: A New Class of Self-Assembling Molecules” J. Am. Chem. Soc. 1993,1 15, 10083-10090.
  • the surfactant may be present in the liquid composition used in
  • preparation of the preformed foam in a concentration of from about 0.1 wt% to about 3 wt%, such as about 0.1 wt% to about 2 wt% or about 0.1 wt% to about 1 wt%.
  • the composition preferably comprises both an anionic and non-ionic surfactant and the ratio may be balanced to obtain the optimum results depending on the specific choices of respective surfactants.
  • a molar ratio in the range of 1 :5 to 5:1 to be useful with 2:1 to 1 :2 being preferred and in many cases a 1 :1 molar ratio being very effective.
  • the process comprises entraining air into an aqueous composition comprising the polysaccharide thickener and surfactant (preferably anionic and non ionic surfactant) to prepare the pre-formed foam.
  • the air may be entrained into the aqueous composition comprising the thickener and surfactant component by intense mixing, by introduction of air under pressure, or a combination of both methods of entraining air.
  • the air is entrained in the aqueous composition used to form the foam by using a mixer, such as a mixer under high shear, for example, using a planetary mixer (such as HOBART brand planetary mixer) fitted with a whisk beater.
  • a mixer such as a mixer under high shear, for example, using a planetary mixer (such as HOBART brand planetary mixer) fitted with a whisk beater.
  • the air is entrained in the aqueous composition by introduction of compressed air.
  • Compressed air may be introduced into the aqueous composition using a compressed air foam generator such as foam generators commercially available under the“DEMA” trademark.
  • the pressure of the introduced air is at least 30 PSI.
  • both mechanical high shear mixing and compressed air are used to entrain air.
  • the density of the aqueous foam resulting from air entrainment is typically in the range of 50 Kg/m 3 to 120 Kg/m 3
  • the bubble size produced in the entraining step is typically in the range of from 0.1 to 3 mm and the volume fraction of air in the foamed aqueous composition may be up to 97% but at the high end of this range the foam is less stable. In general it is preferred that the volume fraction of air is no more than 95 volume % and preferably in the range of 80% to 95% such as 88% to 95% by volume of the aqueous foam composition.
  • the foam and geopolymer paste may be combined by blending.
  • the blending process may be conducted so as to not substantially disrupt the foam and provide the required cured geopolymer density.
  • the foam and paste may be combined by addition of the foam to the paste or by addition of the paste to the foam. Generally it is preferred to add the foam to the paste with a blending action to provide a uniform mixture.
  • the consistency of the geopolymer paste may be regulated to provide effective mixing of the paste and pre-formed foam.
  • the range of mini-slump height is may for example be from 30 mm to 60 mm such as 35 mm to 55 mm for good consistency of paste before addition of foam.
  • the geopolymer paste comprises fly ash, blast furnace slag, activator and water and optionally additional components such as additional binder components such as silica fume, fibre reinforcement, rheology modifiers and aggregates.
  • the paste may be prepared from finely divided mixture of fly ash, blast furnace slag and one or more optional components by addition of an aqueous alkaline activator composition.
  • the alkaline activator preferable comprises sodium silicate and sodium hydroxide. In a preferred embodiment the total of sodium silicate and sodium hydroxide is 3 wt% to 15 wt% based on the total weight of fly ash and blast furnace slag.
  • the activator particularly the sodium silicate component of the activator may be used in particulate form and blended with the dry fly ash and blast furnace slag components.
  • an aqueous composition preferably an aqueous solution of sodium hydroxide is mixed with an intimate mixture of dry components comprising the fly ash, blast furnace slag and optionally silica fume binder components, sodium silicate activator and optionally one or more of aggregate and fibre reinforcing components.
  • an aqueous composition comprising sodium hydroxide and sodium silicate is mixed with an intimate mixture of dry components comprising the fly ash, blast furnace slag and optionally silica fume binder components and optionally one or more of aggregate and fibre reinforcing components.
  • the pre-formed foam is added and blended with the geopolymer paste.
  • Continuous blending may take place during the addition process and blending may be continued until a uniform mixture of foam and paste is provided.
  • Combination of the foam and paste and blending to achieve a uniform mixture may take place over a period of up to 20 minutes depending on the setting time of the geopolymer paste. In general the time period for blending the foam and paste is no more than 10 minutes such as from 1 to 10 minutes or from 1 to 5 minutes.
  • the amount of air introduced into the geopolymer paste may be sufficient to produce a density in the cured geopolymer of no more than 1600 kg/m 3 such as no more than 1200 kg/m 3 , no more than 1000 kg/m 3 or no more than 900 Kg/m 3 .
  • the density of the final product may be at least 300 Kg/m 3 or at least 400 Kg/m 3 providing ranges such as, for example, 300 kg/m 3 to 1600Kg/m 3 or 400 Kg/m 3 to 1200 Kg/m 3 .
  • the proportion of foam blended with the paste will depend on the consistency of the paste and composition of the paste including any aggregate or other additives and the foam composition. Typically the foam and geopolymer paste are combined to provide an amount of 5 wt% to 20 wt% of the foam in the geopolymer foam mixture.
  • the ratio of aqueous liquid to solids in the geopolymer foam mixture will have a bearing on the workability for the composition and the strength of the cured geopolymer foam. While a wide range of ratios of liquid to solid may be used we have found that a weight ratio of 0.25 to 0.5, preferably from 0.3 to 0.45 is particularly useful.
  • the geopolymer composition may comprise further materials such as selected from one or more of additional binder components, fibre reinforcement, rheology modifiers and aggregates.
  • Silica fume is a particularly preferred additional component and may be present in the copolymer composition in and amount of, for example up to 15 wt% of the composition. Higher amounts of silica fume are useful but will increase the expense of the composition.
  • the silica fume may be present in amounts of from 2 wt% to 15 wt% such as 2 wt% to 10 wt% or 5 wt% to 10 wt%. of the total of blast furnace slag, fly ash and silica fume.
  • Silica fume provides significant advantages in the working of the process of the present invention and in the resulting cured geopolymer foam. We have found that the presence of silica fume in the geopolymer paste combined with the aqueous foam results in maintaining a smaller bubble size and resulting pore size. We believe the presence of the silica fume assists in stabilising the foam formed by air entrainment on admixing with the geopolymer paste.
  • the geopolymer foam may, and preferably will, include a fibre reinforcing material.
  • the fibres may be natural or synthetic fibres and may be organic such as natural and synthetic organic polymers or inorganic such as glass and basalt fibres.
  • the preferred fibres are organic polymeric fibres, more preferably selected from the group consisting of polyolefins such as polyethylene and polypropylene, polyesters such as nylon, acrylics and PVA (polyvinyl alcohol).
  • the fibres may, for example, be of length such as 5mm to 25mm.
  • the loading of fibres may, for example be 0.1 wt% to 1.5 wt%.
  • the fibres may be monofilament fibers in deniers (diameter of the fiber) such as 7, 15, and 100.
  • the fibres are typically of diameter 20 to 550 microns.
  • the geopolymer foam composition may, if desired contain a
  • superplasticiser such as the naphthalene formaldehyde condensates or polyacid polymer such as polyacrylic acid polymers known in the art. We have found however that the presence of super plasticisers may reduce retention of air in the blend of foam and geopolymer paste.
  • the superplasticiser may be present in an amount of 0.1 wt% to 2 wt% however in a preferred embodiment the geopolymer composition is free of superplasticiser.
  • the geopolymer composition may comprise an aggregate. While the nature of the aggregate is not limited it is particularly preferred in accordance with the present invention that the aggregate used in the process is selected from particulate silica minerals, particularly comprising at least one of sand and glass and most preferably glass. In ordinary Portland cement concrete the microstructure in the bulk cement is different from that at the aggregate interface resulting in weaknesses for chemical penetration. In contrast the use of silica aggregate, particularly comprising at least one of sand and glass and most preferably glass, very significantly reduces this vulnerability in the presence of these aggregates. Furthermore, we have also found that glass aggregates increase the air content of geopolymer concretes prepared by the process of the invention.
  • Geopolymer paste formed with glass fines provides a geopolymer paste about 100 Kg/m 3 less than the corresponding foam paste with sand fines providing better foaming control and higher strength for the glass aggregate cured geopolymer foam.
  • glass aggregates allowed preparation of lighter cured geopolymer foam, preferably 300 Kg/m 3 to 1000 Kg/m 3 , more preferably 400 Kg/m 3 to 800 Kg/m 3 such as 600Kg/m 3 to 800 Kg/m 3 , with a significantly improved strength.
  • the morphology of pores in cured geopolymer foams with glass aggregate was also found to be more consistent and circular with less interconnectivity between pores, particularly at lower densities.
  • the increased population of regular closed pores enhances insulation capacity of lightweight foams with glass aggregate.
  • a thermal conductivity of 0.15 W/mK was achieved in a sample with a density of 600 Kg/m 3 .
  • the geopolymer foam comprises a particulate glass aggregate.
  • the amount of particulate glass aggregate may be 5 wt% to 65 wt% based on the dry weight of the composition, preferably 10 wt% to 40 wt% based on the dry weight of the composition.
  • the particle size of the particulate glass may, for example, be 100 microns to 2 mm such as 0.1 mm to 2mm.
  • the geopolymer foam may be cured at elevated temperature.
  • the geopolymer foam may be heated using radiant or microwave heating and microwave heating may facilitate a high throughput.
  • the curing temperature may be 40°C to 100°C and a temperature range of 60°C to 80°C is particularly preferred.
  • the process of the invention may be used in preparing building panels.
  • the building panel may be formed by casting the geopolymer foam, setting of the geopolymer in the mould.
  • the geopolymer foam may be completely or at least partially cured in the mould.
  • the geopolymer foam may be removed from the mould before curing at elevated temperature or remain in the mould during curing at elevated temperature.
  • the geopolymer foam is cast and cured within a frame to form the core of a structural panel.
  • the foamed aqueous composition preferably has a drainage rate of the aqueous composition from the foamed aqueous composition of no more than 20% of the aqueous composition volume over 20 minutes, preferably no more than 15% over 20 minutes, from foaming.
  • the drainage rate may be determined by placing a volume of foam, such as 50 ml or 100 ml in a measuring cylinder, such as a 100 ml measuring cylinder. Drainage of liquid from the foam is readily evident and forms a liquid layer at the base of the cylinder allowing the rate of drainage from the foam to be readily determined following foam preparation.
  • GBFS Granulated blast furnace slag
  • FA fly ash
  • XRF X-Ray Fluorescence
  • Geopolymer mixes are made by activating a dry mix of 50% wt. fly ash and 50% wt. slag with an alkali solution (solution to solid ratio of 0.38).
  • the alkali solution is a mixture of 33% wt. D-grade sodium silicate solution and 67%wt. NaOH solution (3 molar).
  • the Vicat instrument is used to measure the setting time of the geopolymer paste before foaming according to ASTM C191.
  • the setting time of the geopolymer paste is measured at room temperature (23 ° C) from the time that the activating solution is added to the dry mixture.
  • Pre-made foams are manufactured by using a high shear mixer.
  • the SDS solution is foamed with high shear mixing for about 10 minutes until all the solution is converted into foam.
  • a controlled SDS foam without stabilizer is made and compared with three SDS foams with xanthan gum (XG) polysaccharide thickener concentrations of 0.18%wt., 0.25%wt. and 0.45%wt.
  • XG xanthan gum
  • the foams are poured in a measuring glass cylinder, and their drainage volume is recorded and compared over time.
  • the same foams are used (immediately after they are made) for foaming geopolymers to compare their influence on the properties of the foamed geopolymers.
  • the foams are firstly combined with geopolymer mixtures manually for 20 seconds and are then mixed for one and half minutes to achieve similar wet densities of about
  • the apparent density of geopolymer foams are calculated by dividing their weight by their volume in the cubic moulds.
  • the geopolymer control sample foamed with SDS only is named CS1
  • the geopolymer samples foamed with the stabilized foams are named A1 ,A2 and A3 (with increasing concentration of XG from A1 to A3).
  • a geopolymer control sample is first mixed with 0.01 %wt. of SDS solution (to improve the pore size distribution of the chemically foamed samples), and then
  • Table 2 Geopolymer foam samples.
  • the wet foams are poured into 50x50x50 mm cubic moulds. The moulds are then sealed and cured in a 60°C oven for 24 hours. After curing, the samples are removed from the oven and kept sealed at room temperature until the day of testing.
  • the Instron 5569A machine is used to measure the compressive strength of the foamed samples. The loading rate of the machine is adjusted with a crosshead displacement rate of 1 mm per minute. The average strength of the three samples is reported.
  • the ultrasonic pulse velocity (UPV) within the cubic samples is measured by a Pundit PL-200 machine (obtained from Proceq). The overall UPV is measured by a 50 mm diameter transducer, and the velocity measurement results are used to compare the compactness of the matrix around the bubbles.
  • the Leica M205FA automated microscopy unit is used to produce
  • the thermal conductivity of the geopolymer foams is also measured and compared using the transient method with a needle probe. Small cylindrical samples with a diameter of 50 mm and a height of 1 10 mm are prepared with a hollow core. A heat transfer gel is applied on the probe, and the probe is inserted in the hollow core. The temperature is then recorded for 10 minutes under constant heat dissipation through the probe length with a voltage of 3V. The inverse value of the thermal resistivity is calculated based on the temperature difference to obtain the thermal conductivity.
  • XG as a foam stabilizer has been added to the premade foams and the chemical foaming agent.
  • the impact of the stabilizer on the foam’s life is measured and compared with different concentrations of XG in the mechanical foaming technique and a single concentration of XG in the chemical foaming method. Since there is no premade foam in chemical foaming, the impact of the stabilizer on the stability of fresh geopolymer foams is studied and compared.
  • the faster hardening of the geopolymer paste helps to maintain a larger amount of small sized bubbles in the porous geopolymer matrix and avoid interconnectivity between voids.
  • the result of the Vicat test showed that it takes about 120 minutes for the geopolymer paste to reach its initial setting time and about 135 minutes to reach final setting time.
  • Another factor that can influence the size of the voids in the matrix is the stability of the premade foams. If the premade foams are strong enough to withstand the mixing and preparation process, the resulting geopolymer foams can hold a larger degree of small sized bubbles to start with. Also, as it takes longer for the stabilized foams to drain out their solution and coalesce i.e., they can easily maintain their size until the hardening of the skeleton governs their permanent size and shape.
  • Figure 1 shows the results of the foam stability test on premade foams. Over time, the volume of the solution drainage from the foams is measured and used as an indicator of foam stability.
  • the premade foam without XG stabilizer is used as a control to compare the impact of the stabilizer on the foam’s lifetime and strength. Different concentrations of XG are added to the premade foams to also observe the impact of the stabilizer concentration on foam stability. While all the stabilized foams stay intact within the first 20 minutes after pouring into the cylinder, the control foam without stabilizer drains out 94% of its solution during the first 20 minutes of the test. After 20 minutes, the foam with 0.18% XG starts to drain slowly with an almost constant rate of about 1.1 mL per minute.
  • the foam with 0.25% XG stays intact for 40 minutes and drains only about 20% of its solution within 80 minutes of the test.
  • the foam stability test result shows no drainage in the foam with 0.45% of XG. From the test on premade foam, the impact of XG on foam stability is obvious especially at a 0.45% concentration, which completely stops the drainage during the entire testing period.
  • Figure 2 shows the volume changes observed in chemically foamed geopolymers with and without XG. In the first 15 minutes, the control sample without XG shows a slightly higher expansion rate compared to the modified sample.
  • this sample starts collapsing after this period and collapses several times until it loses about 30% of its maximum volume at the end of the test.
  • the sample with XG shows more steady and reliable expansion behaviour over time. While the rate of expansion and the maximum volume of the geopolymer foam is not a high as the control sample, this sample shows much less collapse behaviour and only about 3% of its maximum volume collapsed by the end of the test. After 70 minutes, no further volume change is observed in the samples. With a similar amount of foaming agent, the sample with XG can successfully expand the geopolymer paste to about 30% vol. more than that of the control sample.
  • the A1 , A2 and A3 images demonstrated that the addition of polysaccharide thickener such as XG can suppress bubble coalescence and reduce the frequency of irregular shaped pores.
  • polysaccharide thickener XG can suppress bubble coalescence and reduce the frequency of irregular shaped pores.
  • This observation shows the impact of polysaccharide thickener XG on foam stability after the geopolymer paste is mechanically mixed with more stable foams. Similar to their behaviour in premade foams, bubbles in the stabilized geopolymer foams have a much lower tendency to drain and coalesce, resulting in the confinement of finer pores within the geopolymer matrix.
  • FIG. 1 shows the pore size distribution of the foams CS1 , A1 , A2 and A3 formed by mechanical entrainment of air. Pore size distribution analysis showed that while the majority of pores in the stabilized samples A1 , A2 and A3 are in the 0-0.005 mm range, the pore size range in the control sample (CS1 ) was mainly in 0.005-0.2 mm and 0.4-1.47 mm regions. Also, the samples with XG showed a much lower frequency of pores in the 0.4-1.47 mm region. By increasing the concentration of XG from A1 to A3, the pore size distribution becomes narrower.
  • control sample By adding XG, the frequency of large pores in control sample (CS2) has decreased and shifted to an increase in pores of smaller size. The majority of pores are less than 0.03 mm in the stabilized sample while much larger voids are obviously dominant in the control sample.
  • XG helps to increase the cohesiveness of the slurry, thereby forming a thicker geopolymer solution that hampers the growth of gas bubbles.
  • the presence of only SDS in the control sample results in the formation of thin pore walls that will easily collapse until the skeleton gains enough strength during the hardening stage of the geopolymer paste.
  • polysaccharide thickener XG showed some remarkable effects on reducing the bubble coalescence, as well as the liquid drainage and collapse time of the foams, its influence on foam stability during the mechanical mixing process and the pouring and handling of the foamed samples is also notable. Due to the weakness of the control foam (without XG), there was some foam collapse during the mechanical mixing of the foam with geopolymer paste. Also, after pouring the samples in the moulds, bubble coarsening was observed over time. In contrast to the control foam, the stabilized foams with XG were notably stronger during the mixing, pouring and handling process. An increase in concentration of XG was accompanied with an increase in the stability of the foams during the mechanical mixing process.
  • Figure 4 shows the compressive strength distribution of the mechanically foamed samples over time.
  • the stabilized samples with XG show better strength results compared to the control sample at an early age and at 28 days.
  • sample A3 shows about 40% higher strength at 7 days and about 34% higher strength at 28 days. This significant improvement is attributed to the combined enhancements in pore size distribution and the lower foam content in this sample. While the impact of the small percentage of XG in sample A1 was shown to be significant on enhancing the pore size distribution of porous geopolymers, its impact on the strength development is not as substantial at the highest concentrations (A3).
  • Ultrasound Pulse Velocity is a non-destructive technique usually used to study the quality of concrete. The existence of cracks and voids or the formation of honeycomb within the concrete matrix drops the pulse velocity, thereby giving a good indication of the quality of the binding matrix. Recently, this method has been also used for studying the homogeneity of the pore distribution in foam
  • Figure 6 shows the result of the UPV test on geopolymer foam samples. It is evident that the increase in XG concentration increases the ultrasonic pulse velocity.
  • the amounts of various polysaccharide thickener for providing optimum foam stability may be determined from the viscosity effect of xanthan gum observed in Example 1.
  • the amount of polysaccharide thickener is sufficient to provide a Brookfield viscosity in water of at least 200cp such as at least 300cp, preferably 300 to 3000 cp, more preferably 400 to 2000 cp using spindle No. LV3(63) at 20 rpm at 20°C.
  • the spindle is readily available with standard LV torque Brookfield“Ametek” Viscometers.
  • the amounts of polysaccharide thickeners other than XG which may be used can be determined by measuring the amount required to obtain a Brookfield viscosity in water of at least 300cp, preferably 300 to 3000 cp, more preferably 400 to 2000 cp using spindle No. LV3(63) at 20 rpm.
  • the glass fines were washed as received and dried at 60°C for 24 hours.
  • a Rocklabs ring mill was then used to mill the glass and reduce its particle size.
  • the particle size distribution of the milled glass was measured to be 18 pm using the Malvern Mastersizer 2000 laser-diffraction particle-size analyser.
  • the impact velocity tolerance of glass is known to be much less than that of sand. This characteristic of glass allows it to be grinded to fine particles much easier, which is also very attractive for lightweight concrete applications.
  • the results of X-Ray Fluorescence (XRF) analysis of the source materials are presented in Table 4.
  • control group The geopolymer system with pure geopolymer paste and no aggregates is called the control group.
  • the control group was synthesized to facilitate the comparison between two mortars.
  • Two mortars (glass group and sand group) were made by mixing 30% wt. of glass or sand as aggregates with 70% wt. of geopolymer dry mix.
  • the mix design of the geopolymer binder consists of 60 % wt. FA, 40% wt. GBFS and 8.5% wt. sodium metasilicate in a dry mix. A consistent water to binder ratio of 0.38 was used for all three systems.
  • Geopolymer dry ingredients were firstly mixed manually for two minutes, and water was gradually added and blended with the dry mix manually for one minute first and then mixed by a Flobart mixer for another five minutes. The resulting paste was used for studying the characteristics of the binding skeleton in geopolymer foams.
  • the mixtures were poured into 50x50x50 mm cubic moulds, and sealed and cured at ambient temperature until the day of testing.
  • For testing the dry shrinkage of geopolymers specimens with dimensions of 40 c40 x160 mm were prepared according to the AS1012.13:2015 standard. After seven days, the specimens were submerged in lime-saturated water, and the samples were dried at 23.3 °CC in a chamber with 60% humidity. The shrinkage of the samples at 7, 14, 21 , 28 and 56 days was determined by measuring the change in length as a percentage of the initial length.
  • Fresh geopolymer pastes were also foamed with the mechanical foaming technique in order to study the performance of the porous samples in different densities.
  • Premade foam (with ⁇ 100 kg/m 3 density) was used to introduce voids in the binder pastes.
  • a commercial surfactant was diluted with water (1 :60 surfactant to water weight ratio) and used as a foaming agent. Foam was then made with the aid of compressed air in a Dema compressed air foam generator.
  • Pre-made foam was added to each group of geopolymers in order to make samples with target dry densities of 1200, 1000, 800 and 600 kg/m 3 .
  • the Instron 5569A instrument (with a displacement rate of 1 nmm per minute) was used for measuring the compressive strength of the foamed samples.
  • Figure 8 shows the drying shrinkage behaviour of the geopolymer pastes over time. It can be observed that the control group without aggregates has the highest degree of shrinkage, which is expected due to the high amount of gel formation per gram of this system. The aggregate portion of the system will not shrink, and therefore affect the final shrinkage percentage of the system. The sand group shows a considerably higher percentage of shrinkage than the glass group.
  • the glass group shows remarkably lower shrinkage at 7 days and 14 days, but the shrinkage suddenly quadruples in 21 days. This is because the glass fine is pozzolanic, and it will eventually take part in the geopolymerization reaction.
  • the amount of silica dissolution from waste glass at ambient temperature is known to be negligible.
  • the surface of the glass aggregates can react with alkaline solution over time and develop good binding with the geopolymer paste in bulk.
  • increasing the proportion of reactive silica to the mortar increases the ultimate shrinkage.
  • the reacted glass proportion changes its role from aggregate to paste, and it shows a considerably higher degree of shrinkage in the long term.
  • the ultimate shrinkage of the glass group is the lowest among the three systems.
  • control sample is the strongest sample at densities of 1200 and 1000 kg/m , but the
  • glass group is comparable to the control group at 800 and 600 kg/m densities but both become the weakest samples as the density drops further.
  • the strength of the glass group is very similar to the control group with no aggregates at 800 and 600 kg/m 3 densities while the strength of the sand group is noticeably lower at these densities.
  • the density of the non-porous samples it is evident that the sand group is about 100 kg/m 3 heavier than the control and glass groups. This difference in weight has a negative impact on the strength for lightweight samples with low densities (800 and 600 kg/m 3 ). Since the density of the samples is controlled by air bubbles such that it is similar in all three groups, more air bubbles are required to drop the density of the sand group to a similar range as that of the glass and control groups.
  • the pores in the sand and glass groups are not as circular as the pores in the control group.
  • interconnectivity makes the pores deeper, and the depth, which is not visible at the surface, appears black in the microscopic images.
  • the larger area covered by these black spots is an indication of a higher degree of interconnectivity between pores.
  • the control group has a relatively higher amount of interconnectivity to the internal pores compared to the glass group.
  • the sand group has a larger proportion of black area in the image, which reflects a higher degree of pore interconnectivity. Pore connectivity is also obvious on the surface pores in this sample.
  • the interconnectivity of pores has left large cavities in this system with a density of 600 kg/m 3 . These cavities are responsible for the difference between the strength of the sand group and the other two systems.
  • the thermal conductivity of the binding material and the thermal conductivity of the porous structure also depend on the amount of moisture retention in the pores, the size and shape of pores, the compactness of the binding matrix and the extent of air voids in the matrix.
  • a higher degree of geopolymer gel in the system means a higher extent of water retention in the pores, especially for higher densities where less interconnection between the pores is developed. Water plays a major role in the geopolymerization process . It initially works as a medium for dissolution and participates in hydration reactions. As the geopolymer gel forms and develops further in its structure, water is released back to the system.
  • the lower thermal conductivity in the sand group for 1200 and 1000 kg/m 3 densities is also related to the fact that less reacting gel exists in this sample compared to other systems.
  • the participation of glass in the reaction at later ages of the sample and the denser geopolymer matrix in the glass group, which gave it higher strength in 56 days, will make the glass binding matrix more conductive compared to the binding matrix of the sand group.
  • the remarkable drop of thermal conductivity in the sand group for similar densities is mainly attributed to the fact that the sand group was about 100 kg/m 3 heavier than the other two groups.
  • the sand group showed lower strength but better thermal insulation capacity.
  • the size and shape of the voids are also known to be critical in determining the insulation capacity in porous structures with smaller and more circular void being more desirable.
  • the large degree of interconnectivity of the voids and the irregularity of the pores deteriorates the insulation capacity in the sand group with lower densities, and the thermal performance of this system becomes more similar to the other two groups.
  • High circularity of pores in the glass group and the lower degree of pore connectivity are reasons for the desirable thermal performance of the glass group with a density of 600 kg/m 3 .
  • the lighter mass of geopolymer paste with glass aggregates and the pozzolanic behaviour of glass in the long-term provide glass with several advantages for geopolymer foam applications.
  • Glass can be ground easily to very fine particles that can replace fine sand in lightweight geopolymer foams. Over time, the surface of the glass particles reacts with the paste and forms stronger bonds at the interface with the geopolymer binder. These unique characteristics make glass fines a suitable alternative to fine sand in geopolymer foam applications.
  • the degree of shrinkage in the paste decreases by replacing sand with glass, and the strength of the porous matrix shows noticeable improvements at low densities.
  • the glass group becomes the most favourable insulating material at this density.
  • Example 4 Geopolymer Foam Concrete comprising thickener, surfactant mixture, ground glass aggregate and polymer fibre
  • Example 3 The process of Example 3 is repeated using the pre-made foam of about 100 Kg/m 3 in which the aqueous solution used in preparation of the pre-formed foam contained XG in an amount of 0.45%wt, a combination of SDS anionic surfactant and TRITON X-100 non-ionic octylphenolethoxylate having an HLB of 13.4 and about 9.5 moles EO. Equal molar amounts of the surfactants were used in the weight ratio of 1 :60 surfactant to aqueous solution.
  • the geopolymer paste is prepared as in Example 3.
  • the mortar is made by mixing 30% wt. of glass as aggregates with 70% wt. of geopolymer dry mix.
  • the mix design of the geopolymer binder consists of 60 % wt. FA, 40% wt. GBFS and 8.5% wt. sodium metasilicate in a dry mix as in Example 3 but with the addition of 5 wt% of silica fume based on these three dry mix components.
  • PVA fibre is also with added to the dry mix.
  • the loading of fibres is about 1 wt% of the dry mix.
  • the fibres are PVA RECS 100 (length about 13 mm) and are thoroughly mixed with the dry components of the geopolymer prior to activation.
  • Geopolymer dry ingredients are firstly mixed manually for two minutes, and water is gradually added and blended with the dry mix manually for one minute first and then mixed by a Hobart mixer for another five minutes.
  • the premade foam is added to the geopolymer to provide samples of dry density 1200, 1000, 800 and 600 Kg/m 3 and the foamed paste is cured at about 60°C to provide a foamed geopolymer concrete of good strength at 56 days.

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  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
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  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Environmental & Geological Engineering (AREA)
  • Civil Engineering (AREA)
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  • Chemical Kinetics & Catalysis (AREA)
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  • General Life Sciences & Earth Sciences (AREA)
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  • Curing Cements, Concrete, And Artificial Stone (AREA)

Abstract

La présente invention concerne un procédé de préparation d'un béton de mousse de géopolymères comprenant : la préparation d'une pâte de géopolymères comprenant des cendres volantes, du laitier de haut fourneau et un activateur alcalin ; la formation de mousse à partir d'une composition aqueuse comprenant un tensioactif et un agent épaississant à base de polysaccharides par entraînement d'air, éventuellement sous pression, dans la composition aqueuse pour obtenir une composition aqueuse moussée ; le mélange de la composition aqueuse moussée avec la pâte de géopolymères pour former une mousse de géopolymères ; et le durcissement de la mousse de géopolymères pour former un béton de mousse de géopolymères.
PCT/AU2018/050894 2018-08-22 2018-08-22 Procédé de préparation de compositions de mousses de géopolymères WO2020037349A1 (fr)

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CN113213833A (zh) * 2021-06-15 2021-08-06 深圳大学 一种粉煤灰基泡沫地聚合物及其制备方法和应用
CN113735504A (zh) * 2021-09-09 2021-12-03 广西北投交通养护科技集团有限公司 一种新型地聚物基泡沫轻质土的制备工艺
CN113773827A (zh) * 2021-08-31 2021-12-10 广汉市福客科技有限公司 一种自发泡延缓型固体泡沫排水剂及其制备方法
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CN114620969A (zh) * 2022-03-26 2022-06-14 中建西部建设北方有限公司 一种外加剂及其制备方法和混凝土
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CN115403298A (zh) * 2022-09-28 2022-11-29 北京工业大学 一种疏油基地聚物复合发泡剂及其制备方法
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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2022012928A1 (fr) * 2020-07-13 2022-01-20 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V. Matériaux minéraux poreux contenant du calcium pauvre en sulfate
CN116194421A (zh) * 2020-07-13 2023-05-30 弗劳恩霍夫应用研究促进协会 贫硫酸盐的含钙多孔矿物材料
CN112062515A (zh) * 2020-07-30 2020-12-11 浙江大学 一种利用碳化硅制备的高强地聚合物闭孔发泡材料及其制备方法
CN112062515B (zh) * 2020-07-30 2021-07-09 浙江大学 一种利用碳化硅制备的高强地聚合物闭孔发泡材料及其制备方法
CN113213833A (zh) * 2021-06-15 2021-08-06 深圳大学 一种粉煤灰基泡沫地聚合物及其制备方法和应用
CN113773827A (zh) * 2021-08-31 2021-12-10 广汉市福客科技有限公司 一种自发泡延缓型固体泡沫排水剂及其制备方法
CN113735504A (zh) * 2021-09-09 2021-12-03 广西北投交通养护科技集团有限公司 一种新型地聚物基泡沫轻质土的制备工艺
CN114835440A (zh) * 2022-03-17 2022-08-02 一天蓝(山东)新材料科技有限责任公司 固碳矿渣泡沫混凝土墙体材料及其制备方法
CN114620969A (zh) * 2022-03-26 2022-06-14 中建西部建设北方有限公司 一种外加剂及其制备方法和混凝土
WO2023219029A1 (fr) * 2022-05-13 2023-11-16 学校法人大阪産業大学 Composition géopolymère, corps de géopolymère durci et procédé de production de corps de géopolymère durci
CN115403298A (zh) * 2022-09-28 2022-11-29 北京工业大学 一种疏油基地聚物复合发泡剂及其制备方法
CN115572182A (zh) * 2022-10-14 2023-01-06 华新水泥股份有限公司 一种缓释发泡轻质地聚物材料及其制备方法

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