NO762530L - - Google Patents

Description

This invention relates to quick-setting siliceous

mixtures.

It is known to produce silicic acid products by reacting an aqueous solution of an alkali silicate and an organic isocyanate or isothiocyanate. These products are mainly rigid foams which may also contain preformed polymeric materials or inert powdery or fibrous materials.

The present invention provides products

which is obtained by mixing an aqueous solution of an alkali or ammonium silicate with at least one non-silicate compound of a polyvalent metal with a solubility in water at 20°C of at least 0.01 g/l, and/or a hydraulic cement , in an amount which at least corresponds to the amount required for reaction with all the silicate ions present, in the presence of (1) an organic polyisocyanate or (2) an organic polyisocyanate and a mono- and/

or a polyfunctional organic isocyanate-reactive compound, .

and let the mixture harden.

The alkali silicate used can be lithium silicate or potassium silicate, but is preferably sodium silicate, which is a cheap and easily available material, and which is conveniently obtained in the form of an aqueous solution known as "water glass", containing 40% or more of sodium silicate. The sodium silicate in water glass has a molar ratio Si02/Na20 of approx. 3.3:1.0, but any water-soluble sodium silicate with a SiO 2 /Na 2 O molar ratio between 1.65:1 to 3.86:1 can be used.

The said non-silicate of a polyvalent metal can

be any compound of a metal from groups IB

to VIII of the Periodic Table of the Elements (as indicated on the inside cover of the book "Advanced Inorganic Chemistry" by Cotton and Wilkinson, 2nd Edition, published 1966 by Interscience Publishers)

and which is capable of forming a substantially water-insoluble silicate, which compound itself has a solubility in water at 20°C of at least 0.01 g/l. Metal compounds which may be used include compounds of copper, magnesium, calcium, strontium, barium, zinc, cadmium, mercury, aluminium, titanium, tin, lead, chromium, manganese, iron, cobalt and nickel. Mixtures of compounds of polyvalent metals can be used.

Special examples of compounds of polyvalent metals that can be used are copper (II) chloride, copper (II) sulfate, copper (II) nitrate, copper (II) acetate, copper (II) carbonate, copper (II) hydroxide, magnesium sulfate , magnesium chloride, magnesium carbonate, magnesium hydroxide, calcium chloride, calcium sulfate (hydrated), calcium hydroxide, calcium carbonate, strontium chloride, barium chloride, barium hydroxide, zinc chloride, zinc sulfate, zinc chromate, zinc acetate, zinc carbonate, zinc oxide, zinc hydroxide, cadmium sulfate, mercury(II) chloride, aluminum sulfate, aluminum hydroxide, tin (II) chloride, lead (II) chloride, lead (II) nitrate, chromium (III) sulfate, manganese (II) chloride, iron (II) chloride, iron (II) sulfate, iron (III) chloride, iron (III) oxide, iron (III) hydroxide, cobalt (II) chloride, cobalt (II) sulfate, nickel (II) chloride, nickel (II) nitrate and nickel (II) sulfate.

For economic reasons, it is preferred to use such compounds of polyvalent metals which are easily available and cheap, e.g. calcium hydroxide, which has the additional advantage that its compounds with colorless anions are colorless or white.

The compound of polyvalent metal is preferably used in the form of an aqueous solution, or as an aqueous slurry or suspension when the solubility of the compound in water is too low for the desired amount to be obtained in aqueous solution.

It is essential that the polyvalent metal compound has sufficient solubility in water for it to react chemically with the alkali silicate solution. Compounds with very low solubility in water, e.g. barium sulphate and titanium dioxide cannot be used. When an aqueous slurry or suspension of the metal compound is used, the compound should be in very finely divided form, preferably with particle sizes of no more than 75 µm.

The hydraulic cement that can be used includes any one or any of the group or class of building materials that are used in a mixture with water and which then harden as a result of physical and/or chemical changes that consume at least part of the water . In addition to portland cement, for example, the following hydraulic cements can be used: 1. Fast-hardening cements, such as wood cements with a high content of aluminum oxide. 2. Low-heat cements characterized by a high percentage content of dicalcium silicate and tetracalcium aluminoferrite and a low percentage content of tricalcium silicate and tri-kå 1 siuma luminate. 3. Sulfate-resistant cements characterized by an unusually high percentage of tricalcium silicate and dicalcium silicate and an unusually low percentage of tricalcium aluminate and tetracalcium aluminoferrite. 4. Portland blast furnace cement, which characterizes the wood mixture of Portland cement clinker and granulated slag. 5. Cements normally used in masonry work, as characterized by mixtures of portland cement and one or more of the following materials: hydrated lime, powdered limestone, colloidal clay, diatomaceous earth or other forms of finely divided silicon dioxide. 6. Natural cements, characterized by wood material, taken from deposits in the Lehigh Valley, USA. 7. Lime cements, -as characterized by calcium oxide in pure or impure form with or without a content of clay material. 8. Selenite cement, characterized by lime with 5-10% burnt gypsum. 9. Puzzolan cement, which is characterized by the mixture of pozzolan, trass, diatomaceous earth, pumice, tuff, santorini soil or granulated slag and lime mortar. 10. Calcium sulfate cements, as characterized by cements that depend on the hydration of calcium sulfate and contain burnt gypsum, Keene's cement and Parian cement.

11. Waterproof cements, as characterized by wood mixtures

of portland cement and calcium stearate or paraffin.

The preferred hydraulic cement is portland cement, including white portland cement, which is a special quality with a low iron oxide content.

The non-silicate compound of a polyvalent metal can be used alone, as can the hydraulic cement, or they can be used in admixture in any desired ratio.

The organic polyisocyanate used can be

pure polyisocyanate or an isocyanate-terminated prepolymer is

held by reacting an excess of an organic polyisocyanate with a polymeric polyol.

Examples of suitable polyisocyanates include aliphatic diisocyanates, such as hexamethylene diisocyanate, tetramethylene diisocyanate, 2,2,4- and 2,4,4-trimethylhexamethylene diisocyanates, aromatic diisocyanates, such as tolylene-2 ,4-diisocyanates, tolylene-2,6-diisocyanate, diphenylmethane-4,4<1->diisocyanate, 3-methyldiphenylmethane-4,4<1->diisocyanate, m- and p-phenylene diisocyanate, chlorophenylene-2, 4-diisocyanate, xylylene diisocyanate, naphthalene-1,5-diisocyanate, diphenyl-4,4-diisocyanate, 4,4'-diisocyanato-3,3'-dimethyldiphenyl and diphenyl ether diisocyanate and cycloaliphatic di-. isocyanates, such as dicyclohexylmethane diisocyanates, methylcyclo-:...,... hexylene diisocyanates and 3-isocyanatomethyl-3,5,5-trimethyl-cyclohexyl isocyanate. Triisocyanates which may be used include aromatic triisocyanates such as 2,4,6-triisocyanatotoluene and triisocyanatodiphenyl ether. Examples of other suitable organic polyisocyanates include the reaction products of an excess of a diisocyanate and polyhydric alcohols, for example ethylene glycol, 1,4-, 1,3- and -2,3-butanediols, diethylene glycol, dipropylene glycol, pentamethylene glycol, hexamethylene glycol, neopentylene- glycol, propylene glycol, glycerol, hexanetriols, trimethylolpropane, pentaerythritol and low molecular weight reaction products of the above-mentioned polyols and ethylene oxide or propylene oxide.

It is also possible to use uretdione dimers and isocyanurate polymers of diisocyanates, e.g. tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate<p>g mixtures thereof, and the biuret-polyisocyanates obtained by reaction between polyisocyanates and water.

Mixtures of polyisocyanates can be used, including those obtained by phosgenisation of the mixed polyamides produced by reacting formaldehyde with aromatic amines, for example aniline and orthotoluidine under acidic conditions. An example of the latter polyisocyanate mixture is a mixture

with the designation raw MDI, which is produced by reacting formaldehyde with aniline in the presence of hydrochloric acid, and which consists of diphenyl-

methane-4,4<1->diisocyanate in mixture with isomers thereof and with methylene-linked polyphenylpolyisocyanates containing more than two isocyanate groups.

A further polyisocyanate-containing material which can be used is the distillation residue which is obtained by distilling off essentially all volatile diisocyanate from the crude tolylene diisocyanate which is produced by phosgenisation of a tolylene diamine.

Isocyanate-terminated prepolymers which can be used in the preparation of the mixture according to the present invention, are obtained by reaction between an excess of any of

the organic polyisocyanates defined above and a polymer polyol, for example a hydroxyl-terminated polyester, a polyester amide>

a polyether, a polyetherthioether, a polyacetal or polyolefin.

Examples of hydroxyl-terminated polyesters and polyester amides which are suitable for use in the production of prepolymers are those which are obtained in a known manner from carboxylic acids, glycols and, if necessary, smaller amounts of diamines or amino alcohols. Suitable dicarboxylic acids include succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic and terephthalic acid and mixtures thereof. Examples of dihydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, diethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol and 2,2-dimethyltrimethylene glycol. Suitable diamines or amino alcohols include hexamethylenediamine, ethylenediamine, monoethanolamine and phenylenediamines. Mixtures of polyesters and polyester amines can be used if desired. Small amounts of multi-

valuable alcohols, such as glycerol or trimethylolpropane, can also be used, in which case branched polyesters and polyester amides are obtained.

As examples of hydroxyl-terminated polyethers such as

can be reacted with an excess of an organic polyisocyanate as defined above to form a prepolymer, mention may be made of polymers and copolymers of cyclic oxides, e.g. 1,2-alkylene oxides, such as ethylene oxide, epichlorohydrin, 1,2-propylene oxide and 1,2-butylene oxide, 2,3-butylene oxide, oxycyclobutane and substituted oxycyclobutanes and tetrahydrofuran. Mention may also be made of polyethers produced by polymerization of an alkylene oxide in close

be of a basic catalyst and water, glycol or a primary

monoamine. Mixtures of such polyethers can be used.

As examples of polyetherthioethers which are suitable for use in the production of prepolymers, mention can be made of the products of the self-condensation of thioglycols, for example thiodiglycol,

or the condensation of thioglycols with glycols.

Examples of polyacetals that can be used in the production of prepolymers include the reaction products of aldehydes, e.g. formaldehyde, acetaldehyde and butyraldehyde, with dihydric alcohols, e.g. propylene glycol, butylene glycols and diethylene glycol.

As examples of hydroxyl-terminated polyolefins such as

are suitable for use in the production of prepolymers, mention may be made of the products obtained by oxidative breakdown of polyolefins with a higher molecular weight. Typically, polymers of butadiene or copolymers thereof with other monomers, such as styrene or acrylonitrile, can thus be oxidized to form a product with a lower molecular weight and with isocyanate-reactive end groups. Remaining ethylene bonds can be eliminated by hydrogenation. Alternatively, the olefin monomer can be polymerized or copolymerized by (i) a free-radical reaction or by (ii) an anion reaction. Typically, in case (i) above, the olefin polymer is polymerized

in the presence of initiators and optionally chain transfer agents which

both have two isocyanate-reactive groups or groups that are easily converted to isocyanate-reactive groups. In case (ii) above-

for, the monomer is typically polymerized using as initiator a compound which gives a bifunctional polymer whose functional end groups are easily converted into isocyanate-reactive groups in a manner known per se.

Other prepolymers that can be used in the process

according to the invention, those obtained by reacting coal tar pitch containing isocyanate-reactive groups, with an excess of an organic polyisocyanate, e.g. one or more of the organic polyisocyanates defined above, optionally together with an organic compound containing isocyanate-react

tive groups, for example the polyesters defined above, polyester amides, polyethers and other hydroxyl-terminated polymers. Coal tar pitch-based prepolymers of this kind are described in the applicant's British patent no. 1,093,375.

The organic polyisocyanates and isocyanate-terminated polyurethane prepolymers prepared as described above are generally stable at normal temperatures in the absence of moisture. When the free isocyanate groups are present as part of a mixture as defined above, and which also contains an aqueous solution of an alkali metal silicate and a compound of a polyvalent metal, the isocyanate groups will react with the water and form a polymer that acts as a binder.

In the preparation of mixtures according to the invention

the organic polyisocyanate can be used together with a mono- and/or a polyfunctional organic isocyanate-reactive compound.

The monofunctional organic isocyanate-reactive compounds that can be used are preferably monohydric alcohols, but can also be monocarboxylic acids and - less advantageously - monoamines. Examples of monohydric alcohols are methanol, ethanol, n-propanol, isopropanol, the isomeric butanols, hexanol, isooctanol, nonanol, decanol, dodecanol, cetanol, unsaturated alcohols such as

■allyl, oleyl and propargyl alcohols and the polyether alcohols obtained by reaction between alkylene oxides, e.g. ethylene oxide and/or propylene oxide, with monohydric alcohols. You can also use the monovalent diepoxy alcohol with the formula:

Examples of suitable monocarboxylic acids are saturated monocarboxylic acids of the fatty acid series with normal chains containing 2-18 carbon atoms, including the mixed fatty acids obtained by saponification of natural glycerides, and unsaturated fatty acids, e.g. elaeostearic acid, linolenic acid, linoleic acid and oleic acid. The polyfunctional organic isocyanate-reactive compound may be any of the hydroxyl-terminated polymers already indicated above as suitable for the preparation of isocyanate-terminated prepolymers. Other polyfunctional isocyanate-reactive organic compounds that can be used include the simple polyhydric alcohols containing 2-6 carbon atoms and

2-4 hydroxyl groups, and the low molecular weight reaction products there-

off with ethylene oxide or propylene oxide; also amino alcohols, e.g. monoethanolamine, polyamides, e.g. ethylenediamine, hexamethylenediamine, m- and p-phenylenediamines and 2,4- and 2,6-diaminotoluenes, epoxy resins which also contain isocyanate-reactive groups, e.g. the hydroxyl group-containing products obtained by reaction of diphenylolpropane and epichlorohydrin, alkyd resins modified with drying oil or non-drying oil, castor oil, hydrogenated castor oil, urethane oils, which are the reaction products of diisocyanate and alcoholysis products of a drying oil, e.g. mono- or di-glycerides from linseed oil, and urethane alkyds, which are alkyd resins in the production of which part of the phthalic anhydride

is replaced with a diisocyanate. A further and particularly suitable material that can be used as the isocyanate-reactive organic compound is that obtained by high-temperature reaction between castor oil and a complex resin produced by reacting a natural rosin resin, glycerol and a resol resin by high temperature. The castor oil and the complex har-

piks can be converted in ratios from 95:5 to 20:80 on a weight basis with wood

a temperature of 230-250°C for 0.5-2 hours. Castor oil and the complex resin in a ratio of 4:1 by weight are usually heated at a temperature of approx. 240°C for approx. 45 minutes. The complex resin, natural rosin, glycerol and the resole resin (pro-

produced by condensation of 1 mol of diphenylolpropane with approx. 4 mol formaldehyde in an aqueous alkaline environment at moderate temperatures) in a weight ratio of approx. 8.2:1.1:1.0 is heated at a temperature up to 275°C in an inert atmosphere until the acid number is less than 20 mg KOH/g.

Mixtures of various monofunctional and polyfunctional organic isocyanate-reactive compounds, and of monofunctional with polyfunctional compounds, can be used.

Strong aqueous solutions of alkali silicates act as excellent emulsifiers for the organic polyisocyanate and the organic isocyanate-reactive compound if this is used.

Consequently, it is usually only necessary to stir these organic constituents into the alkali silicate solution to ensure satisfactory dispersion.

When preparing the mixtures according to the invention, the organic components are preferably mixed with the binder of multivalent metal and/or the hydraulic cement before adding the aqueous silicate solution. Satisfactory results cannot be obtained if the aqueous silicate solution is mixed with the compound of the multivalent metal and/or the hydraulic cement before the organic constituents are added. Provided that work is done quickly, it may be possible to add the compound of the multivalent metal and/or the hydraulic cement to a mixture of the organic components and the alkali silicate solution^

The reaction between the silicate and the compound of the polyvalent metal and/or the hydraulic cement is usually so

quickly so that the organic components cannot be mixed afterwards. It is therefore important that the silicate solution and the compound of the multivalent metal and/or the hydraulic cement are mixed in the presence of the organic polyisocyanate and the organic isocyanate-reactive compound."

The relative amounts of the various components in the mixture according to the invention can be varied within wide limits. The maximum amount of non-silicate compound of polyvalent metal - when used in the absence of hydraulic cement - in relation to alkali silicate can be up to 100 times the amount theoretically required for complete reaction with the alkali metal or ammonium silicate to form the corresponding silicate of polyvalent metal. The minimum amount of polyvalent metal compound is that theoretically required for complete reaction with the alkali metal silicate.

Preferred amounts of compound of polyvalent metal when this is used alone, i.e. in the absence of hydraulic cement, are from 100 to 8000% of the amount required for reaction with all silicate ions present.

Portland cement and other hydraulic cements as defined above also undergo chemical reaction with ammonium and alkali metal silicate in solution, which leads to rapid hardening of the mixtures. The reactions, especially with portland cement and other cements containing portland cement, are not fully understood, so that it is not generally possible to specify the quantity of such hydraulic cement that can be used, by theoretical expressions for the reaction quantities. The amount of hydraulic cement, however, when used in the absence of a non-silicate compound of polyvalent metal as indicated above, must be at least sufficient to react with the entire amount of ammonium or alkali metal silicate present. An excess of hydraulic cement beyond this minimum can be used and is preferred.

When either a polyvalent metal non-silicate compound and a hydraulic cement are used together or a hydraulic cement is used alone, it is a simple matter for the person skilled in the art to select relative amounts of these two components so that the requirement for complete reaction with the ammonium or alkali silicate are met, and that the mixture obtains the desired curing properties.

The amount of water in the mixture, including the water present in the alkali silicate solution, must be sufficient to ensure that the mixture does not harden so quickly that this causes difficulties in use. It will be understood that this amount will vary considerably in accordance with the relative amounts of alkali silicate, compound of multivalent metal and/or hydraulic cement and organic constituents used, and will also depend on the nature of the latter two constituents. In general, however, the amount of water can be from 5 to 200% of the total weight of alkali silicate, compound of multivalent metal and/or hydraulic cement and resin binder, i.e. all the other ingredients together.

The organic polyisocyanate and the organic isocyanate-reactive compound, if this is used, must be present in the mixture in an amount that ensures - that the mixture remains coherent or cohesive after curing and can withstand mechanical shock to a certain extent, i.e. is not too brittle or crumbles. The required amount will obviously depend to some extent on the nature of the organic constituents, but amounts within the range of 10-400% of the combined weight of alkali silicate and compound of multivalent metal and/or hydraulic cement are usually satisfactory.

In addition to the essential ingredients alkali silicate, compound of multivalent metal and/or hydraulic cement, organic components and water, the mixtures can also contain inert fillers, e.g. sand, fly ash, expanded clay, foam slag, mica, talc, clay materials (eg kaolin), asbestos, barytes, silicic acid, powdered shale and vermiculite. These fillers can be used in amounts from a minimum of 1% of the total weight of the essential dry ingredients. Fibrous fillers, for example rock wool, glass fiber and asbestos can also be used as reinforcement materials.

Inert plasticizers, e.g. butyl benzyl phthalate, dioctyl phthalate or dinonyl phthalate can be added to the mixtures if one wishes to modify their rheological properties before curing.

Inert solvents, e.g. esters, ketones, hydrocarbons and halogenated hydrocarbons can also be used to help with the incorporation of very viscous or other materials that are difficult to incorporate into the mixture, but the use of volatile or easily flammable solvents should preferably be avoided due to the risk they entail for the environment.

Dyes and pigments can also be added if the mixtures are to be used for decorative purposes, or where a decorative effect is desired.

The mixtures produced according to the invention can be spread over surfaces before hardening, e.g. floors, ceilings, walls and sloping or rounded surfaces by troweling, applying, spraying or by troweling, and can be cast, formed or extruded into any desired shape, e.g. discs, blocks or open half-cylinders of the kind that find extensive use for pipe insulation.

The mixtures produced using a hydraulic cement are particularly well suited for use in the building industry. The

shows advantages over similar mixtures in which the silicate is looped, as shrinkage is reduced.

When the mixtures are to be used for insulation purposes, should

the organic components used are selected taking into account the highest temperature to which the polymer formed by their reaction is to be subjected. The resulting polymer should thus

have a softening point well above the aforementioned highest temperature.

Because of. the high content of inorganic materials in such mixtures, they are very resistant to combustion, and the fire risk is minimal. ,

The mixtures can also be obtained in foamed form by using an effervescent agent of the type known to be suitable in the production

ling of polyurethane foam, is introduced into the mixture. Foam stabilizers can also be used if necessary.

The following examples, where all parts and percentages are on a weight basis, will further illustrate the invention.

EXAMPLE 1

60 parts white cement, 90 parts approx. 3 mm crushed granite

and 60 parts sand. ("Garside 21") is mixed with 50 parts of a urethane prepolymer (made from TDI and polypropylene glycol with molecular

weight corresponding to a theoretical isocyanate content of 13.6%). 40 parts of a 40% aqueous solution of sodium silicate are added to the mixture while stirring, and the stirring is continued until a homogeneous mixture is obtained. The resulting paste is poured into a mold, where it hardens within 1 hour. After curing for 24

hours at room temperature, the mixture is hard with little or negligible elasticity.

EXAMPLE 2

50 parts castor oil, 80 parts water, 240 parts synthetic

tic anhydrite (anhydrous calcium sulphate) and 30 parts vermiculite are mixed. 50 parts of technical diphenylmethane diisocyanate (raw MDI) are then mixed followed by 30 parts of 40% aqueous sodium silicate solution. A stiff, paste-like material is obtained, which can be applied to walls with the help of a trowel or the like or, alternatively, cast into sheet material in molds. The sheet material is suitable for use as insulation material.

EXAMPLE 3

10 parts of calcium hydroxide and 10 parts of water are mixed, after which 10 parts of raw MDI are mixed in. When these ingredients

ense is evenly or uniformly dispersed, add 30. parts of

a 40% aqueous solution of sodium silicate with continued stirring

Eng. The stiff paste thus obtained can be used as a filling material and hardens within a few hours, preferably overnight.

EXAMPLE 4

The procedure according to example 3 is repeated with the exception that the 10 parts of raw MDI are replaced by 20 parts of a 75%. solution in ethyl acetate of the adduct of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate. A product with similar properties is obtained.

EXAMPLE 5

The procedure according to example 3 is repeated with the exception that the 10 parts of calcium hydroxide are replaced with 15 parts of portland cement, and the 10 parts of raw MDI are replaced with 20 parts of a 75% solution in ethyl acetate of the adduct of 1 mol of trimethylolpropane and 3 -mol tolylene diisocyanate. A product with similar properties is obtained.

EXAMPLE 6

24 parts calcium hydroxide and 18 parts water are mixed, and after these ingredients are uniformly dispersed, 10 parts raw MDI is mixed in; 4 parts of white cement are added and stirred in, followed by 30 parts of a 4% aqueous solution of sodium silicate.

The stiff paste obtained can be used as a filling material and hardens within a few hours.

Claims (10)

1. Mixture prepared from an aqueous solution of an alkali or ammonium silicate and (1) an organic polyisocyanate or (2) an organic polyisocyanate and a mono- and/or polyfunctional organic isocyanate-reactive compound, characterized in that the alkali or ammonium silicate is present mixed with (a) at least one non-silicate compound of a polyvalent metal with a solubility in water at 20°C of at least 0.01 g/l and/or (b) a hydraulic cement, in an amount at least equivalent to that of is required for reaction with all the silicate ions present, in the presence of (1) or (2) . 2. Mixture according to claim 1, characterized in that the compound of multivalent metal is used in the form of an aqueous solution or an aqueous slurry or suspension. 3. Mixture according to claim 2, characterized in that when an aqueous suspension or slurry is used, the compound of multivalent metal has a particle size of at most 75^ um. 4. Mixture according to any one of the preceding claims, characterized in that the amount of compound thereof multivalent metal used in the absence of hydraulic cement, is from 100 to 8,000% of the amount required for reaction with all silicate ions present. 5. Mixing according to any of the. preceding claim, characterized in that the amount of water used is from 5 to 200% of the total weight of all the other ingredients. 6. Mixture according to any of the preceding claims, characterized in that. the total amount of organic polyisocyanate and the organic isocyanate-reactive compound, if such is used, is within the range 10-400% of the weight of the alkali or ammonium silicate and compound of multivalent metal and/or hydraulic cement together. 7. Mixture according to any of the preceding claims, •,. characterized in that an inert filler material is used in an amount from a minimum of 1% of the total weight of dry ingredients. 8. Mixture according to any of the preceding claims, characterized in that an inert plasticizing agent is added to the mixture to modify the rheological properties of the mixture before hardening. 9. Mixture according to any of the preceding claims, characterized in that an inert solvent is used to aid in the incorporation of very viscous or other materials which are difficult to incorporate into the mixture of ingredients. 10. Mixture according to any of the preceding claims, characterized in that the mixture is obtained in foamed form by incorporating a foaming agent into the mixture of ingredients.