WO2012056125A1

WO2012056125A1 - Geopolymer cement of the calcium ferro-aluminosilicate polymer type and production process

Info

Publication number: WO2012056125A1
Application number: PCT/FR2011/000576
Authority: WO
Inventors: Joseph Davidovits; Marc Davidovits; Frédéric DAVIDOVITS; Ralph Davidovits
Original assignee: Joseph Davidovits; Marc Davidovits; Davidovits Frederic; Ralph Davidovits
Priority date: 2010-10-29
Filing date: 2011-10-26
Publication date: 2012-05-03
Also published as: AU2011322378A1; FR2966823A1; FR2966823B1; MX2013004835A; BR112013010390A2; CN103282325A; EP2632870A1; AP2013006884A0; RU2013124516A

Abstract

The invention relates to a geopolymer binder or cement of ferro-aluminosilicate [-Fe-O-Si-O-Al-O-] polymer type which, after curing, consists of a geopolymer compound in which some of the Al atoms are substituted with Fe atoms, the whole satisfying the following raw formula: (Ca,Na,K)⋅(FeO)_x⋅(SiOAlO)_1-x⋅(SiO)_y in which "x" is less than or equal to 0.5 and "y" is between 0 and 25. This geopolymer binder or cement is the result of the geopolymerization of calcium geopolymer type with geological elements rich in iron oxides and in ferro-kaolinite, coming from the weathering of acid rocks such as granite and gneiss, or of basic (mafic) rocks such as basalt and gabbro. The process for manufacturing this geopolymer binder or cement consists in treating said geological elements at a temperature of 600 to 850°C. During this heat treatment, all the iron oxides [goethite FeO(OH) + magnetite Fe₃O₄] are transformed to hematite Fe₂O₃ and the ferro-kaolinite becomes ferro-metakaolin of Fe-MK-750 type and then these are made to react with a reaction mixture of calcium geopolymer type.

Description

Geopolymer cement of the Ca-poly (ferro-sialate) type and method of obtaining

Description

The present invention relates to a new type of geopolymer cement for construction. This cement is called geopolymer cement because it consists of alkaline aluminosilicates, better known as poly (sialate), poly (sialate-siloxo) and / or poly (sialate-disiloxo). In the case of the present invention, the geopolymer cement is based on Ca-poly (ferro-sialate), Ca-poly (ferro-sialate-siloxo) and / or Ca-poly (ferro-sialate-disiloxo).

Prior art.

There are two types of cement: hydraulic cements and geopolymer cements. Geopolymeric or geopolymeric cements result from an alkaline activation mineral polycondensation reaction, called geosynthesis, as opposed to traditional hydraulic binders in which curing is the result of hydration of calcium aluminates and calcium silicates.

Poly (sialate) has been adopted to refer to aluminosilicate geopolymers. The empirical formula of Polysialates is:

M _n {- (SiO 2) z-AlO ₂ } n, wH ₂ O

with M representing the cation K, Na or Ca and "n" the degree of polymerization; "Z" is equal to 1, 2, 3 or more, up to 32. The silico-aluminate geopolymers are of type:

Poly (sialate) M _n - (- Si-O-AI-O-) _n M-PS Si: Al = 1: 1

Poly (sialate-siloxo) M _n - (Si-O-Al-O-Si-O-) _n M-PSS Si: Al = 2: 1

Poly (sialate-disiloxo) M _n - (Si-O-Al-O-Si-O-Si-O-) _n M-PSDS Si: Al = 3: 1

Binders or geopolymeric cements of poly (sialate), poly (sialate-siloxo) and / or poly (sialate-disiloxo) type, have been the subject of several patents highlighting their particular properties. For example, French patents can be mentioned: FR 2 489.290, 2.489.291, 2.528.818, 2.621.260, 2.659.319, 2.669.918, 2.758.323.

The geopolymeric cements of the prior art (WO 92/04298, WO 92/04299, WO 95/13995, WO 98/31644) are the result of a polycondensation between three distinct mineral reagents, that is to say: a) aluminosilicate oxide (Si205, Al2C) 2)

(b) sodium or potassium disilicate (Na 2 O 3 H 2 SiO 2).

c) Calcium disilicate Ca 2 SiO 2

Ingredients a) and b) are industrial reactive products added to the reaction medium. In contrast, ingredient c), calcium disilicate, occurs in the nascent state, in situ, in the strongly alkaline medium. It is usually the result of the chemical reaction between a calcium silicate such as calcium mellitite present in the blast furnace slag.

In the reference Geopolymer Chemistry & Applications, J. Davidovits, Geopolymer Institute, 2008, these types of geopolymer are described in Chapters 9 and 10 and belong to the category Ca-based Geopolymer, geopolymer obtained by calcium geopolymerization. In accordance with this definition, we describe the geopolymeric binder or cement according to the present invention as being the result of Ca-geopolymeric geopolymerization.

One of the interesting properties of geopolymer cements is that during their production they emit only a small amount of greenhouse gases, carbon dioxide CO ₂ . In contrast, cements based on Portland clinker, emit a lot of carbon dioxide. As can be read in the publication Global Warming Impact on the Cernent and Aggregates Industries, published in World Resource Review, Vol.6, Nr 2, pp 263-278, 1994, one tonne of Portland cement releases 1 tonne of CO ₂ , while a geopolymeric cement releases 5 to 10 times less. In other words, in the context of international laws restricting in the future the release of CO ₂ , a cement factory initially manufacturing Portland cement can produce 5 to 10 times more geopolymer cement, while emitting the same amount of CO ₂ gas . The interest in geopolymer cements is very obvious for the economies of developing countries.

The international publication WO 2003 FR01545 describes a geopolymeric cement based on poly (sialate-disiloxo) resulting from the geopolymerization of a reaction mixture containing

a) a severely weathered granite-type residual rock in which kaolinization is very advanced;

b) a glass of calcium mellilite in which the glass portion is greater than 70% by weight; c) a soluble alkali silicate in which the molar ratio (Na, K) 20: SiO ₂ is between 0.5 and 0.8;

The residual altered granite rock consists of 20 to 80 percent by weight of kaolinite and 80 to 20 percent by weight of residual feldspar and quartz arena. The residual rock is calcined at a temperature between 650 ° C and 950 ° C. Geopolymerization is also of the Ca-geopolymeric type.

The common feature of geopolymer cements of the prior art is that they contain relatively few iron oxides. This stems from the fact that those skilled in the art are wary of the harmful action of certain ferrous Fe ⁺⁺ compounds which block the development of the geopolymeric reaction. On the other hand, the role of goethite iron oxide, FeO (OH), also seems uncertain. The Fe ₂ O ₃ or Fe ₃ O ₄ type of hematite oxides would appear to be more favorable.

However, for geopolymer cements made with fly ash from coal-fired power plants, experts do not recommend the use of fly ash rich in Fe ₂ O 3. Magnetite Fe3O would even be harmful. For example, in the reference book Geopolymer Chemistry & Applications, J. Davidovits, Geopolymer Institute, 2008, Chapter 12 (Fly ash-based geopolymer), Section 2.5.2, we read on page 296 that the quantity in Fe ₂ O ₃ should be less than 10% by weight; similarly, on page 300, it is found that high amounts of Fe ₂ O ₃ hematite and magnetite Fe ₃ O ₄ are unfavorable because they greatly reduce the compressive strength of the geopolymer cement. To his great surprise, the Applicant discovered that, even with 40% by weight Fe ₂ O ₃ hematite amounts in the Ca-poly (ferrosialate) type geopolymer binder or cement, according to the present invention, compression remained high, of the order of 60 to 90 MPa, at 28 days, at the ambient temperature of 20 ° C.

This mistrust of those skilled in the art with regard to the high levels of iron oxides is further increased when it is found that the presence of too many iron atoms prevents the use of certain techniques. analysis, which are essential for understanding the molecular structures of geopolymeric compounds. Thus, the use of Nuclear Magnetic Resonance Spectroscopy NMR is impossible.

However, the mass production of geopolymer cements in the world can not be limited to only geological materials from kaolinitic clays, or residual rocks of weathered granite, low in iron, as described in the prior art. The use of the enormous geological deposits of ferralitic or lateritic rocks and soils is a necessity. This is what are working to solve the geopolymer cements of Ca-poly (ferro-sialate) type according to the present invention.

When studying the prior art, patents and scientific literature, there are tests for the use of lateritic soils for the manufacture of bricks. This technique is known to those skilled in the art under the acronym LTGS, an acronym for Low Temperature Geopolymeric Setting. This low temperature brick making technique is described in Geopolymer Chemistry & Applications, J. Davidovits, Geopolymer Institute, 2008, in Chapter 23, Section 23.1. It implements lateritic soils, which by definition are very rich in iron oxide, to which 1% to 5% by weight of alkaline hydroxides (NaOH and / or KOH) are added and a sufficient quantity of water to be able to make a brick by pressing. This technique was described for the first time in the French patent FR 2,490,626 filed by the Applicant in 1980 and entitled "Method of manufacturing objects for building, using ferruginous, lateritic, ferralitic and object soil thus obtained ". It makes it possible to manufacture bricks. It does not make it possible to manufacture a binder or geopolymer cement which would later be used for making geopolymer concrete. The binders or cements according to the present invention are liquid and make it possible to coat the usual aggregates used in concretes. Their procedure is a geopolymerization of the Ca-geopolymeric type and they cure at room temperature of 20 ° C.

In order to produce the binders and geopolymer cements according to the present invention, the geological elements must undergo a heat treatment between 600 ° C. and 850 ° C., which is not the case with the LTGS process of the prior art.

There are very few scientific studies published in the prior art dealing with the geopolymerization of rocks or soils very rich in iron oxides. One recent study published by CK Gomes et al .: "Iron distribution in geopolymer with ferromagnetic rich precursor", Materials Science Forum Vol. 643 (2010) pp 131-138. It deals with the Mössbauer spectroscopy analysis of the geopolymerization of a lateritic sol containing about 60% of iron oxide expressed in Fe ₂ O ₃ and only 6% of AfeOa. Assuming that all the amount of A ^ Os relates only to the mineral kaolinite generally present in this type of soil, we are with a soil containing less than 15% by weight of kaolinite. This is usually this type of soil that is used to manufacture the LTGS bricks described above. On the contrary, in the context of the invention, the geological elements contain between 5% and 40% by weight of iron oxide Fe ₂ O 3 hematite and 15% to 60% by weight of kaolinite. When the amount of iron oxide Fe ₂ O 3 hematite is greater than 40% by weight of the rock, it acts as an inert filler and prevents the use of geopolymerization for the manufacture of a binder or cement . By cons, this material is ideal for the manufacture of brick type LTGS of the prior art.

The scientific article of CK Gomes & al. cited above also describes the transformation of the geological raw material (called SL1) by a heat treatment at 700 ° C (product referred to as SL2). It confirms that the heat treatment transforms iron oxide goethite FeO (OH) into hematite Fe ₂ O ₃ and we know, according to the prior art, that iron oxide magnetite Fe30 ₄ is also converted into hematite. The Môssbauer spectrum indicates that in the geopolymer from SL1 (without calcination) some Fe ³⁺ iron atoms would be associated with the molecular structure, with a replacement of the Al atom by Fe, in the octahedral position Fe [VI]. On the other hand, after calcination at 700 ° C (SL2), the geopolymer would contain no Fe atom in the molecular structure. Iron is found only in iron oxide Fe ₂ 0 ₃ hematite. Unlike this prior art, in the binder or geopolymer cement of the present invention, part of the Fe atoms is in the tetrahedral structural position Fe [IV] in the geopolymeric bond Fer- sialialate [-Fe-O-Si -O-AI-O-], said Fe atom representing a quantity of between 5% and 50% of the total amount of Fe ₂ O 3 contained in said binder or geopolymer cement, the remainder being between 50% and 95%; %, being combined in crystallized iron oxide Fe ₂ O ₃ Hematite.

Presentation of the invention

The main object of the invention is the description of a binder or geopolymer cement of Ca-poly type (ferro-silico-aluminate) or to simplify Ca-poly (ferro-sialate). It is the result of geopolymerization of Ca-geopolymeric type with geological elements rich in iron oxides and ferro-kaolinite, resulting from the alteration of acidic rocks such as granite or gneiss, or basic (mafic) rocks. like basalt and gabbro. The second subject of the invention is the description of the process for obtaining this binder or geopolymer cement of Ca-poly (ferro-sialate) type.

After curing at room temperature of 20 ° C, or if necessary after heat treatment at a temperature below 85 ° C, the binder or geopolymer cement consists of a geopolymeric compound belonging to the family of geopolymers based on poly (sialate) and / or Ca-poly (sialate-siloxo) and / or Ca-poly (sialate-disiloxo), but unlike the prior art, in said geopolymeric compound a part of the Al atoms is substituted by Fe atoms, all of which corresponds to the following formula

[Ca, Na, K]. [- Fe-O-] x - [- Si-O- (Al-O-) _(1-x) ]. [- Si-O-] _y in which "x" is a value less than or equal to 0.5, "y" is a value between 0 and 25.

To obtain this new binder or geopolymer cement is chosen in the geological elements resulting from the alteration of the rocks, those which have a quantity of iron oxides, [goethite FeO (OH) + hematite Fe ₂ O ₃ + magnetite Fe ₃ O ₄ ], comprised between 5% and 40% by weight of the rock.

The alteration of acidic rocks such as granite or gneiss, or of basic (mafic) rocks such as basalt and gabbro, is accompanied by the formation of kaolinite. However, in the context of the invention, because of the large amount of iron oxides, a certain amount of kaolinite contains Fe atoms which replace those of AI. This substitution can go up to 25% of the AI atoms. It is however impossible to separate the substituted kaolinite from the unsubstituted kaolinite. Therefore, in the context of the invention, we denote by the term "ferro-kaolinite" the substituted kaolinite + unsubstituted kaolinite mixture. In the geological raw materials according to the invention, the amount of ferro-kaolinite is between 15% and 60% by weight.

The alteration of the basic rocks is accompanied by the formation of hydrates of alumina whose quantity may be greater than 50% by weight, as in bauxites. After heat treatment at 600-850 ° C., these alumina hydrates become very reactive with respect to the Ca-geopolymeric reaction medium. In geopolymerization, each AI atom must be equilibrated by an alkaline cation Na ⁺ , K ⁺ or a Ca ⁺⁺ half cation. When the amount of alumina hydrate is very important, it causes very high amounts of alkaline reagents and this can play a detrimental role in the economic balance of such a process. It is therefore better to choose a geological layer in which the alumina hydrates are less concentrated. In the context of the present invention, this quantity of alumina hydrates [gibbsite AI (OH) ₃ + boehmite AlO (OH)] is between 0% and 20% by weight.

Referring to the prior art of the patent Davidovits FR 2 490 626, the presence of these hydrates of alumina corresponds to a raw material which has a molar ratio S102 / Al2O3 less than 2. We learn on page 4 , lines 22-43, that it is then necessary to add a certain amount of reactive silica from either hydrated silica or free silica-releasing materials, or aluminosilicates whose molar ratio S102 / Al2O3 is greater than 2 Various smectite-like clay minerals, such as montmorillonite and / or vermiculite, are cited which give rise to the formation of soluble alkali silicate. However, in certain geological layers called saprolite, the alteration produces an advantageous combination favorable to the preparation of binders or cements according to the present invention. Indeed, although the amount of hydrates of alumina [gibbsite AI (OH) 3 + boehmite AIO (OH)] is relatively high since it may be between 5% and 20% by weight, the addition of geopolymeric reagent Soluble silicate type is reduced by the presence of smectite clay mineral, such as montmorillonite and / or vermiculite. It is therefore not necessary to add them since they are already naturally found in the geological raw material. In this type of saprolite resulting from the alteration of the basalt, the amount of ferro-kaolinite is replaced by 2% to 20% by weight of smectite.

The alteration, in some geological layers, also leads to the formation of another variety of kaolinite, namely halloysite. In this case, the ferro-kaolinite can be replaced by 0% to 20% by weight of halloysite mineral.

As noted above, the high concentration of Fe atoms precludes the use of NMR Nuclear Magnetic Resonance Spectroscopy (NMR) structural analysis. The methods used in the analysis of the geopolymer binder of the present invention are Mossbauer spectroscopy and X-ray diffraction.

X-ray analysis shows us that, after curing, the binder or geopolymer cement consists of an amorphous matrix containing crystallized particles of iron oxide Fe2O3 hematite. The other iron oxides (goethite and magnetite) have disappeared. This X-ray spectrum also contains other Crystalline minerals referred to as inert fillers, naturally occurring in such geologic features as quartz, rutile, anatase, pyroxene, olivine, feldspars, muscovite, biotite, to name but the most common. When the X-ray spectra of the starting geological raw materials are compared with those of the cements obtained, it is found that these crystalline minerals do not seem to have reacted with the Ca-geopolymeric reaction medium. In contrast, the aluminosilicate minerals (kaolinite, ferro-kaolinite, halloysite, montmorillonite, vermiculite) present in the x-ray spectrum of the raw materials are absent from the x-ray spectrum of cement cured. The amorphous halo of the matrix is 27-29 ° 2Θ for the Cu (K) radiation. It is similar and consistent with that of other geopolymer cements of the prior art.

Mossbauer spectroscopy Fe ⁵⁷ allows to differentiate between carbon oxides combined with only Fe [goethite FeO (OH) + hematite + magnetite Fe2O3 Fe3Û _4], from those forming part of the molecular structure of the aluminosilicates or geopolymers, when there is substitution of AI by Fe. In the prior art, there are several scientific studies carried out on the substitution of the IA atom by Fe in kaolin or kaolinitic clays containing iron oxides. . The latter was demonstrated by PJ Malden and RE Meads in the article "Subsition by iron in kaolinite" Nature 215 (1967) 844-846. This substitution occurs only when the Fe atom is of the trivalent Fe ³⁺ type. This is always the case for the geological raw materials used in carrying out the present invention.

As a result, a portion of the kaolinite fraction present in the raw material contains Fe-substituted Al, transforming the -Si-O-Al- (OH) _{2 function} into -Si-O-Fe- (OH) 2. It is not possible to separate the ferro-substituted kaolinite from the unsubstituted kaolinite. We use in the present invention the term "ferro-kaolinite" to designate this particular kaolinite which is characteristic of geological raw materials containing less than 40% iron oxides [goethite FeO (OH) + hematite Fe ₂ O ₃ + magnetite Fe ₃ 0 ₄ ]. In this ferro-kaolinite, said Fe atom represents an amount of between 5% and 50% of the total amount of Fe constituting the iron oxides.

The process for producing the binder or geopolymer cement of the present invention consists of: a) treating said geological elements at a temperature of 600 to 850 ° C. During this heat treatment, all the iron oxides [goethite FeO (OH) + magnetite Fe30 ₄ ] are converted into hematite Fe2O3 and the ferro-kaolinite becomes ferro-metakaolin type Fe-MK-750;

b) then to react with a reaction medium of the geopolymeric type.

The ⁵⁷ Fe Mossbauer spectrum tracks the transformation of ferrokaolinite into ferro-metakaolin Fe-MK-750. Thus, among the two parameters of the spectrum, IS (isomer-shift) and QS (quadrupole-split), the value of the QS increases very significantly since it goes from QS = 0.60 mm / s for ferro-kaolinite to QS = 1.0-1.5 mm / sec for ferro-metakaolin Fe-MK-750. It can be deduced that the electronic environment of the Fe atom has changed a great deal during calcination. Thus, as in the MK-750 metakaolin where the sequence -Si-O-Al- (OH) 2 has become -Si-O-Al = O (alumoxyl), the sequence -Si-O-Fe- (OH) 2 would become - Si-O-Fe = O (ferroxyl) for ferro-metakaolin Fe-MK-750. The latter is very reactive in the geopolymerization of Ca-geopolymeric type.

The binder or geopolymer cement of the invention therefore consists of a geopolymeric compound of Ca-poly (ferro-sialate) type. The substitution of the AI atoms by the Fe atoms can be demonstrated by the presence of a doublet in the Môssbauer spectrum determined by the isomer-shift IS = 0.2mm / s and the quadrupole-split QS = 1, 0-1, 50 mm / s. These two parameters are characteristic of the Fe atom in tetrahedral structural position Fe [IV]. [Cf. Enver Murad and Ursel Wagner, Clays and clay minerals: The firing process, Hyperfine Interactions 117 (1998) 337-356]. However, the ⁵⁷ Fe Mossbauer spectrum is delicate to strip, because it is polluted by that of Hematite which must be subtracted to visualize the doublet of ferro-sialate. If one complies with the writing used by geopolymers (see the introduction to the chapter on Prior Techniques), the geopolymeric compound of Ca-poly (ferro-sialate) type has a formula

[Ca, Na, K] - [- Fe-O-] _x - [- Si-O- (Al-O-) ₍ i- _x ₎ ] - [- Si-O-] _y in which "x" is a value less than or equal to 0.5, "y" is a value between 0 and 25.

The geopolymerization of Ca-geopolymeric type is described in the prior art in Chapter 9 of Geopolymer Chemistry & Applications, J. Davidovits, Geopolymer Institute, 2008. It states that the geopolymer cement obtained according to this reaction is a geopolymeric compound consisting of a solid solution comprising:

a) Calcium poly (di-sialate), Ca [-Si-O-Al-O-] ₂ * nH ₂ O, of structure analogous to anorthite.

(b) sodium and / or potassium poly (sialate)

[Na, K] [-Si-O-AI-O-]

(c) sodium and / or potassium poly (sialate-disiloxo)

[Na, K] [Si-O-Al-O-Si-O-Si-O-]

d) hydrated calcium di (siloxonate) Ca [Si-O-Si-O-], H ₂ O designated by CSH in Portland cement specialist jargon. The formation of this calcium di (siloxonate) depends on the amount of blast furnace slag (mellilite glass) present in the reaction medium.

In the context of the invention, the composition of this geopolymeric compound is modified because of the substitution of certain Al atoms by Fe. It is thought that this takes place mainly in the sodium poly (sialate) geopolymer and and / or potassium and in the poly (sialate-disiloxo) geopolymer of sodium and / or potassium. There will also be a certain amount of Fe associated with

di (siloxonate) of Ca, with replacement of Ca ⁺⁺ by Fe ⁺⁺⁺ . In the current state of science, it is not possible to say that this substitution of AI by Fe is or is not found in calcium poly (di-sialate). That's why we do not introduce it here, but we can not exclude it.

The binder or geopolymer cement Ca-poly (ferro-sialate) according to the invention is a geopolymeric compound consisting of a solid solution comprising at least two constituents chosen from:

a) Calcium poly (di-sialate), Ca [-Si-O-Al-O-] ₂ * nH ₂ O;

b) sodium and / or potassium poly (ferro-sialate)

[Na, K] [- Fe-O-Si-O-Al-O-]

c) sodium and / or potassium poly (ferro-sialate-disiloxo)

[Na, K] [- Fe-O-Si-O-Al-O-Si-O-Si-O-]

In some cases, when the amount of calcium reagent is in excess of the production of calcium poly (di-sialate) anorthite hydrate, the solid solution also contains ferro-calcium di (siloxonate) derived from CSH, with substitution of Ca by Fe. The binder or cement geopolymer Ca-poly (ferro-sialate) according to the invention is then a geopolymeric compound consisting of a solid solution comprising at least three constituents chosen from:

a) poly (di-sialate) Calcium, Ca [-Si-O-Al-O-] ₂ ^'nH ₂ O;

b) sodium and / or potassium poly (ferro-sialate)

[Na, K] [- Fe-O-Si-0-Al-O-]

c) sodium and / or potassium poly (ferro-sialate-disiloxo)

[Na, K] [- Fe-0-Si-O-Al-O-Si-O-Si-O-]

d) ferro-calcium di (siloxonate), [Ca, Fe] [Si-O-Si-O-], H ₂ 0

After the heat treatment, the geological elements contain the geopolymeric precursor Fe-MK-750. The whole is accompanied by hematite and inorganic inert charges initially present in the alteration of acidic rocks, granite and gneiss, or basic (mafic), basalt and gabbro. We will mention only the most usual, namely: quartz, rutile, anatase, ilmenite, pyroxene, olivine, feldspars, muscovite, biotite. The assembly is added to the Ca-geopolymeric reaction medium comprising:

a glass of calcium mellilite in which the glass part is greater than

70% by weight;

a soluble alkali silicate in which the molar ratio SiO ₂ : (Na, K) ₂ O is between 1.40 and 2.0.

If necessary, that is, depending on the mineralogical nature of the weathered rock, and depending on the alkali requirements, the molar ratio of the soluble alkali silicate may be lower with SiO ₂ : (Na, K) ₂ 0 between 1, 20 and 1, 40. It is however preferable to adjust the reaction mixture in order to maintain a non-corrosive medium, that is to say with a molar ratio SiO ₂ : (Na, K) ₂ O of between 1.40 and 2.0.

The binder or cement of the present invention is illustrated by the following examples. They do not have a limiting character on the overall scope of the invention as presented in the claims. All parts shown are by weight.

Example 1

Residual rock of the lateritic lithomarge type resulting from the alteration of the basalt is chosen. It contains about 12% quartz, 45% kaolinite, 30% hematite, 3% goethite, 10% other elements (anatase + ilmenite + olivine). It is calcined at 750 ° C. for 3 hours and then ground at an average particle size of 10-25 microns.

The following reaction mixture is then carried out:

a) calcined lateritic lithomarge, 90 parts

b) Mellilite of crushed calcium at 10-25 microns 30 parts

c) silicate solution of K-silicate

SiO ₂ molar ratio: K ₂ O = 1.56; H ₂ O: 55% 30 parts

water 20 parts

It is cured at room temperature of 20 ° C in a covered mold to prevent evaporation of water. The compressive strength at 7 days is 30 MPa, and the resistance at 28 days is 75 MPa. The pH of the geopolymeric cement measured at equilibrium in a 10% solution is pH = 12.20 at 7 days and pH = 11.65 at 28 days.

The hardened Ca-poly (ferro-sialate) cement is analyzed by X-ray diffraction. The spectrum shows a characteristic amorphous halo at 28 ° 2Θ for the Cu (Ka) radiation, accompanied by lines belonging to the hematite as well as quartz elements, anatase + ilmenite + olivine. There is no more kaolinite, goethite, which all reacted in the Ca-geopolymeric reaction medium.

Example 2

We choose a residual rock of saprolite type resulting from the alteration of the basalt. It contains about 15% plagioclase, 3% quartz, 10% pyroxene, 35% kaolinite, 18% hematite, 3% goethite, 6% gibbsite, 5% montmorillonite, 5% other elements ( anatase + ilmenite + olivine).

It is calcined at 750 ° C. for 3 hours and then ground at an average particle size of 10-25 microns.

The following reaction mixture is then carried out:

a) calcined saprolite, 90 parts

b) Mellilite of crushed calcium at 10-25 microns 30 parts

c) silicate solution of K-silicate

SiO ₂ molar ratio: K ₂ O = 1.26; H ₂ O: 53% 30 parts

water 20 parts It is cured at room temperature of 20 ° C in a covered mold to prevent evaporation of water. The compressive strength at 7 days is 40 MPa, and the resistance at 28 days is 90 MPa. The pH of the geopolymeric cement measured at equilibrium in a 10% solution is pH = 12.25 at 7 days and pH = 11.75 at 28 days.

The hardened Ca-poly (ferro-sialate) cement is analyzed by X-ray diffraction. The spectrum shows a characteristic amorphous halo at 28 ° 2Θ for the Cu (K) radiation, accompanied by lines belonging to the hematite as well as pyroxene, anatase, olivine, ilmenite and quartz. There is no more kaolinite, goethite, gibbsite, montmorillonite, all of which have reacted in the Ca- geopolymeric reaction medium.

⁵⁷ Fe Mossbauer is also analyzed. Because of the large amount of hematite, the first spectrum first shows the Sextet 01 which hides the one of the Doublet. After subtraction of Sextet 01, that of Doublet presents the isomer-shift parameters IS = 0.2mm / s and quadrupole-split QS = 1mm / s. These two parameters are characteristic of the Fe atom in the tetrahedral Fe [IV] structural position in the molecular structure of the geopolymer.

Of course, various modifications may be made by those skilled in the art to binders or geopolymeric cements and methods that have just been described by way of example, without departing from the scope of the invention.

Claims

claims

1) Binder or geopolymeric cement of the poly (ferro-silico-aluminate) type which, after curing, consists of a geopolymeric compound belonging to the family of geopolymers based on poly (sialate) and / or poly (sialate-siloxo) and / or poly (sialate-disiloxo), characterized in that in said geopolymeric compound a portion of the AI atoms is substituted by Fe atoms, all of which corresponds to the empirical formula

[Ca, Na, K] - [- Fe-O-] _x - [- Si-O- (Al-O -) (i- _x ₎ ] - [- Si-O-] _y in which "x" is a value less than or equal to 0.5, "y" is a value between 0 and 25; said Fe atom is found in tetrahedral structural position Fe [IV] in the ferro-sialate [-Fe-O-Si-O-AI-O-] geopolymeric bond; it represents between 5% and 50% of the total amount of Fe ₂ O 3 contained in said binder or geopolymer cement, the remainder, between 50% and 95%, is combined in crystallized iron oxide Fe ₂ O 3 Hematite.

2) binder or geopolymer cement according to claim 1), characterized in that said geopolymeric compound consists of a solid solution comprising at least two constituents chosen from:

a) Calcium poly (di-sialate), Ca [-Si-O-Al-O-] ₂ * nH ₂ 0;

b) sodium and / or potassium poly (ferro-sialate)

[Na, K] [- Fe-0-Si-0-Al-O-]

c) sodium and / or potassium poly (ferro-sialate-disiloxo)

[Na, K] [- Fe-0-Si-0-AI-0-Si-O-Si-O-]

3) Binder or geopolymer cement according to any one of claims 1) and 2), characterized in that said geopolymeric compound consists of a solid solution comprising at least three constituents chosen from:

a) Calcium poly (di-sialate), Ca [-Si-O-Al-O-] ₂ * nH ₂ 0;

b) sodium and / or potassium poly (ferro-sialate)

[Na, K] [- Fe-0-Si-0-Al-0-]

c) sodium and / or potassium poly (ferro-sialate-disiloxo)

[Na, K] [- Fe-O-Si-O-Al-O-Si-O-Si-O-] d) ferro-calcium di (siloxonate), [Ca, Fe] [Si-O-Si-O-], H ₂ 0

4) binder or geopolymer cement according to any one of claims 1) to 3), characterized in that it is the result of geopolymerization type Geopolymer with geological elements rich in iron oxides and ferro-kaolinite from the alteration of acidic rocks such as granite or gneiss, or from basic (mafic) rocks such as basalt and gabbro.

5) binder or geopolymer cement according to any one of claims 1) to 4), characterized in that in said geological elements, the amount of iron oxides, [goethite FeO (OH) + hematite Fe ₂ O ₃ + magnetite Fe ₃ 0 _4], is between 5% and 40% by weight, the amount of ferro-kaolinite is between 15% and 60% by weight and the amount of alumina hydrates [gibbsite Al (OH) 3 + boehmite AIO (OH)] is from 0% to 20% by weight.

6) binder or geopolymer cement according to claim 5), characterized in that the ferro-kaolinite can be replaced by 0% to 20% by weight of halloysite mineral.

7) Binder or geopolymeric cement according to claim 5), obtained by

geopolymerization of saprolite-type geological elements resulting from the alteration of mafic rocks, characterized in that the amount of hydrates of alumina

[gibbsite Al (OH) ₃ + boehmite AlO (OH)] is between 5% and 20% by weight and the ferro-kaolinite is replaced by 2% to 20% by weight of smectic mineral such as montmorillonite and / or vermiculite.

8) A method of manufacturing a binder or geopolymer cement according to any one of claims 1) to 7), characterized in that it consists

a) treating said geological elements at a temperature of 600 to 850 ° C. During this heat treatment, all the iron oxides [goethite FeO (OH) + magnetite Fe ₃ O ₄ ] are transformed into hematite Fe ₂ 0 ₃ and the ferro-kaolinite becomes ferro-metakaolin type Fe-MK-750 ;

b) then to react with a reaction medium of the geopolymeric type.