FR2941448A1 - Sulfo-aluminous clinker, useful in hydraulic binder for grout, concrete and mortar, comprises calcium aluminoferrite phase composition, iron doped calcium sulfoaluminate phase, belite and boron doped calcium silicate - Google Patents

Abstract

Sulfo-aluminous clinker comprises: 5-25% of calcium aluminoferrite phase composition; 15-35% of optionally iron doped calcium sulfoaluminate phase; 10-35% of belite containing at least 5% of polymorphic belite; and 10-25% of boron doped calcium silicate, as a phase composition. Sulfo-aluminous clinker comprises: 5-25% of composition of calcium aluminoferrite phase having structure of formula (C1 2A xF1 (1-x)); 15-35% of optionally iron doped calcium sulfoaluminate phase having structure of formula (C1 4A (3-y)S2F1 y); 10-35% of belite having structure of formula (C1 2S1) containing at least 5% of polymorphic belite; and 10-25% of boron doped calcium silicate having structure of formula (C1 11S1 4B), as a phase composition. C1 : CaO; A : Al 2O 3; F1 : Fe 2O 3; S1 : SiO 2; S2 : SO 3; x : 0.2-0.8; and y : 0-0.5. An independent claim is included for preparing the sulfo-aluminous clinker comprising preparing a raw mixture by dosing raw materials for providing the quantities of elements necessary to obtain the desired composition phase, mixing the raw materials, baking the mixture of raw materials at 1250-1350[deg] C, and cooling the clinker rapidly.

Description

The present invention relates to a novel sulfo-aluminous clinker, a method of preparing this clinker, and the use of clinker for the preparation of hydraulic binder and, subsequently, grout, concrete or mortar.

The manufacture of hydraulic binders, and in particular that of cements, consists essentially of calcining a mixture of carefully chosen and dosed raw materials, also referred to as the raw material. The cooking of this vintage gives an intermediate product, the clinker, which crushed with possible mineral additions will give cement. The type of cement manufactured depends on the nature and proportions of the raw materials as well as the cooking process. There are several types of cement: Portland cements (which represent the vast majority of cements produced in the world), aluminous cements (or calcium aluminate), natural quick cements, sulfo-aluminous cements, cements sulpho-belitic and other intermediate varieties. Since these families are not totally disjunct, it is better to describe them by their chemical and mineralogical constituents.

The most common cements are Portland cements. Portland cements are obtained from Portland clinker, obtained after clinkerization at a temperature of about 1450 ° C. of a calcium carbonate rich raw material in an oven.

The preparation of such cements have the disadvantage of releasing a lot of CO2. The cement industry is therefore looking for a viable alternative to Portland cement, ie cements with at least the same characteristics of strength and quality as Portland cement, but which when they are produced, they would release less CO2.

As such, in recent years, research has focused on so-called sulfo-aluminous and sulfo-belitic cements, which emit less CO2 than Portland cements during their production.

Since the clinker is the result of calcination at high temperature, the elements are essentially present in the form of oxides. Clinkers for the preparation of sulfo-aluminous cements or sulpho-belitic cements refer to a process for producing a clinker from a raw material consisting of a mixture comprising the compounds CaCO3, Al2O3, and / or Al (OH ) 3 CaSO4, SiO2, Fe2O3 and / or a product containing silica or silicates such as clay, all these compounds being present in anhydrous or hydrated form, individually or in combination.

As part of this research, many sulfoaluminous clinkers have been described. For example, mention may be made of international patent application WO 2006/018569 describing belitic sulfoaluminous clinkers comprising 5 to 25% calcium aluminoferrite phase of a composition corresponding to the general formula C2AF (1_x), with x ranging from 0.2 to 0.8; 15 to 35% calcium sulphoaluminate phase yee 'limit (C4A3 $); 40 to 75% belite (C2S); and from 0.01 to 10% of one or more minor phases. As mentioned in this patent application, such clinkers contain, in comparison with the alite phase (C3S), the main component of the Portland cements, a higher amount of belite phase (C2S), which is quite beneficial, since this leads to the reduction of industrial CO2 emissions and energy consumption. On the other hand, belite contributes to the development of the long-term resistance of Belitic sulfo-aluminous cement. However, this patent application does not mention the presence of C11S4B boron doped calcium silicate and C4A3_y $ Fy iron doped calcium sulfoaluminate phases. Moreover, nothing is said in this patent application concerning the presence of the polymorph C2S ,, in the C2S phase.

However, the polymorphism of belite (C2S) governs its reactivity or its hydraulicity. Solid solutions with minor elements such as boron, sodium or potassium lead, to a certain extent, to vary the crystallographic nature of belite. The presence of these minor elements, commonly called mineralizers, can also shift the onset temperatures of some polymorphic varieties.

The reactivity of belite is variable and depends on its form. In the scientific literature, polymorphs of C2S appear as follows, as a function of temperature: C2Sa'low (C2Sa'l) C2SaHigh (C2Sa'h) C2Sr C2Sp C2S ,, 500 ° C 675 ° C 1177 ° C 1425 ° C

The hydraulic reactivity, that is to say the setting speed and increase in mechanical strength, decreases from polymorph C2S ,, polymorph C2Sr. In the case of Portland clinkers, belite, essentially represented by the C2S13 polymorph, contributes to the long-term compressive strength, that is, at 28 days and beyond. The C2Sa polymorph is more reactive than the C2S13 polymer and has a reactivity approaching Alite C3S, the major phase of Portland clinker. The polymorph C2Sa, is also an interesting alternative to C3S Portland clinkers because it allows to approach the reactivity while limiting CO2 emissions due to a stoichiometry less calcium therefore requiring less carbonate to make it. It is therefore desirable in a clinker that the C2Sa polymorph is present in the C2S phase.

On the other hand, the presence of the calcium sulphoaluminate phase C4A3 $ or the calcium sulphoaluminate phase doped C4A3_y $ Fy iron is necessary for the setting and the very short-term compressive strength of the cement prepared from clinker. The simultaneous presence in the clinker of the belite containing the C2Sa polymorph and the calcium sulphoaluminate phase C4A3 $ or the calcium sulphoaluminate phase doped C4A3_y $ Fy iron is therefore necessary for the preparation of a quality cement .

However, the polymorph C2Sa appears above 1425 ° C. To reach such a temperature, a large amount of energy is necessary which causes significant CO2 emissions during the preparation of the clinker. In addition, at this temperature, the C4A3 $ calcium sulfoaluminate phase is already strongly resorbed in Mayenite C12A7, which is detrimental to the final quality of the clinker. In addition, this resorption is accompanied by a release of S02 incompatible with the conduct of an environmentally friendly industrial plant. Identical phenomena are observed for the calcium sulphoaluminate phase doped with iron C4A3_y $ Fy.

Consequently, it is impossible to reconcile the presence of yee'limite (C4A3 $) or of calcium sulphoaluminate doped with C4A3_y Fy iron and reactive belite (C2Sa) by working at the temperature of appearance of the latter (1425 ° C. ). In addition, the CO2 and S02 emissions during the preparation of a clinker at such a temperature remain high in view of current and future ecological constraints.

There is therefore a need to identify new clinkers that can be prepared at temperatures lower than 1425 ° C while ensuring the presence of belite (C2S) containing the C2S polymorph, and yee'limite (C4A3 $) or calcium sulphoaluminate doped with iron C4A3_y $ Fy.

It has now been found new sulfo-aluminous clinkers to solve these technical problems, and in particular to obtain C2S belite containing the C2S polymorph, at temperatures well below 1425 ° C, thereby obtaining a clinker containing both a C2S phase containing the C2S polymorph, and a C4A3 $ calcium sulfoaluminate phase or a C4A3_y $ Fy iron-doped calcium sulfoaluminate phase, while greatly reducing CO2 emissions during their preparation .

In addition, it has been observed quite surprisingly that such clinkers allowed the preparation of cements with hydraulic reactivity and increased strength compared to cements prepared from the clinkers described in the international patent application WO 2006/018569 , while reducing CO2 emissions by up to 35% during their preparation in comparison with Portland type clinkers.

The subject of the present invention is therefore a sulfo-aluminous clinker comprising as phase composition, relative to the total weight of the clinker: from 5 to 25% of calcium aluminoferrite phase of a composition corresponding to the general formula C2AXF (i_X), with x ranging from 0.2 to 0.8; from 15 to 35% calcium sulphoaluminate phase optionally doped with iron corresponding to the formula C4A3_y $ Fy with y varying from 0 to 0.5; from 10 to 35% of C2S belite, said belite containing at least 5% of C2S polymorph; and from 10 to 25% boron doped calcium silicate corresponding to the formula C11S4B. The clinker according to the present invention allows the preparation of cements having greater hydraulic reactivity and strength compared to the cements described in the prior art. In addition, the clinker according to the present invention can be prepared at temperatures not exceeding 1350 ° C, which on the one hand limits the CO2 emissions and on the other hand the destruction of the C4A3_y $ Fy phase. In the context of the present invention, the following notations are adopted for designating the mineralogical components of cement: C represents CaO; - A represents Al2O3; - F represents Fe2O3; S represents SiO 2; and - $ represents S03. Thus, for example, the optionally doped calcium sulfoaluminate phase of iron designated C4A3_y $ Fy is actually a (CaO) 4 (Al2O3) 3_y.SO3 (F2O3) phase.

In addition, in the context of the present invention, the proportions expressed in% correspond to percentages by weight relative to the total weight of the entity (i.e. clinker or hydraulic binder) considered. Preferably, the subject of the present invention is a sulfo-aluminous clinker as described above in which the C2S belite contains at least 10%, preferably at least 20%, more preferably at least 30%, more preferably at least 40% and most preferably at least 50% polymorph C2Sa. Other minority phases may appear in the constitution of the clinker. These minor phases may consist of free lime CaOl, C $ anhydrite, C2AS Gelenhite, Mayenite C12A7, Péricalse MgO, Perovskite CT, C3FT, C4FT2. Preferably, the clinker according to the invention contains: less than 3% of CaO1, preferably less than 1% of CaO1; less than 5% of C $, preferably less than 2% of C $; and / or less than 10% C2AS, preferably less than 5% C2AS.

The present invention also relates to a process for the preparation of a clinker as described above, comprising the following steps: - preparation of a raw material by dosing raw materials in order to provide the quantities of elements necessary for the obtaining the desired phase composition, - mixing (possibly by co-grinding) of the raw materials, - baking the mixture of raw materials at a temperature ranging from 1250 ° C. to 1350 ° C., and - rapid cooling of the clinker.

Preferably, the firing step of the process according to the present invention is conducted at a temperature ranging from 1280 ° C to 1340 ° C.

The clinker according to the present invention can be prepared from different raw materials such as red sludge, bauxite, limestone, gypsum or any other source of calcium sulphate, boric acid, colemanite, borate hydrate. sodium, clay-limestone marl or by-products of the aluminum and alumina industry.

The quality of the cooking, and in particular the respect in every point of an oxidizing atmosphere and the maximum temperatures of 1350 ° C, is fundamental. The preparation of the clinkers according to the invention will therefore be done in an oven for compliance with these conditions.

The clinker according to the present invention can be used to prepare a hydraulic binder, for example cement, by grinding and optional addition of gypsum, anhydrite or hemihydrate. The present invention thus also relates to a hydraulic binder comprising a clinker as previously described in ground form. Preferably, the hydraulic binder according to the present invention also comprises an addition of gypsum, anhydrite or hemihydrate, in proportions of up to 20%.

The hydraulic binder according to the present invention may also comprise additions of the same type as those used for Portland cement, such as, for example, limestone, natural and artificial pozzolans, blast furnace slag, fly ash from coal fireplaces and the like. silica fumes. This addition is carried out by mixing before or after the grinding of the constituents, by mixing the powders or by co-grinding. The setting of the binder is then the result of the activation of the additions by the clinker, consequently the saving of CO2 compared to a cement of the CEM I type (according to the standard EN 197-1) can be considerable, going as far as at 90% reduction of CO2 emissions according to the content of addition. Finally, the present invention also relates to the various products prepared from the binder described above, in particular grouts, concretes and mortars. Thus, the present invention also relates to a grout, a concrete or a mortar comprising the hydraulic binder as described above.

The present invention may be illustrated in a nonlimiting manner by the following example. Example 1

A vintage was made with the following raw materials including chemical analyzes. Limestone Red mud Bauxite Gypsum Boric acid SiO2 (in%) 2.75 7.1 26.11 0.33 Al2O3 (in%) 0.19 13.04 39 0.31 CaO (in%) 52.85 4.51 2 30.31 MgO (%) 0.64 0.17 0.22 0.02 Fe2O3 (%) 0.37 49.52 16.22 0.13 TiO2 (%) 0.04 10.54 1 , 89 0.04 K2O (in%) 0.12 0.08 0.22 0.06 Na2O (in%) 0.08 4.2 0.05 0.3 0 P2O5 (in%) 0.02 0, 45 0.18 0.42 Mn2O3 (in%) 0.01 0.08 0.07 SO3 (in%) 0.33 0.26 0.05 46.58 B2O3 (in%) 0 0 0 0 56.29 Other No 0.04 0 0.04 1.54 Volatiles (in%) Loss on Fire 42.18 9.72 13.7 19.91 43.66 (in%) Total 99.62 99.67 99.75 99 , 95 99.95 Loss of fire is understood to mean the loss of mass observed after firing at 950 ° C. Red mud: industrial residues from the treatment of bauxite by the Bayer process (Rio Tinto). The crystallographic phases: Fe2O3, Goethite, Rutile, Perovskite, Quartz, Gibsite, Boehmite, Portlandite, Calcite, Cancrinite.

Bauxite: from Sodicapei: B40 is 40% Al2O3.

Gypsum: industrial by-product from the manufacture of phosphoric acid. Technical boric acid.

An intimate mixture was made in the following proportions (all passing 100 m):% Limestone 57.26 Red mud 8.5 Bauxite 25.6 Gypsum 5.1 Boric acid 3.4 Cooking in a passage oven was carried out at 1290 ° C for 30 minutes. The crystalline phases obtained are as follows: Mineralogical Composition% C4A2.85 Fo2 28.0 C2Sa, h 3.8 C3A0.6F1.4 11.8 C3FT 14.3 C2Sa 14.8 C11S4B 23.6 MgO / Periclase 1 , 4 C2AS / Gehlenite 2.4 20

Claims (10)

REVENDICATIONS1. Sulfoaluminous clinker comprising, as the phasic composition, based on the total weight of the clinker: from 5 to 25% of calcium aluminoferrite phase of a composition corresponding to the general formula C2AXF (i_X), with x varying from 0.2 to 0 , 8; from 15 to 35% calcium sulphoaluminate phase optionally doped with iron corresponding to the formula C4A3_y $ Fy with y varying from 0 to 0.5; - from 10 to 35% of C2S belite, said belite containing at least 5% of polymorph C2S ,,; and from 10 to 25% boron doped calcium silicate corresponding to the formula C11S4B. 2. Clinker according to claim 1, characterized in that the C2S belite contains at least 30% polymorph C2S. 3. Clinker according to claim 2, characterized in that the C2S belite contains at least 50% polymorph C2S. 4. Clinker according to one of claims 1 to 3, characterized in that it comprises less than 3% of CaOl, less than 5% of C $ and / or less than 10% of C2AS. 5. Process for the preparation of a clinker according to any one of claims 1 to 4, characterized in that it comprises the following steps: - preparation of a raw material by dosing raw materials in order to provide the amounts of elements necessary to obtain the desired phase composition, - mixing of the raw materials, - firing of the mixture of raw materials at a temperature ranging from 1250 ° C. to 1350 ° C., and - rapid cooling of the clinker. 6. Process according to claim 5, characterized in that the firing step 35 is carried out at a temperature ranging from 1280 ° C to 1340 ° C. 7. hydraulic binder comprising a clinker according to any one of claims 1 to 4. 8. Grout comprising a hydraulic binder according to claim 7. 9. Concrete comprising a hydraulic binder according to claim 7. 10. Mortar comprising a hydraulic binder according to claim 7.