FR2892116A1 - PROCESS FOR THE PREPARATION OF A WATER RESISTANT CALCIUM SULFATE COMPOSITION - Google Patents

Abstract

The invention relates to a process for the preparation of an anhydrous or non-water-resistant calcium sulphate-based composition in which the calcium sulphate is combined with a sulpho-aluminous clinker, said clinker being present at from 20 to 40% by weight relative to the total weight of the composition, and said clinker comprising from 50 to 65% by weight of yeelimite relative to the weight of the sulfo-aluminous clinker.The invention also relates to a hydraulic binder comprising such a composition, construction materials obtainable from such a hydraulic binder, and the use of a sulfo-aluminous clinker to improve the water resistance of a composition containing anhydrous calcium sulfate or not.

Description

The present invention relates to a method for preparing a composition

  based on anhydrous or anhydrous calcium sulphate having improved water resistance, a hydraulic binder comprising such a composition, as well as building materials obtainable from such a hydraulic binder. It also relates to the use of a sulfo-aluminous clinker to improve the water resistance of a composition containing anhydrous calcium sulphate or not. Binders based on calcium sulphate and in particular plaster, are economic binders but whose development is limited by their poor resistance to water. For example, the use of plaster is often limited to indoor work. In order to improve the moisture resistance of the plaster, and thus to extend the use of plasters to outdoor work or in areas exposed to moisture, solutions have been developed which consist in adding water-repellent agents. For example, US Pat. No. 6,547,874 discloses a technique of adding to the plaster an organic or inorganic powdery solid having a specific surface area greater than 5 g / m 2 such as pulverulent silica, and an organohydropolysiloxane. U.S. Patent 5,437,722 discloses a water-resistant gypsum-based composition in the form of an aqueous emulsion comprising water and i) a paraffin having a melting point between 40 and 80 C, ii ) lignite wax and iii) a polyvinyl alcohol. These solutions for adding water-repellent agents have the main disadvantage of their high manufacturing cost. In addition, they sometimes show random results. Therefore, there is an increased need to find solutions for water-repellent calcium sulphate and plaster, which do not have the disadvantages mentioned above. The subject of the present invention is a process for preparing an anhydrous or non-water-resistant calcium sulfate-based composition B1590fr in which said calcium sulphate is associated with a sulphoaluminous clinker, said sulpho-aluminous clinker. being present at a level of 20 to 40% by weight relative to the total weight of the composition and said sulfo-aluminous clinker comprising from 50% to 65% by weight of yeelimite relative to the weight of the sulfo-aluminous clinker. The fact of associating calcium sulphate with a sulpho-alumina clinker in such proportions, the clinker itself having a specific percentage of yeelimite, makes it possible to obtain, surprisingly, a composition exhibiting properties of resistance to water improved over known compositions. In the context of the present invention: sulfo-aluminous clinker means a mixture of limestone, bauxite and calcium sulphate, brought to about 1300 C then brutally cooled and ground. Usually, the mass proportions of these various components are: - bauxite with an alumina content greater than 55%: 30 to 40% - calcium carbonate (limestone): 45 to 50%, - calcium sulphate (gypsum): 16 to 18%. The sulfo-aluminous clinker is then formed of the following main phases: yeelimite or kleinite, belite, ferrite, perovskite and, mayenite; hydraulic binder means finely ground mineral materials, forming by addition of water in a suitable amount a binder paste capable of hardening even under water and binding granular materials together; Calcium sulphate means both natural gypsum, i.e. calcium sulphate bihydrate or synthetic (sulphogypsum, phosphogypsum, titanogypsum, borogypsum, lactogypsum and other types of by-products of the same type as well as their mixtures). Plaster, namely calcium sulphate hemihydrate, is also part of the calcium sulphates that can be used in the context of the present invention, as well as all the improved plasters, namely comprising an increased proportion of anhydrous calcium sulphate. . Finally, anhydrous calcium sulfate, or anhydrite, can be calcium sulfate. In the same way as for gypsum, all types of anhydrites are suitable. There may be mentioned natural or synthetic anhydrite such as fluoroanhydrite, phosphoanhydrite, anhydrite III or a and mixtures thereof. Of course, the mixtures of these different types of calcium sulphate in their anhydrous or hydrated forms are suitable for being used in a process according to the invention. Therefore, for reasons of simplification, the use of the term calcium sulfate in the following description covers all types of calcium sulfate mentioned above. The sulphoaluminous clinker used in the process of the invention consists mainly of yeelimite (4 CaO 3 Al 2 O 3, SO 3), and may further contain belite (2 CaO.SiO 2) and calcium ferroaluminate or ferrite phase (4 Cao, Al2O3, Fe2O3). To ensure hydration, a source of calcium sulphate must be added to form ettringite. We then obtain a hydraulic binder, that is to say, which is taken under water. The hydration equations are written: - in the absence of calcium hydroxide C4A3E + 2CEH2 + 34H> C6AE3H32 + 2AH3 Yeelimite + gypsum + water = ettringite + gibbsite - in the presence of calcium hydroxide C4A3E + 8CEH2 + 6CH + 74H = 3 (C6AE3H32) Yeelimite + gypsum + calcium hydroxide + water = ettringite where C = CaO, A = Al2O3, = SO3r H = H2O, according to the cement notation. The sulfo-aluminous clinker used in the process according to the present invention preferably comprises from 50 to 65% by weight of yeelimite. It may further contain from 10 to 25% belite, 0 to 20% ferrite, 0 to 10% mayenite and 0 to 20% by weight perovskite.

  Even more preferably, the sulfo-aluminous clinker used in the process according to the present invention comprises 60 to 65% yeelimite. It may further contain from 10 to 20% belite, 0 to 15% ferrite, 0 to 8% mayenite and 7 to 18% by weight perovskite. The variations in the relative amounts of the various constituents make it possible to obtain a whole range of construction materials whose properties can be modulated. According to a preferred embodiment of the invention, the clinker is present at 30% by weight of the total weight of the composition. The process according to the present invention may be carried out by mixing the various constituents according to conventional techniques known to those skilled in the art. This fabrication does not require any specific tooling, which highlights another advantage of the present invention. The process according to the present invention can be carried out at room temperature in any type of mixer usually used for mixing powders such as: the screw mixer, the worm gear mixer, the turban mixer and the turbine mixer. In addition, the invention relates to hydraulic binders comprising compositions obtained by carrying out the process of the invention. Thus, the hydraulic binder can be prepared from the single composition as such, or be more complex and further contain other components. For example, the hydraulic binders according to the invention may further contain other additives such as superplasticizers, Portland cement, limestone filler, fly ash, ground slag, setting retarders (boric acid), viscosity agents (eg Welan gum, guar gum or xanthan gum), polyvinyl acid and surfactants (polyols). Among the superplasticizers include polycarboxylates.

  It is understood that the possible additives are to be included in reduced proportions when it is desired to obtain hydraulic binders at moderate costs. However, they can be interesting to obtain some hydraulic binders for particular applications. Thanks to the presence of the sulfo-aluminous clinker in the contents described above, the hydraulic binder according to the present invention shows water-resistant qualities which make it possible to use it in humid zones, while retaining its compressive strength qualities when it is used in a mortar according to the "European standard for the composition of mixtures" EN 196-1, as demonstrated by the examples below. The hydraulic binder according to the present invention can be formulated so as to obtain building materials according to the usual techniques known to those skilled in the art. For example, for making breeze blocks from the hydraulic binder according to the present invention, the manufacturing process usually consists of the following successive steps. - Mix for 1 to 2 minutes in a mixer: sand and gravel, hydraulic binder premixed or not, water, - pour the whole into a buffer hopper located above a breeze block press and finally, -fill the molds of this press and subject them to vibro-compaction to obtain blocks. All these operations are at room temperature. Therefore, the subject of the invention is also a construction material containing a hydraulic binder according to the invention. Non-limiting examples of such building materials are filling concrete, building blocks, laying mortar, exterior coatings, screeds and interior coatings.

  The hydraulic binders according to the invention in the form of standardized mortar have a compressive strength at 28 and 90 days respectively between 5 and 30 MPa and 10 and 40 MPa.

  The invention also relates to the use of a sulphoaluminous clinker comprising from 50% to 65% by weight of yeelimite, to improve the water resistance of a composition containing between 60 and 80% of anhydrous calcium sulphate or not. In the context of this use, calcium sulfate is defined as above. The sulphoaluminum clinker used preferably comprises 60 to 65% by weight of yeelimite, and may further contain belite and ferrite. According to a particularly advantageous embodiment, the composition contains 70% anhydrous calcium sulphate or not. The examples and figures which follow illustrate the present invention, without limiting it. FIG. 1 is a representation relating to Example 1 of the underwater preservation of clinker CK1. FIG. 2 is a representation relating to Example 1 of the preservation in a sealed bag of clinker CK1. FIG. 3 is a representation. relating to Example 1 of the underwater conservation of clinker CK2, FIG. 4 is a representation relating to example 1 of the preservation in a sealed bag of clinker CK2. FIG. 5 represents the evolution of the removal of coatings. in connection with Example 4.2, Figure 6 shows the appearance of the coatings after 40 days of natural aging, in connection with Example 4.2.

  Example 1 Tests on the proportion of clinker in phosphogypsum Two types of clinkers were studied: CK1 and CK2. Their compositions are given in Table 1.

  Table 1. Phases of clinkers used Phase CK1 CK2 Belite - C2S 17.2 15.6 Yeelimite - 60, 9 66, 4 C4A3E Mayenite - - 7.1 C12A7 Perovskite - 7.9 9.9 C3FT2 Ferrite - C4AF 14.0 The objective of the first study was to determine the minimum amount of sulpho-aluminous clinker to add to calcium sulphate (phosphogypsum) to ensure its stability to water and to develop sufficient strengths to allow the manufacture of construction. This approach is used for the evaluation of conventional hydraulic binders. The phosphogypsum used in the study consisted of 98% pure isigypse, as shown in Table 2. The average diameter of the particle size distribution was 12 μm and the pH slightly basic (8.8). Table 2. Chemical composition of phosphogypsum (% by weight) Oxides Al2O3 CaO Na2O MgO P2O5 SO3 LOI Content 0.2 32.0 0.2 0.6 0.4 45.7 20.4 Six binders were prepared with clinker CK1 . Their references and compositions are given in Table 3. TABLE 3 Binding compositions and compositions CK1 Binder% gypsum% clinker 1 95 5 2 90 10 3 85 15 4 80 20 75 25 6 70 30 The study with clinker CK2 focused on three binders: 2, 4 and 6 (Table 4). Table 4. References and compositions of binders CK2 Bonding% gypsum% clinker 2 90 10 4 80 20 6 70 30 The composition of the standardized mortar is given below: standardized sand: 1350 g; 450 g binder; water: 225 g, ie resistances in 24 hours, 7, 28 and 90 days on halves of prisms 15 4 x 4 x 16 cm. For the periods 7, 28 and 90 days, two methods of conservation of the specimens were compared:. in a sealed bag: the test pieces are demolded 48 hours after their manufacture and then kept in a sealed bag at 20 C until expiry (d-1), then at 20 ° C. and 50% relative humidity until expiry of the test. under water: the specimens are demolded 48 hours after their manufacture and then kept under water at 20 C until maturity (d-1), then at 20 C and 50% relative humidity until expiry 'trial. a water / binder ratio = 0.5. The compression strengths of the mortars prepared with clinker CK1 are given in FIGS. 1 (underwater storage) and 2 (storage in a sealed bag). As shown in Figures 1 and 2, which represent respectively for the clinker CK1 underwater storage (Figure 1) and the preservation in sealed bag (Figure 2), the 24-hour resistances are very low either in a sealed bag or under water. Between 24 hours and 7 days, the resistances grow rapidly, except for the binder 1. In the case of underwater storage, for binders 5 and 6 (the most resistant), a significant increase in resistance occurs between 7 and 28 days. It does not exist for the binder 4. For others (Li to L3), the resistances decrease. These binders are not stable in water. Between 28 and 90 days, there is an increase in strength for binders 4 to 6. Binders 1 and 2 have virtually no strength. This confirms their instability with water (Figure 1). The best performances are obtained for binders 5 and 6 in underwater storage. Three mortars (L2, L4 and L6) were tested with clinker CK2. Their compressive strengths are given in FIGS. 3 (preservation under water) and 4 (preservation in a sealed bag). It can be seen from these figures that the main increase in strength also occurs during the first days, for both types of preservation and for all binders. Storage in a sealed bag is less effective, except for the binder 2. For binders 4 and 6, it is observed that the samples stored under water have greater strengths. These results show that in order to obtain a water-stable mortar, at least 20% of sulpho-aluminous clinker must be used to activate the gypsum.

  EXAMPLE 2 Influence of the Nature of Calcium Sulphate Assays were performed by replacing phosphogypsum with plaster (hemihydrate (3) and using CK2 clinker.) The compositions of the binders are given in Table 5. Table 5. Composition binders containing clinker CK2 and plaster Binder% CK2% Plaster 1 0 100 2 10 90 3 20 80 4 30 70 The composition of the mortars was as follows: io Sand standardized: 1350 g Binder: 450 g Water / Binder: 0.85 The use of plaster instead of phosphogypsum leads to a considerable increase in the mixing ratio (Water / Binder) to obtain the same maneuverability: + 70% .Manageability is measured by the spreading that takes a truncated cone of mortar * nf = 100 mm, (I) suP = 70 mm, h = 50 mm) after 15 strokes on a shock table. This spread is of the order of 165 mm 10 mm. The mortars have been delayed or not so as to improve the practical duration of use (DPU), that is, maintain maneuverability for a certain period of time. The retarder, a degraded protein, was assayed at 0.02% by weight of binder. The characteristics measured on the mortars were the DPU, and the compressive strength. The results are shown in Tables 6 (DPU) and 7 (Compressive Strength).

  Table 6. Practical duration of use Binder Without With self-timer retarder 100% plaster 5 '55' CK2 90% plaster-10% 10 '60' CK2 80% plaster-20% 10 '70' CK2 70% plaster-30% 10 '75' Table 7. Compressive strength at 28 days (MPa) after immersion in water. Binder Without With self-timer retarder 100% plaster 4.5 4.7 CK2 90% plaster-10% 9 8.3 CK2 80% plaster-20% 14 12.6 CK2 70% plaster-30% 21.8 18.7 With phosphogypsum, there was obtained: - 9 MPa with the 80% phosphogypsum mixture and 20% CK2, 21 MPa with the 70% phosphogypsum mixture and 30% CK2, or rather similar performances starting from a by-product and not from 'a manufactured product like plaster. Example 3 Durability Tests: Immersion Cycles - Drying For durability tests, mortars prepared with L4 and L6 binders containing CK1 and CK2 clinkers and phosphogypsum were tested after 7 and 28 days of hydration. The protocol was as follows: - casting prismatic specimens 4x4x16 cm; - demolding 1 day after pouring; - preservation in a sealed bag until expiry (j). Then, the test pieces were subjected to 25 cycles of immersion / drying of 24h: 1 cycle = 18 hours under water then 6 hours in an oven at 60 C. The immersion-drying cycles are intended to simulate the behavior of mortars in accelerated aging. Table 8 shows the results obtained before (0 cycle) and after 25 cycles of immersion - drying. The reference samples (0 cycles) were stored until the expiry date (d-1) in a sealed bag and were then overwritten at the expiry date (ie 7 or 28 days). For CK1 and CK2 clinkers, no drop in strength was observed after immersion-drying cycles. In fact, there is a fairly significant increase in resistance: from 17 to 37%. Table 8. Compressive strength of mortars prepared with phosphogypsum after immersion-drying cycles. Age of the Clinker Resistance Bond mortar at compression start (MPa) cycles 0 25 (Days) cycle cycles 7 5 5.9 4 28 6.1 7.3 CK1 7 13.7 17.7 6 28 17.4 20.3 7 7.8 10.3 4 28 9.6 11.8 CK2 7 18.3 24.5 6 28 The results obtained after the immersion-drying cycles confirm the good water resistance of the mortars made with a binder containing at least 20% of sulfo-aluminous clinker and phosphogypsum.

  The same tests were carried out on the mortars containing plaster. The results are collated in Table 9. Table 9. Compressive strengths after 28 days of immersion-drying Non-retarded mortars Binder Before After Loss immersion-immersion-drying drying resistance (%) 100% plaster 4.5 0 100 90 % plaster- 9 2.6 71 10% CK2 80% plaster- 14 7.3 48 20% CK2 70% plaster- 21.8 13.4 38.5 30% CK2 Delayed mortars Binder Before After Loss immersion- immersion- drying drying strength (%) 100% plaster 4,5 0.6 86.7 90% plaster- 9 2.4 73.3 10% CSA 80% plaster- 14 5.8 58.6 20% CSA 70% plaster- 21.8 12.2 44 30 % CSA In this case, a loss of resistance varying between 38 and 73% is noted. Here again, binders prepared with phosphogypsum show superior durability. This fact is undoubtedly in direct correspondence with the solubility in water of the different calcium sulphates (Table 10). Table 10. Solubility in water of calcium sulphates expressed as anhydrous CaSO4 (g / L) (Source: Calcium sulphates and derived materials. International Conference of RILEM, 1977, Editors: M. Murat and M. Foucault , p.538) Solubility Gypsum Phosphogypsum Hemihydrate Anhydrite Anhydrite R III II g / 1 2-2.5 3.5-4 8.9-9.5> 10 4 Example 4 Design of Building Materials Based on previous results ( water stability from a sulpho-aluminous clinker dosage greater than 20%), it was possible to formulate building materials: - building blocks B40 and laying mortar, - external coatings, - screed . 1. Building blocks B40. Blocks of dimensions 15x20x40 cm were formulated from binder 6 (70% phosphogypsum + 30% clinker CK2) and were manufactured industrially by vibro-compaction on an ADLER block press. Two types of blocks have been developed and compared to conventional blocks made from Portland cement. The compositions of the different mixes and the performances of the blocks are given in Table 11. All the blocks have been in a cure zone for 48 hours. Fifty blocks were made by wasting. Table 11. Building blocks: mix composition and performance. Components Indicator Type Type (kg) 1 2 Sand 0/5 400 400 400 Chippings 540 540 540 6/10 CPA 42.5 R 70 - Binder 6 - 100 120 Water 91 91 91 Weight 15.4 16.1 16.6 blocks (kg) Resistance to 5.4 6.4 7.1 7 days (MPa) Table 11 shows that it is possible to manufacture blocks of the same quality as the conventional blocks from binder 6.. Exterior coatings. The function of a coating is to protect a wall against the weather while remaining permeable to the water vapor contained in the air and to contribute to the aesthetics of the building. The DTU 26.1. Coatings with cement mortars, lime and mixtures of plaster and aerated lime - A list of technical clauses, gives rules concerning the materials to be used, the requirements with regard to the supports, the execution of the coatings and the characteristics of the coatings. finished coatings (flatness, hardness, appearance, adhesion, thickness). Chapter 5, Execution of masonry plasters for concrete blocks, bricks and earthenware blocks, gives the assays by bonding cementitious coatings with or without lime: 15 Sand / Cement / Water = 6.4 / 1 / 0.5 . Chapter 12, Coatings with Plaster and Air Lime Mortars, gives a higher binder dosage: Sand / Plaster + Lime / Water = 0.65 / 1 / 0.54. The performance of gypsum based commercial coatings is recapitulated in Table 12. Table 12. Characteristics of plaster coatings on the market. Brand Name Thickness DPU * Resistance Resistance (mm) (minutes) in flexion compression (MPa) (MPa) Weber Coated 2 to 10 45 to 60 FP7 Lanko Parbeton 2 to 10 120 15 4 4 1 112 Sider Sider 1 to 5 30 Oxydro nett Lanko Parilien Socket: 20 to 30 Fixit 120 Gips- 10 30 to 50 3 1.5 Grundputz * DPU = practical duration of use.

  In this study, the targeted performances were: - Compressive strength at 28 days: 10 MPa, - DPU: 60 minutes. Binders composed respectively of 80% phosphogypsum and 20% sulfo-aluminous clinker (CSA1) and 70% phosphogypsum and 30% sulfo-aluminous clinker (CSA2) were used for the preparation of coatings. Three coatings have been studied, their compositions and properties are given in Table 13. They all meet the imposed schedule of loads. The evolution of the shrinkage of the coatings (20 C, 50% RH) is given in FIG. 5. The higher dosage of Portland CPA cement in the plaster 3 causes initial swelling due to the formation of swelling ettringite (hydration of the CSA in the presence of lime released by the CPA).

Table 13. Compositions and properties of coatings. Components Coated Coated (kg / m3) 1 (CSA1) 2 (CSA2) 3 (CSA2) Sand 0/5 1350 1350 1350 Phosphogypsum 340 297 280 Clinker CK2 85 128 120 CPA 25 25 50 Self-extinguishing 0.8 0.8 1.6 Water 240 240 240 DPU 50 65 60 (minutes) Start of 70 70 155 intake (min.) Resistance in compression 11.4 20.3 20.9 (MPa) 23.5 30.1 30.1 24 hours 28 days Flexural strength (MPa) 24 hours 2.5 3.1 3.1 28 days 4.0 3.9 3.8 Withdrawal at 28 690 710 70 days (m / m) To observe their natural aging, these coatings were applied to one side of the wall built with the blocks described above (Figure 6). Then they were subjected to watering cycles for 2 hours a day. Coating 2 has been the easiest to implement and has the greatest uniformity. No crack is observed after 27 months of aging. 3. Screeds Two types of screeds were formulated from the CSA2 binder (70 ~ gypsum + 30% CK2 sulphoaluminous clinker): a traditional screed and a self-leveling screed. Their compositions and properties are given in Table 14. Table 14. Compositions and properties of screeds. Components (kg / m3) Screed Traditional self-leveling screed Sand 1350 1250 Bond CSA2 425 420 CPA 5 10 Filler limestone - 50 Self-extinguishing 0.8 - Water 240 260 Viscosity agent - 2 Anti-foam - 0.35 Anti-shrink - 5 Superplasticizer - 6 DPU (minutes ) 50 120 Start of setting 65 360 (minutes) Resistance in 15.2 8.3 compression (MPa) 20.4 8.8 24 hours 35.1 19.0 7 days 360 days Resistance in 3.2 0. 7 bending (MPa) 3.4 0.7 24 hours 7 days Retreat at 50 days 850 400 (m / m) Thus, it appears from these examples that from the binder 70% gypsum + 30% sulfo-aluminous clinker, it is possible to develop the following materials: - building blocks, s coated outside, -chapes. All these materials have improved performance compared to traditional materials on the market.

Claims (18)

  A process for the preparation of an anhydrous or non-water-resistant calcium sulphate-based composition, characterized in that said calcium sulphate is combined with a sulphoaluminous clinker, said sulphoaluminous clinker being present at from 20 to 40% by weight relative to the total weight of the composition and said sulfo-aluminous clinker comprising from 50% to 65% by weight of yeelimite relative to the weight of the sulfo-aluminous clinker. io   2. Method according to claim 1, characterized in that the calcium sulfate is selected from natural or synthetic gypsum, plaster, anhydrite and mixtures thereof.   3. Process according to claim 2, characterized in that the synthetic gypsum is chosen from sulphogypsum, phosphogypsum, titanogypsum, borogypsum, lactogypsum and their mixtures, and the anhydrite is chosen from fluoroanhydrite and phosphoanhydrite. , anhydrite III or a and mixtures thereof.   4. Process according to any one of claims 1 to 3, characterized in that the sulfo-aluminous clinker comprises from 60 to 65% by weight of yeelimite.   5. Method according to any one of claims 1 to 4, characterized in that the sulfo-aluminous clinker further contains belite and ferrite. 25   6. Process according to any one of claims 1 to 5, characterized in that the sulfo-aluminous clinker comprises from 50 to 65% of yeelimite, from 10 to 25% of belite, from 0 to 20% of ferrite, from 10% mayenite and 0 to 20% by weight of perovskite. 30   7. Process according to claim 6, characterized in that the sulfo-aluminous clinker comprises from 60 to 65% of yeelimite, from 10 to 20% of belite, from 0 to 15% of ferrite, from 0 to 8% of mayenite and from 7 to 18% by weight of perovskite.   8. Process according to any one of claims 1 to 7, characterized in that the sulfo-aluminous clinker is present at a level of 30% by weight of the total composition.   9. Hydraulic binder comprising a composition obtained by carrying out the method according to any one of claims 1 to 8.   The hydraulic binder of claim 9 further comprising an additive selected from Portland cement, limestone filler, fly ash, ground slag, polycarboxylate superplasticizers, setting retarders, viscosity agents selected from the group consisting of Welan gum, guar gum and xanthan gum, polyvinyl acid and surfactants.   11. Construction material characterized in that it contains a hydraulic binder according to claim 9 or 10.   12. Building material according to claim 11 characterized in that it consists of filling concrete, building blocks, laying mortar, exterior plaster, screeds or interior coatings. 20   13. Use of a sulphoaluminous clinker comprising from 50% to 65% by weight of yeelimite, to improve the water resistance of a composition containing between 60 and 80% anhydrous calcium sulphate or not.   14. The use as claimed in claim 13, characterized in that the calcium sulphate is chosen from natural or synthetic gypsum, plaster, anhydrite and their mixtures.   15. Use according to claim 14, characterized in that the synthetic gypsum is selected from sulfogypsum, phosphogypsum, titanogypsum, borogypsum, lactogypsum and mixtures thereof, and the anhydrite is selected from fluoroanhydrite, phosphoanhydrite , anhydrite III or a and mixtures thereof.   16. Use according to any one of claims 13 to 15, characterized in that the sulfo-aluminous clinker comprises from 60 to 65% by weight of yeelimite.   17. Use according to any one of claims 13 to 16, characterized in that the clinkersulfo-aluminous further contains belite and ferrite.   18. Use according to any one of claims 13 to 17, characterized in that the composition contains 70% anhydrous calcium sulfate or not.