FR2868772A1 - Calcium sulfate based composition incorporating sulfo-aluminous clinker for the preparation of a hydraulic binder for the subsequent preparation of concrete based construction materials - Google Patents

Abstract

Calcium sulfate based composition incorporates 20 to 60 % by weight of a sulfo-aluminous clinker. The clinker includes at least 50 % by weight of yeelimite : Independent claims are also included for : (a) a hydraulic binder made from this composition; (b) a construction material using this composition.

Description

The present invention relates to a novel hydraulic binder based on

  anhydrous or non-anhydrous calcium sulphate possessing remarkable moisture resistance properties while benefiting from good mechanical strength, as well as its

  manufacturing process. It also relates to building materials obtainable from said new hydraulic binder.

  PRIOR ART 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.

  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 that consist of adding water repellents.

  US Pat. No. 6,547,874 for example describes a technique consisting in 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.

  No. 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) 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.

  It will be noted that in the field of sulfo-aluminous cements, quite distinct from that of the invention, there are certain cements which sometimes contain calcium sulphate; the calcium sulphate content then varies between 15 and 25% by weight relative to the total weight of the cement, which is in proportions that are far apart or even the same as those provided by the compositions of the present invention.

  The present invention relates to a composition based on anhydrous or non-anhydrous calcium sulphate, consisting of a combination of said calcium sulphate and a sulpho-aluminous clinker, characterized in that the clinker is present at from 20 to 60% by weight relative to the total weight of the composition and in that the sulfo-aluminous clinker comprises at least 50% by weight of yeelimite relative to the weight of the sulfo-aluminous clinker. This addition of sulfoaluminous clinker in these proportions makes it possible to improve, surprisingly, the moisture resistance properties of calcium sulphate.

  The invention also relates to the hydraulic binder prepared from this composition and the use thereof for the manufacture of construction materials and said building materials.

  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 of greater than 55%: 30 to 40% - calcium carbonate (limestone): 45 to 50%, - calcium sulphate (gypsum): 16 to 18% The sulpho-aluminous clinker is then formed of the following main phases: o yeelimite or kleinite, o belite, o ferrite, o perovskite and o o mayenite; Hydraulic binder means finely ground mineral matter forming, by the addition of water in appropriate quantity, a binder paste which can harden even under water and bind granular materials together; - calcium sulphate means both natural gypsum, ie calcium sulphate bihydrate or synthetic sulphogypsum, phosphogypsum, titanogypsum, borogypsum, lactogypsum and other types of by-products of the same type and 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 sulphate, or anhydrite, may be the calcium sulphate at the base of the composition according to the present invention. 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 their mixtures. Of course, the mixtures of these different types of calcium sulphate in their anhydrous or hydrated forms, are capable of being used in a composition 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.

  Ettringite is formed by hydration simultaneously with the addition of a source of calcium sulfate. The hydraulic binder is then obtained.

  The hydration equations are written in this case: 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 + ettringite water where C = CaO, A = Al2O3i = SO3r H = H2O, according to the cement notation.

  The sulfo-aluminous clinker comprising at least 50% of yeelimite (4 CaO 3 Al 2 O 3, SO 3) which is used to obtain the compositions of the invention may further contain belite (2 CaO.SiO 2) and ferro calcium aluminate or ferrite phase (4 CaO.Al2O3, Fe2O3). Thus, the sulfoaluminous clinker used in the composition according to the present invention preferably comprises from 50 to 80% 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 composition according to the present invention comprises from 60 to 75% of yeelimite, from 10 to 20% of belite, from 0 to 15% of ferrite, from 0 to 8% of mayenite and 7 to 18% by weight of perovskite.

  Variations in the relative amounts of the various constituents make it possible to obtain a whole range of construction materials whose properties, in particular of compressive strength, can be modulated.

  According to a preferred embodiment of the invention, the clinker is present at 25 to 50% by weight of the total weight of the composition.

  The compositions according to the present invention may be obtained by mixing the various constituents according to conventional techniques known to those skilled in the art. This manufacture does not require any specific tools, which highlights another advantage of the present invention.

  The manufacture of the composition according to the present invention (calcium sulphate + sulpho-aluminous clinker) can be carried out at ambient temperature in any type of mixer usually used for mixing powders such as: - the screw mixer, - the train mixer waltzer, turban mixer and, - turbine mixer.

  In addition, the invention relates to the use of the composition of the invention for the preparation of hydraulic binder as well as the hydraulic binders that can be obtained from the compositions 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, calcareous filler, fly ash, ground slag, setting retarders (boric acid), agents viscosity (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 sulfo-aluminous clinker in the contents described above, the hydraulic binder according to the present invention shows water-resistant qualities that make it possible to use it in humid areas, while retaining its properties. qualities of compressive strength 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 to obtain building materials according to the usual techniques known to those skilled in the art.

  For example, for the manufacture of blocks from the hydraulic binder according to the present invention, the manufacturing process usually consists of the following successive stages: - mixing for 1 to 2 minutes in a mixer: - sand and gravel, - the pre-mixed hydraulic binder or not, - water, - pour the assembly into a buffer hopper located above a block press and finally, fill the molds of this press and subject them to vibro-compaction for get blocks.

  All these operations are done at room temperature.

  Therefore, the invention also relates to the use of the hydraulic binder according to the invention for the preparation of a construction material, as well as said 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 examples and figures which follow illustrate the present invention, without limiting it.

  FIG. 1 is a representation relating to example 1 of the underwater conservation 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 is a representation relating to Example 1 of FIG. CK3 clinker underwater storage, FIG. 6 is a representation relating to example 1 of the sealed bag storage of clinker CK3, FIG. 7 is a representation relating to example 2 of immersion-drying cycles. Figure 8 is a representation relating to Example 2 of the immersion-drying cycles of clinker CK2. Figure 9 is a representation relating to Example 3 on the strength of concretes.

Example 1

  Tests on the proportion of clinker in phosphogypsum Three types of clinkers were studied: CK1, CK2 and CK3. Their compositions are given in Table 1.

Table 1.

  Phases of clinkers used Phase CK1 CK2 CK3 Belite - C2S 17.2 15.6 12, 5 Yeelimite - C4A3E 60.9 66.4 70.4 Mayenite - C12A7 - 7, 1 - Perovskite C3FT2 7.9 9.9 17, 1 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 water stability and develop sufficient strengths to consider the manufacture of building materials. This approach is used for the evaluation of conventional hydraulic binders.

  Six binders were prepared with clinker CK1. Their references and compositions are given in Table 2.

Table 2.

  References and compositions of binders CK1 Binder% gypsum% clinker 1 95 5 2 90 10 3 85 15 4 80 20 75 25 6 70 30 The study with clinkers CK2 and CK3 concerned three binders: 2, 4 and 6 (Table 2). 3).

Table 3.

  References and compositions of the binders CK2 and CK3 Binder% gypsum% clinker 2 90 10 4 80 20 6 70 30 The composition of the standardized mortar is given below: - standardized sand: 1350 g, - binder 450 g, - water 225 g.

  The compressive strengths were measured at 24 hours, 7, 28 and 90 days on 4 x 4 x 16 cm prism halves. For the periods 7, 28 and 90 days, two methods of preserving the specimens were compared: in a sealed bag: the specimens are demolded 48 hours after their manufacture and then kept in a sealed bag at 20 C until the expiry date. -1), then at 20 C and 50% relative humidity until the expiry of the test.

  under water: the test pieces 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 of the test.

  The compressive 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 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 the 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 resistance. 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 resistance 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 the binders 4 and 6, it is observed that the samples stored under water have greater strengths. The resistances obtained with clinker CK3 are given in FIGS. 5 (underwater storage) and 6 (sealed bag storage).

  For binders prepared with clinker CK3 there is not much difference between the two types of preservation. On the other hand, the increase in resistance is different. For all binders, the increase in resistance is greater at the beginning (up to 7 days). However, for the binder 4 under water and the binder 6 in a sealed bag, it can be seen that the increase between 7 and 90 days. is done the same way. For the binder 6, storage under water, and for the binder 4, storage in a sealed bag, the resistance increase is not done in the same way: it grows faster between 7 and 28 days than between 28 and 90 days .

  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

  Durability tests: immersion cycles - drying For durability tests, mortars prepared with L4 and L6 binders containing CK1 and CK2 clinkers 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 specimens were subjected to 25 cycles of immersion / drying of 24 hours: 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.

  Figure 7 shows the results obtained before (0 cycle) and after 25 cycles of immersion - drying. The reference specimens (0 cycles) were kept to the expiration date (d-1) in a sealed bag and then were crushed at the end of the day (ie 7 or 28 days).

  For clinker CK1, no drop in strength was observed after the immersion - drying cycles. In fact, there is a fairly significant increase in resistance: from 16 to 83% (Table 4).

  Table 4. Resistance Indices - Clinker CK1 Binder Timeout Cycles Rc (MPa) Index: (Days) Rc25 / RCO 0 4.9 7 1.20 L4 25 5.9 0 4.0 28 1.83 7.3 0 12 , 8 7 1.38 L6 25 17.7 0 16.6 28 1.16 19.3 For the clinker CK2 (Figure 8: immersion cycles - drying), the mortar made with the weakest binder (L4) undergoes a slight drop in strength (11.75 MPa against 12.70 MPa) when subjected to immersion cycles - drying after 28 days of storage in a sealed bag. For the mortar containing the binder 6, the resistance increases after 28 days and the drying immersion cycles improve its behavior (Table 5).

  Table 5. Resistance Indices - Clinker CK2 Binder Timeout Cycles Rc (MPa) Index: (Days) Rc25 / RC0 0 8, 471 1, 35 L4 25 11.3 0 11, 8 28 25 12.7 1.08 0 The results obtained after the immersion-drying cycles confirm the good water resistance of the mortars prepared with a binder containing at least 20% sulphoaluminous clinker.

Example 3

  DESIGN OF BUILDING MATERIALS

  Construction materials have been formulated, which are described below, including fill concrete, and building blocks B40.

1. Filling concrete.

  The best-performing binder (L6) was chosen to make the concrete. The clinkers used were clinkers CK1 and CK2. Resistance to compression was measured at 7 and 28 days.

  A composition at 300 kg / m 3 of L6 binder was tested with the addition of a superplasticizer, namely the liquid polycarboxylate at 30% solids, in order to improve the workability of the fresh concrete without increasing the quantity of water, which does not affect the resistance. Table 6 gives the composition of the tested concrete.

Table 6. Concrete composition.

  Material Quantities (kg / m3) Gypsum 210 Clinker 90 Sand 0/5 820 Aggregates 5/12 1000 Water 200 Superplasticizer 0.6 It can be seen in Figure 9, which represents the strength of concretes, that concrete prepared with clinker CK2 is significantly better than the one prepared with clinker CK1.

  The progressive increase of the strength of the concrete prepared with CK1 is well observed, whereas the concrete prepared with clinker CK2 reaches, from 7 days, a suitable resistance, almost the same as at 28 days.

  The results presented above confirm the difference in behavior between clinkers CK1 and CK2 found during the standardized mortar study. However, it is here much more marked.

2. Building blocks B40.

  The blocks of dimensions 15x20x40 cm were formulated from the binder 6 (70% gypsum + 30% clinker CK2) and were manufactured industrially by vibro-compaction on a block press ADLER. 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 7. All the blocks have been in a cure zone for 48 hours.

  Fifty blocks were made by spoiling.

Table 7.

  Building blocks: mix composition and performance Components (kg) Indicator Type 1 Type 2 Sand 0/5 400 400 400 Chippings 6/10 540 540 540 CPA 42.5 R 70 - - Binder 6 - 100 120 Water 91 91 91 Block weight (kg) 15.4 16.1 16.6 Resistance to 7 days (MPa) 5.4 6.4 7.1 Table 7 shows that it is possible to manufacture breeze blocks of the same quality as conventional breeze blocks. binder 6.

Claims (15)

  1. Composition based on calcium sulphate anhydrous or not consisting of a combination of said calcium sulphate with a sulpho-aluminous clinker, characterized in that the clinker is present at a level of 20 to 60% by weight relative to the total weight of the composition and in that the sulfoaluminous clinker comprises at least 50% by weight of yeelimite relative to the weight of the sulfo-aluminous clinker.   2. Composition according to claim 1, characterized in that the calcium sulfate is selected from natural or synthetic gypsum, plaster, anhydrite and mixtures thereof.   3. Composition according to claim 2, 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.   4. Composition according to any one of claims 1 to 3, characterized in that the sulfo-aluminous clinker comprises 50 to 80% by weight of yeelimite.   5. Composition according to any one of claims 1 to 4, characterized in that the sulfo-aluminous clinker further contains belite and ferrite.   6. Composition according to any one of claims 1 to 5, characterized in that the sulfo-aluminous clinker comprises from 50 to 80% of yeelimite, from 10 to 25% of belite, from 0 to 20% of ferrite, from 0 to 10% of mayenite and from 0 to 20% by weight of perovskite.   7. Composition according to Claim 6, characterized in that the sulfo-aluminous clinker comprises from 60 to 75% 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. Composition according to any one of claims 1 to 7, characterized in that the sulfo-aluminous clinker is present at 25 to 50% by weight of the total composition.   9. Use of the composition according to any one of claims 1 to 8 for the preparation of hydraulic binder.   Hydraulic binder comprising a composition according to any one of claims 1 to 8.   11. hydraulic binder according to claim 10 further comprising an additive selected from Portland cement, limestone filler, fly ash, crushed slag, polycarboxylate superplasticizers, setting retarders, viscosity agents taken from the gum Welan, guar gum and xanthan gum, polyvinyl acid and surfactants.   12. Use of the hydraulic binder according to claim 10 or 11 for the preparation of a construction material.   13. Use according to claim 12, characterized in that the building material is selected from filling concrete, building blocks, laying mortar, exterior plaster, screeds and interior coatings.   14. Construction material characterized in that it contains a hydraulic binder according to claim 10 or 11.   15. Building material according to claim 14 characterized in that it consists of filling concrete, building blocks, laying mortar, exterior plaster, screeds or interior coatings.