EP3947316A1

EP3947316A1 - Hydraulic binder composition

Info

Publication number: EP3947316A1
Application number: EP20714635.8A
Authority: EP
Inventors: Jérémy BECQUET
Original assignee: Bostik SA
Current assignee: Bostik SA
Priority date: 2019-04-03
Filing date: 2020-04-02
Publication date: 2022-02-09
Also published as: US20220204405A1; FR3094712A1; WO2020201436A1; FR3094712B1

Abstract

The present invention relates to a hydraulic binder composition comprising: - at least one Portland cement; - at least one amorphous calcium aluminate; - calcium sulphate; - at least one alkaline salt S selected from K₂CO₃, Rb₂CO₃, Cs₂CO₃ and mixtures thereof; the composition being characterised in that the mass ratio of alkaline salt(s) S to amorphous calcium aluminate(s) ranges from 0.01 to 0.2.

Description

COMPOSITION OF HYDRAULIC BINDER

FIELD OF THE INVENTION

The present invention relates to a hydraulic binder composition.

The invention also relates to the use of the hydraulic binder composition for preparing mortars or concretes.

TECHNOLOGICAL BACKGROUND

Hydraulic binders are typically made up essentially of mineral compounds and are characterized by their ability to set and harden irreversibly when brought into contact with water.

Calcium aluminates are one of the main constituents of aluminous cements commonly used to manufacture binders, concretes or mortars. In particular, there are two types of aluminous cements: crystalline calcium aluminate cements and amorphous calcium aluminate cements.

Calcium aluminate cements are well known for their rapid reaction with calcium sulphates and the formation of ettringite. Ettringite allows rapid water consumption allowing rapid hardening and build-up of mortars. In addition, ettringite is expansive, advantageously compensating for shrinkage of mortars. The formation of ettringite results in particular from nucleation and growth from species present in solution. The chemical reaction of ettringite formation is as follows:

[Chem 1]

6Ca ²⁺ + 2 Al (OH) + 40 + 3 SO + 26H ₂ 0 - Ca ₆ [Âl (0H) ₆ } ₂ 3S0 ₄ .26H ₂ 0

The use of amorphous aluminous cement leads to a rapid rise in the concentration of calcium ions due to their better dissolution in water compared to crystallized aluminous cements. However, this saturation with calcium ions causes late formation of ettringite which can lead to post-hardening swelling of the product which can lead to the appearance of cracks and its destruction.

There is therefore a need for novel hydraulic binder compositions which avoids, at least in part, at least one of the above-mentioned drawbacks.

More particularly, there is a need for novel hydraulic binder compositions which make it possible to avoid or reduce post-hardening swelling while maintaining good mechanical properties of the mortar or concrete obtained.

DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic binder composition comprising:

- at least one Portland cement;

- at least one amorphous calcium aluminate;

- calcium sulphate;

- at least one alkaline salt S chosen from K2CO3, Rb2CC> 3, CS2CO3 and mixtures thereof;

said composition being characterized in that the mass ratio of alkali salt (s) S: amorphous calcium aluminate (s) ranges from 0.01 to 0.2.

In the context of the invention, the term “hydraulic binder” is understood to mean a finely ground mineral material which, mixed with water, forms a paste which sets and hardens as a result of the reaction and the hydration process and which , after hardening, retains its strength and stability even under water (standard NF EN 197-1 of April 2012).

The hydraulic binder composition according to the invention has at least one of the following advantages:

- makes it possible to reduce or avoid the post-hardening swelling (or expansion) of the mortars or concretes obtained;

- allows rapid hardening and drying;

- allows users to quickly use the mortar or wet concrete prepared by mixing the mortar or dry concrete composition with water, especially in less than 5 minutes, preferably 2 to 5 minutes. Such an advantage is interesting in the preparation of a leveling compound, for example;

- reduces or even prevents the formation of lumps during the mixing with water step, thus limiting the formation of visual defects which can be prohibitive for customers in the field of floor coatings;

- good mechanical properties in compression.

Hydraulic binder composition

According to a preferred embodiment, the binder composition is characterized in that the mass ratio of alkali salt (s) S: amorphous calcium aluminate (s) ranges from 0.01 to 0.1, advantageously from 0, 02 to 0.06, even more advantageously from 0.03 to 0.05, for example said mass ratio is approximately 0.04.

The mass content of alkali metal salt (s) in the composition can range from 0.1% to 0.8% by weight, preferably from 0.15% to 0.7% by weight, and advantageously from 0.20% at 0.65% by weight relative to the total weight of the composition.

Preferably, the alkali salt S is K2CO3. Calcium sulfate can be chosen from anhydrous (or anhydrite) calcium sulfate (generally denoted anhydrous CaSCL), calcium sulfate dihydrate (or gypsum) (CaSC> ₄ .2H ₂ 0), calcium sulfate hemihydrate (hemi hydrate or bassanite), and mixtures thereof.

Calcium sulfate can be natural or synthetic.

Calcium sulphate can be in the form of a powder with a median diameter d50 varying from 3 to 50 micrometers, preferably from 3 to 20 micrometers.

The term “median diameter d50” is understood to mean a diameter such that 50% of the particles by weight have a size smaller than said diameter.

The particle size analysis of the average diameter d50 of calcium sulfate particles can be performed by laser particle size analysis.

Preferably, the calcium sulfate which can be used according to the invention comprises at least 90% by weight, and more preferably at least 95% by weight of anhydrous calcium sulfate relative to the weight of calcium sulfate. Even more preferably, the calcium sulfate is anhydrous calcium sulfate (anhydrite).

The mass content of calcium sulphate in the composition can range from 1% to 30% by weight, preferably from 5% to 25% by weight, even more preferably from 10% to 22% by weight, and advantageously from 15% to 20% by weight relative to the total weight of the composition.

In the context of the invention, and unless otherwise specified, the term “amorphous calcium aluminate” means a calcium aluminate comprising a rate of at least 60% of amorphous phase and therefore a degree of crystallization less than or equal to 40% of crystalline phase. Preferably, the amorphous calcium aluminate comprises a level of at least 65% of amorphous phase, even more preferably at least 70%, even preferably at least 75%, advantageously at least 80%, and even more advantageously at least 85%. Even more preferably, the calcium aluminate comprises a level of at least 90%, and advantageously of at least 95%, or even a level of at least 98% of amorphous phase.

The total mass content of amorphous calcium aluminate (s) in the composition can range from 0.1% to 50% by weight, preferably from 0.5% to 20% by weight, preferably from 0.5 at 10% by weight, preferably from 0.5 to 8% by weight, and even more preferably from 1% to 6% by weight relative to the total weight of the composition.

The crystalline phases present in amorphous calcium aluminate can be Ca0.AI ₂ 0 ₃ , Ca0.2AI ₂ 0 ₃ , 3Ca0.AI ₂ 0 ₃ , 1 1Ca0.7AI ₂ 0 ₃ .CaF ₂ , 12Ca0.7AI ₂ 0 ₃ or

3Ca0.3AI ₂ 0 ₃ + CaSC> ₄ or a mixture thereof.

Preferably, the calcium aluminate comprises by mass relative to its total mass: - from 30% to 60%, advantageously from 40% to 55% by mass of calcium oxide CaO (C);

- from 20% to 50%, advantageously from 30% to 50% by mass of alumina Al ₂ O ₃ (A);

- from 1% to 10% by mass of silica S1O2;

- from 0.05% to 8% by mass of iron oxide Fe2C> 3.

Preferably, the C / A molar ratio of calcium aluminate ranges from 0.6 to 3, preferably from 1 to 2.

The calcium aluminate may comprise other compound (s) in a content ranging from 0% to 5% by weight relative to the total weight of the calcium aluminate, such as for example of l titanium oxide ( ^" PO2) or magnesia (MgO).

Calcium aluminate may have a Blaine specific surface measured according to standard NF EN196-6 ranging from 2000 to 8000 cm ² / g, preferably from 3000 to 7000 cm ² / g.

In the context of the invention, the term “Blaine specific surface area” denotes the specific surface area of a pulverulent solid compound, expressed in cm ² per gram of solid, measured by the air permeability method (or Blaine method ) described in standard NF EN 196-6 of April 2012.

Calcium aluminate can be obtained chemically, for example by a smelting process followed by a rapid cooling process. A process for preparing amorphous calcium aluminate is for example described in FR 3 021 046.

There are also commercially available calcium aluminates.

The hydraulic binder composition can comprise one or more crystalline calcium aluminate (s). Crystalline calcium aluminates have been known for a long time and are typically obtained by a smelting process followed by slow cooling or by sintering.

They are for example described by Kopanda et al. in the publication "Production Processes, Properties and applications for calcium aluminate cements", Alumina Chemicals Science and Technology Handbook, American Ceramic Society (1990), pp 171-181.

Various products containing crystalline calcium aluminates are commercially available. Mention may, for example, be made of Ciment Fondu® from the company Kerneos, or Secar®51 from the company Kerneos.

The term “Portland cement” denotes indifferently any mixing cement as defined in standard EN 197-1: 2000, such as Portland cement mixtures or pozzolanic mixing cements which may comprise, alone or in combination, fly ash, blast furnace slag, as well as natural or calcined pozzolans, metakaolin and limestone fillers.

Portland cement can be chosen from Portland CEM I cements, Portland CEM II cements, Portland CEM III cements, Portland CEM IV cements, Portland CEM V cements, and mixtures thereof. Portland CEM I to CEM V cements are defined in particular by standard EN 197-1: 2000. Portland cement can include:

- at least the following crystallized mineralogical phases:

- tricalcium silicates and dicalcium silicate (3CaO.SiC> 2 and 2CaO.SiC> 2 - denoted respectively C3S and C2S);

- tetracalcium ferroaluminate (AI ₂ O ₃ .Fe ₂ O ₃ .4CaO - denoted C ₄ AF);

- and possibly tricalcium aluminate (Al203.3Ca0 - denoted C3A);

in contents such that the crystallized C2S and C3S mineralogical phases represent at least two thirds of the weight of the weight of Portland cement;

- and possibly magnesium oxide (MgO).

According to one embodiment, the Portland cement contains blast furnace slag or fly ash.

Preferably, the Portland cement is Portland cement OEM I 52.5 N, Portland cement OEM I 52.5 R, Portland cement OEM I 42.5 R or Portland cement OEM I 42.5 N.

The total content of Portland cement (s) in the hydraulic binder composition can vary from 10% to 80% by weight, preferably from 40% to 75% by weight, and advantageously from 60% to 75% by weight relative to the total weight of the hydraulic binder composition.

The hydraulic binder composition is typically in the form of a powder, and can be obtained by simply mixing the ingredients.

Preferably, the hydraulic binder composition is devoid of agents capable of forming foam (foaming agents). Examples of such agents can be oxidants such as percarbonate salts, persulfate salts, perborate salts, permanganate salts, peroxides, and aluminum powder. The presence of such compounds is not desired in hydraulic binder compositions which make it possible to reduce or prevent post-hardening swelling of the mortar or concrete obtained.

According to some preferred embodiments, the hydraulic binder composition consists of:

- at least one Portland cement;

- at least one amorphous calcium aluminate;

- calcium sulphate;

- at least one alkaline salt S chosen from K2CO3, Rb2CC> 3, CS2CO3 and mixtures thereof; said composition being characterized in that the mass ratio of alkali salt (s) S: amorphous calcium aluminate (s) ranges from 0.01 to 0.2.

Composition of dry mortar or concrete

The present invention also relates to a composition of dry mortar or concrete comprising:

the composition of hydraulic binder as defined above; and

- at least one aggregate.

The aggregate can be selected from gravels, chippings, sand, calcium carbonate, dolomite, recycled glass, and mixtures thereof.

Preferably, the aggregate is selected from sand, calcium carbonate, and mixtures thereof.

The content of aggregate (s) in the mortar or dry concrete composition can range from 15% to 80% by weight, preferably from 30% to 80% by weight, preferably from 50% to 80% by weight relative to the total weight of said composition.

The composition of dry mortar or concrete may include at least one additive.

The additives can be selected from the group consisting of setting accelerators, setting retarders, antifoaming agents, water repellents, antiaging agents, rheological agents, and mixtures thereof.

These additives are known to those skilled in the art, and their proportion can be adapted by those skilled in the art.

Examples of setting accelerators are sodium aluminate, sodium silicate, potassium aluminate, aluminum sulfate, lithium sulfate and lithium hydroxide.

Examples of setting retarders are tartaric acid, citric acid and / or boric acid.

Among the rheological agents, there may be mentioned, for example, cellulose ethers, guar ethers, starch ethers, associative polymers, xanthan gums, wellane gums, and mixtures thereof.

The composition of dry mortar or concrete may comprise one or more polymer (s).

The polymer may be in the form of a powder which can be redispersed in water or as a solid-liquid dispersion in water (i.e., in the form of an aqueous dispersion of polymer).

In the case where the polymer is in the form of a powder dispersible in water, it is preferably chosen from the copolymers of vinyl acetate, vinyl versatates and ethylene, and polyvinyl alcohols. Such polymers are for example commercially available from the companies Wacker, Hexion or Elotex.

By way of example, we can for example quote:

- polymers of vinyl acetate, vinyl versatate and maleic ester, available in powder form under the name Axilat® UP 620E (Hexion);

- polymers of vinyl acetate, vinyl versatate and ethylene, available in powder form under the name Elotex® FL3200 or FX3300 (Elotex).

In the case where the polymer is in the form of a solid-liquid dispersion in water, it is preferably chosen from styrene-butadiene, styrene-acrylic, styrene-acrylate, acrylic and vinyl acetate aqueous dispersions. Such dispersions are commercially available from the companies Rohm & Haas, BASF and Synthomer.

Preferably, the composition of dry mortar or concrete comprises:

- from 15% to 80% by weight of the binder composition as defined above; and

- from 15% to 80% by weight of aggregate (s);

- from 0% to 5% by weight of additive (s);

- from 0% to 10% by weight of polymer (s);

the percentages by weight being relative to the total weight of the composition of dry mortar or concrete.

The composition of dry mortar or concrete may comprise a total mass content of amorphous calcium aluminate (s), as defined above, ranging from 0.5% to 20% by weight , preferably from 1% to 15% by weight, even more preferably from 2% to 10% by weight relative to the total weight of the composition of dry mortar or concrete. In particular, the composition of dry mortar or concrete comprises from 2% to 5% by weight of amorphous calcium aluminate (s) relative to the total weight of said composition.

The total mass content of calcium sulphate, as defined above, in the composition of dry mortar or concrete may range from 1% to 30% by weight, preferably from 2% to 20% by weight, and advantageously from 3% to 15% by weight relative to the total weight of said composition.

The total mass content of alkaline salt (s) S, as defined above, in the dry mortar or concrete composition can range from 0.05% to 0.30% by weight, preferably from 0.10% at 0.20% by weight, and advantageously from 0.12% to 0.18% by weight relative to the total weight of said composition.

Typically, mortars are distinguished from concrete on the basis of the size of the aggregates. For example, in mortars, the aggregates have a relatively small average diameter, for example smaller than that of gravel. On the contrary, concrete typically include aggregates with a larger average diameter, it may for example be gravel or chippings.

Preferably, the dry mortar or concrete composition is a dry mortar composition.

Composition of wet mortar or concrete

The present invention also relates to a wet mortar or wet concrete composition obtained by mixing the dry mortar or concrete composition as defined above with water, the amount of water being such that the water / solids ratio is preferably from 0.12 to 0.40, and even more preferably from 0.16 to 0.28.

The wet mortar composition can be a smoothing mortar composition (for example a floor coating such as for example a self-leveling or self-leveling coating for floors), a fixing mortar composition (in particular adhesive mortar), a composition of jointing mortar, a composition of repair or filling mortar.

use

The present application relates to the use of the composition of mortar or wet concrete for leveling and smoothing floors, for making leveling work, screed, for leveling floors, for repairing structures in concrete, for sealing elements, for gluing or jointing tiles.

The present invention also relates to the use of at least one alkaline salt S chosen from K2CO3, Rb2CC> 3, CS2CO3 and their mixtures, in a mortar or dry concrete composition comprising at least one amorphous calcium aluminate, as an agent. anti swelling.

The characteristics of the composition of the mortar or dry concrete detailed as well as the various embodiments apply to the above-mentioned use.

In the context of the invention, by "between x and y", or "ranging from x to y", is meant an interval in which the limits x and y are included. For example, the range “between 0% and 25%” notably includes the values 0% and 25%.

The invention is now described in the following embodiments which are given purely by way of illustration, and should not be interpreted in order to limit their scope.

EXAMPLES

The following ingredients were used: - K ₂ CO ₃ : potassium carbonate from Sigma Aldrich with a purity of 99.995%;

- OPC 52.5 R: Portland cement CEM I 52.5 R CE CP2 NF, marketed by CALCIA (Couvrot) with the following mineralogical composition:

[Table 1]

- PP222: Amorphous aluminous cement (70%) mixed with calcium sulphate (anhydrite) sold by KERNEOS;

- VINNAPAS® 5025 L: Redispersible polymer powder - copolymer of vinyl acetate and ethylene;

- Casufill A5: natural anhydrite marketed by CASEA, with a D50 of around 5 mhi;

- PE2LS: sand marketed by FULCHIRON INDUSTRIELLE SAS;

- S4: crystalline ground silica having a Blaine specific surface of 1500 to 2000 cm ² / g marketed by FULCHIRON INDUSTRIELLE SAS (D50 between 40 mhi and 50 mhi); - DC8: pure natural crystalline calcium carbonate, from DEROMEDI CARRIERES;

- Tartaric acid L E4: tartaric acid marketed by ALTICHEM, having a purity of between 96% and 98%, and a particle size of approximately 63 mhi;

- Melflux® VP2631 F: superplasticizer marketed by BASF (modified polycarboxylic ether); - Agitan® P840: combination of polyglycols on an inorganic support marketed by

MUNZING; - Tylose® H 300 P2 thickener marketed by SE Tylose GmbH & Co (hydroxyethylcellulose).

Example 1 Preparation of Dry Mortar Compositions Mortar compositions 1 to 4 were prepared by mixing the ingredients at room temperature for approximately 120 seconds, in the proportions by weight given in the following table:

[Table 2]

Example 2: preparation of wet mortar compositions

The wet mortar compositions 5, 6, 7 and 8 were prepared from the dry mortar compositions according to Example 1.

The mixing rate used is 24%, ie 100 g of powder (dry mortar composition) are poured into 24 g of water.

The paste is obtained by mechanical mixing using a mixer as described in standard NF EN 1937 of April 2012 by proceeding as follows: 2 kg of powder are kneaded in water for 1 minute at slow speed then the wall of the container as well as the mixer are scraped using a spatula to possibly detach the agglomerated powder, again, the dough is kneaded for 1 minute at slow speed.

The dough is then ready for use (time T = 0).

[Table 3]

Example 3: results

3.1. Lumps observations

The wet mortar compositions obtained in Example 2 were each spread (50g) on a glass plate of dimensions 30 cm x 30 cm.

The presence or absence of lumps was observed visually.

The results are shown in the following table:

[Table 4]

Compositions 5, 6 and 7 (invention) advantageously lead to mortars having no lumps. This advantageously makes it possible to avoid visual defects which can be prohibitive for customers in the field of floor coatings in particular.

In contrast, composition 8 results in a mortar comprising lumps, which is not acceptable to customers.

3.2. Measurement of compressive and flexural strength Preparation of specimens

The wet composition obtained in Example 2 (T = 0) is transferred into the mold (lightly oiled or greased), using a spatula in order to press it against the walls and corners of the mold. In order to remove any air bubbles, the mold was raised approximately 1 cm and released. The operation was repeated 5 times on each end.

After the prism was finished, the excess plaster was leveled off with a plaster knife. 3 strips of 4 * 4 * 16 cm (in polystyrene) were prepared. After 24 hours of storage at 23 ° C and 50% RH, the prisms were removed from the mold and stored for 28 days at 23 ° C and 50% RH.

Determination of flexural strength at 28 days:

The strips were placed on the support rollers of the bending device and the charging roller was applied using the compression testing machine after the start of the application of the load.

An average of the results obtained was made.

[Table 5]

Determination of compressive strength:

The compressive strength was determined by applying a load to the broken portion of the bar which was used to determine the flexural strength.

The specimen was placed between the steel plates, so that the faces of the prism that stuck to the walls of the mold were in contact with the plates over a section of 40 x 40 mm. The top plate was allowed to tilt until contact between the specimen and the plate was perfect. The load was applied until the specimen failed.

[Table 6]

3.3. Dimensional variation

The test is carried out on 3 specimens measuring 4 x 4 x 16 cm fitted with measuring devices at the ends. An average was made.

Before demolding, the molds were stored at 23 ° C. and 50% H. R As soon as they were removed from the mold, the distance between the ends was determined and the test pieces were weighed. The test pieces were stored on the edge in an environment of (23 ± 2) ° C and (50 ± 5)% RH. The measurements are carried out at the following times: demoulding at 24 hours and measurements at 28 days after casting of the specimens.

The results are presented in the following table:

[Table 7]

The mortar composition 5 advantageously results in a mortar having a shrinkage limited to 28 days (-525 pm / m).

Claims

1. A hydraulic binder composition comprising:

- at least one Portland cement;

- at least one amorphous calcium aluminate;

- calcium sulphate;

2. Composition according to claim 1, characterized in that the mass ratio of alkaline salt (s) S: amorphous calcium aluminate (s) ranges from 0.01 to 0.2, preferably from 0.02 to 0, 06, advantageously from 0.03 to 0.05, for example said mass ratio is approximately 0.04.

3. Composition according to any one of claims 1 to 2, characterized in that the mass content of alkaline salt (s) S in the composition ranges from 0.1% to 0.8% by weight, preferably 0, 15% to 0.7% by weight, and advantageously from 0.20% to 0.65% by weight relative to the total weight of the composition.

4. Composition according to any one of claims 1 to 3, characterized in that the alkali salt S is K2CO3.

5. Composition according to any one of claims 1 to 4, characterized in that the calcium sulfate is chosen from anhydrous calcium sulfate (or anhydrite) (generally denoted anhydrous CaSCU), calcium sulfate dihydrate (or gypsum) (CaSC> ₄ .2H ₂ 0), calcium sulfate hemihydrate (hemihydrate or bassanite), and mixtures thereof, the calcium sulfate preferably being anhydrous calcium sulfate.

6. Composition according to any one of claims 1 to 5, characterized in that the weight content of calcium sulfate in the composition ranges from 1% to 30% by weight, preferably from 5% to 25% by weight, again more preferably from 10% to 22% by weight, and advantageously from 15% to 20% by weight relative to the total weight of the composition.

7. Composition according to any one of claims 1 to 6, characterized in that the Portland cement is chosen from Portland CEM I cements, Portland CEM II cements, Portland CEM III cements, Portland CEM IV cements, cements. Portland CEM V, and mixtures thereof.

8. Composition according to any one of claims 1 to 7, characterized in that the Portland cement is a Portland cement CEM I 52.5 N, a Portland cement CEM I 52.5 R, a Portland cement CEM I 42.5 R or a cement. Portland CEM I 42.5 N.

9. Composition according to any one of claims 1 to 8, characterized in that the total content of Portland cement (s) varies from 10% to 80% by weight, preferably from 40% to 75% by weight, and advantageously from 60% to 75% by weight relative to the total weight of the composition.

10. Composition of dry mortar or concrete comprising:

the hydraulic binder composition as defined in any one of claims 1 to 9; and

at least one aggregate.

11. Mortar or dry concrete composition according to claim 10, characterized in that it comprises:

- from 15% to 80% by weight of the binder composition as defined according to any one of claims 1 to 10; and

- from 15% to 80% by weight of aggregate (s);

- from 0% to 5% by weight of additive (s);

- from 0% to 10% by weight of polymer (s);

12. Mortar or dry concrete composition according to claim 11, characterized in that the additives are chosen from the group consisting of setting accelerators, setting retarders, antifoaming agents, water-repellent agents, anti-aging agents, agents. rheological, and their mixtures.

13. Mortar or dry concrete composition according to any one of claims 10 to 12, characterized in that the aggregates are chosen from gravels, chippings, sand, calcium carbonate, dolomite, recycled glass, and their mixtures.

14. Mortar or dry concrete composition according to any one of claims 10 to 12, characterized in that the total mass content of alkaline salt (s) S in the composition ranges from 0.05% to 0.30% by weight. , preferably from 0.10% to 0.20% by weight, and advantageously from 0.12% to 0.18% by weight relative to the total weight of the composition of dry mortar or concrete.

15. Mortar or wet concrete composition comprising:

- the composition of dry mortar or concrete as defined in any one of claims 10 to 14; and

- some water.

16. Use of the composition according to claim 15 for leveling and smoothing floors, for making leveling work, screed, for dressing floors, for repairing concrete work, for sealing d 'elements, for gluing or jointing tiles.

17. Use of at least one alkaline salt S chosen from K ₂ CO ₃ , Rb ₂ CC> ₃ , Cs ₂ CÜ ₃ and their mixtures, in a mortar or dry concrete composition comprising at least one amorphous calcium aluminate , as an anti-swelling agent.