Ettringite binder for dense mortar, comprising calcium sulphates and a mineral compound of calcium aluminates

1. An ettringite binder for dense mortar comprising calcium sulphates and a calcium aluminate mineral compound, characterized in that the calcium aluminate mineral compound comprises calcium C and aluminium A oxides, soluble and combined into one or more crystallized and/or amorphous mineralogical phases, in proportions such that:

i) a C/A molar ratio of the calcium aluminate mineral compound ranges from 1.2 to 2.7,

ii) a sum in weight of the (C+A) phases accounts for at least 30% of the total weight of the mineral compound, and

iii) a calcium sulphate/aluminium A oxide molar ratio in the ettringite binder ranges from 0.5 to 2.

2. The ettringite binder for dense mortar according to claim 1 , characterized in that the calcium aluminate mineral compound /calcium sulphate weight ratio ranges from 0.5 to 4.

3. The ettringite binder for dense mortar according to claim 1 , characterized in that the C/A molar ratio of the calcium aluminate mineral compound ranges from 1.3 to 2.5.

4. The ettringite binder for dense mortar according to claim 1 , characterized in that the calcium sulphate/aluminium A oxide molar ratio in the ettringite binder ranges from 0.6 to 1.8.

5. The ettringite binder for dense mortar according to claim 1 , characterized in that a mortar comprising the ettringite binder has, when mixed with water, a water/solids weight ratio lower than 0.5.

6. The ettringite binder for dense mortar according to claim 1 , characterized in that the mortar comprises lower than 3.5% in weight Portland cement and/or hydraulic lime based on the total weight of dry mortar.

7. The ettringite binder for dense mortar according to claim 1 , characterized in that the sum in weight of the useful (C+A) phases accounts for at least 50% in weight of the total weight of the calcium aluminate mineral compound.

8. The ettringite binder for dense mortar according claim 1 , characterized in that the calcium aluminate mineral compound is obtained through baking in an oven at a temperature higher than 1100° C., in a form of one or more molten or sintered clinkers able to contain crystallized phases or amorphous phases.

9. The ettringite binder for dense mortar according to claim 1 , characterized in that the calcium aluminate mineral compound is in a form selected from the group consisting of a crystallized mineralogical phase CA, a crystallized mineralogical phase C12A7, a crystallized mineralogical phase C3A, a crystallized mineralogical phase C4A3SO3, an amorphous phase, and a mixture of at least one of said crystallized mineralogical phases and one amorphous phase.

10. The ettringite binder for dense mortar according to claim 9 , characterized in that the calcium aluminate mineral compound comprises at least 30% in weight of C12A7.

11. The ettringite binder for dense mortar according to claim 1 , characterized in that the calcium aluminate mineral compound comprises at least one crystallized mineralogical phase selected from the group consisting of G2A (1−x) Fx, C2S, C2AS, C3S and mixtures thereof, where x is an integer belonging to.

12. The ettringite binder for dense mortar according to claim 1 , characterized in that the calcium aluminate mineral compound is ground and has a Blaine surface area higher than or equal to 1500 cm 2 /g.

13. The ettringite binder for dense mortar according to claim 12 , characterized in that the calcium aluminate mineral compound is ground and has a Blaine surface area ranging from 2000 cm 2 /g to 5000 cm 2 /g.

14. The ettringite binder for dense mortar according to claim 1 , characterized in that the calcium sulphate is derived from a compound selected from the group consisting of anhydrites, semi-hydrates, gypsum and mixtures thereof.

15. A dry mortar comprising:

an ettringite binder as defined in claim 1 from 15% to 75% in weight based on the total weight of dry mortar;

chalk fillers or siliceous sands from 25% to 85% in weight based on the total weight of dry mortar;

lime and/or Portland cement from 0% to 3.5% in weight based on the total weight of dry mortar;

redispersible powder polymers from 0% to 8% in weight based on the total weight of dry mortar, and/or solid-liquid dispersion polymers from 0% to 20% in weight based on the total weight of dry mortar; and

rheological additives and/or setting regulating additives.

16. The dry mortar according to claim 15 , characterized in that

the ettringite binder is from 20% to 50% in weight based on the total weight of dry mortar,

the chalk fillers or siliceous sands are from 50% to 80% in weight based on the total weight of dry mortar,

the lime and/or Portland cement is from 0% to 0.5% in weight based on the total weight of dry mortar, and

the redispersible powder polymers are from 0% to 5% in weight based on the weight total of dry mortar, and/or solid-liquid dispersion polymers are from 0% to 15% in weight based on the total weight of dry mortar.

17. The dry mortar according to claim 15 , characterized in that the rheological additives account for from 0.1% to 0.5% of the total weight of dry mortar, and the setting regulating additives account for 0.1% to 0.5% of the total weight of dry mortar.

18. A wet mortar comprising:

the mortar defined in claim 15 ; and

water in such an amount that the water/solids weight ratio is lower than 0.5.