Concrete with a low clinker content

1. A dry binder premix comprising, in mass proportions:

Portland clinker having a Blaine specific surface area comprised from 4500 to 9500 cm 2 /g, a minimum quantity of said clinker by mass percentage relative to the total mass of the premix being determined according to the following formula (I):

[−6.10 −3 ×BSS k ]+75  Formula (I)

in which BSS k is the Blaine specific surface area of the clinker given in cm 2 /g;

fly ash, the quantity of clinker+the quantity of fly ash being greater than or equal to 75%, by mass percentage relative to the total mass of the premix;

at least one alkali sulphate, the quantity of alkali sulphate being such that the quantity of equivalent Na 2 O in the premix is greater than or equal to 5% by mass percentage relative to the mass of fly ash;

at least one source of SO 3 , in a quantity such that the quantity of SO 3 in the premix is greater than or equal to 2% by mass percentage relative to the mass of Portland clinker;

complementary materials having a Dv90 less than or equal to 200 μm selected from the group consisting of limestone powders, calcined shale, metakaolins, siliceous fillers, silica powders, pozzolans, slags, fly ash and mixtures thereof;

the total quantity of clinker in the premix being less than 60% by mass percentage relative to the total mass of the premix.

2. The premix according to claim 1 , further comprising at least one source of calcium.

3. The premix according to claim 1 , wherein the alkali sulphate is selected from the group consisting of sodium sulphate, potassium sulphate, lithium sulphate and mixtures thereof.

4. The premix according to claim 1 , wherein the alkali sulphate is sodium sulphate.

5. The premix according to claim 2 , wherein the source of calcium is selected from the group consisting of calcium salts and mixtures thereof.

6. A dry binder mix comprising, by mass proportions relative to the total mass of the mix:

at least 10% of the premix according to claim 1 ; and

up to 90% of aggregates.

7. A wet concrete composition, comprising from 140 to 220 l/m 3 of effective water in combination with:

at least 10% of the premix according to claim 1 ; and

up to 90% of aggregates;

the mass percentages being given relative to the total dry mass of the composition.

8. A hardened concrete object of the composition according to claim 7 .

9. A process for the preparation of a wet concrete composition comprising:

mixing the mix of claim 6 , with 140 to 220 l/m 3 of effective water; or

mixing the premix of claim 1 , with aggregates and 140 to 220 l/m 3 of effective water.

10. The process for preparation of a wet concrete composition according to claim 9 , comprising mixing:

Portland clinker having a Blaine specific surface area comprised from 4500 to 9500 cm 2 /g,

a minimum quantity of said clinker, in kg/m 3 , being determined according to the following formula (II):

[(−0.021×BSS k )+230]×( W eff ÷140)  Formula (II)

in which BSS k is the Blaine specific surface area of the clinker given in cm 2 /g,

W eff is the quantity of effective water in l/m 3 ;

fly ash, the quantity of clinker+the quantity of fly ash being greater than or equal to 240 kg/m 3 ;

at least one alkali sulphate, the quantity of alkali sulphate being such that the quantity of equivalent Na 2 O in the binder is greater than or equal to 5% by mass percentage relative to the mass of fly ash;

at least one source of SO 3 , in a quantity such that the quantity of SO 3 in the binder is greater than or equal to 2% by mass percentage relative to the mass of Portland clinker;

complementary materials having a Dv90 less than or equal to 200 μm selected from the group consisting of limestone powders, calcined shale, metakaolins, siliceous fillers, silica powders, pozzolans, slags, fly ash and mixtures thereof, the minimum quantity of which, in kg/m 3 , is determined according to the following formula (III):

the sum of(quantity of complementary material)+(quantity of fly ash)+(quantity of clinker)+(quantity of alkali sulphate)+(quantity of a source of SO 3 )is greater than or equal to 220 kg/m 3 of concrete  Formula (III);

from 1500 to 2200 kg/m 3 of aggregates;

a plasticizer;

optionally an accelerator and/or an air-entraining agent and/or a thickening agent and/or a retarder and/or a clay-inerting agent; with

140 to 220 l/m 3 of effective water,

the total quantity of clinker in the wet concrete being less than or equal to 200 kg/m 3 .

11. A process for the preparation of a cast wet concrete, comprising:

casting a wet concrete composition according to claim 7 .

12. A process for the production of a concrete object, comprising:

hardening of a wet concrete composition according to claim 7 .

13. A method comprising activating the fly ash in a premix according to claim 1 using at least one alkali sulphate and optionally at least one source of calcium.

14. A process for the preparation of a cast wet concrete, comprising casting a wet concrete composition obtained according to the process of claim 9 .

15. A process for the production of a concrete object, comprising:

hardening of a wet concrete composition obtained according to the process of claim 9 .

16. A process for the production of a concrete object, comprising:

hardening of a wet concrete composition cast according to claim 11 .

17. The premix according to claim 1 , wherein the Blaine specific surface area is comprised from 5500 to 8000 cm 2 /g.

18. The premix according to claim 1 , wherein the quantity of clinker+the quantity of fly ash is greater than or equal to 78% by mass percentage relative to the total mass of the premix.