Hydraulic binder comprising a ternary acceleration system and mortars and concretes comprising one such binder
A hydraulic binder based on slag cement, the slag cement including 20 to 80 weight % relative to a total weight of slag cement, of a blast furnace slag or a mixture of blast furnace slags, relative to the total weight of the slag cement, the hydraulic binder including an acceleration additive that is a ternary system including at least one alkali metal hydroxide in an amount such that, during mixing with water of the hydraulic binder, a molar concentration of the alkali metal hydroxide in the water is from 0.05N to 0.60N, preferably from 0.20N to 0.40N; an alkali metal sulfate at a rate of from 0.2 to 3 weight % of the slag cement; and a source of calcium sulfate in such a proportion that the content of calcium sulfate (CaSO 4 ), relative to the weight of the slag cement, is from 2 to 7%.
1. A hydraulic binder based on slag cement, the slag cement comprising 20 to 80 weight % relative to a total weight of slag cement, of a blast furnace slag or a mixture of blast furnace slags, the hydraulic binder comprising at least one acceleration additive that is a ternary system comprising:
at least one alkali metal hydroxide in an amount such that, during mixing with water of the hydraulic binder, a molar concentration of the at least one alkali metal hydroxide in the water is from 0.05N to 0.60N, the at least one alkali metal hydroxide being selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide and mixtures thereof;
at least one alkali metal sulfate at a rate of from 0.2 to 3 weight % of the slag cement; and
at least one source of calcium sulfate in such a proportion that the content of calcium sulfate (CaSO 4 ), relative to the weight of the slag cement, is from 2 to 7%,
wherein the hydraulic binder presents a mechanical strength to compression after 2 days of at least 8 MPa.
2. A hydraulic binder according to claim 1 , wherein the blast furnace slag comprises a vitreous phase representing more than 80 weight % of the blast furnace slag.
3. A hydraulic binder according to claim 2 , wherein the blast furnace slag comprises, given in relative weight to the total weight of the blast furnace slag from 28 to 40% SiO 2 , from 31 to 47% CaO, from 9 to 17% Al 2 O 3 , from 0 to 16% MgO, and from 0 to 12% TiO 2 .
4. A hydraulic binder according to claim 3 , wherein the Hydraulic Index HI (CaO+MgO+Al 2 O 3 )/(SiO 2 ) in the blast furnace slag is from 1.22 to 2.
5. A hydraulic binder according to claim 1 , wherein the alkali metal sulfate of the acceleration agent is selected from among lithium sulfate, sodium sulfate, potassium sulfate and mixtures thereof.
6. A hydraulic binder according to claim 1 , wherein the source of calcium sulfate is selected from among gypsum, hemi-hydrates, anhydrite and mixtures thereof.
7. A hydraulic binder according to claim 1 , wherein the slag cement is a cement in the CEM III/A or CEM III/B classes according to the EN 197-1 standard.
8. A mortar or concrete comprising aggregates and a hydraulic binder, the hydraulic binder based on slag cement, the slag cement comprising 20 to 80 weight % relative to a total weight of slag cement, of a blast furnace slag or a mixture of blast furnace slags, the hydraulic binder comprising at least one acceleration additive that is a ternary system comprising:
at least one alkali metal hydroxide in an amount such that, during mixing with water of the hydraulic binder, a molar concentration of alkali metal hydroxide in the water is from 0.05N to 0.60N, the at least one alkali metal hydroxide being selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide and mixtures thereof;
at least one alkali metal sulfate at a rate of from 0.2 to 3 weight % of the slag cement; and
at least one source of calcium sulfate in such a proportion that the content of calcium sulfate (CaSO 4 ), relative to the weight of the slag cement, is from 2 to 7%,
wherein the hydraulic binder presents a mechanical strength to compression after 2 days of at least 8 MPa.
9. A mortar according to claim 8 , wherein the mortar presents a mechanical strength after 2 days meeting the 32.5 R, 42.5N, or 42.5 R classes in the EN 197-1 standard.
10. A process of making a hydraulic binder based on slag cement comprising 20 to 80 weight % relative to a total weight of slag cement, of a blast furnace slag or a mixture of blast furnace slags, the complement being clinker, and having a mechanical compressive strength after 2 days of at least 8 MPa, the process comprising adding to the slag cement or forming within the slag cement at least one acceleration additive that is a ternary system comprising:
at least one alkali metal hydroxide in an amount such that, during mixing in water of the hydraulic binder, a molar concentration of the at least one alkali metal hydroxide in the water is from 0.05 N to 0.60N, the at least one alkali metal hydroxide being selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide and mixtures thereof;
at least one alkali metal sulfate at a rate of from 0.2 to 3 weight % of the slag cement; and
at least one source of calcium sulfate in proportions such that the level of calcium sulfate (CaSO 4 ), relative to the weight of the slag cement, is from 2 to 7%.
11. A process according to claim 10 , wherein the blast furnace slag comprises a vitreous phase representing more than 80 weight % of the blast furnace slag.
12. A process according to claim 11 , wherein the blast furnace slag comprises, given in relative weight to the total weight of the blast furnace slag from 28 to 40% SiO 2 , from 3 to 47% CaO, from 9 to 17% Al 2 O 3 , from 0 to 16% MgO, and from 0 to 12% TiO 2 .
13. A process according to claim 10 , wherein the hydraulic index HI=(CaO+MgO+Al 2 O 3 )/(SiO 2 ) of the blast furnace slag is from 1.22 to 2.
14. A process according to claim 10 , wherein the alkali metal sulfate of the acceleration agent is selected from among lithium sulfate, sodium sulfate, potassium sulfate and mixtures thereof.
15. A process according to claim 10 , wherein the source of calcium sulfate is selected from among gypsum, hemi-hydrates, anhydrite and mixtures thereof.
16. A process according to claim 10 , wherein the slag cement is a cement of the CEM III/A or CEM III/B classes according to the EN 197-1 standard.
17. A hydraulic binder according to claim 1 , wherein the molar concentration of the at least one alkali metal hydroxide in the water is from 0.20N to 0.40N.
18. A hydraulic binder according to claim 6 , wherein the source of calcium sulfate is selected from among anhydrite or mixtures of gypsum, hemi-hydrates and anhydrite.
19. A hydraulic binder according to claim 1 , wherein the hydraulic binder belongs to the 32.5 R, 42.5N, or 42.5 R classes according to the EN 197-1 standard.
20. A process according to claim 10 , wherein the molar concentration of the at least one alkali metal hydroxide in the water is from 0.20N to 0.40N.
21. A process according to claim 15 , wherein the source of calcium sulfate is selected from among anhydrite or mixtures of gypsum, hemi-hydrates and anhydrite.