Cement composition for a self-leveling fluid screed, and self-leveling fluid screed thus produced
The self-leveling fluid screed cement composition with limited shrinkage, formed by a mixture of a cement binder, a fluidizing adjuvant, granulates and water, is characterized in that the binder includes 70% to 85% by weight of Portland cement, 7% to 18% by weight of sulfo-aluminous clinker, and 6% to 14% by weight of calcium sulfate, with a calcium sulfate C$/calcium sulfo-aluminate C 4 A 3 $ molar ratio of between 5 and 7 and a water/binder ratio by weight of between 0.60 and 0.90. The self-leveling fluid screed that is thus produced has a mechanical resistance to its compression at 24 hours that is at least equal to 1 MPa, shrinkage at 7 days, measured under a relative hygrometry of 50%, less than 500 μm/m, and an endogenic expansion value that is measured at 7 days, less than 1,000 μm/m, as well as a very slight lifting of edges.
1. A self-leveling fluid screed cement composition formed by a mixture of a cement binder, adjuvants comprising at least one fluidizing adjuvant, granulates and water, wherein,
the cement binder comprises:
70% to 85% by weight of Portland cement,
7% to 18% by weight of sulfo-aluminous clinker containing a content of calcium sulfo-aluminate C 4 A 3 $ of between 50% and 70% by weight, and
6% to 14% by weight of calcium sulfate,
a calcium sulfate C$/calcium sulfo-aluminate C 4 A 3 $ molar ratio is between 5 and 7, and
a water/binder ratio by weight is between 0.60 and 0.90.
2. The cement composition according to claim 1 , wherein the cement binder comprises:
77% to 85% by weight of the Portland cement,
7% to 18% by weight of the sulfo-aluminous clinker, and
6% to 14% by weight of the calcium sulfate.
3. The cement composition according to claim 1 , wherein the water/binder ratio by weight is between 0.60 and 0.80.
4. The cement composition according to claim 1 , wherein the sulfo-aluminous clinker contains a free lime content of less than or equal to 1% by weight.
5. The cement composition according to claim 1 , wherein the calcium sulfate is anhydrite, gypsum, or calcium hemihydrate.
6. The cement composition according to claim 1 , wherein the granulate is sand with a grain size of less than or equal to 4 mm.
7. The cement composition according to claim 1 , comprising one or more adjuvants selected from the group consisting of: a setting retardant, a hardening accelerator, a cohesion and stability agent, an anti-foaming agent, and a superplasticizer.
8. The cement composition according to claim 7 , wherein the hardening accelerator is an alkaline salt.
9. The cement composition according to claim 1 , wherein the composition has a usable shelf life, according to Standard ASTM C230/C230, M-03 of between 1 hour 30 minutes and 3 hours, at a temperature of between 5° C. and 30° C.
10. The cement composition according to claim 2 , wherein the water/binder ratio by weight is between 0.60 and 0.80.
11. The cement composition according to claim 4 , wherein the free lime content is less than or equal to 0.6% by weight.
12. The cement composition according to claim 7 , wherein the setting retardant is polycarboxylic acid.
13. The cement composition according to claim 8 , wherein the alkaline salt is lithium carbonate, sodium carbonate, or a mixture thereof.
14. A self-leveling screed obtained from the cement composition according to claim 1 , wherein the screed:
has a mechanical resistance to compression at 24 hours greater than or equal to 1 MPa,
shrinkage at 7 days, measured under a relative hygrometry of 50%, of less than 500 μm/m, and
an endogenic expansion value, measured at 7 days, of less than 1,000 μm/m.
15. A cement binder, comprising:
70% to 85% by weight of Portland cement,
7% to 18% by weight of sulfo-aluminous clinker containing a content of calcium sulfo-aluminate C 4 A 3 $ of between 50% and 70% by weight, and
6% to 14% by weight of calcium sulfate,
wherein, a calcium sulfate C$/calcium sulfo-aluminate C 4 A 3 $ molar ratio is between 5 and 7.
16. The cement binder according to claim 15 , comprising:
77% to 85% by weight of the Portland cement,
7% to 18% by weight of the sulfo-aluminous clinker, and
6% to 14% by weight of the calcium sulfate.
17. The cement binder according to claim 15 , wherein the sulfo-aluminous clinker contains a free lime content of less than or equal to 1% by weight.
18. The cement binder according to claim 15 , wherein the sulfo-aluminous clinker contains a free lime content of less than or equal to 0.6% by weight.