Fast hydraulic binder for parts and constructions made of concrete containing a calcium salt
A fast hydraulic binder comprising cement, at least one first superplasticizer, a calcium salt, and at least one second superplasticizer different from the first superplasticizer and comprising a main chain and pendant groups connected to the main chain adapted so as to separate from the main chain in a basic medium, wherein the result is that the second plasticizer has a fluidifying action which increases at least temporarily over time in a basic medium.
1. A hydraulic binder comprising:
cement;
at least one first superplasticizer;
a water-soluble calcium salt; and
at least one second superplasticizer different from the first superplasticizer and comprising a main chain and pendant groups connected to the main chain wherein at least 30% of side chains separate from the main chain in a basic medium at 20° C., the second superplasticizer comprising at least one polymer hydrolyzable in a basic medium, and wherein the second superplasticizer is obtained:
by radical polymerization of at least one ionic or ionisable monomer selected from phosphonic, sulfonic or carboxylic monomers and of at least one monomer selected from polyethylene glycol (PEG) (meth)acrylate, polyethylene glycol maleate, polyethylene glycol vinyl ether or polyethylene glycol allyl monomers, the molecular weight of which is between 100 and 10,000; or
in an equivalent way by a post-esterification method by reacting alcohols or polyoxyalkylamines on a polymer having carboxylic function in order to allow grafting;
wherein concretes prepared from the binder have a workability duration from 1 hour to 2 hours;
wherein (i) a fluid concrete prepared from the binder has a compression strength of at least 1 MPa after 4 hours, (ii) a self-placing concrete prepared from the binder has a compression strength of at least 1 MPa after 5 hours, or both (i) and (ii);
wherein the binder does not comprise any formaldehyde and any formic derivatives.
2. The binder according to claim 1 , wherein the hydrolyzable monomers are selected from acrylamide and its derivatives, acrylonitrile and its derivatives, alkyl acrylates, hydroxyalkyl acrylates, polyethylene glycol acrylates, copolymerizable carboxylic anhydrides and copolymerizable imides.
3. The binder according to claim 1 , wherein the hydrolyzable polymer is a polyalkylene oxide polycarboxylate.
4. The binder according to claim 1 , comprising based on the dry weight of the binder:
99.5 to 90% by weight of cement;
0.5 to 10% by weight of the components considered as a whole;
of said at least first superplasticizer;
of said calcium salt; and
of said at least second superplasticizer.
5. The binder according to claim 4 , comprising based on the dry weight of the binder:
99 to 95% by weight of cement; and
1 to 5% by weight of the components considered as a whole;
of said at least first superplasticizer;
of said calcium salt; and
of said at least second superplasticizer.
6. The binder according to claim 1 , wherein the first superplasticizer is a polyalkylene oxide polycarboxylate.
7. The binder according to claim 1 , wherein the calcium salt is calcium nitrite.
8. The binder according to claim 1 , wherein the amount of water soluble calcium salt in the binder is comprised between 0.5 and 10% by weight based on the binder.
9. The binder according to claim 1 , wherein the amount of calcium salt in the binder is comprised between 1.5 and 5% by weight based on the binder.
10. The binder according to claim 1 , wherein the amount of the second superplasticizer, considered as a dry extract, relative to the calcium salt, is comprised between 1 and 10% of the amount of calcium salt.
11. The binder according to claim 1 , wherein the amount of the second superplasticizer, considered as a dry extract, relative to the calcium salt, is comprised between 2 and 5% of the amount of calcium salt.
12. A concrete comprising a hydraulic binder according to claim 1 mixed with water.
13. The binder according to claim 1 , wherein the PEG allyl monomer is PEG methyl ether monomer in the terminal position.
14. The binder according to claim 8 , wherein the PEG allyl monomer is PEG methyl ether monomer in the terminal position.
15. The binder according to claim 1 , wherein the second superplasticizer is obtained by radical polymerization method including one or more other hydrolyzable or non-hydrolyzable monomers.
16. The binder according to claim 8 , wherein the second superplasticizer is obtained by radical polymerization method including one or more other hydrolyzable or non-hydrolyzable monomers.
17. The binder according to claim 1 , wherein the hydrolyzable polymer comprises hydrolyzable functions selected from ester units.
18. The concrete according to claim 12 wherein the ratio of effective water over dry binder is comprised of between 0.45 and 0.65.
19. The concrete according to claim 12 wherein the concrete has a workability duration from 1 hour to 2 hours.
20. The concrete according to claim 12 wherein the concrete in a fluid form has a compression strength of at least 1 MPa after 4 hours.
21. The concrete according to claim 12 wherein the concrete in a self-pacing form has a compression strength of at least 1 MPa after 5 hours.