Stabilized defoamers for cementitious compositions
View Patent ↗The present invention discloses additive compositions, cementitious compositions, and methods for controlling air in cementitious compositions in which colloidal nano-particles are used for stabilizing a water-dispersible defoamer within a cement-dispersant-containing aqueous additive formulation for modifying hydratable cementitious compositions such as cement or concrete.
1. A stable additive in aqueous carrier composition for modifying cementitious compositions, comprising: water and
a) at least one water-dispersible defoamer comprising polyalkylene oxide, said at least one water-dispersible defoamer having a turbidity value greater than 50 NTU when measured by turbidimeter at 20° C at concentration level of 0.2% based on total weight of the aqueous carrier;
b) at least one polycarboxylate cement dispersant having polyethylene oxide groups, polypropylene oxide groups, or mixture thereof; and
c) colloidal nano-particles having a Z-average size of 8-150 nanometers and being selected from the group consisting of silica, alumina, zinc oxide, tin oxide, cerium oxide, zirconia, and mixtures thereof;
said collidal nano-particles being effect to stabilize the at least one water-dispersible defoamer and the at least one polycarboxylate cement dispersant when combined within the aqueous carrier composition.
2. The additive composition of claim 1 wherein, in said component (a), the at least one water-dispersible defoamer is an ethoxylated or propoxylated alcohol, fatty alcohol, alkyl amine, alkyl polyamine, or fatty carboxylic acid.
3. The additive composition of claim 1 wherein, in said component (a), the at least one water-dispersible defoamer has an end group of hydrogen, or C1 to C30 linear or branched, aromatic or aliphatic alkyl.
4. The additive composition of claim 1 wherein, in said component (a), the at least one water-dispersible defoamer comprises random or block ethylene oxide/propylene oxide units.
5. The additive composition of claim 1 wherein said colloidal nano particles have a Z-average size of 15-120 nm.
6. The additive composition of claim 1 wherein said colloidal nanoparticles are comprised of silica, alumina, or mixture thereof.
7. The additive composition of claim 1 wherein the weight ratio of said at least one water-dispersible defoamer of component (a) to said at least one polycarboxylate cement component (b) based on solid content is from 1:1000 to 1:20; and the weight ratio of said component (a) to said component (c) based on solid content is 1:0.5 to 1:10.
8. The additive composition of claim 1 wherein the weight ratio of said at least one water-dispersible defoamer of component (a) to said at least one polycarboxylate cement dispersant of component (b) based on solid content is from 1:200 to 1:35; and the weight ratio of said component (a) to said component (c) based on solid content is 1:1.25 to 1:3.
9. The additive composition of claim 1 wherein the concentration of said at least one polycarboxylate cement dispersant is 5% to 60% based on weight of said aqueous solution.
10. The additive composition of claim 9 wherein said colloidal nanoparticles are mixed with said at least one water-dispersible defoamer prior to addition of said at least one polycarboxylate cement dispersant.
11. The additive composition of claim 1 further comprising at least one water-soluble defoamer.
12. The additive composition of claim 1 further comprising inorganic salts.
13. Cementitious composition comprising at least one cementitious binder and the additive composition of claim 1 .
14. Method for modifying a hydratable cementitious composition comprising: mixing together at least one cementitious binder and the additive composition of claim 1 .
15. The stable additive in aqueous carrier composition of claim 6 further comprising an accelerator.
16. The additive composition of claim 4 wherein said ethylene oxide/propylene oxide units are ethylene oxide-propylene oxide-ethylene oxide triblock or ethylene oxide-propylene oxide diblock.
17. The additive composition of claim 5 wherein said collidal nano particles have a Z-average size of 25-60 nm.