Liquid additive for intergrinding cement
View Patent ↗Exemplary compositions and methods for reducing hexavalent chromium in cementitious compositions involve the use of a liquid additive composition, comprising stannous chloride. Along with the stannous chloride may be used at least one co-additive comprising an antioxidant, oxygen scavenger, or mixture thereof, and/or at least one agent comprising a cement grinding aid, cement quality improver, or mixture thereof.
1. A method for reducing hexavalent chromium in cementitious compositions, comprising:
grinding cement clinker to produce Portland cement;
introducing to said cement clinker, before or during the grinding thereof, a liquid additive composition comprising stannous chloride present in an amount not less than 20 percent and not greater 95 percent based on total weight of the liquid additive composition,
said liquid additive composition further comprising a co-additive selected from the group consisting of an antioxidant and an oxygen scavenger, or mixtures thereof said co-additive being present within said liquid additive composition in a stannous chloride:co-additive ratio of not less than 99.5:0.5 and not greater than 20:80;
said stannous chloride being added to said cement clinker at a rate no less than 0.001 and no greater than 5.0 percent based on weight of said cement clinker.
2. The method of claim 1 wherein said co-additive is an antioxidant.
3. The method of claim 1 wherein said co-additive is an oxygen scavenger.
4. The method of claim 3 wherein said oxygen scavenger comprises (a) a compound having an ethylenically unsaturated hydrocarbon (b) a phenolic or salt or derivative thereof; (c) a hydroxylamine or hydrazine or derivative thereof; (d) a sulfurous acid or salt or derivative thereof, (e) a transition metal complex, or mixtures thereof.
5. The method of claim 4 wherein said co-additive is a compound having an ethylenically unsaturated hydrocarbon which is substituted or unsubstituted.
6. The method of claim 5 further comprising a transition metal catalyst.
7. The method of claim 6 wherein said co-additive is a compound having at least one enediol group or salt or derivative thereof.
8. The method of claim 7 wherein said co-additive is an ascorbic acid or a salt, stereoisomer, or derivative thereof.
9. The method of claim 7 wherein said co-additive is an alkali metal ascorbate, isoascorbate, or erythorbate.
10. The method of claim 9 wherein said co-additive is sodium or potassium ascorbate.
11. The method of claim 6 wherein said co-additive comprises a phenolic or a salt or derivative thereof.
12. The method of claim 11 wherein said phenolic or salt thereof comprises a quinone or hydroxyl form thereof.
13. The method of claim 12 wherein said quinone is pyrocatechol, hydroquinone, or a derivative thereof.
14. The method of claim 6 wherein said co-additive is hydroxylamine, hydrazine, or a derivative thereof.
15. The method of claim 14 wherein said co-additive is hydroxylamine.
16. The method of claim 6 wherein said co-additive is a sulfurous acid or a salt thereof.
17. The method of claim 16 wherein said co-additive is a sulfite, bisulfite, or thiosulfite.
18. The method of claim 16 wherein said co-additive is an alkali metal salt comprising sodium, potassium, or a mixture thereof.
19. The method of claim 1 further comprising introducing at least two co-additives each comprising an antioxidant, oxygen scavenger, or mixture thereof, to said cement clinker.
20. The method of claim 6 wherein said co-additive is a transition metal complex.
21. The method of claim 1 further comprising at least one agent selected from the group consisting of cement grinding aids and cement quality improvers.
22. The method of claim 21 wherein said agent is selected from the group consisting of an amine, alkanolamine, acrylic acid or salt thereof, glycol, glycerol, acetate salt, a phenol, chloride salt, sugar, dispersants, lignins, air entraining surfactants, nitrite salts, and nitrate salts.
23. The method of claim 1 wherein, in said liquid additive composition, said stannous chloride is solubilized, dispersed, and/or suspended in water, a glycol or glycerol, or mixture thereof.
24. A method for reducing hexavalent chromium in cementitious compositions, comprising:
grinding cement clinker to produce Portland cement; and
introducing to said cement clinker, before or during the intergrinding thereof, a liquid additive composition comprising stannous chloride and a co-additive, agent, or mixture thereof;
said coadditive being selected from the group consisting of an antioxidant and oxygen scavenger or mixtures thereof; and
said agent being selected from the group consisting of a cement grinding aid and cement quality improver.