Patent ID: 6872247

Claim:
A method for reducing hexavalent chromium in cementious compositions, comprising: combining with a cement clinker, during the intergrinding of the clinker to produce cement, a reducing agent selected from the group consisting of (A) a hydroxylamine having a structure represented by the formula wherein R 1 and R 2 each comprise a hydrogen or C 1 -C 18 alkyl, alkene, or aryl group, or a salt or derivative of said hydroxylamine; and (B) a hydrazine having a structure represented by the formula wherein R 1 , R 2 , R 3 , and R 4 each comprise a hydrogen or C 1 -C 18 alkyl, alkene, or aryl group, or a salt or derivative of said hydrazine; wherein the amount of said reducing agent is no less than 10 ppm and not greater than 5000 ppm based on weight of cement.