ADDITION TO CEMENT, CEMENT COMPOSITION AND METHOD OF RESTORING HEXVALENT CHROME WITH THEIR USE

摘要

1. An additive to cement, characterized in that it includes a foaming material containing free lime, a hydraulic connection and calcium sulfate anhydrite, and a substance containing stannous sulfate. The cement additive according to claim 1, characterized in that said substance containing tin sulfate is contained in an amount of 0.2-0.8 parts by weight in terms of tin sulfate for a total of 100 parts by weight of said foaming material and said substance, containing tin sulfate. 3. Additives to cement according to claim 1, characterized in that said blowing material is treated with carbon dioxide gas to form calcium carbonate therein. The cement additives according to claim 1, characterized in that the surface of said expanding material has been treated with a shrinkage reducing agent. A cement composition, characterized in that it contains cement and an additive to cement according to any one of paragraphs. 1-4.6. A method for the recovery of hexavalent chromium, characterized in that it uses a cement composition according to claim 5.