METHOD FOR RETARDING THE SETTING TIME OF RAPID HARDENING CEMENT

摘要

1436473 Cement composition ONODA CEMENT CO Ltd 21 Feb 1974 [21 Feb 1973] 7916/74 Heading C1M The setting time of rapid hardening cement is retarded by addition of at least one of boric acid, boric acid anhydride and water-soluble borate (e.g. Na, K or ammonium borates) to cement manufactured by adding CaSO 4 to clinker which is then ground to ground clinker, the clinker containing 11CaO.7Al 2 O 2 .CaX 2 (X = halogen atom) and solid solutions of 3CaO.SiO 2 .- 2CaO.SiO 2 and 4CaO.Al 2 O 3 .Fe 2 O 3 as mineral components. To the separately ground clinker may be added the CaSO 4 and at least one of the sulphates, nitrates and chlorides of K, Na, Mg, Ca, Al and NH 4 (excepting Ca sulphates) or at least one of saccharides, sodium hydrogen carbonate, water soluble phosphates, aliphatic carboxylic acids, fluorosilicates, sodium silicates, lignin sulphonic acid, sulphuric acid esters of higher alcohols and alkyl sulphonates. Alternatively at least one carbonate of Ca, Na, K and Mg may be added to the clinker, possibly with at least one sulphate of Na, K, Al and Mg, the mixture interground and then the anhydrite added. The clinker may be obtained by mixing powders of clay, bauxite, limestone and fluorspar, intergrinding, granulating, and firing at 1300-1350‹ C. In the examples the use of the boric compound is compared with citric acid, adipic acid or cane sugar.