Patent ID: 7662884

Claim:
An admixture for cement, comprising a polycarboxylic acid polymer and a compound containing a nitrogen atom, but not containing an amide bond, wherein the mass ratio (A/B) satisfies the relation 200>(A/B)>2, where A is the mass of said polycarboxylic acid polymer and B is the mass of said compound containing a nitrogen atom, but not containing an amide bond, and wherein the compound containing a nitrogen atom, but not containing an amide bond contains a polyalkyleneimine-alkylene oxide adduct, and wherein the polyalkyleneimine-alkylene oxide adduct has a group or groups composed of oxyalkylene unit(s) resulting from addition of one or more species of alkylene oxide(s) and the average molar number of addition of the oxyalkylene unit(s) in each oxyalkylene group of the polyalkyleneimine-alkylene oxide adduct is not less than 3, and wherein the polyalkyleneimine-alkylene oxide adduct contains 50 to 100 mole % of oxyethylene units relative to 100 mole % of all the oxyalkylene units, and the polycarboxylic acid polymer is the polymer resulting from the copolymerization of a monomer component comprising a polyalkylene glycol unsaturated monomer and an unsaturated carboxylic acid monomer, and wherein the polyalkyleneimine-alkylene oxide adduct is obtained by addition of oxyalkylene group(s) to polyethyleneimine with a weight average molecular weight of 600 to 100,000.