CONCRETE ADMIXTURE

PROBLEM TO BE SOLVED: To obtain a concrete admixture capable of quickly coagulate a concrete in a short time. SOLUTION: This concrete admixture is composed of at least one kind selected from the following compounds A to F. A: A condensation product of an aminoarylsulfonic acid, a phenol derivative and formaldehyde. B: A condensation product of an aminoarylsulfonic acid, melamine sulfonic acid and formalin. C: A sulfonic group-containing aliphatic diene (co)polymer having a pendant double bond in diene part in an amount of 20-60% and an average molecular weight of 1000-200,000. D: A poly (styrenesulfonic acid) salt having benzene rings each alkylated with a 2-12C alkyl group at 0.01-0.03 mol portion on average and an average molecular weight of 5000-500 000. E: A copolymer of a vinyl monomer substituted with a carboxylic group or a sulfonyl group at a part of a molecules and a polyalkylene glycol. F: A copolymer of a vinyl monomer substituted with a carboxyl group at a part of molecules, a vinyl monomer containing a polyalkylene glycol monoalkyl ether and a polyalkylene glycol derivative.