Abstract: A cement admixture comprising (A) a compound selected from a melaminesulfonic acid formaldehyde condensate, a naphthalenesulfonic acid formaldehyde condensate and salts thereof and (B) a copolymer obtained by copolymerizing a monomer mixture comprising (a) from 30 to 90 mass % of one or more N-vinylcarboxylic acid amide-type monomer represented by the formula (1) below, (b) from 10 to 70 mass % of one or more anionic unsaturated monomer selected from an unsaturated carboxylic acid-type monomer represented by the formula (2) below and an unsaturated sulfonic acid-type monomer represented by the formula (3) below, and optionally (c) from 0 to 40 mass % of one or more nonionic unsaturated monomer, provided that the total of (a), (b) and (c) is 100 mass %, wherein the symbols in the formulae are as described in the specification.

Abstract: A high-flow concrete additive comprises a polymer of 10-100 wt % of an N-vinylacetamide, 0-50 wt % of a compound CH.sub.2 .dbd.CR.sup.3 X.sup.1 R.sup.4 SO.sub.3 X.sup.2 wherein R.sup.3 is hydrogen or methyl, R.sup.4 is alkylene of 1 to 4 carbon atoms, X.sup.1 is CONH or COO, and X.sup.2 is hydrogen, an alkali metal, ammonium salt or organic ammonium salt, and 0-40 wt % of a compound CH.sub.2 .dbd.CR.sup.5 X.sup.3 wherein R.sup.5 is hydrogen or methyl and X.sup.3 is CN, COOR.sup.6, CONH.sub.2, CONHR.sup.7, CONR.sup.8 R.sup.9, COR.sup.10, OCOR.sup.11 or OR.sup.12, in which R.sup.6 is hydrogen, an alkali metal, ammonium salt, organic ammonium salt or alkyl group of 1 to 4 carbon atoms, R.sup.7, R.sup.8 and R.sup.9 are alkyl groups of 1 to 4 carbon atoms, and R.sup.10, R.sup.11 and R.sup.12 are alkyl groups of 1 to 4 carbon atoms.