ADDITIVE FOR CEMENT AND CEMENT COMPOSITION

PROBLEM TO BE SOLVED: To provide an additive for cement that can shorten the knead-finishing time of a cement composition.SOLUTION: An additive for cement of the present invention is an additive for cement containing a polycarboxylic acid type copolymer, and in which said polycarboxylic acid type copolymer comprises a structural unit (I) derived from a particular unsaturated polyalkylene glycol ether type monomer (a), a structural unit (II) derived from a particular unsaturated carboxylic acid monomer (b) and a structural unit (III) derived from an unsaturated carboxylic acid ester monomer (c), and the content ratio of the structural unit (II) in all the structural units constituting the polycarboxylic acid type copolymer is from 13 mass% to 30 mass.SELECTED DRAWING: None 【課題】セメント組成物の練り上がり時間を短縮できるセメント用添加剤を提供する。【解決手段】本発明のセメント用添加剤は、ポリカルボン酸系共重合体を含むセメント用添加剤であって、該ポリカルボン酸系共重合体は、特定の不飽和ポリアルキレングリコールエーテル系単量体（ａ）由来の構造単位（Ｉ）と、特定の不飽和カルボン酸系単量体（ｂ）由来の構造単位（ＩＩ）と、不飽和カルボン酸エステル系単量体（ｃ）由来の構造単位（ＩＩＩ）と、を含み、該ポリカルボン酸系共重合体を構成する全構造単位中の該構造単位（ＩＩ）の含有割合が１３質量％〜３０質量％である。【選択図】なし