Cement retarder and cement retardative sheet

摘要

A polymer comprising an anionic group (e.g. an acid anhydride group, a carboxyl group) and a hydro-philic segment (e.g. a polyoxyalkylene ether unit) is used as a cement retarder. The polymer is obtainable by copolymerization of a monomer including maleic anhydride with a monomer including a vinylalkyl ether-series monomer in which an alkylene oxide is added to allyl alcohol. The polymer may be a copolymer copolymerized with other monomers such as styrene. Use of this cement retarder can provide patterns or washing-finished face on the surface of a concrete product. The cement retarder is suitable for application for a cement retardative sheet.