Compounds having a cyclopentadiene skeleton and at least one sulfonic acid group are novel, and produced by subjecting cyclopentadiene, dicyclopentadiene and/or hydroxydicyclopentadiene to sulfonation, and subjecting the same, before or after the sulfonation, to reaction with alkylbenzene, polymerization and/or condensation through an aldehyde. The aforesaid compounds are useful as dispersants for cement.By incorporating a polymer emulsion into a slurry composition comprising a powder and a dispersant having at least one sulfonic acid group the proportion of said polymer emulsion being 0.05 to 50 parts by weight per 100 parts by weight of said dispersant, the dispersing effect of said dispersant is improved, the fluidizing effect of the dispersant is further enhanced, the slump loss is made very small, and the workability becomes good.