(57) Provided are a cement additive and a cement composition that maintain the favorable fluidity of cement concrete, that reduce autogeneous shrinkage, and that exhibit an immediately effective and long-lasting hexavalent chromium reduction effect. (1) A cement additive that comprises a lime-sulfur mixture having a pH of 10 or more and that has an excellent ability to maintain the fluidity of cement concrete and reduce autogeneous shrinkage. (2) The cement additive indicated in (1), wherein the lime-sulfur mixture has an oxidation-reduction potential (ORP) of -450 mv or less. (3) The cement additive indicated in (1) or (2), wherein the lime-sulfur mixture contains 5-10 % of Ca in terms of T-Ca, 15-30 % of S in terms of T-S, and 0.5-2.0 % of Mg in terms of MgO. (4) A cement composition containing cement and one of the cement additives indicated in (1) to (3). (5) The cement composition indicated in (4), wherein the cement additive content is 0.005-1 part with respect to 100 parts of cement. (6) The cement composition indicated in (4) or (5), wherein the cement contains Portland cement.
(71) Denka Company Limited, Tokyo (JP)
(84) ARIPO (BW, GH, GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, ST, SZ, TZ, UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ, TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW, KM, ML, MR, NE, SN, TD, TG)