| abstract |
(57) [Abstract] [PROBLEMS] To provide an additive for a cement composition, which densifies the cement composition, integrates the reinforcing bar and the like with the cement composition, and exerts an excellent rust suppressing effect on the reinforcing bar and the like. SOLUTION: At least one diphosphonic acid derivative represented by the following general formula (1), and a setting agent for cement composition An additive for a cement composition, which comprises a hardening accelerator. Embedded image (In the formula, R represents an alkyl group having 1 to 21 carbon atoms, an alkenyl group, an alkylaryl group or an aryl group, M 1 , M 2 , M 3 and M 4 represent hydrogen or zinc, and M 1 to M 4 may be the same or different). |