(57) Provided is a cement additive that can significantly improve the strength of a cured product of a cement composition over a long time period. Also provided is a cement composition including such cement additive. The cement additive of the present invention includes: a compound (A) having a weight-average molecular weight of more than 3000, and having a structure in which 5 moles or more of an alkylene oxide is added to 1 mole of a polyhy-dric alcohol; and an alkanolamine compound (B).
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