Cement additive, cement admixture, cement composition, molded body, and method for improving strength of molded body

A cement composition comprising a cement additive, a cement dispersant, and cement,

• wherein the cement dispersant is a polycarboxylic acid-based dispersant,
• the cement additive comprises a water-absorbent resin,
• the water-absorbent resin is formed by polymerizing a monomer mixture containing no less than 50 mol % of a nonionic non-crosslinkable monomer and no less than 0.1 mol % of a nonionic crosslinkable monomer,
• a content of an anionic monomer in the monomer mixture is no more than 4 mol %,
• the nonionic non-crosslinkable monomer is not N-vinylacylamides, and
• a water absorption ratio when the water-absorbent resin is immersed in an aqueous solution having a pH of 12.9 (here, the aqueous solution having a pH of 12.9 is an aqueous solution obtained by mixing 1.72 g of CaSO4·2H2O, 6.96 g of Na2SO4, 4.76 g of K2SO4, 7.12 g of KOH, and 979.4 g of deionized water) at 25° C. for 2 hours is less than 20 g/g.

A method for improving strength of a molded body obtained by molding a cement composition containing cement, the method comprising:

• incorporating a cement additive to the cement composition,
• wherein the strength of the molded body is improved to be more than 100% as compared to a strength of a molded body obtained without the cement additive,
• the cement composition further comprises a cement dispersant, and the cement dispersant is a polycarboxylic acid-based dispersant,
• the cement additive comprises a water-absorbent resin,
• the water-absorbent resin is formed by polymerizing a monomer mixture containing no less than 50 mol % of a nonionic non-crosslinkable monomer and no less than 0.1 mol % of a nonionic crosslinkable monomer,
• a content of an anionic monomer in the monomer mixture is no more than 4 mol %,
• the nonionic non-crosslinkable monomer is not N-vinylacylamides, and
• a water absorption ratio when the water-absorbent resin is immersed in an aqueous solution having a pH of 12.9 (here, the aqueous solution having a pH of 12.9 is an aqueous solution obtained by mixing 1.72 g of CaSO4·2H2O, 6.96 g of Na2SO4, 4.76 g of K2SO4, 7.12 g of KOH, and 979.4 g of deionized water) at 25° C. for 2 hours is less than 20 g/g.