The present invention provides: a copolymer for cement admixtures which
displays high dispersibility with a small adding amount and excellent
dispersibility particularly even in a high water reducing ratio area, a
cement admixture utilizing the copolymer, and a cement composition, and
further, a production process for the copolymer. The copolymer for cement
admixtures comprises: constitutional unit (I) derived from unsaturated
polyalkylene glycol ether monomer (a) having an alkenyl group having 5
carbon atoms and an oxyalkylene group having 2 to 18 carbon atoms with an
average addition number of moles of the oxyalkylene groups to be in the
range of 10 to 300; and constitutional unit (II) derived from unsaturated
monocarboxylic acid monomer (b). The cement admixture includes the
copolymer for cement admixtures as an essential component, and may further
include a defoaming agent. The cement composition includes the copolymer
for cement admixtures, and cement as essential components. The production
process for the copolymer comprises: copolymerizing comonomers including
unsaturated polyalkylene glycol ether monomer (a) and unsaturated
monocarboxylic monomer (b) as essential components by use of a
chain-transfer agent, and/or adjusting pH of a resultant reaction mixture
to not less than 5 after the copolymerization.
