A comb-branched polymer is disclosed. The polymer comprises recurring units of an unsaturated carboxylic monomer, an oxypropylene-rich poly(oxyethylene-oxypropylene) macromonomer and an oxyethylene-rich poly(oxyethylene-oxypropylene) macromonomer. The comb-branched polymer can be used as a water reducing agent in cement. It gives significantly lower air entrainment in cement admixture.