Abstract: An improved hydraulic cement composition having an almost constant air content, which is incorporated with an organic phosphoric acid ester of the formula ##STR1## Wherein R.sub.1 is a group of the formula: R.sub.4 --O--(CH.sub.2 CH.sub.2 O).sub.n -- wherein R.sub.4 is an alkyl having 4 to 18 carbon atoms, an alkenyl having 4 to 18 carbon atoms or an aryl substituted with an alkyl having 4 to 18 carbon atoms and n means an average addition molar number of ethylene oxide and is an integer of 0 to 15 in average, and R.sub.2 and R.sub.3 are the same or different and are each hydroxy or a group of the formula: R.sub.4 --O--(CH.sub.2 CH.sub.2 O).sub.n -- wherein R.sub.4 and n are as defined above, or a salt thereof with an inorganic or organic base, as an air entraining agent, optionally together with a dispersing agent and an accelerator.