Fly ash cement was manufactured for trial with the mixture of the fly ash subjected to hydrophobic surface treatment and Portland cement. Physical properties which were focussed on the properties of setting in the paste of the cement and the flowability in mortar were evaluated . As a result, it was found that most of all water repellent agents has a character of improving flowability of mortar. Some water repellent agents affected on the increase of viscosity which related to the

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... of fly ash. However, the action is inferior to that of thickener. Moreover, setting time of paste was delayed with some kind of water repellent agents.