A hydraulic composition comprising a water-soluble hydroxyalkyl alkyl cellulose, cement, aggregate, reinforcing fibers, and water is provided. The hydroxyalkyl alkyl cellulose has a degree of alkyl substitution of 1.2-1.7, the sum of the degree of alkyl substitution and the molar substitution of hydroxyalkyl is 1.5-2.0, and a proportion of glucose ring not substituted with alkyl and hydroxyalkyl groups per glucose ring unit is up to 10 mol%. The composition cures within a short time and is extrusion moldable even at elevated temperature.