PURPOSE: To obtain a hydraulic composition having high fluidity, comprising each specific amount of a hydraulic powder, a maleic anhydride-an alkyl vinyl ether copolymer and leather powder.

CONSTITUTION: Maleic anhydride is dissolved in an organic solvent, reacted with a radical polymerization initiator at a specific temperature, then with an alkyl vinyl ether and the solvent is removed from a formed copolymer slurry to provide a maleic anhydride-an alkyl vinyl ether alternate copolymer of the formula ((m) and (n) each is 10-100,000; R is a 1-4C straight-chain or branched chain alkyl or a 4-8C alicyclic alkyl). Then 100 pts.wt. of a hydraulic powder such as Portland cement is blended with specific amount of an aggregate, 0.1-10 pts.wt. of the maleic anhydride-an alkyl vinyl ether copolymer and a leather powder, 0.1-5 pts.wt. of leather powder having ≤100μm average particle diameter and optionally about 0.1-5 pts.wt. of an ethylene-methyl methacrylate copolymer having 1,000-30,000 molecular weight and various kinds of the cement admixture to give a hydraulic composition, which is mixed with water to provide a curing composition.