A nonionic water-soluble cellulose ether is characterized in that when 3 pbw of the nonionic water-soluble cellulose ether is added to a mixture of 90 pbw of cordierite, 10 pbw of ordinary Portland cement, and 33 pbw of water, immediately followed by kneading at 20.degree. C. and 20 rpm, a maximum torque for kneading is reached within 180 seconds from the addition. It is suitable as an admixture for extrudable hydraulic compositions. The hydraulic composition to which the inventive admixture is added can be kneaded within a brief time into a uniform mass which is smoothly extrudable.