PURPOSE: To provide a curable composition containing cement or lime and colloidal silicic acid, with the concentration of SiO2 derived from the colloidal silicic acid adjuted within a specified range, which retains fluidity for a long time in pouring operation and flows only in a predetermined region.

CONSTITUTION: The composition contains cement or lime and colloidal silicic acid, with the concentration of SiO2 derived from the colloidal silicic acid being adjusted to 0.01W0.3mol/l. When the concentration of SiO2 excees 0.3mol/l, the liquid mixture instantly forms non-flowing gel while when it is lower than 0.01mol/l, no distinct gelation takes place. The colloidal silicic acid (silica gel) is obtained by removing or minimizing Na ion from water glass, e.g., by passing the glass through an ion exchange resin or neutralizing it with sulfuric acid, followed by removal of Na and sulfuric acid ions.