PURPOSE: To obtain a solidification material having high strength and long-term solidification strength and high permeability, by using an alkali metal silicate and fumed silica as silica components and adding a polyvalent metal compound or a cement as a solidifying material.

CONSTITUTION: The objective solidification material contains an alkali metal silicate and fumed silica as essential silica components and a polyvalent metal compound or a cement as a solidifying material. The alkali metal silicate is a liquid or powdery water-glass such as water-glass #3, sodium orthosilicate or sodium metasilicate especially having a low molar ratio of SiO2/Me2O, i.e., ≤2.5. The water-glass may be produced by using a water-glass having high SiO2/Me2O molar ratio and adding an alkali to the high-molar ratio water-glass to lower the ratio to ≤2.5. The polyvalent metal compound used as a solidifying material is polyvalent salt, base, oxide, etc., of Ca, Al, Fe, Mg, etc., especially preferably lime.