To provide the subject solidifying material capable of improving the quick-hardening properties of a roadbed material and also providing the roadbed material with high strength at an earlier stage without requiring any large-scale or complex equipment by using a hydraulic material which consists of gypsum and a fired material having a specified composition and has a Blaine specific surface area of ≥ a specified value, as this solidifying material.

As this solidifying material, a powdery hydraulic material consisting of gypsum and a fired material which is produced with at least one of municipal waste incineration ash and sewage sludge incineration ash as the raw material and contains 10 to 40 wt.% of at least one of 11CaO.7Al2O3.CaCl2, 11CaO.7Al2O3.CaF2 and 3CaO.Al2O3 and also contains at least one of 2CaO.SiO2 and 3CaO.SiO2, is used. Preferably, the production of the powdery hydraulic material comprises: adding 1 to 30 pts.wt. of gypsum to 100 pts.wt. of the fired material and mixing them together to obtain a mixture; and grinding the mixture so that the ground powdery mixture has a Blaine specific surface area of ≥3,000 cm2 to produce the powdery hydraulic material to be used as the objective solidifying material. The production of this roadbed material comprises: adding this solidifying material, together with water, to a roadbed raw material to obtain a mixture; and kneading the mixture to harden it by hydration; wherein the amount of the solidifying material to be added to the roadbed raw material is preferably 5 to 30 pts.wt. based on 100 pts.wt. of the roadbed raw material.