A soil structure, for example a roadbed or levy, is made by admixing into soil from the course of the soil structure (a) calcium oxide, (b) at least one of cement kiln dust, lime kiln dust, fly ash, or cement, (c) a polymer binder for soil that is substantially gravelly, or liquid glass if the soil contains substantial quantities of pozzolanic material, and (d) water. The admixed soil is compacted into a roadbed or other soil structure of predetermined dimensions. After a predetermined amount of time, the liquid sodium metasilicate will catalyze hardening of the admixture if the soil contains sands or substantial quantities of pozzolans, otherwise the binder will cause hardening of the soil.