A hydraulic binder based on a sulfoaluminate clinker including the mineralogical phases ye'elimite C4A3$, mayenite C12A7, free lime CaO, and optionally belite C2S, characterized in that, in the clinker, the mineralogical phases are 20% to 50% by weight of ye'elimite C4A3$ phase, 5% to 80% by weight of mayenite C12A7 phase, and 1% to 5% by weight of free lime CaO, the weight ratio between the mayenite C12A7 and ye'elimite C4A3$ phases being between 0.1 and 10. The binder can be used to treat polluted soils, in particular soils with a leachable fraction greater than 0.4% that contains predominantly anions and/or heavy metal cations by mixing the soil with the hydraulic binder, in soil/binder weight proportions of between 1 and 40 parts of binder for 100 parts of soil. It makes it possible to stabilize soils which are polluted or to stabilize soils before dumping.
