Abstract: A tilling/stabilization apparatus for tilling and stabilizing a roadbed or other base layer of soil includes a large manifold for receiving metered amounts of pressurized fly ash or other powdery filler, binder, and/or sealer material and injecting it in the vicinity of a rotating tiller that is tilling the roadbed. A water manifold passing through a housing surrounding the tiller produces a dense water mist inside the housing, causing dust to settle and providing a cementitious mix of the fly ash with the tilled roadbase material. Reliable, economical filling of roads and stabilization of a road base is achieved.