Abstract: Improved cementitious composition results from a process comprised of mechanical size reduction and activation of a mixture of lime and fly ash and the addition thereto of fly ash and aggregate, as needed, to make a mix of the desired proportions. A quicker and more complete reaction between the lime and fly ash results from deagglomeration of lime particles caused by interaction with the fly ash and/or by the increased availability of reactant materials due to particle size reduction of both the lime and the fly ash. The mechanical size reduction and activation process may be carried out, for example, in a ball mill or centrifugal impact mill.

Abstract: Waste sludges containing small amounts of certain types of reactive materials are treated by adding to such sludges materials capable of producing aluminum ions, lime and/or sulfate bearing compounds to produce a composition having a sufficient concentration of sulfate ions, aluminum ions and equivalents thereof, and calcium ions and equivalents thereof. Fly ash is preferred source of aluminum ions for this purpose. Over a period of time such compositions harden by the formation of calcium sulfo-aluminate hydrates. Hardening of the sludge facilitates its disposition and may permit the reclamation of the land now occupied by large settling ponds for such sludge. Still further, the solidification of such settling ponds may provide permanent land fill which permits immediate use of the land without the necessity for removal of the sludge. Aggregate materials may also be incorporated in the solidified waste.