The invention provides a novel formed product and method of producing a hard, dry, e.g., agglomerated or formed, product useful as a construction material comprising: a) papermill sludge made up of paper fiber, clay and calcium carbonate, b) ash such as coal ash (typically stack scrubber solids obtained from the burning of coal), and c) water. The amount of water present is selected to render the product plastic so that it can be molded to the desired shape. An oxidizer is provided in a sufficient amount to oxidize unstable compounds and to convert potassium, calcium or magnesium bisulfite to the sulfate form. Following the addition of the oxidizer, the admixture is exposed to electromagnetic energy, preferably ultraviolet light, to help drive the oxidation reaction to completion. In an optional form of the invention, a minor amount of a cation exchange resin is added to the mixture to sequester heavy metals. The admixture is formed or molded into pieces or bodies of the desired shape, such as blocks, slabs or pellets or agglomerates. The resulting pieces dry and harden at room temperature. They are unfused, contain retained wood fiber, are substantially dust free, hard, dry, and environmentally stable. They give off little or no objectionable odor. They are clean and when placed in water, will not release significant quantities of heavy metals. The formed bodies have enough strength to be used as an aggregate in a concrete product that exhibits good compression strength.