Abstract: A method for making aggregate includes the following steps: (a) preparing a wet mixture by mixing water with a combination of ingredients in a mixer, the combination of ingredients including by weight about, 68% to 95% fly-ash and 2% to 10% lime; (b) dropping the wet mixture into at least one pile on a base surface; (c) allowing the wet mixture in the pile to substantially completely hydrolyze into a hard product; and (d) crushing the product to form the aggregate. Preferably, step (b) further includes forming an arcuate stack having multiple overlapping conical piles of the dropped wet mixture such that the stack extends a circular distance over the surface. The wet mixture may be transported from the mixer to a height above the surface and dropped to the surface by a radial stacker. The combination of ingredients, preferably, further includes by weight 0.5% to 12% alkali hydroxide and, more particularly, sodium hydroxide.