Fly ash among many kinds of ash is currently being recycled effectively; on the other hand most of the reject ash (RA) having 5% or more unburned carbon content is being simply reclaimed in the ash pond. In order to recycle RA effectively, various kinds of aggregates were manufactured and trials for making porous aggregate by bloating have been made by using RA and dredged soil (DS). As it is, of course, more economical way to use raw material itself as bloating agent comparing to adding some bloating agents to ALA for making it light, the reject ash was separated by magnet by two parts for the purpose of using it as natural bloating agent; one is magnetic reject ash (MRA) having more ferrous components and the other is non-magnetic reject ash (NMRA) having more unburned carbon. The magnetically separated ash was mixed with dredged soil for making ALA. As a result, lightweight aggregate having less than 1.0 specific gravity could be obtained by using MRA which contains more ferrous components than as received RA and NMRA. MRA acts like an effective bloating agent itself for making ALA lighter.

Keywords: Artificial lightweight aggregate, Firing, Interfaces, Porosity, Functional application.