Environmental problems have been arisen from the ash produced from coal power plants. That is the reason that there have been many studies on recycling coal ash by making artificial lightweight aggregates (ALA) from coal ash. Although fly ash among many types of ash is currently being recycled effectively, 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 types of aggregate were manufactured and trials for making a porous aggregate by bloating have been made by using RA and dredged soil (DS). As it is, of course, a more economical way to use the raw material itself as a bloating agent compared to adding some bloating agents to ALA to make it light, the reject ash was separated by a magnet into two; one is a magnetic reject ash (MRA) having more ferrous component and the other is a non-magnetic reject ash (NMRA) having more unburned carbon. The magnetic separated ash was mixed with dredged soil to make ALA. As a result, a lightweight aggregate having less than 1.0 specific gravity could be obtained by using MRA which contains more ferrous components than as received RA or NMRA and therefore acts like a bloating agent itself to make ALA lighter.

Keywords: Artificial lightweight aggregate, Reject ash, Dredged soil, Specific gravity, Absorption rate, Bloating, Wet magnetic separation.