The dependence of composition and sintering temperature on physical properties of ALA was investigated. Mechanism of black discoloration(sometimes called black core) usually found in the interior cores of artificial lightweight aggregate was also investigated by the optical observations. As a result, the primary cause of black discoloration in the interior of the lightweight aggregate body resulting from incomplete burn-out of carbonaceous impurities and iron-containing materials.In the cross-sectional morphology of ALA, bloating phenomena as well as formation of large pores were found in the samples containing ferrous materials. By increasing content of ferrous materials, both specific gravity and water absorption have been decreased.

This study was conducted to evaluate the feasibility of using bottom ash after magnetic separation and dredged soil from the coal power plants as raw materials for artificial lightweight aggregate (ALA). The dependence of composition and sintering temperature on physical properties of ALA was investigated. Fe compounds play an important role in the bloating reaction, thus specimens containing more ferrous materials such as Fe3O4 are more easily bloated. Both black core region and bloating phenomenon were increased with an increase in the contents of dredged soil. Specimens made use of MBA(Magnetic separated bottom ash which has magnetic components) showed lower bulk density than those of NMBA(non-magnetic separated bottom ash which has much less ferrous materials. It was confirmed that MBA could be used as an effective raw material for making ALA having low density because the ferrous components in it act as bloating agents.

This research concerns the characteristics of ALA made of magnetically separated desulfurized fly ash (DFA) generated from the coal power plant having fluidized bed type boiler. Being believed that these alkali-rich components could be separated by magnetic separation, desulfurized fly ash was separated by using 10,000 Gauss magnets as magnetic desulfurized fly ash (MDFA) and non-magnetic desulfurized fly ash (DFA). The dependence of composition and sintering temperature on physical property of ALA was studied. It seems to be apparent that the glass phase which is one of the main problems in the ALA manufacturing process could not be controlled by the magnetic separation only, but the formation of pores could be considerably controlled by the magnetic separation. It is also clear that neither DFA nor MDFA can be used as raw materials for making ALA; however, magnetic separation of desulfurized fly ash from fluidized bed type boiler is effective to collect bloating components for self-bloating of ALA without addition of an extra bloating agent.