The artificial lightweight aggregates (ALAs) were manufactured using dredged soil produced at thermal power plant and waste catalyst slag by direct sintering method at 1050~1250°C for 10min. The ALAs of 100% dredged soil showed the black core phenomenon even at the low sintering temperature as 1050°C and become lightened by bloating pores in black core area with sintering temperature. On the other hand, the aggregates with 100% waste catalyst slag did not showed black coring and bloating phenomenon and had the low forming ability and many cracks inside. Adding the dredged soil to the waste catalyst slag decrease the specific gravity by promoting the black coring and bloating inside. The water absorption(%) of ALAs decreased with sintering temperature. The ALAs fabricated in this study showed the specific gravity of 0.8~2.0 and water absorption of 2~16% so it could be applied to various fields such as the lightweight concrete or the field of the porous carriers for purification of a contaminated soil or water.

Improvement in the mechanical properties of non-cement mortars using ASTM Class C fly ash (FA) containing high amounts of CaO produced from a fluidized bed-type boiler and blast furnace slag (BS) was studied. This type of FA has been used to carbonate non-cement mortar under supercritical conditions for CO2 fixation, because such mortars cannot be recycled and easily reclaimed owing to the presence of high amounts of CaO that may adversely affect their eco-friendliness because of the high volume expansibility of CaO. Because a substantial increase in the compressive strength was observed for the specimen containing 20% FA, two types of Ca compounds—CaO and Ca (OH)2—were added to the BS specimens to investigate the effects of Ca compounds on the mechanical properties of non-cement mortar specimens. Three types of curing methods—room temperature, room temperature with hermetic sealing, and high temperature with hermetic sealing—were used and the specimens were aged for 3, 7, and 28 days. Because both CaO and Ca (OH)2 enhance the compressive strength at the concentration corresponding to that in the FA, it is speculated that the amorphous materials in the BS is destroyed without adding any acid or reagents because of the increase in pH by the Ca compound present in the specimen. An increase in the specimen pH may affect the strength improvement because of ion elution and curing reaction. It is concluded that enhancement in the mechanical property by the addition of 20% FA to BS can be explained from the results obtained by adding Ca compounds.