In this work, the physical & chemical properties of bottom ash generated from power plant are analyzed. Characteristic mortar property and thermal conductivity for building material were investigated with content of added bottom ash. According to the analytic result of bottom ash, chemical compositions of bottom ash is similar to those of fly ash and compressive strength after 7days related to pozzolanic activity shows 2.5N/cm2 and it is confirmed that bottom ash possess a certain amount of moisture activity. Although the fluidity of cement mortar is rapidly decreased with increasing addition of bottom ash, compressive strength for 3 and 7days is increased. The thermal conductivity is not sensitive to the addition of bottom ash.