Geopolymers release 80% less carbon dioxide than Portland cement and simultaneously provide sufficient mechanical strengthfor structural applications. Therefore, they were worth as cement substitutes and have attracted from eco-friendly constructionindustries. Spent silicon sludge is increasing as the demand of silicon wafer for the solar energy generation and semiconductoris steadily increasing. Silicon sludge is produced from the cutting and grinding process of silicon ingot for making silicon wafer. In this study, silicon sludge is used as bloating agent for making porous geopolymers with spent industrial wastes such as fusedslags from IGCC (integrated gasification combined cycle) process or municipal waste treatment system. The compressivestrength and density of porous geopolymers decreased with silicon sludge addition. Because high addition of silicon sludge tofused slags under the high alkaline atmosphere releases much of H2 gas, highly porous geopolymers could be obtained in ashort curing period. However, high silicon content also showed adversely effects on polymerization process. Geopolymers withspecific gravity less than 0.4 was fabricated by using silicon sludge and fused slag; having compressive strength up to 1.3 MPa. In conclusion, very light and porous geopolymers having relatively higher compressive strength could be fabricated with fusedslag and spent silicon sludge as a bloating agent.

Keywords: Geopolymer, Silicon sludge, Recycling, Bloating agent, Fused slag