Understanding the Behavior of Industrial Wastes as Replacement of 20 wt.% of Metakaolin Before Geopolymerization: A Comparative Study

This study investigates the behavior of four industrial wastes—suction dust (SW1), red mud (SW2), electro-filter dust (SW3), and extraction sludge (SW4)—as partial substi-tutes (20 wt.%) for metakaolin in geopolymer synthesis. The objective is to assess how their incorporation before alkali activation affects the structural, thermal, mechanical, chemical, and antimicrobial properties of the resulting geopolymers. The materials were characterized through FT-IR spectroscopy, TG-DTA analysis, compressive strength, integrity and boiling water resistance tests, heavy metal leaching, and anti-microbial assays. FT-IR analysis confirmed successful geopolymerization in all sam-ples, and stability tests revealed that none of the composites disintegrated under ther-mal or water stress. However, compressive strength was reduced across all waste-containing geopolymers, and leaching tests showed that SW1- and SW4-based geopolymers released antimony above legal limits for landfill disposal. Thermal analy-sis indicated that waste composition influenced dehydration and decomposition be-havior. Antimicrobial activity of waste-based geopolymers was observed against E. coli, while E. faecalis showed stronger resistance. Overall, the incorporation of these industrial wastes before geopolymerization presents both opportunities and challeng-es. While enabling valorization of waste, careful selection and characterization of the wastes are essential to ensure the environmental safety and functional performance of the resulting geopolymers.