LAUSR

Abstract In this study, red mud (RM) and coal metakaolin (CMK) were alkali-activated to produce geopolymer material (RM-CMK). The effects of different Na/Al molar ratios on mechanical properties and microstructure of the geopolymer were studied. When Na/Al was 1.0, RM-CMK showed the highest 28d compressive strength of 56.2 MPa and peak strain of about 2%. When Na/Al was too high, the compressive strength decreased due to carbonation of excessive alkali reacting with CO2 in the air. Microstructure study of the RM-CMK material showed that amorphous geopolymer gel and zeolite mineral formed. When Na/Al was 1.0, the pore structure of RM-CMK was greatly improved compared to that of the RM-CMK with Na/Al of 0.8. Results showed that the appropriate Na/Al molar ratio can contribute to the geopolymerization, but ultra-high Na/Al molar ratio caused high alkali state to destroy the microstructure of geopolymers.