Abstract: Geopolymers were prepared with the iron tailings as main raw materials， metakaolin as the adjusted materials， with NaOH solution and sodium silicate as alkali activator agent， the effects of raw materials ratio on the properties of geopolymers were investigated by orthogonal testThe results show that under the conditions of raw materials with n(SiO₂):n(Al₂O₃) of 3.0， liquid-solid ratio of 0.35， and alkali activator modulus of 1.2， the compressive strength value of geopolymers is the highest at 28 d， which comes up to 59.0 MPa. The microstructure of the samples were characterized by XRD， FTIR and SEM. Microscopic analysis indicate that the samples have the microstructure characteristics of the normal geopolymers， and the main compositions are amorphous aluminosilicate， semi-crystalline CSH(I) and α-C₂SH. As the curing ages are prolonged， more gelatinous substances are generated and bond the fine particles together to form compact internal structure in samples， which improves the compressive strength of geopolymers.

Key words: Iron tailings, Metakaolin, Geopolymers, Compressive strength, Microstructure