Experimental study on the preparation of cementitious materials from iron ore tailings by activation

•The results show that the activation of iron ore tailings(IOT) can increase the specific surface area, improve the surface energy and activity, increase the degree of participation in hydration reaction, promote the formation of a large number of acicular ettringite and C-S-H gel, improve the pore structure of hydration products, and lead to denser microstructure.•The types of hydration products of the samples under different activation methods of iron ore tailings(IOT) did not change, but the diffraction peak intensity of hydration products changed.•The effect of mechanical-chemical activation is better than that of mechanical activation.•When the coupling effect of mechanical-chemical activation of iron ore tailings(IOT) with 10 % metakaolin is 1.5 h, the performance of cementitious materials is the best.