Copper mine tailings and metakaolin as precursors for sustainable alkali-activated mortars

The production of mine tailings is becoming a serious problem due to their storage and possible releases of environmental pollutants. This paper evaluated the possibility of manufacturing alkaliactivated mortars by copper mine tailings (CMT) and metakaolin (MK). Results showed that it is possible to activate CMT with at least 25 % MK by mass and the resulting alkali-activated mortars can reach compressive strength higher than 30 MPa. The studied mortars show high durability to sulphate attack especially when produced with 100 % MK, since MK contains highly reactive silica and alumina species which refine the pores structure, limiting water evaporation and hence salt crystallization. Conversely, the lowest capillary water absorption (15 % lower than that containing solely MK) has been found for the mortar containing 75 % CMT, due to its lowest total porosity. These innovative materials can be used both for structural and non-structural elements, especially in those areas with high production of CMT where their disposal is an issue.