Mechanical property and structural evolution of alkali-activated slag-phosphate mine tailings mortars.

The present work studies consolidation of phosphate mine tailings through alkaline activation process with the addition of slag for adjusting the gel structure. As increasing slag contents in the raw materials, more (Na,K)2O-CaO-Al2O3-SiO2-H2O (C-A-S-H) and (Na,K)2O-Al2O3-SiO2-H2O (N-A-S-H) gels were formed in the mine tailings-based mortars. Compressive strength of the mortars increased as increasing the slag contents from 0 to 40%, and then it kept a plateau. Evolution in microstructure of these mortars were characterized through scanning electron microscopy (SEM), X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) measurements. The study provides fundamentals for the co-disposal of phosphate mine tailings with blast furnace slag through alkaline activation process.