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.　©　2020　Elsevier　Ltd