The　utilization　of　ferronickel　slag　into　the　alkali-activated　system　is　promising　to　mitigate　environmental　pollution.　Due　to　slower　reaction　rate　and　satisfactory　strength,　a　combined　activator　of　Ca(OH)2　and　Na2CO3　(molar　ratio　of　1:　1)　was　used　to　investigate　the　effect　of　combined　activator　content　(i.e.　3,　5,　7　and　9%　Na2O　equivalent)　on　the　workability,　water　requirement　of　normal　consistency,　setting　time,　soundness　and　compressive　strength　of　alkali-activated　ferronickel　slag　(AFS)　system.　X-ray　diffraction,　thermogravimetric　analysis,　scanning　electron　microscopy　and　mercury　intrusion　porosimetry　were　used　to　characterize　the　reaction　products　and　pore　structure.　Results　indicate　that　the　workability　of　AFS　system　decreases　with　the　increase　of　Na2O　equivalent,　while　the　compressive　strength　first　increases　and　then　decreases.　The　reaction　process　is　accelerated　with　Na2O　equivalent　from　3%　to　7%,　thereby　promoting　the　formation　of　C-(A)-S-H　gel,　calcite　and　hydrotalcite　that　can　improve　the　compressive　strength.　Whereas　an　increasing　porosity　due　to　microcracks　is　observed　at　9%　Na2O　equivalent,　thus　resulting　in　the　decrease　of　compressive　strength.　Considering　the　workability　and　compressive　strength,　the　optimal　Na2O　equivalent　in　AFS　system　is　5%.　©　2021　Elsevier　Ltd