In　order　to　efficiently　utilize　steel　slag　and　reduce　carbon　emissions,　the　performance　of　alkali-activated　slag/stainless　steel　slag　mortar　(ASM)　prepared　with　a　composite　activator　is　investigated.　In　this　work,　CaO,　Na2CO3　and　water　glass　(WG)　are　used　as　composite　activators,　where　the　alkali　equivalents　of　CaO　and　Na2CO3　are　maintained　at　4%　and　the　alkali　equivalents　of　WG　(i.e.　WG　content)　as　variables　were　0,　0.5%,　1.0%,　1.5%　and　2.0%　respectively.　The　properties　of　ASM,　including　mechanical　properties,　autogenous　and　drying　shrinkage,　are　investigated.　Results　show　that　the　mechanical　properties　of　ASM　decrease　and　then　increase　as　the　WG　content　increases,　with　the　worst　mechanical　properties　of　ASM　occurring　when　the　WG　content　is　0.5%.　The　autogenous　shrinkage　of　ASM　decreases　as　the　WG　content　increases　from　0　to　0.5%　followed　by　an　increase　as　the　WG　content　increases　further　to　2.0%.　Autogenous　shrinkage　depends　on　chemical　shrinkage,　small　pore　(＜50　nm)　volume,　MCL　and　capillary　pressure.　When　the　WG　content　is　increased　from　0　to　0.5%,　the　hydration　reaction　is　inhibited　by　the　reaction　of　the　WG　and　CaO　which　reduces　the　pH　of　activator　solution　and　gel　amount,　leading　to　a　reduction　in　chemical　shrinkage,　small　pore　volume,　MCL　and　capillary　pressure.　However,　the　high　WG　content　accelerates　the　hydration　reaction　when　the　WG　content　is　greater　than　0.5%,　which　increases　the　autogenous　shrinkage.　The　drying　shrinkage　of　ASM　decreases　and　subsequently　increases　as　the　WG　content　increases.　The　higher　drying　shrinkage　is　associated　with　weight　loss　due　to　the　excellent　connectivity　of　the　pores.　The　pore　structure　also　affects　the　drying　shrinkage,　which　can　be　justified　on　the　basis　of　capillary　pressure.　©　2023　Elsevier　Ltd