This　study　investigated　the　influence　of　drying　shrinkage　on　the　bond　strength　between　alkali-activated　steel　slag　(SS)/fly　ash　(FA)　lightweight　mortar　(ASFLm)　and　concrete　substrates.　The　alkali　contents,　defined　as　the　mass　ratio　of　Na2O　in　sodium　hydroxide　to　the　total　mass　of　SS　and　FA,　were　set　at　4　%,　6　%,　8　%,　and　10　%.　The　compressive　strength,　drying　shrinkage,　fire　resistance　and　bond　strength　of　ASFLm　were　analyzed.　Results　indicated　that　increasing　alkali　content　initially　enhances　bond　strength,　followed　by　a　subsequent　decline.　The　bond　strength　was　maximum　at　6　%　alkali　content　with　a　value　of　0.65　MPa.　The　drying　shrinkage,　porosity　and　micromechanical　properties　of　ASFLm　determined　bond　strength.　Porosity　decreased　and　the　micromechanical　properties　increased　when　the　alkali　content　increased　from　4　%　to　6　%　because　of　the　increment　in　the　contents　of　C-A-S-H　and　C-N-A-S-H　gel.　Only　a　few　microcracks　were　observed　despite　the　increase　in　drying　shrinkage,　so　the　bond　strength　of　ASFLm　increased.　ASFLm＇s　elastic　modulus　improved　when　the　alkali　content　increased　from　6　%　to　10　%.　However,　high　drying　shrinkage　resulted　in　numerous　microcracks　in　the　ASFLm　matrix.　These　microcracks　decreased　the　microhardness　and　increased　the　porosity　of　ASFLm.　Hence,　the　bond　strength　of　ASFLm　was　reduced.　©　2024　Elsevier　Ltd