The　structural　performance　of　a　newly　developed　lightweight　and　thermally　efficient　alternate　of　normal　concrete　(NC)　i.e.　infra-lightweight　concrete　(ILC)　had　been　under　question　due　to　its　low　elastic　modulus,　surface　roughness,　and　cracking.　In　the　present　study,　the　structural　performance　of　ILC　has　been　improved　by　using　a　layer　of　high　strength　concrete　(HSC)　on　each　side　of　the　ILC.　As　the　efficiency　of　the　ILC-HSC　composite　structure　depends　on　the　bond　between　them,　therefore,　an　extensive　study　has　been　performed　to　assess　and　improve　the　bond　strength　in　two　parts.　In　the　first　part,　shear　(push-out)　and　tensile　(pull-off)　bond　strength　tests　have　been　conducted　on　ILC-HSC　specimens　which　revealed　that　the　interfacial　bond　strength　is　weaker　than　the　weakest　material　i.e.　ILC550.　Hence,　the　bond　strength　has　been　improved　by　carbon　and　glass　fiber-reinforced　polymers　(CFRPs　and　GFRPs)　with　two　different　grid　dimensions　i.e.　25　mm　and　38　mm　in　the　second　part.　Test　results　indicated　that　both　the　CFRPs　and　GFRPs　significantly　improved　the　bond　strengths　and　this　improvement　depends　on　the　reinforcement　ratios.　Maximum　bond　strength　has　been　achieved　for　GFRP-25　reinforced　ILCs　where　shear　and　tensile　bond　reinforcement　ratios　of　0.492%　and　0.445%　increased　the　shear　and　tensile　bond　strengths　by　331%　and　456%　respectively　as　compared　to　un-strengthened　specimens.　In　addition,　the　comparison　of　experimental　shear　bond　strengths　with　five　commonly　used　prediction　models　revealed　the　inaccuracy　of　all　the　presently　available　models.　Moreover,　there　is　no　prediction　model　available　for　tensile　bond　strength　prediction.　Therefore,　two　new　prediction　models　have　been　developed　for　shear　and　tensile　bond　strengths.　The　comparison　of　experimental　results　with　developed　models　has　revealed　the　accuracy　and　applicability　of　these　models　for　both　the　un-strengthened　and　FRP　strengthened　ILCHSC　composite　structures.　(C)　2020　Elsevier　Ltd.　All　rights　reserved.