Because　of　the　carbonation　treatment　of　recycled　coarse　aggregates　(RCAs),　the　properties　of　the　weak　multiple　interface　transition　zones　(ITZs)　in　recycled　aggregate　concrete　(RAC)　can　be　improved,　contributing　to　the　enhanced　behaviour　of　the　RAC.　In　this　study,　different　carbonation　conditions　(carbonation　pressure,　initial　moisture　contents　of　the　RCAs　and　carbonation　duration)　were　considered.　A　model　of　the　RACs　(MIRAC)　was　prepared　to　accurately　locate　multiple　ITZs.　Nanoindentation　tests,　scanning　electron　microscopy　(SEM)　tests　were　conducted　to　study　the　effect　of　carbonation　treatment　on　the　microproperties　of　RAC.　At　the　same　time,　the　influence　of　the　carbonation　treatment　on　the　compressive　strength　and　chloride　ion　penetration　resistance　of　the　RAC　was　evaluated.　Moreover,　the　relationship　between　the　microproperties　and　macroproperties　of　the　RAC　was　discussed.　The　results　showed　that　the　modulus　of　the　ITZs,　the　old　mortar　matrix　and　the　new　mortar　matrix　increased　while　the　thickness　of　the　ITZs　decreased　when　the　carbonation　pressure　or　carbonation　duration　were　increased.　However,　there　was　no　further　significant　change　after　the　carbonation　pressure　exceeded　1　bar,　and　the　carbonation　rate　began　to　decrease　significantly　after　3　h　of　carbonation.　The　carbonation　efficiency　was　superior　when　the　moisture　content　was　1.81%.　The　effects　of　different　carbonation　parameters　on　the　microproperties　and　macroproperties　of　the　RAC　were　consistent.　The　compressive　strength　and　chloride　ion　penetration　resistance　of　the　RAC　had　a　linear　correlation　with　the　modulus　of　the　ITZ　between　the　aggregate　and　old　mortar.　©　2022　Elsevier　Ltd