Carbonation　treatment　was　employed　to　improve　the　quality　of　recycled　coarse　aggregate　(RCA),　and　the　RCA　or　carbonated　RCA　(CRCA)　was　used　to　prepare　recycled　aggregate　concrete　(RAC　or　RAC-C).　The　influence　of　the　RCA　replacement　rate　and　CRCA　on　the　mechanical　properties　and　stress-strain　relation　of　concrete　was　investigated.　The　results　have　shown　that　carbonation　treatment　enhances　the　physical　properties　and　interfacial　transition　zone　(ITZ)　of　CRCA,　and　effectively　prevents　the　degradation　in　mechanical　properties　of　concrete.　Increased　RCA　or　CRCA　replacement　rate　reduces　the　peak　stress　and　ascending　slope　and　increases　the　peak　strain　of　RAC　or　RAC-C.　The　stress-strain　curve　of　RAC-C　has　higher　ascending　slope,　peak　stress　and　lower　peak　strain　than　that　of　RAC　and　is　closer　to　that　of　natural　aggregate　concrete　(NAC)　due　to　the　improved　new　ITZ.　The　stress-strain　relation　result　agrees　well　with　the　proposed　model.　(C)　2018　Elsevier　Ltd.　All　rights　reserved.