Purpose　This　paper　aims　to　propose　the　five-phase　sphere　equivalent　model　of　recycled　concrete,　which　can　be　used　to　deduce　the　theoretical　formulas　for　the　Poisson＇s　ratio　and　effective　elastic　modulus.　Design/methodology/approach　At　a　mesoscopic　level,　the　equivalent　model　converts　the　interfacial　layer,　which　consists　of　the　new　interfacial　transition　zone　(ITZ),　the　old　mortar　and　the　old　(ITZ),　into　a　uniform　equivalent　medium.　This　paper　deduces　a　strength　expression　for　the　interfacial　transition　zone　at　the　microscopic　level　using　the　equivalent　model　and　elastic　theory.　In　addition,　a　new　finite　element　method　called　the　base　force　element　method　was　used　in　this　research.　Findings　Through　numerical　simulation,　it　was　found　that　the　mechanical　property　results　from　the　five-phase　sphere　equivalent　model　were　in　good　agreement　with　those　of　the　random　aggregate　model.　Furthermore,　the　proposed　model　agree　on　quite　well　with　the　available　experimental　data.　Originality/value　The　equivalent　model　can　eliminate　the　influence　of　the　interfacial　layer　on　the　macroscopic　mechanical　properties,　thereby　improving　the　calculation　accuracy　and　computational　efficiency.　The　proposed　model　can　also　provide　a　suitable　model　for　multi-scale　calculations.