This　study　explores　the　carbonation　behavior　of　seawater　sea-sand　recycled　aggregate　concrete　(SSRAC),　considering　the　effects　of　recycled　coarse　aggregate　(RCA)　replacement　ratio,　sea-sand　content,　and　carbonation　age.　The　influence　of　these　parameters　on　carbonation　depth　was　systematically　investigated.　A　suite　of　characterization　techniques,　including　scanning　electron　microscopy　(SEM),　X-ray　diffraction　(XRD),　thermo-gravimetric　analysis　(TGA),　and　mercury　intrusion　porosimetry　(MIP),　was　employed　to　elucidate　the　effects　of　seawater,　sea　sand,　and　RCA　on　hydration　products,　carbonation　compounds,　pore　structure,　and　microstructural　features　of　the　concrete.　The　results　revealed　that　increasing　the　RCA　replacement　ratio　led　to　a　decline　in　both　compressive　strength　and　carbonation　resistance.　In　contrast,　the　incorporation　of　sea　sand　exhibited　a　non-monotonic　effect:　compressive　strength　initially　decreased　and　then　recovered,　while　carbonation　resistance　first　improved　and　subsequently　diminished,　with　optimal　performance　achieved　at　a　30　%　sea-sand　replacement　level.　Post-carbonation　analysis　showed　a　reduction　in　total　porosity　of　approximately　5　%,　accompanied　by　an　increase　in　the　most　probable　pore　diameter　by　about　2　mm.　A　predictive　model　for　carbonation　depth　in　SSRAC　was　developed　based　on　RCA　and　sea-sand　replacement　ratios.　The　model　demonstrated　strong　predictive　capability,　with　an　average　correlation　coefficient　of　0.92　between　calculated　and　experimental　results.　Utilizing　this　model,　the　long-term　carbonation　depth　of　various　concrete　compositions　was　estimated　over　a　50-year　service　life,　offering　meaningful　insights　into　the　durability　performance　of　SSRAC　in　practical　applications.　©　2025　Elsevier　Ltd