Carbonation　has　long　been　considered　harmful　to　the　durability　of　steel　reinforced　concrete　structures　especially　with　the　increasing　CO2　and　temperature　globally.　In　coastal　construction,　the　chloride　ions　even　make　it　worse.　By　replacing　the　steel　with　chloride-insensitive　reinforcement　such　as　fiber　reinforced　polymer　(FRP),　sea　sand　is　a　potential　alternative　to　river　sand,　even　carbonation　could　be　utilized　due　to　the　acid　resistance　of　FRP.　In　this　paper,　seawater　sea-sand　recycled　aggregate　concrete　(SSRAC)　was　prepared,　which　had　different　hydration　and　carbonation　from　ordinary　concrete　(OC).　The　test　results　showed　that　the　carbonation　depth　at　28 days　of　SSRAC　increased　up　to　179.13%　of　OC.　A　modified　carbonation　model　based　on　pore　evolution　was　established.　On　the　other　hand,　the　increasement　of　carbonatable　material　in　SSRAC　was　up　to　14.32%.　Combined　with　this　characteristic,　the　carbon　emission　and　absorption　assessment　were　carried　out.　It　is　found　that　the　CO2　absorption　of　SSRAC　can　be　up　to　325%　of　OC　in　10 years’　service,　and　the　total　carbon　emission　including　carbon　sequestration　over　the　whole　life　of　SSRAC　with　a　salinity　of　4%　is　45.73%　of　OC.　This　research　verifies　that　it　is　expected　to　achieve　more　CO2　sequestration　rapidly　in　SSRAC,　which　could　probably　help　design　low-carbon　concrete　structures.　©　The　Author(s),　under　exclusive　licence　to　RILEM　2025.