The　freeze-thaw　damage　behavior　of　seawater　sea　sand　concrete　(SWSSC)　under　two　freeze-thaw　media,　freshwater　and　seawater,　was　investigated　through　rapid　freeze-thaw　tests.　By　analyzing　changes　in　microstructure　and　reaction　products,　the　reasons　for　the　more　severe　damage　of　SWSSC　compared　to　ordinary　concrete　(OC),　and　the　influence　of　freeze-thaw　media　on　the　damage　mechanism　were　explored.　Based　on　the　fatigue　cumulative　damage　theory,　a　freeze-thaw　damage　and　life　prediction　model　for　SWSSC　in　both　freshwater　and　seawater　freeze-thaw　environments　was　proposed,　using　the　relative　dynamic　elastic　modulus　as　the　damage　variable.　The　results　indicate　that　chloride　ions　and　sulfate　ions　within　SWSSC　react　with　cement　hydration　products　to　form　non-cementitious　Friedel＇s　salt,　expansive　columnar　gypsum,　and　needle-like　ettringite　crystals,　which　damage　the　pore　structure　and　significantly　reduce　the　compactness　of　the　SWSSC　microstructure.　Compared　to　freeze-thaw　in　freshwater,　the　intrusion　of　more　Cl-　and　SO42-　during　seawater　freeze-thaw　accelerates　the　damage　process　of　SWSSC.　After　60　freeze-thaw　cycles　in　freshwater,　the　mass　loss　rate　of　SWSSC　reached　4.08　%,　and　the　relative　dynamic　elastic　modulus　decreased　to　61　%　of　its　initial　value.　In　seawater,　the　mass　loss　rate　increased　to　7.02　%,　and　the　relative　dynamic　elastic　modulus　dropped　to　48　%　of　its　initial　value.　The　freeze-thaw　life　of　SWSSC　in　freshwater　and　seawater　was　348.9　years　and　84.5　years,　respectively,　while　that　of　OC　was　395.3　years　and　94.8　years,　respectively.　Under　the　same　freeze-thaw　medium,　the　freeze-thaw　life　of　SWSSC　is　shorter　than　that　of　OC,　and　the　influence　of　the　freeze-thaw　medium　on　freeze-thaw　cycles　is　far　greater　than　that　of　the　concrete　material　itself.　SWSSC　meets　the　durability　requirements　of　Chinese　standards　in　freshwater　environments,　but　in　seawater　environments,　additional　anti-freezing　measures　(such　as　adding　air-entraining　agents)　are　required　to　meet　durability　requirements.　The　freeze-thaw　damage　and　life　prediction　model　proposed　in　this　study　provides　a　theoretical　reference　for　the　application　of　SWSSC　in　freshwater　and　seawater　freeze-thaw　environments.　©　2025