The　application　of　seawater　and　sea　sand　concrete　(SWSSC)　can　reduce　the　construction　period　and　cost　of　island　infrastructure,　but　it　may　also　bring　the　risk　of　alkali-silica　reaction　(ASR)　owing　to　the　presence　of　alkali　ions　in　seawater　and　sea　sand.　To　compare　the　characteristics　of　ASR　between　SWSSC　and　seawater　and　desalinated　sea　sand　(DSS)　concrete,　the　properties　and　the　ASR　products　of　mortar　bars　with　different　DSS　content　were　studied.　When　the　DSS　proportion　increased　from　0%　to　100%,　the　sodium　(Na+),　potassium　(K+)　and　calcium　(Ca2+)　ion　concentration　of　the　specimens　decreased　by　22.6,　2.0　and　45.1　mg　L-1,　respectively,　the　pH　decreased　by　0.05　and　the　expansion　of　mortar　bars　was　reduced　by　0.16%.　Desalination　of　sea　sand　could　not　eliminate　the　risk　of　ASR　of　SWSSC　completely.　The　14　days　expansion　of　mortar　bars　with　100%　DSS　was　0.13%,　and　the　precursors　of　ASR-P1　were　observed　by　SEM.　The　experimental　results　of　micriscopic　tests　all　showed　that　with　the　increase　of　DSS　proportion,　the　content　of　Na-shlykovite　and　ASR-P1　were　reduced.　A　small　amount　of　magnesium　(Mg)　in　ASR　products　was　detected.　This　study　can　provide　a　basis　for　the　application　of　SWSSC　in　island　infrastructure.　©　2023　Emerald　Publishing　Limited:　All　rights　reserved.