Axial behavior of circular seawater sea-sand coral concrete columns reinforced with BFRP bars and spirals

•Axial behavior of BFRP bars reinforced seawater sea-sand coral concrete columns was studied experimentally.•The load bearing capacity of B-SSCC columns declined as the spiral spacing narrowed paradoxically owing to the significant discontinuity of coral concrete internally.•Columns with dense stirrups showed more pronounced ductility in the post-peak stage compared with B-SSCC square columns.•An ultimate bearing capacity prediction model is established.