Durability of tubular sea water sea sand concrete and fibre-reinforced polymer hybrid structures: Mechanisms and effective parameters: Critical overview and discussion

The continuous increase in adverse environmental impacts of ordinary concrete with steel reinforcements has demanded using more environmentally friendly materials in the construction industry. Seawater and sea sand concrete (SWSSC) reinforced with fibre-reinforced polymer (FRP) composites have been backed by numerous researchers as an environmentally friendly alternative, especially for offshore structures and near-coastal areas. Tests on various fibre reinforcements (glass, carbon, and basalt) evaluated carbon FRP to dominate structural performance. However, the considerable expense, compared to the other fibres, discouraged the mainstream applications of CFRP tubes. Further, glass and basalt have shown significant mechanical properties degradation when subjected to SWSSC environment. Therefore, to overcome such challenges, a clear understanding of the mechanisms and the level of degradations as the effective parameters of different FRP tubes when used with SWSSC are essential. This paper critically reviews the recent studies conducted on the short-term and long-term durability of SWSSC-filled FRP tubes. Failure modes, degradation mechanisms, knock-down factors and the effective parameters, such as fibre type, fibre orientation, tube cross-section dimensions, and condition type for different FRP tubes, were discussed in detail. Finally, recommendations for future studies have been proposed based on the discussions and current research gaps.