Deterioration of mechanical properties of basalt/carbon hybrid FRP bars in SWSC under seawater corrosive environment

Abstract

Basalt fibre-reinforced polymer (BFRP) bars are becoming potential substitutes as reinforcements in seawater sea-sand concrete (SWSC). Unidirectional basalt/carbon hybrid fibre-reinforced polymer (HFRP) bars consisting of carbon and basalt fibres have better durability than those of BFRP bars. To examine the hybridisation effects of carbon fibres on the mechanical properties of BFRP bars, herein, the BFRP and HFRP bars embedded in SWSC and normal concrete (NC) were exposed to seawater. Correlations between the tensile properties, Cl− contents, matrix digestions, and microstructural characteristics of FRPs were investigated. Results showed that HFRP bars had higher mechanical properties and durability than those of the BFRP bars. The HFRP bars exhibited a different failure mode from that of the BFRP bars. Degradation rates of the tensile strengths of BFRP and HFRP bars in SWSC were higher than those in NC. Hydrolysis of resin played a dominant role in the degradation of HFRP bars. Alkali silica reaction between the alkali ions in SWSC and silica in the basalt fibres also degraded the HFRP bars. According to the findings of this study, the HFRP bars have better durability than those of the BFRP bars duo to the excellent mechanical properties and better corrosion-resistance of carbon fibres.