Durability study of concrete-covered basalt fiber-reinforced polymer (BFRP) bars in marine environment

Abstract To understand the durability of basalt fiber-reinforced polymer (BFRP) bars for the reinforcement of concrete structures applied in marine environments, BFRP bars with 20-mm concrete covers were immersed in ocean water or simulated seawater at room temperature (~23 °C), and the evolution of the thermomechanical properties was studied. A set of uncovered BFRP bars immersed in ocean water and laboratory accelerated simulated seawater (23 °C, 40 °C, and 60 °C) was investigated for comparison. After one year, the mechanical properties of the uncovered BFRP immersed in 60 °C simulated seawater showed the most degradation, followed by the concrete-covered BFRP in the laboratory immersion. Concrete-covered BFRP showed more deterioration than uncovered BFRP in the ocean water. The results indicated that the alkalinity is the key factor causing the degradation of BFRP, especially for standing water in the laboratory environment. In addition, an alkali-aggregate reaction (AAR) of SiO2 in basalt fiber was found at the interface between the BFRP bars and concrete. The degradation of the resin matrix and sizing led to the direct exposure of basalt fiber to alkaline solution, which established the foundation of the AAR.