Durability of BFRP bars embedded in seawater sea sand coral aggregate concrete in simulated seawater environment: Effects of coral coarse aggregate and cement contents

This study evaluates the influences of coral coarse aggregate (CCA) and cement contents on the durability performance of basalt fiber-reinforced polymer (BFRP) bars embedded in seawater sea sand coral aggregate concrete (SSCC). The evaluation is conducted by characterizing the changes in interlaminar shear strength after accelerated exposure in a simulated seawater environment. Accelerated aging tests were conducted under varying exposure durations (60, 120, and 180 days) and temperatures (25, 40, and 55 °C). The 1H low-field nuclear magnetic resonance, Fourier transform infrared spectroscopy, and scanning electron microscopy analyses were conducted to investigate the deterioration mechanisms of embedded BFRP bars. It was found that SSCC-embedded BFRP bars typically have a lower interlaminar shear strength than that of seawater sea sand concrete (SSC)-embedded BFRP bars subjected to the same immersion conditions. This is mainly attributed to the high porosity of CCA, resulting in higher permeability of SSCC than that of SSC. In addition, increasing cement content enhances the initial amount of OH– in SSCC, expands the pitting area of BFRP bars, and maintains OH– concentration better in the exposure tests, accelerating the interlaminar shear strength deterioration of BFRP bars. Microstructure analysis clearly reveals that the deterioration of embedded BFRP bars is mainly caused by resin hydrolysis, fiber-resin interface debonding, and fiber damage after corrosion. Based on the Arrhenius relationship, accelerated aging test results were utilized to predict the service life of SSCC-embedded BFRP bars under the real service condition. The findings of this study are valuable for the application of BFRP bars reinforced SSCC structures under marine environments and provide some insights into improving the long-term performance of SSCC-embedded BFRP bars, i.e., modifying the CCA to minimize the permeability of SSCC and producing low-alkalinity SSCC.