Study of the Bond Performance between GFRP Bar Reinforcement and Seawater–Sea Sand–Coral Concrete

The world has abundant marine resources, and the use of seawater, sea sand, and coral instead of seawater, river sand, and gravel can compensate for the lack of traditional building materials for marine engineering construction. Additionally, glass fiber–reinforced polymers (GFRPs) have excellent corrosion resistance and can effectively solve the corrosion problem of steel reinforcement in harsh environments. The bond performance between GFRP bars and sea sand–coral concrete (SSCC) is an important factor in deciding whether this approach can be applied in actual projects such as RC. In this study, the effects of the SSCC strength grade, diameter, bond length, and rib height on the bond performance between GFRP bars and SSCC were investigated using direct pullout tests. The bond performance between GFRP bars and SSCC was compared with that between GFRP bars and ordinary concrete (OC). Furthermore, the microstructure and damage characteristics of the GFRP bars and SSCC were observed using scanning electron microscopy (SEM). The test results show that the main failure modes of the specimens include GFRP bar pullout failure and SSCC splitting failure. The rib height has a greater effect on the bond performance, and in specimens with a strength grade of SSCC25, diameter of 12 mm, and bond length of 5d, the bond strength between a deep-ribbed GFRP bar and the SSCC was 75.6% greater than that of specimens with a shallow-ribbed GFRP bar. The bond strength between the GFRP bars and SSCC decreased with increasing diameter and bond length, but the bond stiffness was almost the same. When the diameter increased from 8 to 14 mm, the bond length increased from 3d to 7d, and the bond strength decreased by 57.3% and 36.9% respectively. The bond strength and bond stiffness increased with increasing strength grade of the SSCC. Moreover, SEM showed that the surface damage of GFRP bars with pullout failure was severe, whereas the surface integrity of GFRP bars with splitting failure specimens was better. Based on the experimental results, the bond–slip constitutive model of the GFRP bar with SSCC yielded satisfactory results.