Title: Performance of Glass Fiber-Reinforced Polymer-Reinforced Concrete Piles Exposed to Laboratory-Simulated Marine Environments

Author(s): Ahmed Elhamaymy, Hamdy M. Mohamed, and Brahim Benmokrane

Publication: Structural Journal

Volume: 120

Issue: 3

Appears on pages(s): 31-45

Keywords: axial capacity; glass fiber-reinforced polymer (GFRP) bars; marine environment; piles; reinforced concrete (RC); spirals and ties

DOI: 10.14359/51738501

Date: 5/1/2023

Abstract:
This research aimed at investigating the possibility of using glass fiber-reinforced polymer (GFRP) reinforcement in concrete piles submerged in marine environments. In addition, the validity of the available design provisions in the codes in predicting the nominal axial capacity of submerged GFRP-reinforced concrete (RC) piles in marine environments was investigated. The experimental program aimed at assessing the durability and structural response of RC square piles entirely reinforced with GFRP bars and spirals (or ties) exposed to laboratory-simulated marine environments. Fifteen laboratory-scale square concrete piles, including 10 conditioned and five unconditioned specimens, with a cross section of 300 mm (12 in.) and 1000 mm (40 in.) in length and reinforced with GFRP bars and spirals, were fabricated and tested. The structural parameters included longitudinal reinforcement ratio, diameter of GFRP bars, and configuration of the GFRP spirals or ties. The 10 specimens were submerged in two different marine environments for 365 days and then tested under concentric loading. Marine environments in tropical and hot regions were simulated by submerging the specimens in saline solution (3.5% NaCl) at 22°C (72°F) and in a heatwave chamber at 60°C (140°F), respectively. Microstructural analyses—including glass transition temperature, optical microscopy (OM), and scanning electronic microscopy (SEM)—were conducted on GFRP reinforcement extracted from the submerged pile specimens to assess the possible degradation of GFRP reinforcement and changes in its bonding to concrete and microstructure. The microstructure analysis results confirm that the GFRP reinforcement was well-bonded to the concrete and did not show any sign of microstructural deterioration. The structural test results indicate that axial capacities of the submerged GFRP-RC pile specimens increased up to 22% compared to the unconditioned counterpart specimens due to the increase in concrete compressive strength. Moreover, the test results have shown that increasing the GFRP reinforcement ratio and using GFRP spirals improved the post-peak response of the GFRP-RC piles.