Title: Durability Enhancement of the Basalt Fiber-Reinforced Polymer Seawater Sea-Sand Concrete Beam by Alkalinity Regulation

Author(s): Shuaicheng Guo, Zhenqin Xu, Deju Zhu

Publication: Structural Journal

Volume:

Issue:

Appears on pages(s):

Keywords: accelerated aging; basalt fiber-reinforced polymer; beam; durability performance; flexural performance; low alkalinity; seawater sea sand concrete

DOI: 10.14359/51740569

Date: 2/14/2024

Abstract:
Reinforcing the seawater sea-sand concrete (SSC) with the basalt fiber-reinforced polymer (BFRP) bars can adequately resolve the chloride corrosion issues. However, the multiple-element ions in seawater and sea sand can increase the concrete alkalinity and accelerate the degradation of BFRP bars. This study aims to enhance the durability performance of the BFRP-SSC beam by regulating concrete alkalinity. The low-alkalinity SSC (L-SSC) is designed by incorporating a high-volume content of fly ash and silica fume. A total of 16 BFRP-SSC beams were designed based on the current standards and prepared using normal SSC (N-SSC) and low-alkalinity SSC (L-SSC). The beam flexural performances before and after long-term exposure are characterized through the four-point bending test. The test results indicate that exposure in the simulated marine environment can obviously reduce the load-bearing capacity and change the failure mode of the BFRP beam with N-SSC. After exposure at 55℃ for 4 months, the load-bearing capacity of the BFRP-SSC beam can be reduced by 70.0%. Moreover, the slight enhancement of load-bearing capacity and ductility of the BFRP-LSSC beam can be observed due to the enhanced interface performance with further concrete curing. Furthermore, the long-term performance of the sand-coated BFRP bar is better than that of the BFRP bar with deep thread. The load-bearing capacity of the BFRP-LSSC beam can increase by about 20% after 4 months of accelerated aging due to concrete strength growth, and the BFRP-LSSC beam maintained the concrete crushing failure mode after exposure. Finally, a load-bearing capacity calculation model for the BFRP-SSC beam is proposed based on the experimental investigation, and its prediction accuracy is higher than that of the current standards. This study can serve as a valuable reference for applying BFRP-SSC structures in the marine environment.