Effects of alkaline concentration and saline contents on degradation of tensile properties, microstructure and chemical characterization of glass fiber reinforced polymer (GFRP) rebars

• Published in: Journal of Building Engineering Vol. 69; p. 106222
• Main Authors: Wang, Peng, Ke, Linyuwen, Wang, Zike, Zhao, Jun, Li, Weiwen, Leung, Christopher K.Y.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.06.2023
• Subjects: Alkaline/saline environments; Fiber/matrix deterioration; Glass fiber reinforced polymer; Tensile strength degradation; Water/ion diffusion; Tensile strength degradation; Water/ion diffusion; Glass fiber reinforced polymer; Alkaline/saline environments; Fiber/matrix deterioration
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2023.106222

Glass fiber reinforced polymer (GFRP) rebar has attracted widespread attention in construction industries to mitigate steel corrosion problems which significantly affect the engineering sustainability. However, GFRP tensile strength may degrade under exposure to alkaline/saline environments, and the inherent quantitative relationship between tensile strength degradation and exposure conditions is still unclear. In this study, the tensile strength retention of GFRP rebars was found to drop to 45.9%, 47.2%, 44.2%, 41.1%, 27.6%, 30.3% and 31.9% in distilled water (DW, pH = 7), seawater (SW, pH = 8.2), sodium hydroxide solutions (NaOH, pH = 11, 12 or 13), simulated normal concrete (NC, pH = 13.6) and seawater sea-sand concrete pore solutions (SSC, pH = 13.6), respectively, after 12 months of exposure at 60 °C. Both the residual tensile strength retention and activation energy in the Arrhenius equation were found to decrease with pH in a descending quadratic parabola form. The underlying degradation mechanism was then revealed by relating the macroscopic tensile strength degradation to the water/ion diffusion and fiber/matrix deterioration at the microscopic level. The pH level rather than saline ions was uncovered to be the major influence factor for GFRP degradation. The findings of this study supply engineers with a comprehensive database on GFRP tensile strength degradation, suggesting that lowering the exposure pH rather than the saline content is critical for enhancing the durability of GFRP composites. •GFRP residual strength and activation energy in Arrhenius equation decreased with pH.•Microstructure changes in glass fibers and matrix were investigated by SEM and EDS.•Mechanism was revealed by relating macroscopic degradation to microstructure change.•pH level rather than saline content was the major influence factor for degradation.•An empirical equation relating GFRP degradation to pH and temperature was developed.