Abstract
The combined effects of preexposure to high temperature and alkalinity on the tensile performance of structural GFRP reinforcing bars are experimentally investigated. A total of 105 GFRP bar specimens are preexposed to high temperature between 120°C and 200°C and then immersed into pH of 12.6 alkaline solution for 100, 300, and 660 days. From the test results, the elastic modulus obtained at 300 immersion days is almost the same as those of 660 immersion days. For all alkali immersion days considered in the test, the preheated specimens provide slightly lower elastic modulus than the unpreheated specimens, showing only 8% maximum difference. The tensile strength decreases for all testing cases as the increase of the alkaline immersing time, regardless of the prehearing levels. The tensile strength of the preheated specimens is about 90% of the unpreheated specimen for 300 alkali immersion days. However, after 300 alkali immersion days the tensile strengths are almost identical to each other. Such results indicate that the tensile strength and elastic modulus of the structural GFRP reinforcing bars are closely related to alkali immersion days, not much related to the preheating levels. The specimens show a typical tensile failure around the preheated location.
Highlights
Numerous studies have highlighted the tensile properties and performance of GFRP bars under high temperature conditions considering fire accident
Comparing the present test results with those of Robert et al [16], in which the rebar is made of the same resin type and immersed into alkaline solution maintained with identical temperature level, the tensile strength of the bare bars is similar to that of the mortar-wrapped bars until 120 immersion days
The purpose of this study is to identify the variation in the tensile properties of the structural GFRP reinforcing bars exposed to high temperature
Summary
Numerous studies have highlighted the tensile properties and performance of GFRP bars under high temperature conditions considering fire accident. The test is conducted using the tensile loading machine which is equipped with electric furnace controlling specified high temperatures. Such type of test is called “hot tension test.”. In postheating tension tests the GFRP bars are firstly exposed to temperatures between 100∘C and 400∘C for 0.5 to 3 hours. Kumahara et al [1] compared the results obtained from hot and postheating tension tests, showing that the GFRP reinforcing bars are almost recovered to their original tensile strength until 150∘C of exposed temperature level. It indicates that the recovery of tensile properties of GFRP rebar closely depends on the exposed temperature level and cooling process
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