Experimental Investigation of the Effects of Concrete Alkalinity on Tensile Properties of Preheated Structural GFRP Rebar

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.

Microstructure Characteristics of GFRP Reinforcing Bars in Harsh Environment

“…In the latter industry, they have been employed in new and existing buildings as internal and external reinforcing bars and for repair, strengthening, and retrofitting purposes. e literature has especially focused on the ability of FRPs to replace steel as the main reinforcement in concrete structures [8][9][10][11][12][13][14][15]. However, before being widely adopted by the construction industry, their durability performance was rigorously investigated.…”

“…In fact, elevated temperatures could accelerate the degradation induced by conditioning. As a result, the limits were found to be [37] 432-1478 41.9-60. x x 150 to 450 20 to x [11] x x 150 to 450 20 to 25 [12] x X Up to 1445 -20-65 [13] x 60 to 180 23 to x [14] x x 60 to 240 23 to x [15] x 100 to 660 40 x [23] x 41.67 to 208. 33 22 to x [42] x 90 to 365 23 to x [24] x 90 60 x [25] x 0.0208 to 0.1285 −100 to 325 x [26] x x 60 to 365 23 to x [27] x 30 to 180 23 to x [28] x 30 to 270 23 0-25 [29] x x x x 28 to 50 60 to x [30] x x x 180 to 540 23 to x [31] x 30 to 720 60 x [32] x 0.0417 to 0.125 100 to 300 x [33] x x x 90 to 730 60 20 & x 2 [34] x x 60 to 240 23 to 20-80 [35] x x 30 to 120 20 to 19-29 [36] x x x 30 to 132 −25 to 80 x [37] x x x 180 to 540 23 to x [38] x inappropriate and required revision through further research data.…”

“…Fiber/matrix interface damage Microcracks Fiber etching and leaching [8] x x x [9] No deterioration reported [10] x x x [11] x x x [12] x x x [13] No deterioration reported [14] No deterioration reported [15] x x x x [23] x x x [42] x x [24] No deterioration reported [25] x x x [26] No deterioration reported [27] x x x [28] x x x x [29] x x x [30] x x x [31] No deterioration reported [32] x x x [33] x x x [34] No deterioration reported [35] x x x [36] x x x x [37] x x x [38] No deterioration reported [39] x x x [44] x x x [45] x x x [46] x x x x [47] x x x [49] x x x [50] x x x x [51] No deterioration reported [11]. (c) Adapted from [13].…”