Statistical analysis and theoretical predictions of the tensile-strength retention of glass fiber-reinforced polymer bars based on resin type

Abstract

This paper presents experimental investigation, statistical analysis, and theoretical predictions of tensile-strength retention of glass fiber-reinforced polymer bars, made with vinyl-ester, polyester, or epoxy resins. The durability of glass fiber-reinforced polymer bars was evaluated as a function of time of immersion in alkaline solution. The aging of the three glass fiber-reinforced polymer bar types consisted of immersion glass fiber-reinforced polymer bar samples in an alkaline solution (up to 5000 h) at different elevated exposure temperatures. Subsequently, the physical and tensile properties of the unconditioned bars were compared with that of the conditioned bars to assess the durability performance of the glass fiber-reinforced polymer bars. Microstructure of all of the glass fiber-reinforced polymer bar types was investigated with scanning electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy for both the conditioned and unconditioned cases, to qualitatively explain the experimental results and to assess changes and/or degradation in the glass fiber-reinforced polymer bars. In addition, the long-term performance of glass fiber-reinforced polymer bars was assessed considering the effect of service years, environmental humidity, and seasonal temperature fluctuations. The test results showed that the tensile strength of the glass fiber-reinforced polymer bars was affected by increased immersion time at higher temperatures and the reduction in tensile strength was statistically significantly dependent on the type of resin system. The prediction approach of the glass fiber-reinforced polymer bars based on the environmental reduction factor (CE) after 200 years indicated that the CE values for vinyl-ester, epoxy, and polyester glass fiber-reinforced polymer bars can be conservatively recommended to 0.81, 0.75, and 0.71, respectively, for a moisture-saturated environment (relative humidity = 100%) and at 30℃. The polyester glass fiber-reinforced polymer bars experienced greater debonding at the fiber–resin interface than the vinyl-ester and epoxy glass fiber-reinforced polymer bars.

Microstructure Characteristics of GFRP Reinforcing Bars in Harsh Environment

“…e most commonly used glass and matrix materials were E-glass and vinylester, with 90 and 74% of the conducted research having used this fiber and matrix, respectively, as shown in Figure 2. Epoxy, on the other hand, has been only recently employed as the resin of GFRP reinforcing bars, with 14% of published work having explored its combination with E-glass [8,10,11,23,41,42]. e diameter has also been varied between 8 and 44.5 mm, with the majority being approximately 12 mm.…”

“…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.…”

“…Each factor will be discussed in the sections below. x [8] x x x x [9] x x x [10] x x x [11] x x x x [12] x x x [13] x [14] x x x [23] x x x [42] x x [24] x x [25] x x x [26] x x x [27] x x x [28] x [29] x [30] x [31] x x x x [32] x [33] x [34] x x x x [35] x x x [36] x [37] x [38] x x x [39] x x x [40] x x [44] x [45] x [46] x x [47] x [48] x x x [49] x [50] x [51] x e effect of sustained load can be noted by comparing the results of [10,11]. e only difference between these two researches is the addition of a sustained load of 25% UTS in [11].…”

“…In fact, Figure 9 shows that 56 and 62% of bars, tested under the worst conditions in each study, failed to fall within the high durability limits of ACI 440.6 [62] and CSA S807 [63], respectively. In general, samples conditioned in alkaline solution at temperatures beyond 50°C were deemed unacceptable [8,23,27,39,46]. GFRP bars imbedded in concrete resulted in uptakes within the acceptable range, except for El-Hassan, et al [11], where a sustained load of 25% UTS was applied, which is higher than the maximum allowable load recommended by ACI 440.1R [2].…”

“…Wavelength (cm −1 ) O-H stretch C O stretch C-H stretch C-O stretch O-H bend [8] 3200-3650 -2800-3000 -- [9] 3300-3600 1600-1800 2800-3100 1400-1600 900-1100 [10] 3200-3600 -2800-3000 -- [11] 3200-3600 -2800-3000 -- [13] 3300-3600 -2800-3100 -- [14] 3300-3600 -2800-3000 -- [23] 3200-3650 -2800-3000 -- [24] 3300-3600 1600-1800 2800-3100 1400-1600 900-1200 [26] 3200-3500 -2800-3000 -- [27] 3300-3600 -2850-3100 -- [31] 3400 -3026 -- [34] 3200-3400 -2800-3100 -- [35] 3430 -2900 -- [38] 3430 -2900 -- [39] 3540 -2900 -- [40] 3334 1557 2900 1420 1019 the degradation only initiated after 1% moisture uptake. Further increase in uptake up to 2% did not cause signi cant impact on the change in OH/CH ratio, after which it dramatically increased up to 115%.…”