(207e) Microstructural Characterization of Gfrp Reinforcing Bars in Severe Environment

Microstructural Characterization of
GFRP Reinforcing Bars in Severe Environment

Hilal
El-Hassan^a,*, Abdelrahman Al-Sallamin^a, and Tamer El-Maaddawy^a

^a Department of Civil and
Environmental Engineering, United Arab Emirates University, Al Ain, United Arab
Emirates, P.O. Box 15551

Abstract

Glass
fiber-reinforced polymer (GFRP) bars are increasingly used as internal
reinforcement in concrete structures because of their noncorrosive nature, lightweight,
high strength, and ultraviolet resistance [1-5]. The microstructure and composition changes of GFRP
bars exposed to severe environmental conditions are investigated in this paper.
Test specimens were placed in moist seawater-contaminated concrete for up to 15
months at temperatures of 20, 40, and 60°C. Microstructural analysis was performed
using differential scanning calorimetry (DSC), Fourier transform infrared
(FTIR) spectroscopy, scanning electron microscopy (SEM), and matrix digestion
using nitric acid. A decrease in glass transition temperature (T_g) of
GFRP bars was recorded after conditioning as shown in Table 1. Conditioned GFRP
bars exhibited matrix plasticization and chemical degradation. Findings from
FTIR showed an increase in hydroxyl ions with conditioning at higher
temperatures. Results of SEM indicated a separation at the fiber-matrix interface
and matrix deterioration in conditioned specimens (Figure 1). Further microstructure
examination showed a decrease in the matrix content because of conditioning.

Keywords:
microstructure, GFRP;
concrete; severe environment

^* Corresponding author. Tel:
+971(56)350-4110; Fax: +971(3)713-5156

E-mail address: helhassan@uaeu.edu
(Hilal El-Hassan)

References

1.         Uomoto, T., et al., Use
of fiber reinforced polymer composites as reinforcing material for concrete.
Journal of Materials in Civil Engineering, 2002. 14(3): p. 191-209.

2.         Debaiky,
A.S., et al., Residual Tensile Properties of GFRP Reinforcing Bars after
Loading in Severe Environments. Journal of Composites for Construction,
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3.         Robert,
M., P. Cousin, and B. Benmokrane, Durability of GFRP Reinforcing Bars
Embedded in Moist Concrete. Journal of Composites for Construction, 2009. 13(2):
p. 66-73.

4.         American
Concrete Institute (ACI), Guide for the design and construction of concrete
reinforced with FRP bars. 2006.

5.         Chen,
Y., J.F. Davalos, and I. Ray, Durability prediction for GFRP bars using
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Table 1: Glass transition temperature
of GFRP bars using DSC analysis

Figure 1: Cross-sectional
micrograph of GFRP bars: (a) control (b) immersed for 15 months at 20°C (c)
immersed for 15 months at 40°C (d) immersed for 15 months at 60°C