The College of Graduate Studies and the College of Engineering Cordially
Invite You to a
Master Thesis Defense
Entitled
Durability of glass fiber-reinforced polymer bars in seawater-contaminated concrete
by
Abdelrahman Abdullah Alsallamin
Faculty Advisor
Dr. Tamer El Maaddawy, Department of Civil and Environmental Engineering
College of Engineering
Date & Venue
11:00 AM
Thursday, 18 May 2017
Room 1117, Building F1
Abstract
This research aims to investigate the durability performance and microstructure characteristics of two
different types of glass fiber-reinforced polymer (GFRP) bars in severe environment. GFRP bars encased
in seawater-contaminated concrete were immersed in tap water for 5, 10, and 15 months at
temperatures of 20, 40, and 60°C. Half of the specimens were conditioned under a sustained load of
25% of their ultimate strength whereas the other half was conditioned without load. Following
conditioning, the GFRP bars were retrieved then tested to failure under uniaxial tension.
Microstructure analysis was performed by employing differential scanning calorimetry (DSC), Fourier
transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and matrix digestion using
nitric acid. Type I GFRP bars, with the lower moisture uptake, exhibited insignificant strength reductions
in the range of 2 to 15% when conditioned without load. Their Type II counterparts exhibited higher
moisture uptake, higher hydroxyl ions, lower matrix retention, and thus, substantial strength
reductions in the range of 19 to 50% were recorded. The extent of degradation was more sensitive to
the conditioning temperature rather than conditioning duration. A decrease in the glass transition
temperature (Tg) of both types of GFRP bars was recorded, indicating matrix plasticization. Results of
SEM highlighted matrix disintegration and fiber debonding after conditioning. Specimens conditioned
under a sustained load exhibited higher moisture absorption than that of their counterparts
conditioned without load. None of the loaded specimens conditioned at 20oC were creep-ruptured
during conditioning. The presence of the sustained load during conditioning at 20oC for 15 months
reduced the tensile strength retention by approximately 14 and 5% for Type I and Type II GFRP bars,
respectively. In contrast, many bars were creep-ruptured and significant reductions in the tensile
strength retention were recorded due to the presence of the sustained load during conditioning at the
higher temperatures of 40 and 60oC. The accelerated aging test data along with the Arrhenius concept
were employed to develop a durability design model that can predict the tensile strength retention of
both types of GFRP bars in moist seawater-contaminated concrete.
Keywords: accelerated aging, GFRP, concrete, durability, microstructure