Durability of E-Glass/Vinylester Reinforcement in Alkaline Solution

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Title: Durability of E-Glass/Vinylester Reinforcement in Alkaline Solution

Author(s): Rajan Sen, Gray Mullins, and Tom Salem

Publication: Structural Journal

Volume: 99

Issue: 3

Appears on pages(s): 369-375

Keywords: alkali; concrete; durability; polymer; reinforcement.

Date: 5/1/2002

Abstract:
This paper presents results from a 9-month experimental study to evaluate the durability of E-glass/vinylester reinforcement used by the U.S. Navy in the construction of the MRI Pier in San Diego, Calif. A total of 36 specimens were tested. These were split into four groups of 9 specimens each that were exposed to simulated pore solution (SPS) with a pH ranging between 13.35 to 13.5 for periods of 1, 3, 6, and 9 months. Of the nine specimens in each group, a third were unstressed, a third stressed to 10%, while the remaining third were stressed to either 15 or 25% of their ultimate short-term tensile strength. At the end of the designated exposure periods, surviving specimens were tested to failure to determine their residual tensile strength. The results showed that the E-glass/vinylester bars tested had very limited durability in this environment, especially at stress levels of 15% or higher. All six specimens stressed to 25% failed within 25 days of exposure. Five of six specimens stressed to 15% failed within 180 days. Specimens stressed to 10% lost 70% of their original strength after 9 months of exposure. Even unstressed specimens lost 63% of their original strength after 9 months, indicating that diffusion of the alkaline solution through the resin matrix was largely responsible for their degradation. The faster deterioration of the stressed specimens indicated that resin cracking also played a significant role in the degradation. Prediction of remaining life for the test specimens based on a Fickian (diffusion) model was between 1.6 to 4.6 years (unstressed) and between 0.5 to 1.7 years for the specimens stressed to 10%. Overall, the results confirm the unsuitability of first-generation glass fiber-reinforced polymer bars as structural reinforcement in concrete members.