Graduation Year

2006

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Civil Engineering

Major Professor

Rajan Sen, Ph.D.

Keywords

Corrosion rate, Steel loss, Load test, Carbon, Glass, Field

Abstract

The goal of the dissertation was to quantify the role of FRP in repairing corroded prestressed piles in a marine environment and to demonstrate the feasibility of using it for field repairs. Three laboratory studies and two field demonstration projects were undertaken to meet this goal.In the first study, corroded specimens were repaired under water and tests conducted to determine the extent of strength retained immediately after wrapping and after further accelerated corrosion. Results showed that the underwater wrap was effective in restoring and maintaining lost capacity in both situations.The second study attempted to determine the effectiveness of FRP for specimens where corrosion had initiated but with no visible signs of distress. In the study, 22 one-third scale model of prestressed piles fabricated with cast-in-chlorides were wrapped at 28 days and exposed to simulated tidal cycles outdoors for nearly three years. Two materials --

carbon and glass were evaluated and the number of layers varied from 1 to 4. Results of gravimteric tests showed that the metal loss in FRP wrapped specimens was about a quarter of that in identical unwrapped controls indicating its effectiveness in this application.The third study attempted to identify the most suitable pre-wrap repair. For this purpose, 26 scale model prestressed specimens were first corroded to a targeted metal loss of 25%, repaired and then exposed to simulated hot salt water tidal cycles for over two years. Two disparate types of repairs were evaluated --

an elaborate full repair and a simpler epoxy injection repair. Results of ultimate and gravimetric tests conducted at the end of the exposure showed that the performance of the full and epoxy injection repairs were comparable but vastly superior compared to identical unwrapped controls.Two field studies were conducted in which full-sized corroding piles were instrumented and wrapped to monitor post-wrap performance. Corrosion rate measurements indicated that rates were lower for wrapped piles compared to identical unwrapped piles. Overall, the study demonstrated that underwater wrapping of piles using FRP is viable and a potentially cost effective method of pile repair in a marine environment.

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