Dr. Ece Erdogmus
Dr. George Morcous
Dr. Chungwook Sim
Date of this Version
Amiri, A. S. (2020). A Comparison Between Ultrasonic Guided Wave Leakage and Half-Cell Potential Methods in Detection of Corrosion in Reinforced Concrete Structures
Corrosion of reinforcing steel bars (rebar) in reinforced concrete decks can lead to serious structural issues in bridges. Ultrasonic Testing (UT) methods provide small wavelengths that can be used for early detection of several types of deterioration. The recently-developed Ultrasonic Guided Wave Leakage (UGWL) Method utilizes steel as the waveguide and measures the energy leaked into the surrounding concrete. Previous studies completed at University of Nebraska-Lincoln demonstrated that the measurements of the leaked energy using receivers from the concrete surface can successfully identify early stages of various flaws such as corrosion, delamination, and cracking. In this method, the longitudinal waves are generated along the rebar by a transmitter placed directly on the rebar, and recorded by an array of receivers on the concrete surface. Previous studies have shown promise in testing stretches of concrete decks as long as 10 feet using a single transmitter and an array of sensors placed 6 inches apart.
The primary goal of this Master’s thesis is to demonstrate that the recently developed UGWL method has several advantages over the commonly used Half-Cell Potential (HCP) method in the detection of corrosion in reinforced concrete (RC) bridge decks. To achieve this goal, laboratory experiments as well as a pros-and-cons analysis is conducted. Laboratory specimens are placed in a corrosive environment by submerging them in 10% NaCl solution. These slabs were then monitored for 6 months. During this period, UGWL and half-cell potential data were collected every 6 days. After testing was completed, chloride threshold levels (CTLs) were measured on cores taken from the specimens. The secondary goal of this thesis is to develop a quantitative correlation between UGWL data and CTLs, similar to those established between HCP and CTLs in the literature.
The experimental results demonstrated that the UGWL technique detected the corrosion activity approximately 21 days sooner than the HCP method. The findings also suggest that chloride content determined after the completion of the corrosion process, which lasted for 6 months, exceeded the standard chloride threshold levels; confirming that the selected method of inducing corrosion in the lab was successful.
Advisor: Ece Erdogmus