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RESEARCH PAPERS

# Estimation of Corrosion Damage in Steel Reinforced Mortar Using Guided Waves

[+] Author and Article Information
Henrique Reis

Department of General Engineering,  University of Illinois at Urbana-Champaign, 104 S. Mathews Ave., Urbana, IL, 61801h-reis@uiuc.edu

Benjamin L. Ervin

Department of General Engineering,  University of Illinois at Urbana-Champaign, 104 S. Mathews Ave., Urbana, IL, 61801

Daniel A. Kuchma

Department of Civil and Environmental Engineering,  University of Illinois at Urbana-Champaign, 205 N. Mathews Ave.,Urbana, IL 61801

Jennifer T. Bernhard

Department of Electrical and Computer Engineering,  University of Illinois at Urbana-Champaign, 1406 W. Green St., Urbana, IL, 61801

J. Pressure Vessel Technol 127(3), 255-261 (Feb 18, 2005) (7 pages) doi:10.1115/1.1989352 History: Received February 06, 2005; Revised February 18, 2005

## Abstract

Corrosion of reinforced concrete is a chronic infrastructure problem, particularly in areas with deicing salt and marine exposure. To maintain structural integrity, a testing method is needed to identify areas of corroding reinforcement. For purposes of rehabilitation, the method must also be able to evaluate the degree, rate, and location of damage. Toward the development of a wireless embedded sensor system to monitor and assess corrosion damage in reinforced concrete, reinforced mortar specimens were manufactured with seeded defects to simulate corrosion damage. Taking advantage of waveguide effects of the reinforcing bars, these specimens were then tested using an ultrasonic approach. Using the same ultrasonic approach, specimens without seeded defects were also monitored during accelerated corrosion tests. Both the ultrasonic sending and the receiving transducers were mounted on the steel rebar. Advantage was taken of the lower frequency $(<250kHz)$ fundamental flexural propagation mode because of its relatively large displacements at the interface between the reinforcing steel and the surrounding mortar. Waveform energy (indicative of attenuation) is presented and discussed in terms of corrosion damage. Current results indicate that the loss of bond strength between the reinforcing steel and the surrounding concrete can be detected and evaluated.

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## Figures

Figure 6

Group velocity vs frequency for 1∕2inch (13 mm) diameter cylindrical steel bar in vacuum with experimentally measured values at 40, 80, and 140 kHz using both direct and indirect transducer configurations

Figure 7

Accelerated corrosion testing setup showing the specimen partially submerged in water, the copper mesh, and the transducer locations in indirect configuration

Figure 8

Measured corrosion vs predicted corrosion using Faraday’s law for accelerated corrosion testing of reinforced mortar specimens

Figure 9

Signal energy vs time using 80 kHz input signal during wetting of mortar. The variation of signal energy illustrates the changes in material properties in mortar as water permeates the pores. The energy drop at point C reflects the presence of water in the pores adjacent to the steel bar.

Figure 10

Signal energy and current vs percentage of corrosion for accelerated corrosion specimen using 80 kHz input signal. The changes in energy and in current reflect different stages of corrosion, including accumulation of corrosion product between the reinforcing steel bar and the mortar, cracking of the surrounding mortar, and ingress of water.

Figure 5

Theoretical attenuation curves for the F(1,1) mode for a 1∕2inch (13 mm) diameter steel cylindrical bar in vacuum and the same bar immersed in water. The curves were calculated using DISPERSE (38). An experimentally obtained value of the attenuation of the F(1,1) mode at 80 kHz for the same bar immersed in water is also shown.

Figure 4

Qualitative variation of bond strength as a function of percentage of corrosion

Figure 3

Reduction of cross-sectional area caused by pitting corrosion of the reinforcing steel bar

Figure 2

Progressive degradation of concrete reinforcement due to corrosion

Figure 1

Schematic diagram of ultrasonic through transmission experimental set up for indirect and direct transmission

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