Title:
Condition Assessment of Reinforced Concrete Structures Using Electromagnetic Waves
Author(s):
Udaya B. Halabe, Kenneth R. Maser, and Eduardo A. Kausel
Publication:
Materials Journal
Volume:
92
Issue:
5
Appears on pages(s):
511-523
Keywords:
bridge decks; concretes; dielectric constant; microwaves; reinforcing steels; Materials Research
DOI:
10.14359/890
Date:
9/1/1993
Abstract:
Deterioration of reinforced concrete infrastructure is a major problem in the U.S. today. Electromagnetic (EM) techniques, such as ground- penetrating radar, have shown increasing potential for the rapid evaluation of concrete conditions in situ. The objective of this research is to develop models for synthesis and inversion of radar waveforms from reinforced concrete structures. These models can be used to analyze radar data and predict the condition of the structure. A previous paper by the authors presented several models to predict the velocity and attenuation of electromagnetic (EM) waves in concrete as a function of frequency, temperature, moisture content, chloride content, and concrete mix constituents. This paper develops an empirical model based on experimental results to account for the reflection produced from reinforcing bars embedded within the concrete. Concrete and reinforcing bar models have been utilized to synthesize waveforms for representative reinforced concrete bridge deck geometries. Numerical studies have been carried out to observe the influence of various conditions (e.g., cracks) on the computed waveform. A least squares inversion procedure has been applied to the synthetic waveforms. Results from this inversion show that spatial variations in volumetric water content, salt content, and reinforcing bar cover can be determined by analyzing radar waveforms.