Electromagnetic Metrology on Concrete and Corrosion

Abstract

To augment current methods for the evaluation of reinforcing bar (rebar) corrosion within concrete, we are exploring unique features in the dielectric and magnetic spectra of pure iron oxides and corrosion samples. Any signature needs to be both prominent and consistent in order to identify corrosion within concrete bridge deck or other structures. In order to measure the permittivity and propagation loss through concrete as a function of temperature and humidity, we cut and carefully fitted samples from residential concrete into three different waveguides. We also poured and cured a mortar sample within a waveguide that was later measured after curing 30 days. These measurements were performed from 45 MHz to 12 GHz. Our concrete measurements showed that the coarse granite aggregate that occupied about half the sample volume reduced the electromagnetic propagation loss in comparison to mortar. We also packed ground corrosion samples and commercially available iron-oxide powders into a transmission-line waveguide and found that magnetite and corrosion sample spectra are similar, with a feature between 0.5 GHz and 2 GHz that may prove useful for quantifying corrosion. We also performed reflection (S11) measurements at various corrosion surfaces and in loose powders from 45 MHz to 50 GHz. These results are a first step towards quantifying rebar corrosion in concrete.

Corrosion detection in steel-reinforced concrete using a spectroscopic technique

“…Electromagnetic characterization of relevant concrete samples and components, as well as iron corrosion minerals, has been carried out, using standard techniques [4], measuring attenuation, dielectric permittivity, and magnetic susceptibility as a function of frequency, composition, and temperature [5,6]. Dr. James Baker-Jarvis of NIST led this part of the project until his sudden death from an accident in 2011.…”

Measurement and simulation of millimeter wave scattering cross-sections from steel-reinforced concrete

“…Measurement (a) gives the background and (b) gives total reflection. The post processing of the experimental measurements is performed as follows: (2) where the measurements in both the numerator and denominator of eq. (2) are time gated to remove multiple reflections between the target and the antenna and any extraneous reflections from the experimental setup.…”

“…For the case of uniform corrosion coverage, cracking in concrete can occur as a result of corrosion layers as thin as 3 μm to 74 μm [2]. Therefore, in this subsection the electromagnetic scattering from corrosion layers ranging in thickness from 3 μm to 74 μm are investigated.…”

“…The early detection of corrosion in steel-reinforced (rebar) structural concrete is of high importance since it can lead to savings of billions of dollars in the repair and maintenance of the transportation infrastructure [1][2]. A key technical challenge is the detection of corrosion at an early stage before cracking in the concrete starts to occur.…”

“…A key technical challenge is the detection of corrosion at an early stage before cracking in the concrete starts to occur. This early detection is challenging because cracking can start to occur when the corrosion layers are only a several tens of micrometers thick in the range of 50 μm to 100 μm [2]. Some iron oxide corrosion products exhibit antiferromagnetic magnetic resonances (AFMR) in the millimeter wavelength/THz frequency range [3].…”