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Dielectric constant and conductivity, the so-called EM properties (electromagnetic), are widely adopted for NDT (Nondestructive Technique) in order to detect damage or evaluate performance of concrete without damage to existing RC (reinforced concrete). Among deteriorating agents, chloride ion is considered as one of the most critical threats due t...
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Citations
... Kim et al. considered 3 water-cement ratios and 4 levels of chloride ion addition in cement mortar samples for dielectric experiments. The results show that the electrical conductivity and dielectric permittivity decrease linearly with the increase of carbonization rate and the decrease of compressive strength, and the coefficient of determination is large [23]. Chen et al. conducted dielectric spectroscopy measurements in the low frequency range (10 -2~1 0 6 Hz) for different grades of pure asphalt and wax-modified asphalt (WMB) [24]. ...
In order to reveal the dielectric properties of the nonaqueous reactive polyurethane grouting material, combined with the electron microscope test analysis, it can be seen that the nonaqueous reactive polyurethane material is a porous two-phase body composed of a polyurethane matrix and closed cells. At the microscopic scale, the porous two-phase physical model is established, and the dielectric model of the material is constructed on this basis. In order to verify the dielectric model, 40 groups of nonaqueous reactive polyurethane specimens with different densities were designed and prepared in this paper. The dielectric permittivity was measured by a vector network analyzer (VNA) with an open coaxial probe within the frequency range of 1050 MHz~5010 MHz for the first time, and the dielectric properties and influencing factors were revealed according to the test data. The result shows that the dielectric permittivity of nonaqueous reactive polyurethane materials increases with the increase of density, and decreases slightly with the increase of frequency. Compared with the three models of the Rule of Mixture, Clausius-Mossotti Model and Lichtenecker Model, the calculation accuracy of the Maxwell-Garnett Model is higher, and the calculation results are more consistent with the experimental results of nonaqueous reactive polyurethane grouting materials. The experimental results can be applied to the nondestructive testing of polyurethane grouting materials and provide reference and basis for the quality evaluation of polymer structures.
... In a recent study, by applying an open-ended coaxial probe technique, feasibility for practicing MNDT to measure chloride content was reviewed. Thus, results provide evidence of the theory supporting the progress of research using open waveguide applicators for the design of the MNDTs [46]. Later, the eddy current method and with microwave excitation, the active infrared thermography is applied for the reinforced concrete structures, furthermore for the inspection and exposure of steel bars [47]. ...
This study deals with the measurement of dielectric constant, the magnitude of reflection coefficient, and compressive strength for G30, G40, G50, and G60 concrete mix after 0, 3, 7, 14, 21, and 28 days curing. The open-ended coaxial probe of 4.8 cm, WR510, and WR340 waveguide models operating over a frequency range of 85 MHz to 1.8 GHz, 1.45 to 2.2 GHz, and 2.17 to 3.3 GHz, respectively, are applied. Fifteen concrete cube samples 150 × 150 × 150 mm size were casted for each mix. The experimental result shows that the dielectric constant and magnitude of the reflection coefficient decrease gradually until 21 days, then increase at 28 days age of concrete. Correlated the concrete dielectric constant with design compressive strength. The results corroborate that microwave techniques correlate well for evaluating the strength of concrete. The strength characterization is suitable with related material composition, necessary experimental setup, and environmental conditions applied in this study. Furthermore, curing conditions, effects must be accounted; it is valuable in establishing a correlation between conventional properties and microwave properties of concrete.
... In the previous studies, a close correlations has been demonstrated between properties of concretes and Electromagnetic Properties (EMPs) as a nondestructive testing approach [25][26][27][28][29]. The various microwave techniques have been proposed to reveal this correlation such open ended waveguides, free space measurement by horn antennas placed both sides and coaxial probe approach [25,[27][28][29]. ...
... In the previous studies, a close correlations has been demonstrated between properties of concretes and Electromagnetic Properties (EMPs) as a nondestructive testing approach [25][26][27][28][29]. The various microwave techniques have been proposed to reveal this correlation such open ended waveguides, free space measurement by horn antennas placed both sides and coaxial probe approach [25,[27][28][29]. The disadvantageous of the coaxial probe approach is its limited scanning depth between 0.49 mm and 0.53 mm in microwave frequency region [30]. ...
... In the previous studies, a close correlations has been demonstrated between properties of concretes and Electromagnetic Properties (EMPs) as a nondestructive testing approach [25][26][27][28][29]. The various microwave techniques have been proposed to reveal this correlation such open ended waveguides, free space measurement by horn antennas placed both sides and coaxial probe approach [25,[27][28][29]. ...
... In the previous studies, a close correlations has been demonstrated between properties of concretes and Electromagnetic Properties (EMPs) as a nondestructive testing approach [25][26][27][28][29]. The various microwave techniques have been proposed to reveal this correlation such open ended waveguides, free space measurement by horn antennas placed both sides and coaxial probe approach [25,[27][28][29]. The disadvantageous of the coaxial probe approach is its limited scanning depth between 0.49 mm and 0.53 mm in microwave frequency region [30]. ...
Including fibers in concretes improves their mechanical properties such as flexural strength, impact load resistance and limited crack propagation. The dispersion, orientation and types of the fibers placed in the concretes affect these mechanical properties. The aim of the study is to propose a standard and a novel prediction method for determining the dispersion and orientation of the concretes in which fibers are reinforced in microwave frequency range. This study demonstrates that determination of both orientation and dispersion of the fibers regardless of the fiber types in concretes is possible by extracting electromagnetic properties of the structures in microwave regime as a nondestructive method. The measurement technique requires sample under test(SUT) and two wideband linearly polarized antennas placed in the front and backside of material under the free space condition. Although there are some studies investigated the fiber content of concrete samples through certain electromagnetic techniques, the proposed novel approach concentrates on the electromagnetic behavior of the fiber reinforced concretes in a very wideband range from 3 GHz to 17 GHz. Unlike the other studies, open space measurement with the help of a vector network analyzer which is capable of measuring up to 43 GHz along with two high gain horn antennas was carried out in the laboratory environment. Time required for exact measurement of dielectric constant and loss factor of the concrete between antennas is less than a minute. A simple and confidential model is carried out to determine both orientation and dispersion of fibers in concrete by observing the changes of dielectric constant and loss factor. The determination of electromagnetic properties of concretes with fibers has potential applications for future nondestructive sensors. In addition, observation of negative dielectric constant and some other electrical properties such as low loss factor and impedance match with free space presented in the study for particular frequency intervals gives a chance for future radome applications in harsh environmental conditions.
... Concrete is a dielectric material which polarizes when exposed to the external electric field and thus can be characterized using its electromagnetic properties (Rhim and Buyukozturk 1998, De Zaeytijd, Maes et al. 2007, Ong and Akbarnezhad 2014. MNDT of concrete has been previously investigated in the literature to develop NDT methods for monitoring of compressive strength, water to cement ratio (W/C), and aging of concrete (Berg, Niklasson et al. 1992, Wen and Chung 2001, Kharkovsky, Akay et al. 2002, Kharkovsky and Zoughi 2007, Kwon, Feng et al. 2010 Furthermore, in a recent paper, the possibility of using MNDT for chloride content measurement was discussed by evaluating the EMPs of concrete containing chloride using an open-ended coaxial probe (Kim, Kang et al. 2016). The results presented in this study highlight the potential for developing an MNDT for chloride content measurement. ...
... In addition to dielectric measurement, the compressive strength of mortar samples was characterized using 50 cubic samples, which were cured in lime water until testing day. Figure 2 compares the compressive strength of the samples with and without chloride at the different water to cement ratios and ages. As shown, the samples containing chloride show a slightly higher compressive strength compared to their counterpart samples without chloride as seen in the literature as well (Kim, Kang et al. 2016). Figure 3 to5 demonstrate the measured EMPs for the samples. ...
Concrete durability is to a large extent governed by the concrete resistance to the penetration of aggressive substances. One such aggressive substances, present predominantly in marine or coastal environments, is the chloride ion. Chloride in presence of water and oxygen cause corrosion and the measurement of chloride content is an important factor in the detection of early corrosion damage induced by chloride attack. However, there is currently a lack of a reliable nondestructive method to examine the chloride content of the structure in practice. This paper presents the results of an experimental study to investigate the viability of Microwave Non-Destructive Testing (MNDT) to monitor the ingress of the chloride into the concrete. The variations in the electromagnetic properties of mortar specimens with variations in their chloride contents are measured to identify correlations between chloride content and two main electromagnetic properties of mortar; viz. dielectric constant and loss factor. EMPs are measured through two-port measurement performed using a vector network analyzer and S-band rectangular waveguide. The existence of correlations between chloride content of mortar and its electromagnetic properties is confirmed by the preliminary results, highlighting the potential for development of an MNDT technique to monitor the chloride content of concrete in practice.
... These include the rebound hammer test [1], the use of embedded sensors [2][3][4][5], the ultrasonic approaches [6][7][8][9], the acoustic methods [10], the electrical resistance or resistivity tests [11][12][13][14][15], the microwave non-destructive inspection/monitoring (mNDI) techniques [16][17][18][19][20][21][22][23][24][25]. Recently using electromagnetic or microwave approaches as a NDI method has been gaining more attention especially for concrete structures [24][25][26][27][28][29][30]. Microwave signals can penetrate inside a dielectric medium (e.g., CBMs) and interact with its microstructure. ...
This research article presents dual-frequency correlation models for predicting the growth of elasticity and flexural strength of engineered cementitious composites (ECCs) using microwave nondestructive inspection technique. Parallel measurements of microwave properties and mechanical properties of ECC specimens were firstly undertaken in the sense of cross-disciplinary experiments. Regression models were developed via means of nonlinear regression to the measured data. The purpose of the study is: (i) to monitor the flexural strength and elasticity growth; and (ii) to predict their mature values under the influence of different initial water contents, via microwave effective conductance at early ages. It has been demonstrated that both the modulus of rupture (MOR) and modulus of elasticity (MOE) can be accurately modeled and correlated by microwave conductance using exponential functions. The moduli developed as a function of conductance whereas the regression coefficient exhibited a linear relation with water-to-binder ratio. These findings have highlighted the effectiveness of the microwave non-destructive technique in inspecting the variation of liquid phase morphology of ECCs. The dual-frequency correlation can be used for structural health monitoring, which is not only for prediction but also provides a means of verification.
... Due to identified close correlations between concrete properties and its EMPs, MNDT has been widely advocated by previous studies as a reliable NDT method for monitoring properties of concrete structures in practice [14][15][16][17][18]. While the use of open-ended waveguides and horn antennas have been also reported in a number of studies [12,19], a majority of existing MNDT methods developed in previous studies are based on co-axial probe measurements which rely mainly on measured reflections from a thin surface layer of concrete to estimate EMPs [14,[16][17][18]. ...
... Due to identified close correlations between concrete properties and its EMPs, MNDT has been widely advocated by previous studies as a reliable NDT method for monitoring properties of concrete structures in practice [14][15][16][17][18]. While the use of open-ended waveguides and horn antennas have been also reported in a number of studies [12,19], a majority of existing MNDT methods developed in previous studies are based on co-axial probe measurements which rely mainly on measured reflections from a thin surface layer of concrete to estimate EMPs [14,[16][17][18]. Due to its design characteristic, the scanning depth of a coaxial probe operating in microwave frequency range is limited only to less than a millimeter from the surface of concrete which the area of scan is limited roughly to the contact area of the probe which ranges from 0.49mm to 0.53mm within the microwave frequency range [20]. ...
Microwave Non-Destructive Testing (MNDT) has been highlighted in previous studies as a viable technique for monitoring of concrete structures throughout their service life. MNDT relies on the correlation between electromagnetic properties and mechanical properties of concrete to monitor the variations in the latter. The main two electromagnetic parameters of materials include dielectric constant and loss factor, which characterize how a material responds to an external electric field. The electromagnetic properties of concrete can be affected by variations in a number of parameters including microwave frequency, moisture content, curing age, mix proportions, type and properties of concrete constituents, presence and type of contaminants, etc. However, despite the effort made in the literature to characterize such correlations, the focus has been mainly placed on co-axial measurement of hardened cement mortar properties which relies on reflections from the incident surface. The present study highlights a lack of precision in measurement of concrete's dielectric properties using the commonly used coaxial probe MNDT by comparing the co-axial measurements with those obtained through two-port technique in the frequency range of 2.6-3.95GHz (S-Band waveguide). Two-port measurement relies on both reflections from the incident surface and transmissions from the far end surface of the specimens to provide a reliable measurement of average dielectric properties of the entire sample, thus providing a good baseline for evaluating the accuracy of the commonly used co-axial method. The results of this study warn about the large variations in the measurements obtained using the coaxial probe and highlight the importance of an application of more reliable MNDT techniques such as transmission line in practice.
... In the previous studies, a close correlations has been demonstrated between properties of concretes and Electromagnetic Properties (EMPs) as a nondestructive testing approach [25][26][27][28][29]. The various microwave techniques have been proposed to reveal this correlation such open ended waveguides, free space measurement by horn antennas placed both sides and coaxial probe approach [25,[27][28][29]. ...
... In the previous studies, a close correlations has been demonstrated between properties of concretes and Electromagnetic Properties (EMPs) as a nondestructive testing approach [25][26][27][28][29]. The various microwave techniques have been proposed to reveal this correlation such open ended waveguides, free space measurement by horn antennas placed both sides and coaxial probe approach [25,[27][28][29]. The disadvantageous of the coaxial probe approach is its limited scanning depth between 0.49 mm and 0.53 mm in microwave frequency region [30]. ...
