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From page 293... ... 293 a p p e N D I x S Introduction Ground-penetrating radar (GPR) has been widely used for subsurface characterization by geologists, archeologists, and engineers. Read the entire page →
From page 294... ... 294 the relative permittivity er as a function of the dielectric response of the different materials within the cementitious composite that may or may not contain an imaginary part. This will be explored in greater detail in the theory section. Read the entire page →
From page 295... ... 295 Dielectric relaxation of materials typically depends on frequency of the applied electric field and temperature, where lower temperature lowers the relaxation frequency. Jonscher (20) Read the entire page →
From page 296... ... 296 where ce is the electric susceptibility of the material. Dielectric displacement can thus be written as shown in Equation S.3: ( ) Read the entire page →
From page 297... ... 297 where z is the location from the origin, t is the time, E0 is half of the magnitude of the wave, a is the attenuation factor, and b is the phase coefficient. In a no-loss propagation medium such as air, a and b are given as shown in Equation S.8: (S.8) Read the entire page →
From page 298... ... 298 the surrounding field and the constitutive property of the phases are positive and real. The bounds are subsequently derived using Hashin–Shtrikman's variational principles. Read the entire page →
From page 299... ... 299 properties than bulk water, such that the dynamics of water molecules are hindered, as mentioned in the literature review. This geometrical confinement is well documented in the literature. Read the entire page →
From page 300... ... 300 Laboratory Testing The desorption isotherm of specimens was determined with the mass loss method, where the specimens were placed in an RH-controlled chamber at constant temperature and the mass loss was recorded. Porosity was determined by completely drying the specimen in an oven. Read the entire page →
From page 301... ... 301 Measurements were taken with the percometer periodically. The coaxial probe (from VNA) Read the entire page →
From page 302... ... 302 started to equilibrate by diffusion rather than evaporation of water on the specimen holder and specimen surface. Saturation was determined from the amount of free water in the specimens. Read the entire page →
From page 303... ... 303 surface probe used in this research, <2,000 µS/cm is the recommended value. Values beyond that will affect the measurements. Read the entire page →
From page 304... ... 304 w/c ratio, that is, a higher w/c ratio resulted in a higher e′ and e″. However, the loss part of permittivity appeared to be much less sensitive to change in moisture content, with the 0.6 w/c being the only exception. Read the entire page →
From page 305... ... 305 For the imaginary part of complex permittivity, confined water did not seem to play a role in relaxation for the five-bar specimens because of the lack of a peak at the lower frequencies. For 15-bar specimens, a higher loss part was found at lower frequencies. Read the entire page →
From page 306... ... 306 the complex plane for comparison. Figure S.16 shows the difference between measured values at different frequencies versus the complex permittivity predictions from a two-phase composite. Read the entire page →
From page 307... ... 307 0.4 w/c 0 2 4 6 8 10 12 14 16 0 1 2 3 4 5 6 7 0% RH (OD) 43% RH 63% RH 75% RH 85% RH 100% RH " Frequency (GHz) Read the entire page →
From page 308... ... 308 adjusting the real and imaginary components at each frequency and was fitted to the experimentally measured complex permittivity on the complex plane (i.e., Figure S.17, but at different frequencies) Read the entire page →
From page 309... ... 309 moisture content and the real part of complex permittivity was observed. Figure S.13 and Figure S.14 show the different w/c versus complex permittivity for specimens conditioned to different RH. Read the entire page →
From page 310... ... 310 0 5 10 15 20 25 0.1 0.2 0.3 0.4 0.5 0.6 1 GHz (model) 1 GHz (measured) Read the entire page →
From page 311... ... 311 9. Huisman, J Read the entire page →

From page 293...

... 293 a p p e N D I x S Introduction Ground-penetrating radar (GPR) has been widely used for subsurface characterization by geologists, archeologists, and engineers.