Frequency-dependent dispersion of high-frequency ground penetrating radar wave in concrete

This paper studies the dielectric dispersion of high frequency radar wave in concrete in early-aged and hardened concrete specimens. Frequency-dependent spectra of phase velocity v(ω) were measured to deduce the spectra of real part of dielectric permittivity ε′(ω). The dispersion was measured by three high nominal ground penetrating radar frequencies (1.5, 1.6 and 2.6 GHz), experimenting on two steel bars with concrete cover 50 and 100 mm. It was found that v(ω) and ε′(ω) dispersed at lower frequency, but became stable at high frequency regions, which agrees with the classical GPR plateau. The same frequency components at different nominal antenna frequencies show a close range of v(ω) and ε′(ω) in concrete of different ages. The results in this paper warrant further investigation of using GPR wave to study material properties.