A Study of Concrete Hydration and Dielectric Relaxation Mechanism Using Ground Penetrating Radar and Short-Time Fourier Transform

Abstract

Ground penetrating radar (GPR) was used to characterize the frequency-dependent dielectric relaxation phenomena in ordinary Portland cement (OPC) hydration in concrete changing from fresh to hardened state. The study was experimented by measuring the changes of GPR A-scan waveforms over a period of 90 days, and processed the waveforms with short-time Fourier transform (STFT) in joint time-frequency analysis (JTFA) domain rather than a conventional time or frequency domain alone. The signals of the direct wave traveled at the concrete surface and the reflected wave from an embedded steel bar were transformed with STFT, in which the changes of peak frequency over ages were tracked. The peak frequencies were found to increase with ages and the patterns were found to match closely with primarily the well-known OPC hydration process and secondarily, the evaporation effect. The close match is contributed to the simultaneous effects converting free to bound water over time, on both conventional OPC hydration and dielectric relaxation mechanisms.

Quantitative Attribute Analyses with Ground Penetrating Radar for Infrastructure Assessments and Structural Health Monitoring

“…Specifically, the role of water in both the electromagnetic properties and the physical properties of concrete has been highlighted as an important factor to consider in the field of nondestructive material characterization using GPR [8,18,21,22]. This mirrors the relationships used in remote sensing and noninvasive estimation of soil moisture by dielectric constant [23,24,25,26,27]. Applying these relationships to concrete indicates that these attributes are also related to the physical properties (i.e., pore water content and related measures of porosity) of construction materials, as in [28,29].…”

Evaluation of the GPR frequency spectra in asphalt pavement assessment

“…Ground penetrating radar (GPR) is frequently used in pavement assessments, mainly using the evaluation 33 of wave travel times. However, GPR data provide further information that could be used in order to deter- 34 mine the inner conditions and characteristics about materials.…”

“…The method is based on determining the stiffness modulus of 49 each layer that makes up the pavement using back-calculation in 50 order to obtain the state of stress and strain in significant points [3]. and locating cavities beneath the structure of a road (e.g., [5][6][7][8] to concrete [32,33], to ballast for railway infrastructure [34,35] 168 and to other media [36]. 169 Other studies have analysed the alterations in the frequency 170 spectra as the ratio of two materials changes.…”

Dispersion of ultrasonic guided surface wave by honeycomb in early-aged concrete

“…5, therefore the surface wave velocity was increased from 1333 m/s to 1666 m/s respectively, as a result of concrete curing with time. Another comparison is between the guided surface wave traveled in homogeneous water specimen 6 and heterogeneous concrete specimens (1)(2)(3)(4). Given the same spacing of sensors (i.e.…”

“…For example, the internal structure of a hardened concrete can be visualized by high-frequency ground penetrating radar (GPR). Despite its superior data collection ability, GPR is not suitable for fresh or very young concrete because most radio signals would be absorbed by the free water contained in the fresh concrete matrix [1][2][3][4]. Another means is by impact echo which is a stress wave method, in which analysis in time domain and frequency domain can be used to assess the early-age properties of cementituous materials [5,6].…”