A Study of Concrete Hydration and Dielectric Relaxation Mechanism Using Ground Penetrating Radar and Short-Time Fourier Transform
A Study of Concrete Hydration and Dielectric Relaxation Mechanism Using Ground Penetrating Radar and Short-Time Fourier Transform
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DOI：
10.1155/2010/317216
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发表时间：
2010-01-01
影响因子：
1.9
通讯作者：
Wiggenhauser, H.
中科院分区：
文献类型：
--
作者：
Lai, W. L.;Kind, T.;Wiggenhauser, H.
利用探地雷达(GPR)研究了普通硅酸盐水泥(OPC)水化过程中的频率相关介电松弛现象。通过测量探地雷达A扫描波形在90天内的变化，并在联合时频分析(JTFA)域中对波形进行短时傅立叶变换(STFT)处理，而不是仅在传统的时频域进行处理。对混凝土表面直达波和埋入钢筋的反射波信号进行短时傅立叶变换，跟踪峰值频率随龄期的变化。峰值频率随着年龄的增长而增加，其模式主要与众所周知的OPC水化过程密切匹配，其次是蒸发效应。这种接近的匹配是由于随着时间的推移，在传统的OPC水化和介电松弛机制上，自由水转变为束缚水的同时效应。
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.