Type of Document Dissertation Author Haddad, Rami H. URN etd-08232007-112417 Title Characterization and deterioration detection of Portland cement concrete using electromagnetic waves over a wideband of frequency Degree PhD Department Civil Engineering Advisory Committee
Advisor Name Title Al-Qadi, Imadeddin L. Committee Chair Barker, Richard M. Committee Member Duke, John C. Jr. Committee Member Riad, Sedki Mohamed Committee Member Walker, Richard D. Committee Member Weyers, Richard E. Committee Member Keywords
- concrete properties
Date of Defense 1996-01-05 Availability restricted AbstractAn experimental program was conducted to establish a better understanding of the effect of Portland cement concrete's (PCC' s) basic properties on its dielectric properties over a wideband of frequency (0.1 MHz-10 GHz). Other parameters that may influence measured dielectric properties were investigated. These include chlorides presence in PCC, deterioration (due to alkali silica reaction [ASR] and freezing and thawing [Fff] damage), delamination, and segregation. In addition, the effect of different sizes of delaminated areas (filled with water) was evaluated using measured dielectric properties and waveform amplitude. Three different electromagnetic wave (EM) setups were used to conduct those measurements: parallel plate capacitor (0.1-40 MHz), coaxial transmission line (100 MHz to 1 GHz), and TEM antenna (0.5-10 GHz). The setups were designed and built by engineers from the Civil and Electrical Engineering Departments at Virginia Tech as a part of the overall research study.
Testing results indicated the feasibility of using EM to detect changes in the basic properties of PCC over low RF using the parallel plate capacitor. This included the effect of curing time, water to cement (w/c) ratio, aggregate type, cement type, and air entrainment. The effect of curing time on the complex dielectric constant of PCC was quantitatively determined. However, the success in detecting changes in the PCC basic properties was limited at the microwave frequency range of 100 MHz to 10 GHz. Changes in the complex dielectric constant due to chloride intrusion into PCC were quantitatively significant only over the low radio wave frequency. The ASR in PCC was successfully identified by measured complex dielectric constant over the low RF, especially less than 20 MHz. Insignificant changes in the complex dielectric constant over the frequency range of 0.1 MHz to 1 GHz was noted when PCC was exposed to FIT cycles.
Complex dielectric constant and waveform amplitude measurements of pce slabs over frequency range of 1 to 10 GHz showed significant changes with water content (in PCC); due to further hydration or injecting of water into empty delaminated areas. Waveform amplitude showed significant sensitivity to delamination and chlorides and low sensitivity to segregation. After testing several mixture theories to identify the most appropriate theory that is capable of predicting the dielectric constant of PCC (based on the dielectric properties of its components), Bruggemenn mixture theory was found to be the most feasible.
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