Electrical Impedance Characterization of Cement-Based Materials
This work introduces the use of AC-impedance spectroscopy (AC-IS) as a characterizing tool for cement-based applications. A thorough examination of the AC electrical behavior vs. microstructure relationships in cement-based composites has proven that AC-IS is sensitive to the presence of discontinuous conducting fibers in the composites. Below percolation, composite theory describes the relationship between the composite conductivity and filler volume fraction in terms of the intrinsic conductivity, which is a function of shape, orientation and electrical conductivity of filler. Such relationship can be related to the resistance values derived from AC-IS measurements to establish a foundation for AC-IS electrical characterization. Deviation from the predicted behavior is thus an indication of inhomogeneity and/or preferred orientation of the fibers. Some microstructural characterizations enabled by the AC-IS technique mentioned in the present work include after-processed fiber length (with known fiber volume fraction, and vice versa), fiber aggregation, and degree of fiber percolation. Good agreement with other characterization techniques confirms the validity of the AC-IS technique. Besides microstructural characterizations, AC-IS can potentially be used to characterize pozzolanic activity (i.e., the ability to provide SiO2 to react with Ca(OH)2 from cement hydration to form a strengthening product in cementbased materials) of rice husk ash (RHA), the most promising cement-replacement material for Thailand. Based on the rate of conductivity drop after the RHA is mixed with Ca(OH)2 and water, pozzolanic activity characterization by AC-IS shows very good agreement with the amorphous SiO2 content of the RHA studied.
KeywordsOrdinary Portland Cement Fiber Volume Fraction Pozzolanic Activity Intrinsic Conductivity Fiber Dispersion
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- 1.Macdonald JR (1987) Impedance spectroscopy: Emphasizing solid materials and systems. John Wiley and Sons, Inc., New YorkGoogle Scholar
- 11.Wansom S (2006) Electrical impedance characterization of ceramic-matrix composites with various inclusions. Ph. D. Dissertation. Northwestern University, Evanston, IL, USAGoogle Scholar
- 13.Wansom S, Janjaturaphan S, Sinthupinyo S (2009) Pozzolanic activity of rice husk ash: comparison of various electrical methods. J Met Mater and Miner 19(2):1–7Google Scholar