Fundamental study on dielectric relaxation characteristics of cementitious materials

Abstract

Dielectric frequency response measurement is utilized for a microstructure analyses of materials in various fields. The movements of the positive and the negative charges cause the response, which is so- called dielectric relaxation, and its measurement enables to clarify the interfacial composition of material. For example, the dielectric relaxation analysis of the human body cells is popular in the medical area. Gener- ally speaking, the indices of dielectric relaxation are capacitance, conductance, and susceptance. If the die- lectric relaxation measurement is applied to the concrete structure, there is a possibility to perform analyses of the concrete microstructures, because the interfacial compositions of aggregates, cement matrix, or pore solution dominate the dielectric relaxation responses of concrete theoretically. The correlations between concrete properties and dielectric relaxation responses are the significant information of concrete internal microstructures. This paper presents the results of the experimental examinations which were conducted to grasp the influence of the pore solution composition and the electrode interval on the dielectric relaxation properties. As a result, it became apparent that the behaviors of conductive electric charge, electric response charge, and displacement charge explain how sodium chloride and the distance between electrodes affected not only the magnitude of dielectric relaxation properties but also frequency spectrum.