전기 임피던스 분광법을 이용한 시멘트 응결 모니터링

Abstract

Micro-structural compositions of cement-based materials are evolved during hydration process. Setting and hardening take place sequentially along hydration. Since the cement-based materials are solidified and hardened after setting process, placement and compaction works should be done before setting. Therefore, the setting time is important parameter to control concrete quality and work scheduling. Standard test methods are available to determine the setting time of cement-based materials in laboratory. However, since the setting time varies not only with material compositions but also with environmental conditions, results from laboratory test may not match well with the setting time of in-situ concrete. Therefore, an in-place test method is needed for the determination of the setting time of in-situ concrete. Cement-based materials possess water and conductive ions in pores so that electrons can migrate through the pores of the materials making the materials conductive. However, the pore structure and the amount of conductive ions of the cement-based materials are changed during hydration so that the electrical conductivity of the material may not be uniform during hydration process. In this study, electrical impedance spectroscopy (EIS), which is widely used for evaluating electrical characteristics of cement-based materials, is applied to investigate the setting process of hydrating cement-based materials and the effectiveness of the EIS to monitor the setting process of the in-situ cement-based materials is discussed.