Stress-Induced Polarization of CNT-Mixed Cement Paste under Cyclic Loading and Moisture Variation: Mechanisms and Electrical Characteristics

Abstract

In recent years, the deterioration of infrastructure built during Japan’s rapid economic growth has become a major issue, highlighting the need for efficient and sustainable maintenance strategies. To address this, self-diagnostic and sensing technologies for structural health monitoring have gained attention. Among various approaches, functional materials utilizing the electrical and mechanical properties of carbon nanotubes (CNTs) are promising. CNTs can form conductive networks within cementitious materials, imparting a self-sensing capability. This study investigates carbon nanotube-mixed cement paste (CNTCPs) to clarify how changes in electrical conductivity affect stress-induced polarization. Electrical impedance spectroscopy was conducted to assess frequency-domain conductivity variations, and cyclic loading tests were performed under varying moisture and material age conditions.

Results show that a periodic voltage response is preserved across all formulations, and the voltage amplitude peaks at a 2 wt.% CNT dosage. Furthermore, a high moisture content or advanced material age diminishes the voltage response, which is governed by the electrochemical time constants (τ=RC) identified in the impedance plots. These insights provide critical guidelines for optimizing the stress-induced polarization characteristics and design of self-sensing cementitious composites.