Visualized Moisture Distribution in Cement Paste by Electrical Impedance Tomography

Mechanisms of rebar corrosion in reinforced concrete structures are to be clarified, as it significantly affects long-term structural durability. Among various causes of corrosion, moisture plays a primary role of deterioration by promoting electrochemical reactions in embedded rebar. Here, to grasp spatially and temporally moisture distribution within cementitious materials is a key issue for durability assessment and maintenance planning in reinforced concrete structures. Consequently, an application of Electrical Impedance Tomography (EIT) to monitoring moisture in cement-based materials is studied. The distribution of moisture was manipulated by varying the location and size of the water reservoir, as well as the ambient temperature. The EIT system successfully visualizes conductivity changes associated with moisture diffusion, and the reconstructed images show good agreement with discolored areas caused by water penetration. It is also found that potential difference data could estimate moisture content. Some limitations in spatial resolution are observed, particularly for regions farther from the electrodes, due to the diffusive nature of the electrical current in EIT. These results state the potential use of EIT for moisture monitoring in cementitious materials, while further study must be addressed for practical field applications.