Tomographic Imaging of Crack Damage in Cementitious Structural Components

Cement-based materials are widely used in the construction of civil infrastructure systems. However, normal wear-and-tear and extreme loading can result in the damage and deterioration of such important civil structures. In this study, a novel approach to the detection of cracks in fiber reinforced cementitious composites (FRCC) is proposed. The approach is based upon the electrical properties of cementitious materials. Alternating current (AC) signals are introduced in a cementitious component while voltages are measured along the component outer surface. Redundant sets of electrical input-output behavior of a cementitious element can then be used to solve a complex inverse problem in which a multi-dimensional mapping of the internal conductivity of the cementitious material is found. Termed electrical impedance tomography (EIT), the approach has the potential to be used for monitoring the performance and health of cementitious structures in the field. Since cement-based materials are naturally piezoresistive, mapping of the internal conductivity of a structural element would provide an indirect means of mapping internal strain fields. Furthermore, cracks represent a drastic reduction in the conductivity of the component; as a result, conductivity mapping has the potential to also detect and quantify (orientation and dimensions) crack damage. In this study, the EIT approach is formulated and validated upon a set of FRCC structural elements loaded in axial tension. The EIT method proves reliable in identifying localization of crack damage during loading.