Three-dimensional electrical capacitance tomography – A tool for characterizing moisture transport properties of cement-based materials

Abstract

Water often plays a major role in the degradation processes of cement-based materials and structures, and thus the durability of these structures strongly depends on their ability to impede transport of water. This paper reports the results of imaging three-dimensional (3D) unsaturated moisture flow in mortar specimens using electrical capacitance tomography (ECT) imaging, which is based on non-intrusive and contact-free capacitance surface measurements. In a series of experiments, three mortar specimens with differing moisture transport properties were imaged with ECT during a 3D ingress of water. For comparison, we also modeled the flow of moisture numerically, by Finite Element Method (FEM) approximation of the 3D equation of unsaturated moisture flow in porous media, commonly referred to as Richard's equation. The ECT reconstructions are in good agreement with the flow model for all specimens which supports the ability of ECT to image 3D water transport in cement-based materials. Keywords: Cement-based materials, Unsaturated moisture flow, Electrical capacitance tomography, Imaging, Numerical flow model, Transport properties