Affiliations: Departments of Construction Management & Civil and Environmental Engineering, University of Washington, Seattle, WA 98195-1610, USA | Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, USA
Note:  Currently: Visiting professor in the Department of Civil Engineering at Tokyo Institute of Technology, Tokyo 152-8552, Japan
Abstract: In freshly compacted concrete, water films form around aggregate particles, which results in a higher water/cement ratio closer to the aggregate than away from it. The interface between cement paste and aggregate, known as interfacial transition zone (ITZ), has a significantly higher porosity than bulk cement paste. This higher porosity in ITZ affects the transport properties of concrete. The Wood's metal technique was used to intrude molten metal alloy into voids and fractures in concrete which was then solidified to preserve the microstructure. The penetration of this alloy into concrete samples indicates that the porosity in the interfacial zone is permeated preferentially to the bulk paste. This technique also indicates the width of the interfacial zone in which the porosity is interconnected. The results of this experimental study were evaluated in a probabilistic sense and subject to statistical considerations. In particular, the results and interpretations of this study properly account for the aleatory and epistemic uncertainties inherent in the data.
Keywords: Cement, concrete, image analysis, scanning electron microscopy, porosity, microstructure, backscattered electron imaging, interfacial transition zone, aleatory, epistemic, uncertainties