One of the main issues facing reinforced concrete structures, which are the largest category of infrastructure, is corrosion. Corrosion of metallic reinforcing in concrete is influenced by a variety of attributes of the concrete, including depth of cover and the porosity of the hardened or mature concrete. Ground penetrating radar (GPR) is a leading tool for determining and verifying cover depth and other physical features like delamination. It is an emerging tool for characterization of the concrete material itself, including applications to study hydration processes and early age properties. Recent work has identified relationships between GPR signals and mature concrete porosity measured using cold-water saturation. This work presents an initial study that compares GPR attributes and physical properties (cold water saturation porosity, compressive strength, and density) to new measurements of the porosity performed using the vacuum saturation method. This method is applied to a small set of mature samples and the results are compared across each measurement and sample characteristic. On average, all mixes except concrete paste (containing no coarse aggregate) have higher vacuum saturation porosity than cold water saturation porosity because the method captures smaller pore sizes. Basic GPR attributes (maximum amplitude, total energy, and average amplitude) have no strong direct linear correlation with either porosity measurement, but there are some promising relationships found in the average trends. This study gives insight into the porosity-controlled mechanisms of GPR signal propagation and how they may be used to evaluate mature in situ concrete without collecting or directly testing samples.
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