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It is necessary to quantify the amount of delamination present in load bearing rock bolts, as small amounts may be deemed acceptable and large amounts may lead to catastrophic failure. In this work, a semi-analytical FEM model is used to calculate the theoretical wave structures for a rod embedded in concrete. A qualitative relationship between percent delamination and wave reflection energy is demonstrated. It is shown that with the proper selection of inspection parameters, it is possible to inspect large lengths (10+ ft.) of embedded rod using an ultrasonic guided wave pulse-echo technique.

Dynamic modulus mastercurves are essential for the design and modeling of asphalt concrete (AC). One way of improving the accuracy of the upper asymptote of the mastercurve is to test at extremely high frequencies or extremely low temperatures. Ultrasound is used extensively in the nondestructive testing of materials and the work completed here demonstrates the potential for the application of this technology to AC. Since testing at extremely low temperatures is not practical, a new ultrasonic technique is developed for measuring the complex moduli of AC. A theoretical explanation of the measurement process is provided. Two AC specimens were tested using the ultrasonic method and the dynamic modulus method in the indirect tensile test (IDT) mode. Both test techniques were performed at four different temperatures. The mastercurves were constructed using time-temperature superposition on the IDT test data and the upper asymptotes were extrapolated. The ultrasonic data was shifted to the desired reference temperature and the predicted moduli were compared to those of the IDT test. It was found that the moduli predicted using the ultrasound measurement agreed well for the specimen with a lower air-void content and differed more for the specimen with a higher air-void content. The phase angles predicted by the ultrasonic method were higher than those obtained from the IDT test. It is believed that this was a result of wave scattering from air-voids and aggregates. Suggestions are made to further increase the accuracy of the technique.

Guided wave phased-array focusing techniques have been studied and applied in the longrange guided wave inspection of industrial pipelines. Advantages include longer inspection distance, greater wave penetration power and higher detection sensitivity. For reasons of protection, safety and thermal efficiency, a large percentage of pipes are coated and/or encased and buried underground. A phased-array focusing study for guided waves is now considered on pipelines with viscoelastic coatings. In this paper, longitudinal guided wave focusing as well as axisymmetric wave propagation is studied in a bare pipe and a pipe with a viscoelastic coating. A finite element model is studied. First, an investigation on whether the coating has an affect on the axisymmetric guided wave propagation is reported. Based on the result of a single channel, phased array focusing with 8-channel segments is studied. This study provides a very useful tool and guidance for the analysis and examination of guided wave focusing in a real field pipeline under various coating and environmental conditions.