COMPUTERIZED-TOMOGRAPHY STUDIES OF CONCRETE SAMPLES

X-ray computerized tomography (CAT or CT) is a sophisticated imaging technique that provides cross-sectional views of materials, components and assemblies for industrial nondestructive evaluation (NDE). We have studied the feasibility of using CT as an inspection tool for reinforced concrete and the use of multi-energy, linear, attenuation techniques to deduce variations in density (rho) and/or atomic number (Z) that could be caused by varying the types of concrete mixes and/or compaction in the concrete itself. To perform this study, we designed and built a prototype medium-/high-energy (200- to 2000 keV) CT scanner - ZCAT - to image small concrete samples (less-than-or-equal-to 30 cm in diameter and less-than-or-equal-to 75 cm in height) with a spatial resolution of about 2 mm. We used ZCAT to quantitatively inspect a 20 cm concrete cube with 1.27 cm diameter reinforcing bars (rebars) and to measure rho and/or Z variations in a 20 cm diameter concrete cylinder. We describe the ZCAT scanner design, some of its physical limitations and the data-acquisition parameters used in our study. Our results and those of others [1,2] show that CT can be used to inspect reinforced concrete and to distinguish material rho and/or Z variations within concrete.