Experimental Validation of a Numerical Model for Simulating Radiographic Imaging of Portland Cement-Based Materials

This paper presents a numerical modeling approach, developed within the CIVA RT virtual radiography software, for simulating radiographic imaging of Portland cement-based materials. The modeling approach is validated experimentally for 20 and 30 cm thick Portland cement concrete specimens, which were imaged over a range of source intensities using a 450 keV COMET MXR-451 X-ray tube. Both a discrete coarse aggregate (DCA) model and a computationally efficient homogenized concrete (HC) model were investigated. The study found that for concrete sections thicker than 10 cm, the HC model provides radiation transmission predictions comparable to the DCA model, which was attributed to the increase in photon scattering with specimen thickness. The experimental validation study utilized film-based radiography and considered target optical density measurements of 1.0, 2.0, and 3.5. In general, numerical predictions from the virtual radiography model were in good agreement with the experimental data. For the 20 cm thick specimens, relative error in the numerical predictions ranged from 18 to 20 %. Relative error in numerical predictions for the 30 cm thick specimens ranged from 4 to 8 %. The improvement in model prediction accuracy for the thicker specimens was attributed to increased filtration of lower energy radiation, which reduced the influence of approximation error in the lower energy region of the photon emission spectrum.