Comparing time-resolved infrared thermography and X-ray computed tomography in distinguishing soil surface crusts

Surface crusts represent a major limitation for reclamation projects in arid regions. With the advancements in spatial and radiometric resolution, infrared thermography is a potential technique for non-destructive characterization of soil crusts. The objective of this study is to evaluate time-resolved thermography, within the context of the composition by XRD, and configuration, by X-ray CT, of intact soil crust samples. Three samples were obtained from Dara region, west Gulf of Suez, the Eastern Egyptian Desert, representing the surface crusts formed in the Dara piedmont plain and Dara dry valley, as well as bedrock specimen found deep in Dara piedmont plain soil profiles. A step-heating test was applied to all samples with duration of 420 min. Temperate–time plots indicate that surface temperature reached an approximate temperature of 60 °C for all three samples after being heated for 270 min, the minimum surface temperature (58.3 °C) was obtained for the bedrock specimen because of large quartz content (64%) and weak development of pore space (1.3% of total volume). The slope of the early linear phase of temperature plotted against the square root of time was found to be steeper in the case of Dara piedmont plain and valley crust specimens (3.82, 3.84, respectively) than the slope obtained by scanning the bedrock specimen (3.32). Remarkably, despite the differences in composition of surface crust found in the Dara piedmont plain and valley, their surface temperature patterns were found to be similar. The similarity in thermal response is explained by the overlap in estimated thermal inertia range from the XRD and X-ray CT data. This final result demonstrates that the results of time-resolved thermography technique are not self-exploratory and ancillary data such as X-ray CT is needed for interpretation.