Visualizing cation treatment effects on frozen clay soils through μCT scanning.

X-ray micro-computed tomography (μ CT) scanning is a proven technique with applications in geoscience, soil science, and geotechnical engineering. Here we apply the technique to investigate the effects of cation treatments on clayey soil micro-fabric in a frozen state. We imaged six suites of frozen cation-treated soils (montmorillonite, kaolinite, illite, illite-smectite, chlorite, and Copper River heterogeneous soil) at a resolution of 8.17 μm. Although this resolution was insufficient to observe differences in microaggregate formation as a result of cation treatment, we did observe micro-lenticular ice structures in the smectite-bearing soils that were invisible to the unaided eye. Quantitative analysis of the morphometric parameters from the illite-smectite and Copper River sample suites provided results that supported the visual observations, with the Copper River heterogeneous soil being more frost susceptible than illite-smectite, regardless of cation treatment. The μ CT results of these small soil cores also indicate that within the Copper River suite, the Ca2+-treated and Na+-treated samples are the most and least frost susceptible, respectively, which is in agreement with previous frost heave testing. Results from this study indicate that μ CT morphometric parameters can be used to quantify micro-lenticular ice lens formation in small samples and to serve as a quality control on sample preparation. • Uses μ CT scanning to visualize micro-fabric changes as a result of cation treatment on clayey soils • Provides images with high resolution (8.17 µ m), which is not typical for µ CT scanning of frozen soils • Discusses how μ CT scanning revealed the presence of ice lensing in certain types of soils and cation treatments [ABSTRACT FROM AUTHOR]