Figure 1: Clipped 3D Volumetric rendering of concrete sample

While the words concrete and cement are often used interchangeably in everyday conversation, concrete is actually a mixture of aggregate material (rocks, other filler) and cement. X-ray microscopy permits non-destructive examination of geological samples and construction materials, such as cement and concrete, for studying the properties of the materials. These properties can include quantification of porosity, inspection and quantification of cracks during freeze-thaw cycles, aggregate distribution, and many other interesting properties.

X-Ray Microscopy Imaging of Concrete

For our article this month, we chose to focus on imaging dense samples using the SkyScan 1273 high powered desktop micro-CT with a maintenance-free 130 kV X-ray source capable of up to 39 W of power. As can be seen from the digitally cut view in Figure 1 above, the SkyScan 1273 provided ample power to image a piece of concrete several inches in diameter while still resolving fine pores and structural features.

Figure 2: Clipped volumetric rendering of a concrete sample with calculated pore diameters highlighted

As shown in Figure 2, the SkyScan 1273 provides a quick way to gain a quantitative understanding of the pore size distribution within the concrete sample without the need for destructive testing. Using a sphere fitting algorithm, CTAnalyser computes the pore diameters within the sample and records both the pore size and exact position within the sample. This pore data can then be later overlaid upon the original reconstructed images using CTVox to provide both a qualitative view of position as well as the quantitative view of the pore diameters.

Figure 3: Clipped volumetric rendering of a concrete sample showing only the calculated pore diameters and positions within the sample

Using CTVox, we can also examine the pores on their own without the context of the original reconstructed data, which helps us look for trends within the pores (Figure 3).

Figure 4: Clipped volumetric renderings of four different phases within the concrete sample separated by apparent X-ray density

Using segmentation tools within CTAn, we separated four individual phases from the concrete sample based on apparent X-ray density Figure 4. These four phases include high density inclusions within the aggregate rocks, the aggregate rocks themselves, the cement, and low-density regions within the concrete sample. These four phases were visualized in CTVox and can be viewed together or in any combination.

Figure 5: Colorized volumetric rendering of the aggregate materials with the high-density regions of the aggregates highlighted in red

In particular, we can note the presence of high-density inclusions only in some of the rocks used as aggregate material within the concrete sample (Figure 5). From this view, the high-density regions are shown in red while the remainder of the aggregate rocks are displayed in orange.

Conclusion

For this work, the SkyScan 1273 allowed us to non-destructively inspect a piece of concrete several inches in diameter while inspecting the pore distribution and also examining the individual components within the mixture used to create the cement based on apparent X-ray density. We hope you found this Image of the Month informative and encourage you to subscribe to our newsletter and social media channels in preparation for the continuation of our image of the month series next month.

Scan Specifications

These scans were completed on our desktop SkyScan 1273 system at the Micro Photonics Imaging Laboratory in Allentown, PA. Reconstructions were completed using NRecon and visualization of 2D and 3D results were completed using Dataviewer, CTVox, and CTAn. Would you like your work to be featured in our monthly newsletter? If so, please contact us by calling Seth Hogg at 610-366-7103 or e-mailing seth.hogg@microphotonics.com