The dimensions of aggregate particles can be determined quite accurately using imaging techniques.
by consensus, the flat and elongated aggregate particles are defined using the ratios of three orthogonal dimensions.
The three orthogonal dimensions (Figure 1,visualization of a particle that is obtained through x-ray tomography imaging) are defined by its longest dimension DL, its medium dimension DM that is orthogonal to the direction of the longest dimension, and its smallest dimension DS that is orthogonal to the direction of the medium dimension. Based on these three measurements, two parameters, the Flatness (DM /DS ) and the Elongation (DL /DM ) can be determined. Traditionally, these two parameters are measured manually by using a caliper, the Superpave ratio device, or the multi ratio analysis device.
Kuo et al. [3] developed a simple imaging method to measure the three orthogonal dimensions.
A more advanced imaging system has been developed by Rao and Tutulemuer [10] to measure the three dimensions as well.
The image based dimension measurements compare well to the manual measurement (Figure 2).
Besides, computer-based image measurements are more accurate because they can determine the directions of the longest, the medium and the shortest dimensions more accurately than operators.
This is especially true for determining the orientation of DM.
However, both methods [3,10] are difficult to implement for fine aggregates.