For the selected independent parameters and gradation curve of the air voids, the program generates a virtual concrete sample with randomly dispersed air voids of varying size throughout the sample.
While 20 traverse lines are generally used in computing the chord length index, research is needed to show the actual number of traverse lines that are necessary to accurately compute the chord length index and subsequent gradation curves.
The effect of the number of traverse lines on the accuracy of the chord length gradation curve was evaluated from graphs of the simulated volume of the air voids ([mm.
The number of traverse lines needed to accurately reflect the chord length index can be evaluated by computing the chord-length gradation curve for a varying number of lines.
This is illustrated by the differences in the air void and chord length gradation curves of Figure 1.
Different specimens will have different air void gradation curves.
In Figure 3, the gradation curve for an 8% volume fraction of air is skewed right, meaning the chord lengths measured from the traversing lines are predominantly of the smaller magnitude, with most of the air void volumes being less than 0.
With a left-skewed air void gradation curve (Figure 4), the chord length gradation curve shows a much greater difference than for the right-skewed distribution.
An Accurate Method of Constructing a Gradation Curve