Research and application of statistical law of VCA formed from the packing of basalt coarse aggregates

• Basalt coarse aggregates were used in the study of void in coarse aggregate (VCA).
• It was the VCA values obtained by vibrating experiments that were employed in analysis.
• A best and effective regression model that reveals the forming mechanism was developed.
• The VCA value of a forward S-shaped curve is larger than that of the theoretical maximum density line (TMDL).
• The VCA value of a reverse S-shaped curve is smaller than that of the TMDL.

The void in coarse aggregate (VCA) has an important influence on the void in mineral aggregate (VMA) of hot mix asphalt (HMA) and naturally affects the grading design. In order to find a universal law of the VCA changing with the grading of coarse aggregates to provide a theoretical support for grading design of HMA, some basalt coarse aggregates with diffident sizes were used and sixteen experimental schemes were arranged by Uniform Experiment Design Method (UEDM). The VCA values of each experimental scheme were obtained through tamping test and vibrating compaction experiments. Based on the smaller VCA values obtained by vibrating compaction experiments four effective regression model were established and the best one was selected; then the scope of application of the best regression model was discussed and the formation law and forming mechanism of VCA were analyzed. The analysis results show that, for the coarse aggregate, compared with other shapes of grading curves, the forward S-shaped grading curves have larger VCA values, and the farther it is from the theoretical maximum density line (TMDL), the greater the VCA value is; while the reverse S-shaped grading curves have the smallest VCA values even compared with the TMDL of coarse aggregates.