Comparison of volumetric properties for 150-mm versus 100-mm diameter gyratory compacted HMA specimens

As the volume of traffic and vehicle wheel loads increase, it has become necessary to improve the effectiveness and efficiency of the design of Hot Mix Asphalt (HMA). Superpave was introduced with the intent to make it possible for the bituminous paving industry to use a rational design approach to produce superior quality pavements. The Superpave Gyratory Compactor (SGC) is a vital part of this improved mix design system. Currently, the SGC uses a 150-mm (6-inch) diameter cylindrical mold to produce HMA specimens for mix design testing and volumetric evaluation. This study explores the possibility of using a 100-mm (4-inch) diameter mold to produce these specimens.

Loose HMA was collected from typical TDOT paving projects across the state of Tennessee. After compaction, the volumetric properties of both 150-mm and 100- mm diameter specimens were determined and statistically compared. The results of the statistical analysis showed that the differences in volumetric properties of the 150- mm and 100-mm diameter specimens were very small. However, the statistical p-value of the paired t-test used indicated that these properties were not comparable. Further analysis of this data indicated that the difference in volumetric properties between the different size samples was smaller than the variation permitted in the test results used to determine them. It has been recommended to the Tennessee DOT that it is possible to use 100-mm diameter specimens in lieu of using 150-mm diameter specimens for design and/or quality control of HMA.