Comparative Analysis Of Superpave Gyratory Compactors and TxDOT Gyratory Compactors
By Dale Alan Rand
Research Engineer, Texas Dept. of Transportation
This project is a Comparative Analysis of Superpave Gyratory
Compactors (SGCs) and TxDOT Gyratory Compactors (TGCs). The project
is separated into two phases. Phase I focuses on precision and
bias of the two types of compactors and Phase II focuses on strength
properties that can be determined from specimens molded on the
compactors. The emphasis of Phase II is to compare the slope
of the compaction curve of specimens molded in the SGC to Hveem
Stability and Static Creep test results of specimens molded in
the TGC. This research also produces data that demonstrate the
relationships between mixture variables (gradation, asphalt content
and percent fines) and mixture mechanical properties.
- On mixtures with gradations similar to those required under the Superpave system, SGCs produce specimens in which the bulk specific gravities (Gmb ) are 33% to 42% less variable than TGCs.
- On very coarse mixtures, SGCs produce specimens in which the bulk specific gravity (Gmb ) is slightly more variable than TGCs. The difference is statistically insignificant.
- For mixtures batched in the laboratory, SGCs produced specimens in which the Gmb is consistently lower than those compacted on TGCs. This pertains to specimens compacted to Ndesign of 96 gyrations with a compaction temperature of 121.1_C.
- The slope of the SGC compaction curve does not correlate well with either Hveem Stability or Static Creep slope.
- The slope of the SGC compaction curve correlates very well with the coarse aggregate content (% passing 2.36 mm sieve) of a mixture. Hveem Stability and Static Creep slope also correlate well with coarse aggregate content.