Comparative Analysis Of Superpave Gyratory Compactors and TxDOT Gyratory Compactors

By Dale Alan Rand
drand@mailgw.dot.state.tx.us
Research Engineer, Texas Dept. of Transportation

Abstract

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.

Conclusions

  1. 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.
  2. 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.
  3. 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.
  4. The slope of the SGC compaction curve does not correlate well with either Hveem Stability or Static Creep slope.
  5. 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.


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