Effects of aggregate structure on hot-mix asphalt rutting performance in low traffic volume local pavements

The objective of this study is to evaluate the effect of mix gradations associated with the Superpave restricted zone on rutting potential specifically for low traffic volume roadways. Although the elimination of the restricted zone requirement in Superpave mix design is highly recommended, some questions still remain unanswered as the research conclusions supporting the elimination of the restricted zone were largely made for medium to high traffic volume roadways, where aggregates are highly crushed and of good quality. The applicability of such research conclusions based on high traffic volume mixes needs to be verified for low volume mixes because many states in the US use non-crushed local aggregates for low traffic volume pavements, which might be related with aggregate gradation. This paper summarizes the research findings obtained from a systematic approach consisting of (1) statistical analyses of pre-existing data accumulated for quality assurance purposes, (2) experimental investigations based on the statistical analysis results, and (3) in-field investigation of the rutting performance of low traffic volume pavement. The comparison and analysis results indicate that similar to that for medium to high traffic volume pavements, the restricted zone is not a controlling factor affecting hot-mix asphalt rutting performance for low traffic volume local pavements. The fineness of aggregate gradation rather than the restricted zone seems to be a factor that affects rutting performance.