Evaluation of Superpave HMA Mixture Properties at the Plant versus behind the Paver: Statistical Comparison of QC and QA Data

Abstract

State highway agencies concerned with lower asphalt levels and potential durability problems in hot-mix asphalt (HMA) mixtures designed with superior performing asphalt pavements (Superpave) have lead efforts to explore strategies for improving Superpave mix design. This study addressed the differences in HMA properties that have been observed over the years between samples taken at the plant versus behind the paver for Superpave designed mixtures in Maryland. A large set of Maryland State Highway Administration (MSHA) quality assurance (QA) and quality control (QC) data were analyzed statistically in the context of current specifications. Statistical analysis found that the means and standard deviations of the QC and QA data represent different populations. Because the material leaving the asphalt plant is the same material that is compacted behind the paver, some relationship between the plant and field properties is expected. However, attempts to define transfer functions between QA and QC measurements to use both data sets in HMA acceptance testing encountered low levels of statistical significance.