Balanced Mix Design Production Analysis of Asphalt Mixtures in Vermont

Abstract

Performance testing has been recognized by state highway agencies and the asphalt paving industry as an important tool to complement volumetric properties for improving asphalt pavement performance. Thus, the Vermont Agency of Transportation (VTrans) began evaluating the Hamburg wheel-tracking test in 2015, Illinois flexibility index test in 2018, and indirect tensile cracking test in 2020 as steps toward balanced mix design (BMD) implementation. These tests were conducted on reheated common plant-produced asphalt mixtures for multiple shadow projects, and the results were analyzed to determine the typical production variability observed in the performance testing results. Production variability is important to assess potential specifications in field production, especially for statistical quality acceptance procedures, such as percent within limits. Based on the percent within limit analysis, most of the modified Type IVS (i.e., 9.5 mm) mixtures would be acceptable based on the proposed performance requirements, while those found not acceptable were close to meeting the performance requirements and would need minimal adjustments. The lot data was further examined to generate typical lot production variability values for potential use in specification development. The information from this research effort will help VTrans achieve its goal to move beyond solely volumetric properties for asphalt mixture design and acceptance and serve as an example for other agencies exploring the implementation of BMD for improving asphalt pavement performance.