Ground Penetrating Radar Sensitivity to Marginal Changes in Asphalt Mixture Composition

Abstract

Abstract Ground penetrating radar (GPR) is gaining renewed attention from many state highway agencies because of its promising application prospects for rapid, full-coverage, continuous, and nondestructive measurements of the density in newly constructed asphalt pavements. However, several operational and technical issues need to be addressed before this technology can be efficiently deployed for quality control/quality assurance practices. The operation-related challenges are relatively easily addressed with proper project-specific management practices. The technical ones, on the other hand, require improvements to the testing devices and procedures and strategic investigations for further understanding of the relationship between the GPR-measured dielectrics and the density of asphalt mixtures. The latter is particularly crucial given the production and construction variability of asphalt mixtures and the accepted practices of field adjustments to mix designs. This study investigated the sensitivity of dielectric measurements to changes in mix composition and assessed the appropriateness (or lack thereof) of using a single dielectric-density transfer model to analyze field data measured on multiple production days. The study examined asphalt mixtures designed and manufactured in the laboratory with varying amounts of limestone, a high-dielectric aggregate source, as well as plant-produced asphalt mixtures collected on multiple production days. The findings indicated that the source/composition of the aggregate structure affected density-dielectric relationships of asphalt mixtures considerably. On the contrary, the relationship appeared to be less sensitive to normal asphalt production variability (day to day variations) as long as the aggregate source proportions were maintained intact. The experimental investigation proposed in this study can be easily employed to determine the proper amount of calibration models or the extent of allowable adjustment to the mix design for asphalt pavement construction projects.