In-lab and on-site measurements of hot mix asphalt density: Convergence and divergence hypotheses

The life cycle of hot mix asphalt (HMA) depends on the material density. Bulk specific gravity and air void content are crucial factors for quality control and quality assurance (QC/QA) procedures used to evaluate contract specifications. Densities measured in the laboratory are reliable and accurate but are obtained very slowly. On-site measurements are made using non-nuclear portable devices and are often considered biased and unreliable. The object of this work was to evaluate a proposed theoretical framework for interpreting in-lab and on-site measurements and to propose strategies for using non-nuclear portable devices in QC/QA. A decrease in porosity yielded in-lab specific gravities that converged. In contrast, due to the high dielectric constant of water the divergence of in-site measures was observed. A conceptual framework and two practical equations are provided.