Abstract
Hot mix asphalt mat density data collected during the 1990–1993 implementation of a quality control and quality assurance (QC/QA) program for pavement construction by the Alabama Highway Department (AHD) were analyzed. The influence of different measuring agencies (buyer and seller), mix type, application rate, and overlay interface conditions on the variability of nuclear gage and core density measurements was studied. The data were also used to study the influence of the several measurement variables on the ability to achieve target density. Variability and the ability to achieve target density improved as the QC/QA program was implemented, but there remained a consistent inability to achieve the target compaction level. Analysis of the significance of differences between AHD and contractor measurements was inconclusive, but AHD density measurements were consistently lower. Thicker binder mix layers had lower variability than thinner surface mix layers, but the level of compaction achieved was greater for surface mixes. Milling of the surfaces of old pavements significantly reduced the variability of density in overlay mats.
