FEATURE
A Review of Commercially Available Systems for In-Place Asphalt Density Measurements and How They Work
A sphalt compaction is widely recognized as the most significant indicator of roadway quality because it directly affects the performance and lifespan of pavement. Compaction is influenced by a range of factors, from the asphalt mix design to the rolling pattern used during construction, making it a reliable measure of actual in-place air voids, referred to later as simply“ air voids”, present in the finished roadway. Decades of research have demonstrated a clear link between air void content and pavement longevity. Key studies collectively show that improper air void levels can result in decreased stiffness and strength, reduced fatigue life, accelerated aging, diminished durability, increased rutting, raveling and heightened susceptibility to moisture damage( Kennedy et al., 1984; Pell and Taylor, 1969; Epps and Monismith, 1969; Linden et al., 1989; McLeod, 1967; Kandhal and Koehler, 1984; Scherocman, 1984; Cooley
By Garrett Winkelmaier, Ph. D et al., 2002). As a result, air void measurement has become central to quality control and assurance practices in road construction. The gold standard for measuring air voids is core sampling, which involves extracting cylindrical samples from the roadway to directly assess the air void content. While core sampling remains the benchmark, this article will explore modern, commercially available devices for in-place density measurement by reviewing the technologies behind them. The nuclear gauge is one of the most widely recognized devices for in-place density measurement tools for contractors. After standardization of the device, the measurement process follows a specific sequence: First, the nuclear gauge is positioned directly on the asphalt surface. The device then emits radioactive particles that penetrate the pavement. Some of these particles interact with the asphalt and are scattered, meaning they are reflected back to the device— a phenomenon known
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