Asphalt pavement density measurement using non-destructive testing methods: current practices, challenges, and future vision

Asphalt concrete (AC) pavement density, an indicator of compaction degree, requires accurate prediction for quality control (QC) and quality assurance (QA) purposes. Non-destructive testing (NDT) methods are preferred to achieve non-invasive, high-speed, accurate, and large-scale density measurements. However, their working principles, prediction accuracies, and reliabilities are often questionable to users. This article presents a review of state-of-the-art and state-of-the-practice NDT methods for AC pavement density measurements, including non-nuclear density gauge (NNDG), intelligent compaction (IC), infrared (IR) thermography, and ground-penetrating radar (GPR). The basic operating and density measurement principles of these methods, as well as their advantages and limitations, are first documented. Then, the main factors that could affect density measurement accuracies are presented. In the end, possible NDT hardware integration platforms such as robotics and unmanned aerial vehicle (UAV) are discussed. This review article may provide reference and guidance for users to appropriately utilize NDT methods for new and in-service pavement density measurements.