Several studies have shown that the long-term performance of asphalt pavement near a longitudinal joint can be predicted by the material density near the joint just after construction. However, the asphalt material near a joint is less homogeneous than the material in the middle section of a lane. As a result, estimating the density of a joint requires obtaining density measurements at several different locations. Density gauges that employ non-destructive methods are excellent tools for this purpose. This paper outlines the key features of both nuclear and nonnuclear density gauges that can be used to measure density near longitudinal joints in asphalt pavements. It discusses the gauge properties, such as precision, lateral extent of measurement, depth of measurement, effect of an air gap between the pavement surface and the gauge, and absolute density. A good understanding of gauge properties will assist the user in selecting the proper gauge for the specific job.
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