Evaluation of a Density Profiling System for Asphalt Pavement Density Measurement

About the report:

During asphalt pavement construction, obtaining adequate and uniform density throughout the pavement layer through the compaction process is critical to achieving the desired performance. Optimum pavement density reduces oxidation potential and moisture damage, decreases rutting potential, and improves fatigue life. Numerous national research projects have cited pavement density as one of the most influential parameters defining the service life of asphalt pavement.

The Virginia Department of Transportation’s (VDOT) asphalt pavement program requires the contractor to perform nuclear density readings and density measurements from cores and sawn plugs for acceptance. This process is not only destructive and potentially time-consuming but assesses only the density of a small portion of the pavement mat (about 0.003%). Although VDOT and other agencies use these processes, localized substandard density may not always be identified. Furthermore, this process cannot provide real-time feedback during the paving operation. VDOT needs to use methods that can assess a larger sample more rapidly to reduce the risk of accepting substandard material. One such method is by employing density profiling system (DPS) technology. The benefits to agencies using DPS technology include the ability to conduct measurements over the entire surface area of the new asphalt pavement layer, measure the density along the longitudinal joint where many pavements experience premature failures, and implement a statistical evaluation of the achieved density. The benefits to contractors include the ability to evaluate their compaction processes and make adjustments during the course of the work when improvements can still be implemented before paving completion.

The study concluded that DPS technology can describe relative changes in the density of asphalt mixtures placed in the field based on measurements of the dielectric value and that it offers sufficient data volume for density uniformity estimates. The study also concluded that DPS is a promising technology for process control purposes but is still premature for VDOT to use for density acceptance.

The study recommends that VDOT’s Materials Division not consider using DPS at this time to assess the density of paved asphalt mixtures for acceptance purposes because additional studies are needed to better understand the effects of mixture variables on the dielectric results. The study recommends that VDOT’s Materials Division consider using DPS to assess relative changes in paved asphalt mixture density during construction where desired. The study recommends that VDOT’s Materials Division consider using DPS density testing results to evaluate achievable density uniformity. The study also recommends that the Virginia Transportation Research Council and VDOT’s Materials Division submit a research needs statement to the Pavement Research Advisory Committee to help further understand the remaining unknowns through additional testing during future construction seasons.

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