VAA Virginia Asphalt Fall/Winter 2022

10 FALL /WINTER 2022 Figure 3 shows an example of the density results for part of one project. The numbers 1, 3, 4 and 6 correspond to four of the six antenna passes along the lane. Passes 1 and 3 were along the left edge and left-center of the lane while Passes 4 and 6 were along the right-center and right edge of the lane. This figure shows that the density is fairly uniform between Passes 1, 3 and 4 but the density is much lower for Pass 6. Pass 6 was collected close to an unconfined edge. The figure also shows local density minimums at distances of approximately 860, 960, 1050, 1175 and 1260 feet. These are the approximate locations where trucks delivering asphalt to the paver were switched. Figure 4 shows another way to view the density profile data. From this figure, it can be seen that the 50th percentile density for Passes 1, 3, 4 and 6 is approximately 93.7%, 93.4%, 92.8% and 87.6%, respectively. If specifications required a minimum of 92.5% density, the percent conforming for Passes 1, 3, 4 and 6 is approximately 79.4%, 79.2%, 62.0% and 0.0%, respectively. Conclusions and Future Testing The study concluded that the DPS device is a promising tool for continuous density assessment. Additional testing is recommended to study additional mixture types and to determine a process to reduce the need for field-obtained calibration cores. The VTRC project team continues to collect data using the DPS on projects during the 2022 construction season. In addition to gathering data on additional mixture types (including intermediate and base mixtures), the research team is investigating the use of a lab-based DPS component that could eliminate or reduce the need for calibration cores collected from the field. The lab-based DPS consists of a single GPR antenna and data collection computer and is designed to facilitate testing of gyratory pills that could be fabricated during the mix design process or the day of paving. It is anticipated that gyratory pills, having a range of density values, could be produced and tested in the laboratory prior to paving. The study of these changes and other topics is underway as part of a VTRC study and also through a transportation pooled fund study (TPF 5(443)) led by the Minnesota Department of Transportation. References Brown, E. R. Basics of Longitudinal Joint Construction. Transportation Research Circular E-C105. Factors Affecting Compaction of Asphalt Pavements. Transportation Research Board, 86-95, 2006. Hughes, C. S. Compaction of Asphalt Pavement. NCHRP Synthesis of Highway Practice 152, National Cooperative Highway Research Program, Transportation Research Board, Washington, D.C. 1989. Maupin, G. W. Preliminary Field Investigation of Intelligent Compaction of Hot-Mix Asphalt. VTRC-08-R7, Virginia Department of Transportation, 2007. Saarenketo, T., 1997. Using Ground-Penetrating Radar and Dielectric Probe Measurements in Pavement Density Quality Control. Transportation Research Record, No. 1575, pp. 34-41. Scherocman, J. A. Compacting Hot Mix Asphalt Pavements: Part 1. Roads and Bridges, December 28, 2000. Sebesta, S. and T. Scullion, 2007. Infrared Imaging and Ground-Penetrating Radar as Quality Assurance Tools for Hot Mix Paving in Texas. Journal of the Association of Asphalt Paving Technologists, Vol. 76, pp. 1-40. Tran, N., P. Turner, J. Shambley. Enhanced compaction to improve durability and extend pavement service life: a literature review, NCAT Report 16-02R, 2016. Percent Maximum Density Distance, ft 800 850 900 950 1000 1050 1100 1150 1200 1250 1300 100 98 96 94 92 90 88 86 84 82 80 1 4 3 6 Figure 3. Percent maximum density with respect to project distance for four antenna passes Cumulative Percentage Percent Maximum Density 80 82 84 86 88 90 92 94 96 98 100 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 1 4 3 6 Figure 4. Cumulative distribution of percent maximum density for data shown in Figure 3 △ continued from page 09 ASPHALT PAVEMENT DENSITY PROFILING