VAA Spring/Summer 2020

28 SPRING/SUMMER 2020 Brian Diefenderfer, VTRC; Gerardo Flintsch, Wenjing Xue, and Fabrizio Meroni, VTTI THE SCIENCE OF RECYCLING Instrumentation Shows I-64 Segment II Pavement Recycling Project Meets Initial Expectations In 2016, VDOT awarded the reconstruction and addition of new lanes along a portion of I-64 in Newport News, York, and James City Counties. The pavement design for this project, known as Segment II, included pavement recycling techniques, specifically full depth reclamation (FDR) of the existing pavement foundation for the reconstructed lanes and imported materials for the added lanes, and cold central plant recy- cling (CCPR) for the base asphalt layers. VDOT based the design on lessons learned from previous pavement recycling projects, including the segment of I-81 in Augusta County constructed in 2011 and the VDOT-sponsored sections at the National Center for Asphalt Technology (NCAT) Test Track paved in 2012. The concept of using high-quality SMA surface layers, CCPR, and FDR has proven to provide long-lasting pavement sections in these high traffic applications. Figure 1 shows the cross-section for I-81, NCAT Section S12, and I-64 Segment II. A modification to the design used for I-64 Segment II is the inclusion of an asphalt-stabilized open- graded drainage layer (OGDL) to enhance drainage within the pavement structure. To better understand the performance of the recycled pavement design used on I-64, a team of researchers from VTRC and VTTI installed instrumentation during the construction of the pavement section in 2018. The intent was to run trucks, loaded to known weights, over the instrumented section, and measure the pavement response. The instrumentation included pressure cells, strain gauges, thermocouples, and moisture sensors that were installed to quantify the pavement performance mechanistically. The instruments were placed in the right wheel path of the right lane in the westbound direction just past the ramp to Exit 242B (to northbound Marquis Center Parkway, SR 199). The contractor (Allan Myers) provided signifi- cant logistical and installation support to the researchers. When instrumenting an asphalt pavement, the primary areas of focus usually include the mid-depth pavement temperature, the horizontal strain at the bottom of the asphalt layers, and the vertical pressure on the subgrade. The location of the instru- mentation for I-64 Segment II is shown in Figure 2. For this pavement section, the strain sensors would ideally have been placed at the bottom of the OGDL layer. 4-in AC 4-in AC 4-in AC 6-in CCPR 2-in OGDL 12-in FDR Subgrade 5-in CCPR 8-in FDR Subgrade 8-in CCPR 12-in FDR Subgrade 6-in AC 6-in CCPR Figure 1. Cross-section of I-81 (right), NCAT Section S12 (center), and I-64 Segment II (right). AC = asphalt con- crete, CCPR = cold central plant recycling, OGDL = open graded drainage layer, FDR = full depth reclamation. The concept of using high-quality SMA surface layers, CCPR, and FDR has proven to provide long-lasting pavement sections in these high traffic applications.