VAA Virginia Asphalt Fall/Winter 2021

VAASPHALT.ORG 15 PAVEMENT RECYCLING This was attributed to the cement-treated FDR layer, which was not expected to expe- rience a change in stiffness with tempera- ture changes. The temperature dependent behavior was expected for the CCPR layers and is known to happen in AC layers. From the testing of the NCAT test sections, VDOT learned several key pieces of informa- tion regarding the structural performance of pavements built using CCPR and FDR. First, it was possible to build pavements using CCPR that could be expected to have long service lives under heavy truck traffic. Virginia continues to be a leader in apply- ing pavement recycling techniques on high-volume roadways, and the test sec- tions’ measured responses supported this position. Second, the inclusion of the FDR base layer played a major role in the per- formance of Section S12 and was credited with keeping the strain values low, similar to other previously-built track sections determined to have perpetual performance. Third, since FDR equipment was used to produce the stabilized layer in Section S12, it suggested that a similar process could be followed elsewhere (either to stabilize existing pavement foundations or to create a stabilized foundation on newly built roads or added lanes using materials imported to the project site). In addition to the structural response, the researchers also studied the economic and environmental impacts of including CCPR and FDR. Since Section S12 was consid- ered a perpetual pavement structure, it was compared with two other pavement sections built in 2003 (that did not include CCPR and FDR) and were similarly regarded as perpetual. Table 1 shows unit costs for selected materials based on recently awarded VDOT pavement rehabilitation projects. Table 1 also shows the assumed 1600 1400 1200 1000 800 600 400 200 0 10/1/2012 12/30/2012 3/30/2013 6/28/2013 9/26/2013 12/25/2013 3/25/2014 6/23/2014 9/21/2014 12/20/2014 3/20/2015 6/18/2015 9/16/2015 12/15/2015 3/14/2016 6/12/2016 9/10/2016 12/9/2016 3/9/2017 6/7/2017 9/5/2017 12/4/2017 3/4/2018 6/2/2018 8/31/2018 11/29/2018 2/27/2019 5/28/2019 8/26/2019 11/24/2019 2/22/2020 5/22/2020 8/20/2020 11/18/2020 Tensile Microstrain Test Date Cycle 1 Cycle 2 Cycle 3 Section N4 Section N3 Section S12 Figure 2 Strain response for VDOT test sections. continues on page 16 △