VAA Virginia Asphalt Spring/Summer 2022

VAASPHALT.ORG 13 TOWARDS SUSTAINABLE PAVING Figure 2. (a) loose RPM asphalt mixtures, (b) RPM pavement being compacted, (c) RPM pavements in-service after 4 months. (a) (b) (c) the night progressed, all core densities passed the requirements. The first night of trials generated several lessons learned. No issues were encountered when producing and paving the second RPM mix (with plastic P2). Figure 2 shows some of the paving operations. No changes from routine established practices in relation to surface preparation or paving operations were reported; standard construction practices and equipment were used. Finally, personnel involved with this effort had not encountered any safety-, health- or environmental-related considerations specific to RPMmixtures that do not apply to standard conventional asphalt mixtures. Do RPM Mixtures Perform Well? An extensive suite of laboratory tests are being performed on asphalt binders and specimens fabricated from the RPM and corresponding control produced mixtures to assess the compatibility of using recycled plastic waste with the raw materials locally available in Virginia. The asphalt specimens include plant mixed plant compacted specimens (no-reheat), plant mixed laboratory compacted specimens (reheat) and plant mixed field compacted specimens (cores) right after paving. The selected tests belong to three levels 10 8 6 4 2 0 Cantabro Mass Loss (%) (a) N/A SM-12.5 D 7.6 8.1 4.4 5.9 3.8 5.4 6.3 8.1 SM-12.5 E SM-12.5 P1 SM-12.5 P2 Design=7.7 Design=6.6 Design=5.0 Non-Reheated Reheated AC = 6.1% FT = 10.1% AC = 6.0% FT = 9.2% AC = 6.8% FT = 11.7% AC = 6.1% FT = 8.8% 350 300 250 200 150 100 50 0 CT Index at 25°C (b) N/A SM-12.5 D 201 182 228 168 257 204 185 118 SM-12.5 E SM-12.5 P1 SM-12.5 P2 Design=68 Design=100 Design=68 Non-Reheated Reheated AC = 6.1% FT = 10.1% AC = 6.0% FT = 9.2% AC = 6.8% FT = 11.7% AC = 6.1% FT = 8.8% Figure 3. Performance test data of RPM and control asphalt mixtures: (a) Cantabro mass loss and (b) IDT-CT. I-bars indicate the parameter variability plus/minus standard deviation. AC = asphalt content and FT = film thickness. of testing complexity: “basic” tests characterized by a short time for specimen preparation and testing without requiring any specific cutting, coring and gluing; “intermediate” tests requiring a longer time for specimen preparation and testing; and “advanced” tests requiring expensive machinery and multiple days to complete and analyze the test results. Figure 3 presents some of the results of the Virginia Balanced Mix Design (BMD) tests when performed on RPM and control specimens fabricated during design and production (i.e., reheats and non-reheats). Overall, the RPMmixture exhibited Cantabro mass loss values relatively greater than the ones observed for SM-12.5 E mix but lower than the ones observed for SM-12.5 D mix; thus, indicating promising durability. As expected, no issues related to rutting were observed when evaluating all mixes using the asphalt pavement analyzer (APA) rut test at 147°F (64°C). The indirect tensile cracking test (IDT-CT) at 77°F (25°C) was performed on all mixtures to evaluate the resistance to cracking. In general, RPMmixes showed cracking tolerance index (CT index) values similar or greater to those of SM-12.5 D and SM-12.5 E mixes. Although, current efforts are comprehensively assessing continues on page 14 △