VAASPHALT.ORG 11 ASSESSING SUSTAINABILITY continues on page 12 △ example, asphalt mixtures that incorporate warm mix asphalt (WMA) technologies, highly polymer-modified asphalt (HP) binders, and bio-binders can increase sustainability in a number of ways. WMA technologies can reduce temperatures and emissions at the plant; HP binders can extend the performance life of asphalt materials; and bio-binders can reduce dependence on fossil fuels. Further, like many other state highway agencies, VDOT is extensively working to determine how best to incorporate recycled materials— such as recycled plastic waste, RAP at higher contents both with and without recycling agents (RA), recycled asphalt shingles (RAS), recycled tire rubber, and hybrid rubber—into their roads. During the 2021 construction season, the Virginia Transportation Research Council (VTRC) partnered with VDOT’s Richmond District to conduct a significant benchmarking experiment. The study focused on the performance of recycled plastic modified (RPM) dense-graded surface mixtures (SMs) with a nominal maximum aggregate size (NMAS) of 12.5 mm. Two RPM mixtures featuring the use of polyethylene-based polymer (P1) and polyethylene terephthalate-based plastomeric amorphous polymer (P2) were designed and constructed on Old Stage Road in Chesterfield County, Virginia, alongside two typical VDOT reference dense-graded mixtures (SM-12.5 D and SM-12.5 E). 2022 Field Trials The 2021 field trial provided valuable insights into mixture design and production. However, further investigation proved necessary to better understand and address the laboratory-related and field-related attributes of mixtures with recycled materials. To that end, construction of demonstration trials of two RPM and one high RAP with RA mixtures took place during the 2022 construction season. The first trial, constructed by Colony Construction, Inc. on State Routes (SRs) 630 and 645 in Prince George County, included two RPM SMs alongside one reference mixture (i.e., SM-D). The first RPM mixture had an NMAS of 9.5mm and featured recycled plastic P1 again (5% by total weight of binder) using the dry process. The second RPM mixture was a 9.5mm NMAS high RAP mixture (40% RAP) that featured the use of an engineered blend of polymers (P3) (8% by total weight of binder) using the dry process. The corresponding mixtures are ideally suited to surfacing parking lots, driveways, and local roads, where sustainability and economics are the primary drivers for applying this material (See Figure 1). The second trial, constructed by Allan Myers on SR 622, Dorset Road, in Powhatan County, included two RPM SMs alongside one SM-D reference mixture. The first RPM mixture was a 9.5mm NMAS mixture that featured a highly engineered polymer (P4) made from post-consumer and post-commercial plastic (2% by total weight of binder) using the dry process. The second RPM mixture was a 9.5mm NMAS mixture that featured the use of a plastic-based value-added wax and specialty polymer (P5) incorporated using the wet process (3% by total weight of binder) (See Figure 2). The high RAP with RA mixture was a 9.5mm NMAS mixture with 40% RAP content that featured a green bio-based asphalt rejuvenator. This RA was expected to soften and restore the functional properties of the aged binder; aid the workability and compactibility of the asphalt mixture; deliver the required roadway performance and durability; and reduce the need for virgin binder. The corresponding mixture was produced over two days by Superior Paving Corp. and placed on Riverside Parkway/ Woodridge Parkway in Ashburn, Virginia (See Figure 3). Figure 1. Production, Paving Operations, and Placement of Recycled Plastic Modified Mixture with Plastic Additive P3 P3 P3 Figure 2. Production, Paving Operations, and Placement of Recycled Plastic Modified Mixtures with Plastic Additives P4 and P5 P5 P4 P4 P4 P5
RkJQdWJsaXNoZXIy Nzc3ODM=