LowEmissionAsphalt-136pg-WhitePaper-May2023

P a g e | 41 The range of [HMA+10%RAP] to [HMA+20%RAP] appears to be the marginal benefit to carbon break-even limit in the numerous studies we researched 82 because the most energy-intensive component of asphalt, its binder, 83 is not recoverable. Aged binder acts more as a filler (“black rock”) because it has lost its fluidity dynamics (maltene fraction attrition) due to oxidation, requiring either additional virgin binder, maltene replacement, or accepting reduced LCA. Additionally, aggregate carbon savings 84 in RAP are minimal and often exhausted by energy consumed in crushing/processing and additional trucking. The use of nonpetroleum solvents (bio-based solvents) aid in improving workability during paving of high RAP content mixes, but also shortens LCA as biobased chemicals are incompatible with maltene fractions, causing accelerated binder oxidation, and hence will impair EPD assessments. The National Asphalt Pavement Association (NAPA) has calculated a modest net benefit of RAP, concluding that for every 1% increase in RAP (within the 20% carbon break-even limit we outline) nationwide, would equate to just 0.01% vehicle equivalents. 85 This is why construction materials recycling garners such low values in carbon offset markets. Aggregate-centric recycling offers low overall environmental impact, unfortunately. However, up to 20% RAP, when processed on-site (reduced hauling), should be considered on large scale projects, where in-situ processing is feasible, as the potential cradle-to-pave carbon savings can reach 4%-6% . 86 Warm Mix Asphalt Warm Mix Asphalt (WMA) is a technique to simply reduce the energy used in asphalt manufacturing. 10°F to 40°F lower temperatures typically can be achieved, rendering, at scale, cradle-to-gate carbon reductions that can range up to 2% . 87 82 National Center for Asphalt Technology (NCAT); Colas Group S.A.; FHWA; Western Research Institute (WRI); and Texas A&M Transportation Institute (TTI). 83 The production of asphalt binder is >50% of the energy used in manufacturing and paving with AC. 84 Aggregate is ~5% of the energy used in manufacturing and paving with AC. 85 National Asphalt Pavement Association (NAPA): The Road Forward, A Vision for Net Zero Emissions for the Asphalt Pavement Industry , www.asphaltpavement.org/climate . 86 NAPA. 87 Ingevity Corporation; FHWA; NAPA.