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Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities (2023)

Chapter: Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study

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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix G: Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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283 Appendix G Durability and Life-Cycle Implications of Repurposing Plastics Waste in Infrastructure: A Case Study Zhiye Li and Michael Lepech Stanford University MOTIVATION The increasing consumption of plastic products worldwide exacerbates global warming, energy resource depletion, landfill shortage, and environ- mental pollution. This paper aims to identify opportunities for repurposing plastics waste in infrastructure by studying the current status, challenges, and needs of recycling plastics in a circular economy and examining the long-term durability and environmental impacts on a life-cycle basis. The second section introduces the current status and challenges of recycling polymers in civil infrastructure. The third section presents two life-cycle assessment (LCA) case studies of recycling plastics waste in ar- chitectural composite panels and asphalt pavements for 100 years and 50 years, respectively. LCA results provide pragmatic examples of how long- term durability influences life-cycle environmental impacts and how to estimate tolerance of durability reduction on a life-cycle basis. LIFE CYCLE OF RECYCLED POLYMERS This section introduces the life cycle of recycled plastics from their sources to application and role in a circular economy. It describes two major sources of recycled plastic products and gives details about two major

284 RECYCLED PLASTICS IN INFRASTRUCTURE applications of recycled plastic in civil infrastructure: buildings and asphalt pavements. Finally, it summarizes the definition and category of circular economy and discusses the role of repurposing plastics in various applica- tions among the categories. Sources of Recycled Polymers Plastics Waste Post-consumer and post-industrial plastics wastes are the largest resources of recycled polymers. ASTM D7611/D7611M-21 defines the ASTM Inter- national Resin Identification Coding System (RIC), which provides codes for six commonly used resin types, with a seventh category created for all other types, as shown in Figure G-1 (ASTM 2020). This system was initially introduced by the U.S. Society of the Plastics Industry (SPI) in 1988 as the “Voluntary Plastic Container Coding System” (Wilhelm 2016). The original intention of RIC was to facilitate plastics waste to be adequately recycled while preserving its value based on its RIC. In the United States, the rate of recycling and composting of plastics increased from less than 1 percent in 1980 to 9 percent in 2018, as a percentage of its generation (USEPA 2022). However, compared to the increasingly large flow of plastic product consumption, recycling of plastics is still negligible. The 2017 U.S. plastics material flow in Figure G-2 shows that more than three-quarters of the plastics reaching end of life went to landfill, and less than 8 percent was recycled. Packaging was the largest defined use market for plastics, but two-thirds of the plastic put into use in 2017 went into other markets, including consumer products, electronics, buildings, and transportation (Heller et al. 2020). In particular, the upper left portion of Figure G-2 indicates that the major plastic wastes that have been recycled are polyethylene terephthalate (PET), high-density polyethylene (HDPE) and low-density polyethylene (LDPE). The major outcomes of recycling processes are also PET, HDPE, and LDPE. As the most recycled plastic in the United States and worldwide, re- cycled PET reuse is dominated by bottle curbside collection and bottle FIGURE G-1 The ASTM International Resin Identification Coding (RIC) system facilitates recycling of plastics. SOURCE: ASTM 2020.

285 FI G U R E G -2 P ro du ct io n, im po rt s, e xp or ts , u se , d is po sa l, an d le ak ag e of p la st ic s in t he U ni te d St at es in 2 01 7. N O T E S: W id th o f flo w s sc al ed t o m as s (f or r ef er en ce : pr od uc ti on o f H D PE = 8 .5 76 m ill io n m et ri c to ns ). C ol or s co rr es po nd t o po ly m er ty pe s (s ee le ge nd ). N um be rs in p ar en th es es r ef er to n ot es in T ab le G -1 . N ot e th at th e di ff er en ce in m as s be tw ee n pr od uc ti on (l ef t si de ) an d en d of li fe ( ri gh t si de ) in t hi s 20 17 s na ps ho t re pr es en ts a n et a dd it io n to in -u se s to ck . SO U R C E : H el le r et a l. 20 20 .

286 RECYCLED PLASTICS IN INFRASTRUCTURE deposit collection. Figure G-3 shows U.S. flows of PET. The figure shows that the bottles reclaimed in the United States from the two paths is around 2.7 times the plastics reclaimed from other paths (e.g., other reclaimer feed- stock and imported bottles). On the input side of the PET recycling process, the amount of PET collected from other products (e.g., sheet, film, nonfood, and food packages) is only one-twelfth of the amount of PET from bottles (Smith et al. 2022). In the United States, the data on plastics flow (see Figure G-2) and PET flow (see Figure G-3) indicate a national problem: for example, PET bottles that are collected through the curbside program and the deposit program exclusively dominate the input of the PET recycling loop while plastics from other resources and other products fail to enter the circular economy. The reasons for this phenomenon include but are not limited to three main factors: FIGURE G-3 U.S. flows of PET in million pounds. NOTES: Yellow represents nonbottle “thermoform” PET resin, blue represents col- lected bottle PET resin, and light red represents uncollected bottles. Green represents recycled PET (rPET) converted into products, while dark red represents disposal and mismanaged waste. The gray U.S. reclaimer residue represents unknown stream exiting reclaimer processes. This figure is adapted from NAPCOR (2019). SOURCE: Smith et al. 2022.

APPENDIX G 287 1. Reclaimed plastic from other sources cannot be economically sorted to satisfy recycling facility requirements. 2. The sorted plastics waste is contaminated and cannot be economi- cally cleaned to meet recycling facility requirements. 3. Other products, unlike reclaimed bottles, do not have plastics that are designed to be recycled, and they are too heterogeneous to be economically separated to satisfy recycling facilities’ requirements. In addition, the first challenge in sorting also indicates that current sorting methods and technology cannot utilize the RIC system effectively at scale. For other types of resin, the highest demand for polymers by type is polypropylene (PP), yet this is not widely recycled (Kosior and Mitchell 2020). In the building and construction sector, the distribution of plastics consumed in the United States in 2015 was, in descending order, polyvinyl chloride (PVC), other resins, HDPE, polystyrene (PS), LDPE/linear low- density polyethylene (LLDPE), and PP. The amount of HDPE is comparable to other resins (Di et al. 2021). HDPE and LDPE/LLDPE recyclates can be used as additive in road pavement; their application will be discussed in subsections below. Despite many emerging efforts and analyses that have been conducted to propel the use of recycled plastics in infrastructure, the current allocation of plastic recyclates in areas of buildings and construc- tion is very small. The authors have conducted a series of interviews with some com- panies and institutions that have been trying to use recycled plastics. All interviewees valued sorting plastics waste adequately as the most urgent and challenging problem. It is an inevitable problem for all stakeholders in the circular economy, such as recycling companies that produce recyclates, customers who buy and use recyclates in their products, and customers of recyclate-related products. Another significant issue of repurposing plastics waste in infrastructure is that the high cost-benefit ratio and relatively low- performance recyclate-based products can hardly compete for a share in a long-standing, well-developed, and regulated supply chain. Government must play a leading role in sponsoring innovation and making policies to help recyclate-based products acquire a sufficient share in the market. Polymeric Composite Wastes Recycling fiber-reinforced composites (FRPs), such as glass fiber–reinforced polymer (GFRP) composites and carbon fiber–reinforced epoxy (CFRE) composites, has gained increasing focus with their emerging applications in renewable energy such as wind turbine blades. Polymeric composites are theoretically completely recyclable. However, recycling FRPs is difficult

288 RECYCLED PLASTICS IN INFRASTRUCTURE in out-of-laboratory conditions at scale (Zabihi et al. 2020). The authors interviewed several experienced engineers who have been trying to recycle composite for a long time. From the interviewee’s feedback, economic cost and energy consumption are the primary barriers to recycling FRP composites at scale in the industry. Specifically, the cost of collecting and transporting retired wind-turbine blades can almost cancel the financial benefit of recycling GFRP. Moreover, recycling FRP composite materials by the chemical method at scale is challenging owing to their high mechanical performance and high resistance to a harsh corrosive environment. As a result, by the state of the art, the four composite recycling meth- ods, arranged in ascending order of difficulty, energy requirement, cost, and scale, are (1) to reuse mechanically shredded composites as aggregate, (2) to recycle fiber and lost polymers (usually via thermal methods), (3) to obtain fibers and fuels (usually via hybrid methods), and (4) to use solvolysis or dissolution, which allows recycling of both fibers and polymers (usually via hybrid or chemical method). In the category of recycling fibers, recycling of carbon fibers has been investigated more because of their higher value compared to glass fibers (Karuppannan Gopalraj and Karki 2020). Among the four categories, the mechanical method requires the low- est energy and has been mostly studied in construction materials; chemical recycling requires the highest energy, and the thermal method falls between the two in terms of energy consumption (Rani et al. 2021). Beauson et al. (2014) studied recycled thermoset GFRP composites from wind-turbine blade waste in the form of shredded composites and glass fibers. They reused recyclates as replacement of some amount of virgin glass fibers to make new composites (Beauson et al. 2014). Most thermal methods only recycle fibers; some methods, such as the pyrolysis method and mi- crowave-assisted pyrolysis hybrid method, output fibers primarily and oil secondarily but lose the polymer matrix (Åkesson et al. 2012; López et al. 2017; Torres et al. 2000). Cousins et al. (2019) conducted experimental and life-cycle assessment studies to investigate the feasibility of recycling composite wind-turbine blade components that are fabricated with glass fiber–reinforced thermoplastic composites through dissolution. Research found that dissolution-based methods can recover good quality material, but the energy cost is high compared to grinding and thermal decomposi- tion. Specifically, the dissolution distillation extrusion consumes five times the energy compared to the dissolution evaporation extrusion method. Their economic analysis of the technical data shows that recycling thermo- plastic glass fiber composites via dissolution into their constituent parts is commercially feasible under certain conditions. Specifically, this analysis concludes that 50 percent of the glass fiber must be recovered and resold for a price of US$0.28/kg, and 90 percent of the resin must be recovered and resold at a price of US$2.50/kg (Cousins et al. 2019).

APPENDIX G 289 In summary, the challenges of recycling FRP composites are the follow- ing: (1) FRP has a complex and mixed material composition, (2) recycled glass fiber often has length reduction and properties degradation and lower value, (3) thermoset resin is cross-linked and cannot be remolded (Liu et al. 2019), and (4) there are high energy requirements for recovering fiber and matrix in good quality. However, as more research and innovation on recycling composites waste emerges, technical innovations and industrial resources will increase in the future. Applications of Recycled Polymers in Civil Infrastructure Globally, the largest market segments for recycled plastic are non-food packaging, food contact packaging, construction, and automotive, as shown in Figure G-4a (Locock et al. 2017). Between 2006 and 2016, the number of patent filings in the area of recycled plastic also focused on pack- aging, construction, and the automotive industry and kept the same ranking as their market segments (see Figure G-4b and Locock et al. 2017). With more academic, industrial, and governmental focus and effort, recycled plastic usages in building and construction present the potential to exceed the packaging segment and become the largest market segment for recycled plastic by 2030, according to a new report by Grand View Research, Inc. (Bloomberg 2022). This section gives a review of applications of recycled polymers in civil infrastructure. Two major applications are discussed: (1) building materials and (2) asphalt pavements. These are the largest FIGURE G-4 (a) Global end use of recycled plastic in 2017 (Technavio 2018). (b) Patent filing stratified by application, polymer type, and before recycling (polymers being recycled) versus after recycling (application area for recycled polymers). SOURCE: Locock et al. 2017. (a) (b)

290 RECYCLED PLASTICS IN INFRASTRUCTURE construction sectors, and their worldwide demand is increasing with global rates of urbanization. Buildings Emerging polymer-based composites, such as CFRE and GFRP, have rapidly gained outdoor application across aerospace, marine, and civil infrastruc- ture applications and are gradually leading the way to establish a sustain- able, green, and smart engineering system. Adoption in civil infrastructure, specifically, exploits high strength-to-weight ratios, corrosion resistance, and fire-retardant properties that typically meet the needs of environment- friendly, sustainable, and resilient civil infrastructure (Li and Lepech 2023; Li et al. 2022). Other polymer-based materials such as polymeric thermal insulation panels, waterproofing panels, wood–polymer composites, con- crete–polymer composites, and polymer-based mortars are also investigated in the area of innovative sustainable building materials (Li and Lepech 2023). Among all materials mentioned above, GFRPs and CFREs are primar- ily investigated and applied since they have originally been studied, tested, and used in the automotive and aircraft industries (Li and Lepech 2023). The earliest case of using GFRP in civil infrastructure is the roof structure of a Petrol station located in Thun, Switzerland, in 1962 (Knippers et al. 2012). After that, fiber-reinforced polymeric composites have been applied in civil infrastructure, such as building envelopes, facade, load-bearing structures, and internal and external reinforcement (Moskaleva et al. 2021). Even though GFRPs and CFREs have a more extended history in civil in- frastructure than other composites (e.g., cement and concrete composites), they still have the problem that all innovative architectural materials have: long-term experience and field performance data of polymer composites in buildings and civil infrastructure applications do not exist. Specifically, the current expected life span of GFRPs and CFREs is 60 years, wood–polymer composite (WPC) structures are expected to last 25 years (much longer than wood structures), and capped polymer boards are expected to last 50 years or more. The life span of concrete incorporating plastics waste has not been precisely calculated. Still, it is expected to be comparable to the life span of conventional concrete, which should last up to 100 years if properly cared for. To date, none of the field applications of these materials has been built long enough to test if they can satisfy their expected life span. Likewise, the durability of using recycled plastics fully or partially substituting the polymers in those composites lacks long-term performance data (Li and Lepech 2023). Zhu et al. (2017) recycled glass fibers (GFs) from nonmet- als of waste printed circuit boards and recycled polycarbonate (PC) from waste compact discs (CDs) that were simultaneously reused to produce

APPENDIX G 291 GFRP composites. Through the comparison and analysis of waste-based composites and pure materials, the performance of recycled material–based composites is weaker but comparable to the pure material–based compos- ites (Li and Lepech 2023). The overall performance order from high to low is pure PC + pure GF > pure PC + recycled GF > recycled PC + pure GF > recycled PC + recycled GF > recycled PC (Zhu et al. 2017). Ribeiro et al. (2015) applied GFRP recyclates as aggregate replacement for polymer mortars and found that GFRP waste–filled polymer mortars show improved mechanical behavior over unmodified polyester-based mortars, thus indi- cating the feasibility of GFRP waste reuse as raw material in concrete– polymer composites (Ribeiro et al. 2015). Awoyera and Adesina (2020) explored various approaches of recycling plastics waste into construction products and concluded that the possible use of plastics waste as binder, aggregates, and fibers makes it a viable replacement for all components in cementitious composites, with somewhat acceptable detrimental effects on the performance of the resulting composite. Jubinville et al. (2021) applied reprocessed (simulating recycled) PP as a matrix for highly loaded WPCs. Their study has shown that although recycled PP introduced viscosity loss due to chain scission, recycled PP allowed a greater amount of wood fiber to be loaded into the system. As a result, the WPC with higher wood fiber content will exhibit an increase in density and material hardness but re- duced elongation (Li and Lepech 2023). Since historical, experience-based service life models for composite building applications are not available, the solution to propel those inno- vative materials is to build predictable computational mechanics models. Such models can be validated by static and fatigue tests, investigated by uncertainty quantification studies, and reach reasonable confidence inter- vals to predict composite service life performance on a semicentennial or centennial time scale (Li and Lepech 2023). Li et al. (2021a, 2021b, 2022) have developed computational and data-driven methodology to predict long-term performance of GFRP under environmental aging and fatigue. This effort extends the literature on composite aging from short time- accelerated experiment records to multiphysics-based models that are able to predict long-term service life. This method can help material engineers assess the viability of new polymer composite building materials by leverag- ing experimental, computational, and data-driven approaches. LCA studies, which consider life-span prediction given by the multiphysics-based model, found that there is a potential for polymeric composite buildings and build- ing elements to be a significant part of the sustainable built environment (Li and Lepech 2023). However, (i) significant gaps in the design knowledge re- main in the life-cycle inventories of recycled plastic pellets (RPPs), blended materials, and building elements being used, (ii) there is little scientific or engineering basis for service life assumptions and end-of-life modeling of

292 RECYCLED PLASTICS IN INFRASTRUCTURE RPP blended composite building elements and materials, and (iii) there is a significant need to study opportunities for improved end-of-life manage- ment (i.e., recycling) of RPP blended composite building materials. Polymer-based construction materials is an emerging area, in which all kinds of innovations have the opportunity to gain investigation and invest- ment. Competitors to recycled plastics, such as biobased and biodegradable composites, are also in the early stage of customer discovery. Therefore, there is a great opportunity to establish a new circular economy and com- plete standard without facing challenges such as trying to cope with, yield to, or modify a long-standing, solidly established supply chain of conven- tional material (Li and Lepech 2023). Asphalt Pavements In addition to building materials, the pavement industry is another prom- ising sector for using recycled plastics. As of 2020, the United States has more than 4,577,000 kilometers of paved roads (BTS 2022). The United States has about 3,600 asphalt production sites and produced about 420 million tons of asphalt mixture in 2019 (NAPA 2022). Different sorts of waste have been investigated to be recycled into asphalt concrete and bitu- men, including but not limited to low-density polyethylene, high-density polyethylene, marble quarry waste, building demolition waste, ground tire rubber, cooking oil, palm oil fuel ash, coconut, sisal, cellulose and polyester fiber, starch, plastic bottles, waste glass, waste brick, waste ceramic, waste fly ash, and cigarette butts (Rahman et al. 2020). With regard to incorporating recyclates in asphalt pavement, there are two main methods: (1) the wet method and (2) the dry method (Santos et al. 2022). The major difference between the two methods is the melting point of the additive materials compared to the melting point of the asphalt mixing temperature (i.e., 165°C to 175°C [Santos et al. 2021]). In the wet method, recyclates with a melting point lower than the asphalt mixing temperature are added to the bitumen as polymer modifiers before mix- ing with aggregates. Possible recyclates can be plastics, ground tire rubber (Ding et al. 2019), waste cooking oil (Rahman et al. 2017), and palm oil fuel ash (Rahman et al. 2017). Specifically, when it comes to plastic recy- clates, LLDPE (Nizamuddin et al. 2020), LDPE (Duarte and Faxina 2021), and HDPE (Yin et al. 2020) are generally suitable for the wet method. In the dry method, high-melting-point recyclates are added to the aggregate before adding bitumen (Brasileiro et al. 2019). Possible recyclates can be plastics (Azarhoosh et al. 2018), glass (Mohajerani et al. 2017; Zakaria et al. 2018), quarry waste (Akbulut and Gürer 2007; Zakaria et al. 2018), building demolition waste (Tavira et al. 2018), coconut and sisal fiber (Agunsoye et al. 2014), waste ceramic (Muniandy et al. 2018; Shamsaei et

APPENDIX G 293 al. 2020) and cigarette butts (Rahman and Mohajerani 2021; Rahman et al. 2020). Specifically, plastic recyclates with a high melting point, such as PP (Al-Hadidy 2018), PET (Ahmad 2017), PS (Padhan et al. 2020b), and PC (De la Colina Martínez et al. 2019; Mahanta et al. 2012) are suitable for the purpose of replacing aggregates. In the wet methods, adding polymers generates a polymer network within the bitumen matrix and a plastic coat around aggregates. Those ef- fects modify the asphalt binder, enhance the asphalt performance, and even- tually increase the overall road pavement durability. Virgin resins such as ethylene vinyl acetate (EVA) and styrene-butadiene-styrene (SBS) have long been used as bitumen modifiers to successfully produce high-performance polymer-modified asphalt pavements (Enfrin and Giustozzi 2022; Kalantar et al. 2012; Zhu et al. 2014). One limitation of the wet method is that polymers used in the “wet” process account for a very small percentage of the overall mass of the asphalt pavement, commonly ranging from 2 to 8 percent by weight of the polymer-modified bitumen (PMB) such as hot- mix asphalt (HMA). The total asphalt pavement contains around 94 to 95 percent of aggregates and 5 to 6 percent bitumen or PMB by weight. Wu and Montalvo (2021) summarized the dosage of each waste plastic used for asphalt modification in literature, as shown in Figure G-5. The highest dos- age in Figure G-5 is substituting PS for 2 percent aggregate, equivalent to 23 percent substituted by the weight of asphalt (Vila-Cortavitarte et al. 2018). FIGURE G-5 Dosages of plastic used for asphalt. NOTE: ABS = acrylonitrile butadiene styrene; EVA = ethylene vinyl acetate; HDPE = high-density polyethylene; LDPE = low-density polyethylene; PC = polycarbon- ate; PET-E = polyethylene terephthalate; PP = polypropylene; PS = polystyrene; PU = polyurethane; V = polyvinyl chloride. SOURCE: Wu and Montalvo 2021.

294 RECYCLED PLASTICS IN INFRASTRUCTURE Due to the potential of the wet method to increase the overall durability of pavement, many studies have recently investigated the effect of qualified waste plastics as a possible bitumen modification. Audy et al. (2022) inves- tigated the suitability of 31 post-industrial or post-consumer recycled waste plastic samples based on their chemical and physical properties against those of bitumen/asphalt. This comparison study found that LDPE, LLDPE, acrylonitrile butadiene styrene (ABS), and PET should be preferentially used as bitumen/asphalt modifiers. Specifically, recycled LDPE has the highest predicted affinity with bitumen as polymer modifier (wet method) and recycled ABS has the highest predicted affinity with asphalt as aggregate replacement (dry method) (Audy et al. 2022). Abduljabbar et al. (2022) evaluated the effect of using waste LDPE on the mechanical properties of dense thin asphalt overlay. The laboratory test results indicate that, when adding dosage in 0, 2, 4, and 6 percent of asphalt binder by weight, durabil- ity in terms of water sensitivity increases as the polymer dosage increases. Similarly, increasing LDPE dosage up to 6 percent enhances resistance to low-temperature crack and crack progression, while creep compliance improved by 83 percent in comparison to the control mix. And 2 percent LDPE is the optimum proportion, as it provides the best abrasion resistance (Abduljabbar et al. 2022). Wu and Montalvo (2021) published a literature review on repurposing waste plastics into asphalt pavement materials. Ac- cording to the reviewed studies, incorporating HDPE into asphalt gener- ally results in higher stiffness and viscosity and better moisture resistance; nevertheless, the effect on the fatigue resistance is not well agreed upon. As for the LDPE, different types of LDPE result in various modification effects. Various studies generally agreed that adding recycled LDPE to asphalt can improve rutting, fatigue, and moisture resistance. However, thermal crack- ing resistance is controversial. Although many laboratory studies demonstrated the feasibility of and certain performance improvements associated with using recycled plastics for asphalt modification, the application of this concept in the field at a large scale is still at an early stage and needs further validation. Dalhat and Al-Abdul Wahhab (2017) investigated the effect of recycled PP, HDPE, and LDPE on the viscoelastic performance of the local asphalt binder. All samples exhibited improved performance in terms of rutting parameter and resilient modulus. Despite the improvement, all the samples could not meet the elastic recovery requirement for polymer-modifier asphalt binder set by AASHTO TP 70 (2013). In order to ascertain the feasibility of large-scale production of recycled plastic–modified asphalt binder, they need to be supplemented by some amount of elastomeric polymer and to be further investigated in terms of the chemical compatibility between waste plastics and bitumen (i.e., storage stability).

APPENDIX G 295 Despite the improved performance observed in laboratory experiments and the fact that a number of field projects using recycled polymer–modified asphalt mixtures have been constructed in the past few years, the long-term pavement performance data for many of these projects is not available. “Long-term data” does not mean the life span of the pavement only. Other indicators like emissions during production, potential contamination, and the future recyclability of asphalt are also lacking characterization. Plastics emit fumes when processed above their melting temperature. Recycled plastic relies on collecting, sorting, and cleaning to control its quality and generally has more severe fuming and emission pollution (Ansar et al. 2021; Lindberg et al. 2008). Heikkilä et al. (2003) conducted comparison experiments and found that using recycled plastic additives in asphalt increases the mutagenicity of the laboratory emissions significantly. Add- ing plastics to the pavement also generates concern about microplastics (Andersson-Sköld et al. 2020). When recycling plastics in asphalt pavement gained exponential interest and investigations, very few studies tested the recyclability of the recycled plastic–modified asphalt mixtures (Rodríguez- Fernández et al. 2020). Currently, asphalt is fully recyclable. However, whether and how the quality of recycled plastics affects the recyclability of the asphalt mixtures after the life span remains unknown. Long-term per- formance data are of extreme importance to quantify the impact of recycled plastics on the service life of asphalt pavements, which also provide a criti- cal input for the life-cycle cost analysis (LCCA) of recycled plastic–modified asphalt mixtures (NCAT et al. 2021). Nevertheless, with the potential advantages of waste plastic–modified asphalt (wet method) being frequently reported in recent studies, the eco- nomic and environmental effects of repurposing plastic in road pavement are also being investigated through LCA. There is work that obtained primary data from recycling facilities (Santos et al. 2021), and there is also work that integrates laboratory test results and LCA results to find the best type of “road grade” recycled plastics (Audy et al. 2022). Some work aims to quantitatively evaluate the economic and environmental performance by incorporating LCA and LCCA in sensitive studies. The sensitivity analysis demonstrated that the durability of the alternative materials was the key factor in maintaining their environmental and economic advantages in the entire pavement life cycle (Yao et al. 2022). Some authors discuss the un- certainties of the results introduced by gaps in knowledge about potential health and contamination risks (Enfrin and Giustozzi 2022). In general, LCA results in publications agree that using qualified waste plastic (whose durability is comparable to conventional asphalt mixture) can reduce the environmental impact by substituting more virgin plastic, consuming less energy related to virgin plastic manufacturing, and saving landfill space.

296 RECYCLED PLASTICS IN INFRASTRUCTURE Despite these promising conclusions, long-term data are still lacking, and further studies are needed. Rangelov et al. (2021) presented a comparative LCA, and the cradle-to-gate results indicated that recycled plastics mixtures present impacts higher than HMA but lower than a polymer-modified mix. Praticò et al. (2020) developed LCA based on the ISO 14040 series and found that the combined use of warm-mix asphalts and recycled materials in bituminous mixtures entails lower energy consumption and environmen- tal impacts due to a reduction of virgin bitumen and aggregate consump- tion. Santos et al. (2021) collected primary data from a recycled plastic company and implemented them into an LCA. Their research concludes that recycling soft plastics as a polymer for bitumen modification delivers significant environmental benefits compared to using virgin polymers. In the dry methods, high-melting-point recycled plastics are substituted for the natural quarry aggregates that are commonly used for asphalt mixes. Although the dry method uses more recycled plastic material than wet, the dry process does not contribute to any enhanced behavior such as com- pactability, strength, or durability of the asphalt mix. Zakaria et al. (2018) found that combining 1 percent recycled plastic and 4 percent recycled glass shows similar and satisfactory results compared to the control sample for all tests. Xuan Lu and Giustozzi (2022) investigated the performance of asphalt concrete containing recycled plastics as synthetic aggregates in the dry mixing process. Research indicated that the presence of plastics reduces the com- pactability of the asphalt mixes, and coarse plastic particles with spheri- cal and fragmented shape reduce compactability minimally. Among 0.5, 1, 2, and 4 percent of the mix mass, using 1  percent recycled plastic can best balance between sustainability and comparable material per- formance goals (Xuan Lu and Giustozzi 2022). Generally, LCA studies report a reduced environmental impact as a result of replacing virgin materials with recycled ones, while they fail to consider the fact that us- ing recycled plastic as aggregates is likely to shorten the life span (Santos et al. 2021, 2022). Since the dry method does not affect durability like the wet method does, this paper focuses on the wet method in the case study section. Waste Plastics in a Circular Economy Circular economy is a concept gaining global momentum owing to a fundamental reconsideration of resource producing, consuming, and re- covering systems. Hahladakis et al. (2020) defined a circular economy as “a system that has the ability to restore, retain and redistribute materials, components and products back into the system in an optimized manner

APPENDIX G 297 and for as long as it is environmentally, technically, socially and economi- cally feasible.” The definition means that inappropriate and/or uncon- trolled disposal practices should be excluded from the circular system (Jambeck et al. 2015, 2018). Accordingly, recycling plastics waste belongs to the circular economy and is often distinguished into downcycling, re- cycling, and upcycling. • Downcycling: Downcycling is a recycling path, with low require- ments on recycled material, that produces low-quality or low-value end products. It often involves the mechanical recycling method (Hahladakis et al. 2020). Examples include the manufacturing of items for road construction, playgrounds, etc. (de Mello Soares et al. 2022). • Recycling: Recycling denotes the reuse of a previously processed or waste material (Korley et al. 2021). An example can be the re- cycling of PET bottles into new bottles and recycling of packages into new packages. • Upcycling: Korley et al. (2021) define “upcycling” as the upgrading and reuse of an existing chemical or material and “upgrading” as the addition of value to an existing chemical or material. An exam- ple of upcycling can be the use of monomers chemically recycled by depolymerization in manufacturing a long-term, high-performance product (e.g., the use of recycled plastic in GFRP composites). For each category listed above, the reclaimed plastics waste must meet its standard to enter the corresponding circular loop. The quality of sorted and reclaimed plastic is crucial for the capability and efficiency of the circular economy. Given the current challenge of reclaiming and sorting discussed earlier, better sustainability-driven policies are urgently needed to reclaim and sort high-quality wastes and to drive the demand for second- ary material markets. Product developers must design products for the end of their life and communicate along the supply chain (Kosior and Mitchell 2020). LCA CASE STUDIES ON USING RECYCLED PLASTIC IN CIVIL INFRASTRUCTURE In this section, two LCA studies on using recycled plastic in civil infrastruc- ture are conducted. The first part of this section explores the environmental impact of using RPPs in building materials within 100 years, while the second focuses on the environmental impact of using RPPs in asphalt pave- ment within 100 years.

298 RECYCLED PLASTICS IN INFRASTRUCTURE Recycling Waste Plastics in SFMOMA GFRP Facade Panels Goal and Scope Definition This case study conducts an environmental perspective analysis to examine the long-term durability and the environmental impact of mixing recycled plastic pellets with virgin polyester as the matrix of GFRP composite pan- els. The reference case is the GFRP architectural composite panel that is used in the Facade System of the San Francisco Museum of Modern Art (SFMOMA). The SFMOMA Facade System was remodeled in 2016 using a GFRP composite facade material made by Kreysler & Associates. The design of SFMOMA’s facade was inspired by the rippling waters of the San Francisco waterfront, and the architectural design required about 1,400 unique composite panels. FRP materials are made of a polymer matrix re- inforced with fiberglass. GFRP has a high stiffness and strength-to-weight ratio, which reduces load demand on its supportive aluminum frame and reduces the building’s primary load and, in turn, reduces construction costs. The authors and students have conducted a series of LCAs comparing the use of aluminum frame and GFRP panels in the Facade System with a traditional facade system (e.g., precast concrete cladding [PCC] facade sys- tem and ceramic facade panels [CFPs]). The studies indicated that GFRPs score higher than PCCs and CFPs if the functional unit is defined by weight. However, since GFRPs are lightweight, the environmental impact per sur- face area of GFRP is lower than that for traditional materials, especially for high-rise exterior cases. In addition, using GFRPs in large amounts in buildings also means the corresponding amount of fossil fuel is not burned as fuel, thereby averting combustion-related emissions. As polyester resin is currently produced from fossil fuel refining processes, its material acquisi- tion and production emit greenhouse gases (GHGs). To find solutions for further GHG emissions reduction, this study ex- plores the potential replacement of part of the polyester resin with RPPs. In the parametric study, the amounts of RPPs as a substitute for part of the polyester matrix range from 0 to 75 percent at 25 percent intervals. The parametric study of road pavement durability ranges from −20 to 20 years. Materials and Method This LCA study is conducted using the Eco-indicator 95 V2.06 Europe method in SimaPro. The functional unit used to compare the two panels in this LCA is one 29’10” × 5’7” or 166.5 ft2 panel, since this is the most common size of panel used for the Snohetta expansion. The average panel thickness is 4.8 mm. This is a simplified assumption, since the facade of the

APPENDIX G 299 SFMOMA is contoured comprising 700 completely unique forms to achieve the architect’s aesthetic intent. As an attributional LCA, this study compares the existing fossil fuel– based GFRP facade panel to a GFRP facade panel that uses recycled plastic pellets over a 100-year life cycle. The reference GFRPs are made of 42.1 wt.% unsaturated polyester resin, 63.2 wt.% glass fiber, and 2 wt.% other organic chemicals. Environmental deterioration of polymeric composite is related to degradation of the polymeric portion of the matrix by moisture and ultraviolet (UV) exposure. To protect the GFRP laminate from UV- and moisture-induced microcracking, the laminate surface is protected by an opaque gel coat that is made of sand and resin in a ratio of 1:1 by weight. Figure G-6 shows the top surface protected by gel coat and the unprotected bottom surface of the laminate. To satisfy Tunnel Test Flame Spread (FSI) and Tunnel Test Smoke Density (SDI), a product named Fireshield 285 is used as the fire-retardant additive. The SFMOMA facade panel can pass the ASTM E-84 surface burning characteristics test with a Class 1 smoke development and flame spread. Using polymeric composites as a building material is a new and emerg- ing area, with much less research and data on using RPPs to substitute part of the GFRP’s polymer matrix. Since there is no evidence to show the effect of using RPPs in GFRP on its durability, this study assumes that the RPPs cannot fully substitute all polyester as the matrix of the composites by state of the art. The amount of the RPPs used in the parametric study is as follows: FIGURE G-6 Photo of a small sample of SFMOMA GFRPs facade panel. (a) The top surface of the panel is covered by a protective gel coat. (b) The bottom surface is covered by polyester matrix resin; woven fiber yarn can be observed from this side. (b)(a)

300 RECYCLED PLASTICS IN INFRASTRUCTURE • Use RPP to substitute 0 wt.% of fossil fuel–based polymer (SFMOMA facade panel). • Use RPP to substitute 25 wt.% of fossil fuel–based polymer. • Use RPP to substitute 50 wt.% of fossil fuel–based polymer. • Use RPP to substitute 75 wt.% of fossil fuel–based polymer. The processes involved in the production of the facade panel with different amounts of RPPs from 0 to 75 wt.% are depicted in Figure G-7. They include (1) the production of the raw materials required to produce the GFRP laminate and gel coat, (2) the production of GFRP laminate and gel coat, (3) applying gel coat on the top surface of the laminate, and (4) shipping the panel to SFMOMA and assembly on site. Since this case study focuses on the amount of RPP used and the uncertainty of durability, a few parts of the system are not considered in this study: (1) preconstruction site preparation, (2) manufacturing and assembly of the aluminum frame, and (3) transporting raw material to the manufacturing site. As described earlier, long-term experience and field performance data on polymer composites in buildings and civil infrastructure applications do not exist. This study assumes that the reference life span of fossil fuel– based GFRP composites is 60 years (EY in Table G-1). This assumption is made for two reasons: (1) the facade panels attached to the supporting aluminum frame are not subject to significant mechanical loads and (2) FIGURE G-7 Process flow diagram and system boundaries of GFRP panel production.

APPENDIX G 301 the facade panels do not stay in a corrosive environment. In highly cor- rosive environments and heavy mechanical loading cases such as marine and water applications, the life span of FRP in boats is 30–45 years (Frej et al. 2021). Another two comparative quantities for life span are 40 and 60 years. This study also assumes that the facade will be inspected and undergo simple maintenance every 20 years. Table G-1 shows the main- tenance and replacement schedules for GFRP composites with different life spans (EY). Each repair activity includes manufacturing, transporting, and applying gel coat on 5 percent of the panel surface by area. Each re- placement activity includes (1) disassembling, transporting, and landfilling all old panels and (2) manufacturing, transporting, and assembling new panels. Results and Discussion Figure G-8 summarizes the normalized environmental impact scores associ- ated with the use of RPPs in the GFRP panels according to various contents and various expected life spans. The figure shows that the direct impact of using GFRPs on the environment is GHG emission, which contributes to climate change. Secondary impacts are acidification, eutrophication, and photochemical oxidation, while the least is ozone layer depletion, which can be negligible. For each category, the normalized impact scores associated with the manufacture and assembly of the GFRP composite panels are illustrated in Figure G-9b-f. All the results are normalized based on result of GFRPs using all fossil fuel–based polymers without RPP substitution, with life span (EY = 60 in Table G-1). The characterized impact scores of the reference case for all considered impact categories are shown in Figure G-9a. When analyzing the environmental effects arising from the replacement of virgin polymers by RPPs in the production of GFRPs, Figure G-9b-f shows that the expected life span remains at 60 years, and all scores are TABLE G-1 Maintenance and Replacement Schedule in 100 Years EY (year) YIC (year) Nrepair Nreplace20 40 60 80 100 40 repair replace repair replace repair 3 2 60 repair repair replace repair repair 4 1 80 repair repair repair replace repair 4 1 NOTES: EY is expected life span in years. YIC means year after initial construction. Nrepair is the total number of repair activities in 100 years. Nreplace is the total number of rehabilitation activities in 100 years.

302 FI G U R E G -8 N or m al iz ed e nv ir on m en ta l i m pa ct s co re s as so ci at ed w it h th e us e of r ec yc le d pl as ti c pe lle ts ( R PP s) in t he G FR P pa ne ls fo r va ri ou s co nt en ts a nd v ar io us e xp ec te d lif e sp an s.

APPENDIX G 303 FIGURE G-9 Environmental impact scores associated with the use of recycled plas- tic pellets (RPPs) in the GFRP composite panels at various contents (25%, 50%, and 75% of polymer matrix) and for various expected life spans (40, 60, and 80 years). NOTES: (a) Environmental impact scores associated with reference case in Figure G-18: one composite panel uses 100 percent fossil fuel–based polymer with no recycled plastics. These results are reference values to obtain the normalized results in (b)-(f): (b) climate change, (c) acidification, (d) eutrophication, (e) ozone layer depletion, and (f) photochemical oxidation.

304 RECYCLED PLASTICS IN INFRASTRUCTURE less than one, which means this decision is environmentally preferable. For all categories, the case that uses the highest amount of RPP has the lowest impact (lowest score) when its durability is the same. In addition, impact scores for a 60-year life span and an 80-year life span are identical. As indicated in Table G-1, the reason is that the total numbers of repairs and replacements within 100 years are equal when EY = 60 years and EY = 80 years. This will change if the entire LCA time span is elongated to 120 years or more. Finally, it is worth mentioning that reducing the durability of GFRP will cancel the saving of climate change scores achieved by substituting polymers with RPPs. If looking at the GHG score in Figure G-10, the dashed red line represents the normalized score of the reference case. The dashed yellow line represents the projection between a 40-year life span and a 60-year life span when substituting 75 wt.% virgin polymers with RPPs. By finding their intersection point, the tolerance of durability reduction when using RPP 75 wt.% compared to the reference case is 13 years. FIGURE G-10 Finding durability reduction tolerance of using 75 percent RPP in polymer matrix by projection, comparison to reference case (no RPP used and no life-span increment case).

APPENDIX G 305 Recycling Waste Plastics in Asphalt Pavement Goal and Scope Definition This case study conducts an environmental perspective analysis to examine the long-term durability and the life cycle of converting waste plastics into recycled plastic pellets to be used as an additive (wet method). As described earlier, since the dry method does not affect durability, as the wet method does, this paper focuses on the wet method in the case study section. Data from recycling facilities (Santos et al. 2021) are used as the basis for a comparative LCA study. In the wet method of this study, two types of HMA are used. Specifi- cally, the top surface HMA (HMA PG-70-22) contains 6 percent asphalt binder and 94 percent coarse and fine aggregate crushed stone, while the sublayer HMA (HMA PG-64-22) is a mixture of 5.85 percent asphalt binder and 94.02 percent coarse and fine aggregate crushed stone. The amounts of RPPs used in the parametric study are selected in commonly suggested dosages, which range from 2 to 8 percent (defined in Table G-2) by weight of the asphalt binder of HMA PG-70-22 and HMA PG-64-22. For each RPP dosage, an LCA using the identical dosage of virgin LDPE as the additive is conducted for comparison. The time span of the LCA is 50 years. The road pavement durability of the parametric study ranges from −4 to +4 years at 2-year intervals. Data Collection, Materials, and Method This LCA study was conducted using the Athena Pavement LCA tool (Ahammed et al. 2016). The Athena Pavement LCA tool reports footprint data for the following environmental impact measures consistent with the U.S. Environmental Protection Agency (USEPA) Tool for Reduction and Assessment of Chemicals and other Environmental Impacts (TRACI) meth- odology: global warming potential, acidification potential, human health respiratory effects potential, ozone depletion potential, smog potential, and eutrophication potential. The Athena LCA database is comprised of ISO 14040/14044–compliant unit process LCA data (e.g., concrete manu- facturing LCA results per m3 concrete) related to basic materials, building products and components, fuel use, and transportation (Athena Sustain- able Materials Institute 2018). The road design of this case study comes from Concrete Sustainability Hub-MIT Supplementary Information for Comparative Pavement Life Cycle Assessment and Life Cycle Cost Analysis Section 18 (Arizona DOT) (Swei et al. 2014). The roadway cross-section design is given in Figure G-11.

306 RECYCLED PLASTICS IN INFRASTRUCTURE TABLE G-2 Characteristics of the Road Pavement Section “California-Dry No Freeze Urban Interstate-HMA-8,000 AADTT-Mr 9,500psi-LDPE0” in Which the Asphalt Surface Layer Is Made Using Asphalt Binder Produced with Different Additive Contents (i.e., 0%, 2%, 4%, 6%, and 8%) Roadway Information Project Type Roadway Pavement Types Flexible Pavement Project Life Span 50 years Project Location California Lane Length 1.609347 km Average Distance Plant to Site 31 km Average Distance Site to Stockpile 31 km Average Distance Equipment Depot to Site 31 km Number of Lanes in Both Directions 3 Number of Pavement Lifts 3 Number of Granular Layers 1 Material of Lift 1 (top) HMA PG-70-22-LDPE# or HMA PG-70-22-RPP# Material of Lift 2 or 3 HMA PG-64-22-LDPE# or HMA PG-64-22-RPP# Material of Granular Layer 1 Granular A Width of Granular Layer 1 10.9728 m Thickness of Granular Layer 1 304.8 mm Width of Lift 3.6576 m Thickness of Lift 1 (top) 63.5 mm Thickness of Lift 2 or 3 139.7 mm HMA PG-70-22-LDPE# or HMA PG-70-22-RPP# #% = 0%, 2%, 4%, 6%, 8% Asphalt Binder No Additives (1-#%) × 6% by weight Additives (LDPE or RPP) #% × 6% by weight Coarse Aggregate Crushed Stone 60.28% by weight Fine Aggregate Crushed Stone 33.72% by weight HMA Plant Process 0.0010 m3 HMA PG-64-22-LDPE# or HMA PG-64-22-RPP# #% = 0%, 2%, 4%, 6%, 8% Asphalt Binder No Additives (1-#%) × 5.85% by weight Additives (LDPE or RPP) #% × 5.85% by weight Coarse Aggregate Crushed Stone 50.54% by weight Fine Aggregate Crushed Stone 43.61% by weight HMA Plant Process 0.0010 m3 Granular A Coarse Aggregate Natural Fine Aggregate Natural Mineral Filler Natural 43.11% by weight 56.84% by weight 0.05% by weight

APPENDIX G 307 The functional unit of the LCA study is 1 mile of roadway in use for 50 years. The road has three lanes. Each lane has three lifts on top of the granular layer. The top lift is made of HMA PG-70-22, while sublayers (Lift 2 and Lift 3) are made of HMA PG-64-22. The processes involved in the production of the road pavement with different kinds and amounts of asphalt binder additives are depicted in Figure G-12. They include (1) the production of the raw materials required to produce the binder, additives, and granular and emulsified asphalt coat; (2) transportation through heavy vehicles; (3) the production of the asphalt mixes; and (4) construction of the roadway. Design parameters and formulations of the HMAs and granular FIGURE G-11 Roadway cross-section design. FIGURE G-12 System boundaries considered for modeling the roadway pavement.

308 RECYCLED PLASTICS IN INFRASTRUCTURE layer can be found in Table G-2. Since this case study focuses on the amount of RPPs used and the uncertainty of durability, preconstruction site prepa- ration, road operating energy consumption in use phase, and excess fuel consumption due to pavement vehicle interaction (PVI) (Louhghalam et al. 2013) in the use phase are excluded from this study. To ensure the LCA study of pavement studies the effect of durability at a reasonable assumed life-span increment, the authors interviewed engi- neers at Caltrans who worked on the Butte 162 Pilot Project and learned from them about the current viability and performance of recycling plastics in asphalt pavement. According to public information, this project uses a new technology developed by TechniSoil Industrial of Redding, California. Using this technology, a recycling train of equipment grinds up the top 3 inches of pavement and then mixes the grindings with a liquid plastic poly- mer binder, which comes from many recycled, single-use bottles (Caltrans 2022a, 2022b). However, field application (for the Butte 162 Pilot Project, in California during summer) indicates that the asphalt mixture cools and desiccates too fast, such that the mixture hardens before it can be spread evenly on the surface of the road. When this happens, the surface has to be removed and repaved again. This unexpected replacement, which has not been mentioned in laboratory study test reports (Hajj and Piratheepan 2016; Saadeh and Katawal 2022) before, increases the uncertainty when evaluating the project’s efficiency, economic benefits, and sustainability. Moreover, there is concern about the higher stiffness of the asphalt mixture compared to conventional materials. Higher stiffness means that micro- cracks are more likely to nucleate in the pavement during the use phase. And the microcracks may propagate and coalesce into wide and deep cracks that reduce the durability of the asphalt mixture using recycled plastic. Yao et al. (2022) estimated the service lives of the PET-modified asphalt mixtures based on the change of their fatigue factor values derived from the dynamic shear rheometer (DSR) test, as shown in Table G-3. The estima- tion also shows that every additional 2 percent recycled plastic will affect the service life between −3 and 1 year. Considering all the information the authors have learned about the Butte 162 Pilot Project, the interval of the parametric study with respect to durability is determined to be 2 years. Table G-4 shows the specific year and amount each maintains when the first active year and expected life span is changed [−4, −2, 0, +2, +4] years. The product information for no asphalt binder additive, HMA PG-70- 22, HMA PG-64-22, and additive LDPE is built into the LCA tool. LDPE- modified product information can be obtained by editing and combining existing pavement and LDPE material and manufacturing data. Data on manufacturing and applying RPPs are not available in the LCA database. Santos et al. (2021) collected primary LCA data of manufacturing RPPs per

APPENDIX G 309 tonne and gave LCA results for applying RPPs per tonne (in different cases such as RPP as 0, 2, 4, 6, and 8 percent of asphalt binder by weight). For Santos et al.’s study (2021), the main recycling processes and subprocesses considered in the system boundaries and associated inputs and outputs are shown in Figure G-13. The main recycling processes include sorting, shredding, and pelletization of waste plastic. These data were transferred into the results from the Athena Pavement LCA Tool to obtain results for asphalt binder with RPPs. TABLE G-3 Binder Fatigue Performance and Estimated Service Lives of Different Mixtures Binder Type G*sinδ (kPa) Percentage Change Relative to 4% SBS (%) Estimated Service Life (years) 4% SBS 2391a 0 12.00 2% PET 2130b 10.92 13.31 15% RAP, 2% PET 2457b 2.76 11.67 25% RAP, 2% PET 2522b 5.48 11.34 40% RAP, 2% PET 2848b 19.11 9.71 a Data source is Padhan et al. 2020a. b Data source is Leng et al. 2018. NOTE: RAP = reclaimed asphalt pavement; SBS = styrene butadiene styrene. SOURCE: Yao et al. 2022. TABLE G-4 Rehabilitation Schedule in 50 Years Incl –4 –2 0 +2 +4 YIC EY YIC EY YIC EY YIC EY YIC EY 11 9 13 11 15 13 17 15 19 17 20 9 24 11 28 13 32 15 36 17 29 9 35 11 41 13 47 15 — — 39 9 46 11 — — — — — — 47 9 — — — — — — — — Nre 5 4 3 3 2 NOTES: EY is expected life span in years. Incl is increment of expected life span in years. YIC means year after initial construction. Nre is the total number of rehabilitation activities in 50 years. Each rehabilitation activity includes an asphalt full-depth reclamation and an asphalt partial-depth reclamation. For the last rehabilitation activities in 50 years, asphalt full-depth reclamation is assumed to be asphalt patching for 2 percent of surface area; otherwise asphalt patching is assumed to be 1 percent of surface area. Asphalt partial-depth reclamation means partial-depth reclamation for 100 percent surface area.

310 RECYCLED PLASTICS IN INFRASTRUCTURE Results and Discussion The normalized impact scores associated with the construction of the sur- face layer of a road pavement with the characteristics presented in Table G-2 are illustrated in Figure G-15b-f per impact category. All the results are normalized based on the result of road pavement using asphalt binder without additive and with no increment of the expected life span (Incl = 0 in Table G-4). Product usage for the reference case (no additive case, no life-span increment) for 1 functional unit over 50 years is shown in Figure G-14. The characterized impact scores of the reference case for all consid- ered impact categories are shown in Figure G-15a. When analyzing the environmental effects arising from the replacement of virgin polymer additives by the same weight as RPPs in the production of asphalt binder, Figure G-15b-f shows that as long as the life-span increment remains the same, this decision is proportionally environmentally prefer- able. If the life-span increment is unchanged (equal to zero), the lowest saving compared to the reference case in the environmental impact scores is observed for the impact category photochemical oxidation (from 1.0039 FIGURE G-13 System boundaries considered for modeling the mechanical plastic recycling system. NOTES: In the base scenario, it is assumed that the complete recycling process takes place inside the same facility. Therefore, the transportation process depicted in the shredding phase with the dashed line does not occur. SOURCE: Santos et al. 2021.

APPENDIX G 311 FIGURE G-14 Products usage for referenced case: 1 mile of road using no asphalt binder additives in 50 years. NOTE: First rehabilitation occurs 15 years after initial construction; expected life span of each rehabilitation is 13 years. for 2 percent RPPs to 0.9938 for 8 percent RPPs). This is closely followed by ozone layer depletion (from 0.9929 for 2 percent RPPs to 0.9955 for 8 percent RPPs) and eutrophication (from 0.9978 for 2 percent RPPs to 0.9863 for 8 percent RPPs). The most considerable change is acidification (from 1.0658 for 2 percent RPPs to 1.2564 for 8 percent RPPs), followed by climate change or GHGs (from 0.9894 for 2 percent RPPs to 0.9632 for 8 percent RPPs). However, the amplitudes in Figure G-15a show that the climate change score yields a higher order of magnitude than other scores. Thus, the most expressive reduction in emission is GHGs. Finally, it is worth mentioning that reducing durability will quickly cancel the saving of all environmental impact scores by substituting LDPE with RPPs. Among all categories, the acidification score is the least sensi- tive type to change in durability. When looking at the GHG score in Figure G-16a, the dashed red line represents the normalized score of the reference case. The dashed blue line represents the projection between zero life-span reduction and life-span reduction of 2 years when using 8 percent RPPs as an asphalt binder additive. By finding their intersection point, the toler- ance for durability reduction when using 8 percent RPPs compared to the reference case is around 1 year. In general, the use of LDPE is always more environmentally burdensome than the asphalt binder with no additive due to the consumption of at least one more material. If the standard of tolerance is broader, say, the score of using LDPE 8 percent instead of the reference case, the tolerance of durability reduction when using 8 percent RPPs compared to using 8 percent LDPE is around one and half years. This number is obtained by finding the interaction point of the dashed purple line and the dashed blue line in Figure G-16b.

312 RECYCLED PLASTICS IN INFRASTRUCTURE FIGURE G-15 Environmental impact scores associated with the use of recycled plastic pellets (RPPs) and low-density polyethylene (LDPE) in the production of asphalt pavement according to various contents (2%, 4%, 6%, and 8%) of asphalt binder and various expected life spans. NOTES: The construction characteristics of all comparison cases per functional unit are presented in Table G-2a. Environmental impact scores associated with reference case in Figure 14: 1 mile of pavement using asphalt binder with no additives. These results are reference values to obtain the normalized results in (b)-(f): (b) climate change, (c) acidi- fication, (d) eutrophication, (e) ozone layer depletion, and (f) photochemical oxidation.

APPENDIX G 313 Additional Environmental Costs Resulting from Changes in Durability In general, a reduction in performance and durability may lead to ad- ditional costs such as longer construction time, unexpected material and time waste (e.g., Butte 162 Pilot Project case), higher inspection and repair frequency, and a shorter life span. All the above time, material, and energy costs are associated with higher economic costs. For example, temporary infrastructure/road closures due to construction and repair will cause a financial loss to the community. Comparison between tolerance of durabil- ity reduction for architectural composite panels (see Figure G-10) and road pavement (see Figure G-16) shows a very representative comparison case between upcycling and downcycling. The case study on adapting RPPs in the SFMOMA facade is an example of upcycling compared to the case study of using RPPs in asphalt pave- ment. The primary reason is its higher tolerance of durability reduction (13 years compared to 1.45 years). Higher durability reduction relates to its low mechanical load, low fatigue, and less corrosive working environ- ment. Fiber-reinforced polymeric composites in this working environment can have long life spans. Another considerable advantage is the higher RPP consumption capacity in GFRP. Polymers, as the matrix of GFRP, are typically between 40 and 60 wt.%. This is also the ideal upper limit of RPP dosage in GFRPs. It is higher than the recommended RPP dosage in asphalt pavement, whether by wet or dry methods. In addition, using RPP in GFRP architectural panels rarely causes the problem of microplastic pol- lution and accumulation in the soil associated with using RPPs in asphalt pavement. Nevertheless, fossil fuel polymer-based GFRP in buildings is a relatively new and emerging application. Few experiments and research FIGURE G-16 Finding durability reduction tolerance of using 8 percent RPPs in asphalt binder by projection, compared to (a) reference case (no additive and no life-span increment) and (b) using 8 percent LDPE in asphalt binder and no life- span increment.

314 RECYCLED PLASTICS IN INFRASTRUCTURE have investigated the performance of blending RPPs in architectural GFRP panels. In the future, sufficient experiments and modeling studies must be conducted to provide adequate data to support the feasibility of using RPP- blended or RPP-based FRP composites in buildings. The case study of adapting RPPs in asphalt pavement is an example of relative downcycling compared to building materials. It does not conflict that adapting RPPs in asphalt pavement may be a relative upcycling com- pared to recycling RPP to packaging or converting RPPs to fuel. Working in a heavy-load, high-cyclic (especially highway), and corrosive environment, the life-cycle impact of asphalt pavement is highly sensitive to mechanical durability load and environmental aging. Thus, the tolerance for durability reduction is low. The durability reduction of the dry method is generally higher than the wet method. The amount of polymer usage in the wet method that theoretically can improve performance is very limited. Thus, there is a countereffect between allowable dosages, and performance degra- dation limits the RPP consumption in both wet and dry methods. However, given a significant and increasing need in the pavement sector and many types of research that focus on using RPPs in pavement, a considerable amount of RPPs can be consumed in the pavement, which can relieve land- fill pressure. It is worth mentioning that different binders, e.g., binders in porous pavement applications, may exhibit different suitability to recycled plastics than conventional asphalt. Just because tests are not favorable with one kind of pavement, that does not mean that recycled plastics are unsuit- able for all asphalts. Further studies on improving RPP-supplemented road pavement performance and durability are necessary in the future. CONCLUSIONS This paper identifies opportunities and examines life-cycle consideration of repurposing plastics waste in infrastructure. This study first identifies major opportunities, challenges, and the potential scalability of emerg- ing solutions through literature studies and a series of interviews among manufacturers and end users in polymer recycling economies. Based on the feedback from interviews, current challenges of repurposing plastic in infrastructures include the following: (1) there is tremendous difficulty and insufficient effort of sorting reclaimed plastics waste; (2) the recycled material-based infrastructure product requires support and effort to add to the long-term established supply chain that has been dominated by conventional construction materials; (3) insufficient experimental, field, and modeling data are available for decision makers who are responsible for building environmental impacts, health, and safety; and (4) there is a lack of feasibility and scalable technique of controlled depolymerization to transition downcycling and recycling polymers to upcycling polymers.

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318 RECYCLED PLASTICS IN INFRASTRUCTURE Li, Z., Bosse, A. W., and Lepech, M. D. 2022. Net irreversible synergistic effects of environ- mental deterioration on fatigue and flexure properties of fiber reinforcement composite: A homogenization based model. Composites Part B: Engineering 246:110234. Lindberg, H. K., Väänänen, V., Järventaus, H., Suhonen, S., Nygren, J., Hämeilä, M., Val- tonen, J., Heikkilä, P., and Norppa, H. 2008. Genotoxic effects of fumes from asphalt modified with waste plastic and tall oil pitch. Mutation Research/Genetic Toxicology and Environmental Mutagenesis 653(1-2):82-90. Liu, P., Meng, F., and Barlow, C. Y. 2019. Wind turbine blade end-of-life options: An eco-audit comparison. Journal of Cleaner Production 212:1268-1281. Locock, K. E., Deane, J., Kosior, E., Prabaharan, H., Skidmore, M., and Hutt, O. E. 2017. The Recycled Plastics Market: Global Analysis and Trends. Australia: CSIRO. https://www. csiro.au/en/research/environmental-impacts/recycling/plastic-recycling-analysis López, F., Martín, M., Alguacil, F., Rincón, J. M., Centeno, T., and Romero, M. 2017. Ther- molysis of fibreglass polyester composite and reutilisation of the glass fibre residue to obtain a glass–ceramic material. Journal of Analytical and Applied Pyrolysis 93:104-112. Louhghalam, A., Akbarian, M., and Ulm, F. J. 2013. PVI Mechanistic Model Gen II. https:// cshub.mit.edu/sites/default/files/documents/CSHub%20Research%20Brief-12-2013- edit2.pdf Mahanta, D., Dayanidhi, S. A., Mohanty, S., and Nayak, S. K. 2012. Mechanical, thermal, and morphological properties of recycled polycarbonate/recycled poly (acrylonitrile- butadiene-styrene) blend nanocomposites. Polymer Composites 33(12):2114-2124. Mohajerani, A., Vajna, J., Cheung, T. H. H., Kurmus, H., Arulrajah, A., and Horpibulsuk, S. 2017. Practical recycling applications of crushed waste glass in construction materials: A review. Construction and Building Materials 156:443-467. https://doi.org/10.1002/ pc.22342 Moskaleva, A., Safonov, A., and Hernández-Montes, E. 2021. Fiber-reinforced polymers in freeform structures: A review. Buildings 11(10):481. https://doi.org/10.3390/buildings 11100481 Muniandy, R., Ismail, D. H., and Hassim, S. 2018. Performance of recycled ceramic waste as aggregates in hot mix asphalt (HMA). Journal of Material Cycles and Waste Management 20(2):844-849. https://doi.org/10.1007/s10163-017-0645-x National Asphalt Pavement Association (NAPA). 2022. The Asphalt Pavement Industry Fast Facts. https://www.asphaltpavement.org/uploads/documents/NAPAFastFactsNovember- 2020FINAL.pdf National Association for PET Container Resources (NAPCOR). 2019. Postconsumer PET Recycling Activity in 2018. https://napcor.com/reports-resources National Center for Asphalt Technology (NCAT), Western Research Institute (WRI), GHK, and Dow. 2021. Performance Properties of Laboratory Produced Recycled Plastic Modi- fied (RPM) Asphalt Binders and Mixtures. https://onlinepubs.trb.org/Onlinepubs/nchrp/ docs/NCHRP9-66InterimReportwithAppendixFINAL.pdf Nizamuddin, S., Jamal, M., Gravina, R., and F. Giustozzi, F. 2020. Recycled plastic as bitu- men modifier: The role of recycled linear low-density polyethylene in the modification of physical, chemical and rheological properties of bitumen. Journal of Cleaner Production 266:121988. https://doi.org/10.1016/j.jclepro.2020.121988 Padhan, R. K., Leng, Z., Sreeram, A., and Xu, X. 2020a. Compound modification of asphalt with styrene-butadiene-styrene and waste polyethylene terephthalate functionalized ad- ditives. Journal of Cleaner Production 277:124286. Padhan, R. K., Sreeram, A., and Gupta, A. 2020b. Evaluation of trans-polyoctenamer and cross-linking agents on the performance of waste polystyrene modified asphalt. Road Materials and Pavement Design 21(4):1170-1182.

APPENDIX G 319 Praticò, F. G., Giunta, M., Mistretta, M., and Gulotta, T. M. 2020. Energy and environmental life cycle assessment of sustainable pavement materials and technologies for urban roads. Sustainability 12(2):704. Rahman, M. T., and Mohajerani, A. 2021. Thermal conductivity and environmental aspects of cigarette butt modified asphalt. Case Studies in Construction Materials 15:e00569. Rahman, M. T., Hainin, M. R., and Bakar, W. A. W. A. 2017. Use of waste cooking oil, tire rubber powder and palm oil fuel ash in partial replacement of bitumen. Construction and Building Materials 150:95-104. Rahman, M. T., Mohajerani, A., and Giustozzi, F. 2020. Recycling of waste materials for asphalt concrete and bitumen: A review. Materials 13(7):1495. Rangelov, M., Dylla, H., and Sivaneswaran, N. 2021. Life-cycle assessment of asphalt pavements with recycled post-consumer polyethylene. Transportation Research Record 2675(12): 1393-1407. Rani, M., Choudhary, P., Krishnan, V., and Zafar, S. 2021. A review on recycling and reuse methods for carbon fiber/glass fiber composites waste from wind turbine blades. Com- posites Part B: Engineering 215:108768. Ribeiro, M., Meira-Castro, A. C., Silva, F., Santos, J., Meixedo, J. P., Fiúza, A., Dinis, M., and Alvim, M. R. 2015. Re-use assessment of thermoset composite wastes as aggregate and filler replacement for concrete-polymer composite materials: A case study regarding GFRP pultrusion wastes. Resources, Conservation and Recycling 104:417-426. Rodríguez-Fernández, I., Cavalli, M. C., Poulikakos, L., and Bueno, M. 2020. Recyclability of asphalt mixtures with crumb rubber incorporated by dry process: A laboratory investiga- tion. Materials 13(12):2870. Saadeh, S., Katawal, P. 2022. Evaluation of Polymer Binder Technisoil G5® in Con- crete Mixture. Technical report, San Jose State University. https://transweb.sjsu.edu/ research/2139-Polymer-Concrete-Mixture Santos, J., Pham, A., Stasinopoulos, P., and Giustozzi, F. 2021. Recycling waste plastics in roads: A life-cycle assessment study using primary data. Science of the Total Environment 751:141842. https://doi.org/10.1016/j.scitotenv.2020.141842 Santos, J., Pizzol, M., and Azarijafari, H. 2022. Life cycle assessment (LCA) of using recycled plastic waste in road pavements: Theoretical modeling. In Plastic Waste for Sustainable Asphalt Roads (pp. 273-302). Elsevier. Shamsaei, M., Khafajeh, R., Ghasemzadeh Tehrani, H., and Aghayan, I. 2020. Experimental evaluation of ceramic waste as filler in hot mix asphalt. Clean Technologies and Envi- ronmental Policy 22(2):535-543. Smith, R. L., Takkellapati, S., and Riegerix, R. C. 2022. Recycling of plastics in the United States: Plastic material flows and polyethylene terephthalate (PET) recycling processes. ACS Sustainable Chemistry & Engineering 10(6):2084-2096. Swei, O., Xu, X., Noshadravan, A., Wildnauer, M., Gregory, J., and R. Kirchain, R. 2014. Sup- plementary Information for Comparative Pavement Life Cycle Assessment and Life Cycle Cost Analysis. http://dspace.mit.edu/bitstream/handle/1721.1/105110/Supplementary %20Information%20V2.pdf?sequence=1&isAllowed=y Tavira, J., Jiménez, J. R., Ayuso, J., Sierra, M. J., and Ledesma, E. F. 2018. Functional and structural parameters of a paved road section constructed with mixed recycled aggregates from non-selected construction and demolition waste with excavation soil. Construction and Building Materials 164:57-69. Technavio. 2018. Global Recycled Plastics Market 2018-2022. https://www.technavio.com/ report/recycled-plastics-market-size-industry-analysis Torres, A., De Marco, I., Caballero, B., Laresgoiti, M., Legarreta, J., Cabrero, M., González, A., Chomon, M., and Gondra, K. 2000. Recycling by pyrolysis of thermoset composites: Characteristics of the liquid and gaseous fuels obtained. Fuel 79(8):897-902.

320 RECYCLED PLASTICS IN INFRASTRUCTURE U.S. Environmental Protection Agency (USEPA). 2022. National Overview: Facts and Figures on Materials, Wastes and Recycling. https://www.epa.gov/facts-and- figures-about-materials-waste-and-recycling/national-overview-facts-and-figures-materials Vila-Cortavitarte, M., Lastra-González, P., Calzada-Pérez, M. A., and Indacoechea-Vega, I. 2018. Analysis of the influence of using recycled polystyrene as a substitute for bitu- men in the behaviour of asphalt concrete mixtures. Journal of Cleaner Production 170:1279-1287. Wilhelm, R. 2016. Resin identification codes—new ASTM standard based on Society of the Plastics Industry code will facilitate recycling. Standardization News (September/October 2008), ASTM International. Wu, S., and Montalvo, L. 2021. Repurposing waste plastics into cleaner asphalt pavement materials: A critical literature review. Journal of Cleaner Production 280:124355. Xuan Lu, D., and Giustozzi, F. 2022. Recycled plastics as synthetic coarse and fine asphalt aggregate. International Journal of Pavement Engineering 1-16. https://doi.org/10.1080/ 10298436.2022.2068550 Yao, L., Leng, Z., Lan, J., Chen, R., and Jiang, J. 2022. Environmental and economic assess- ment of collective recycling waste plastic and reclaimed asphalt pavement into pavement construction: A case study in Hong Kong. Journal of Cleaner Production 336:130405. Yin, F., Moraes, R., Fortunatus, M., Tran, N., Elwardany, M. D., and Planche, J. P. 2020. Performance Evaluation and Chemical Characterization of Asphalt Binder and Mixtures Containing Recycled Polyethylene. Washington, DC: Plastic Industry Association. Zabihi, O., Ahmadi, M., Liu, C., Mahmoodi, R., Li, Q., Ghandehari Ferdowsi, M. R., and Naebe, N. 2020. A sustainable approach to the low-cost recycling of waste glass fibres composites towards circular economy. Sustainability 12(2):641. Zakaria, N. M., Hassan, M. K., Ibrahim, A. N. H., Rosyidi, S. A. P., Yusoff, N. I. M, Mo- hamed, A. A., and Hassan, N. 2018. The use of mixed waste recycled plastic and glass as an aggregate replacement in asphalt mixtures. Jurnal Teknologi 80(1). Zhu, J., Birgisson, B., and Kringos, N. 2014. Polymer modification of bitumen: Advances and challenges. European Polymer Journal 54:18-38. Zhu, P., Liu, X., Wang, Y., Guan, C., Yang, Y., Zhu, J., Li, X., Qian, G., and Frost, R. L. 2017. Production and characterization of recycled polycarbonate based composite ma- terial containing recycled glass fibers. Journal of Environmental Chemical Engineering 5(4):3439-3446.

APPENDIX G 321 ANNEX G-1 Case Study: SFMOMA GFRP Facade Panel Comparison between “polyester resin, unsaturated RER market for polyes- ter resin, unsaturated, APSO, U” and “recycled post-consumer PET pellet/ RNA” in SimaPro database. FIGURE G-17 Comparison of normalized environmental impact scores between 1 tonne unsaturated polyester and 1 recycled post-consumer PET pellet. TABLE G-5 Comparison of Potential Environmental Impact Scores Between 1 Tonne Unsaturated Polyester (P) and 1 Recycled Post- Consumer PET Pellet Impact Category Unsaturated Polyester Recycled Plastics Unit Climate change 5.21E+3 1.12E+3 kg CO2-eq Acidification 1.92E+1 9.45E+0 kg SO2-eq Eutrophication 6.22E+0 8.99E-1 kg PO4-eq Ozone layer depletion 8.22E-4 4.95E-6 kg CFC11-eq Photochemical oxidation 3.25E+0 1.74E-1 kg C2H4-eq SOURCE: SimaPro database.

322 RECYCLED PLASTICS IN INFRASTRUCTURE FIGURE G-18 SimaPro network model of GFRP panel using fossil fuel–based poly- mer in 100 years with expected life span of 60 years.

APPENDIX G 323 ANNEX G-2 Case Study: Asphalt Pavement TABLE G-6 Potential Environmental Impact Scores for Producing 1 Tonne of Recycled Plastic Pellets in Victoria, Australia Impact Category Value Unit Climate change 4.28E+02 kg CO2-eq Acidification 3.47E-02 kg SO2-eq Eutrophication 4.50E-02 kg N-eq Ozone layer depletion 1.59E-07 kg CFC11-eq Photochemical oxidation 1.92E-03 kg O3-eq NOTE: Data from recycling facilities in Victoria, Australia, were collected and used as the basis for a comparative life-cycle assessment study. SOURCE: Santos et al. 2021.

Next: Appendix H: The Life-Cycle Environmental Benefits and Trade-Offs of Plastics Waste Recycling and Reuse in Infrastructure »
Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities Get This Book
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In the U.S., most plastics waste is disposed in landfills, but a significant amount also ends up as litter on land, rivers, and oceans. Today, less than 10 percent of plastics waste is recycled in the U.S. annually. The use of recycled plastics in infrastructure applications has potential to help expand the market and demand for plastics recycling.

These are among the findings in TRB Special Report 347: Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities from the Transportation Research Board of the National Academy of Sciences, Engineering, and Medicine.

The report emphasizes that pursuing the recycling of plastics in infrastructure depends on goals, policy, and economics. To that end, life cycle economic and environmental assessments should be conducted to inform policies on plastics waste reuse.

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