Assessing the Life Cycle Benefits of Recycled Material in Road Construction

Abstract

Executive SummaryThere is interest in determining and validating the environmental and economic benefits of incorporating recycled materials into road construction using life cycle assessments (LCA) and life cycle cost analysis (LCCA) tools. However, the process of collecting the necessary data for LCAs and LCCAs from departments of transportations (DOTs) and road construction contractors is not well defined. This thesis provides a study of real-time data collection to compare with the results of pre-construction estimated LCA data. The goal of this comparison is to determine a data collection precedent for environmental analyses of future transportation projects. Additionally, two prominent LCA tools were used in conducting the assessment and the results were compared to validate the predicted impacts.The primary body of this thesis focuses on a specific, project-based LCA and LCCA of the reconstruction and expansion of a 2.4-km (1.5-mi) stretch of the eastbound Beltline Highway in Madison, Wisconsin. Recycled materials used in this reconstruction include: fly ash, slag, recycled asphalt shingles (RAS), recycled asphalt pavement (RAP), and recycled concrete aggregate (RCA). Fly ash and slag were used as a partial replacement of cement in the ready-mix concrete.RAP was used in both hot mix asphalt (HMA) pavement as well as a base course material. RAS was substituted for binder and aggregate material in some HMA mix designs. RCA, both recycled onsite and imported, was substituted for base and subbase material.Two data collection methodologies were employed to gather the necessary inputs for the LCA of the reconstruction: 1) material quantities estimated from designs and specifications as planned prior to construction (referred as Planned), and 2) material quantities explicitly tracked and collected while construction was on-going (referred as Constructed). In the Planned data collection methodology, quantities were calculated using plan drawings and average mix designs.In the Constructed data collection methodology, key site-specific Wisconsin DOT (WisDOT) and contractor files were accessed for material quantity information. When comparing the LCAs of two or more products, a relative ranking of alternatives can be analyzed as well as the absolute impacts. For this study, the design of the actual roadway that incorporated recycled material (referred to as Recycled) was compared to a hypothetical design comprised of no recycled material (referred to as Virgin). In the Virgin design, recycled material quantities were replaced with equivalent virgin materials. This method demonstrates the impact reductions from the use of recycled material. To validate the LCA results, impacts predicted by PaLATE versus SimaPro were compared, with the primary focus on the common impact categories of energy and CO2 emissions.Results show that the material quantities obtained from the two data collection methods are within one order of magnitude for all categories, demonstrating general agreement regardless of Constructed or Planned da...

Evaluation of the Incorporation of Tire-Derived Aggregates (TDA) in Rigid Pavement Mix Designs

“…Advantages of using PaLATE 2.0 include its ease of access and the possibility of modifying its materials and process databases, which take local conditions into account. Further details concerning PaLATE 2.0 can be found in Horvath [34] and Bloom [35]. PaLATE 2.0 evaluates the following environmental impacts: Human toxicity potential (noncancer), accounting for adverse health effects on human beings caused by the intake of toxic substances.…”

Recycled Material Web Map: Connecting Consumers and Producers

“…RAP, RCA, and fly ash were used most extensively across the states, while Illinois also tracked steel slag, by-product lime, glass beads, microsilica, dowel bars, rebar, and welded wire reinforcement. The study found the average environmental impacts savings of using recycled material in highway construction instead of virgin resources to be between 80-97% (Bloom et al, 2016). As DOTs continue to increase the use of recycled material for construction projects, a tool to track source material and quantities for each project would be beneficial and useful for many applications such as life cycle assessment.…”

“…Application for the reuse of the byproducts include aggregate in pavement, structural fill, road embankments, and manufactured consumer products. Examples of some of the most commonly used nonhazardous industrial byproducts in construction applications include recycled concrete aggregate (RCA), recycled asphalt pavement (RAP), recycled asphalt shingles (RAS), coal fly ash, blast furnace slag, and rubber (Bloom et al, 2016). There have been many efforts to characterize the engineering properties of these materials, test the materials in varied applications, raise awareness about the potential usefulness of these materials, and market the byproducts as commodities.…”

Environmental Performance of Road Asphalts Modified with End-of-Life Hard Plastics and Graphene: Strategies for Improving Sustainability

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