Date of Award

Summer 8-15-2025

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Civil Engineering (MCE)

Department

Civil Engineering

First Committee Advisor

T. Reed Miller

Second Committee Member

William G. Davids

Third Committee Member

Roberto Lopez-Anido

Abstract

In response to the growing emphasis on sustainability in civil infrastructure, this thesis presents a comprehensive three-phase study evaluating the environmental performance and material efficiency of thermoplastic (TP) rebars compared to conventional reinforcement materials namely stainless steel (SS), chromium steel (ChromX), and thermoset (TS) rebars in reinforced concrete bridge decks.

Phase 1 conducts a cradle-to-gate Life Cycle Assessment (LCA) of unidirectional (UD) fiber-reinforced thermoplastic tapes that serve as feedstock for TP rebars. Using primary manufacturing data and established LCA databases, the environmental impacts of four composite tape variants: GF-PP, GF-PA12, GF-PBT, and BF-PP are quantified across 16 categories, with particular focus on global warming potential (GWP), ozone depletion potential (ODP), and eutrophication potential (EP).

Phase 2 evaluates the environmental impacts of producing TP rebars from these UD tapes using a continuous forming process developed at the University of Maine. The analysis revealed that air freight transport was the dominant contributor to environmental impacts, often surpassing emissions from both tape production and rebar forming processes.

Phase 3 quantifies the material efficiency of various rebar types by analyzing real-world bridge plans provided by the Maine Department of Transportation. Bridges with consistent structural configurations, grouped by girder spacings of 7 ft, 8 ft, and 9 ft, were evaluated to determine the volume and mass of reinforcement required per unit of deck volume. Results indicated a clear distinction between reinforcement types, ChromX and SS exhibited lower volume but higher mass requirements while TS and TP required greater volume but significantly reduced mass. TP rebars, modeled as direct replacements for TS rebars, demonstrated practical equivalence with TS in terms of structural demand, supporting their viability as sustainable alternatives in bridge construction.

Despite TP rebars demonstrating promising potential, their current production and logistics pathways result in higher environmental impacts. The study highlights the potential to improve TP rebar sustainability through localized production, energy optimization, and reduced reliance on air freight. Future research should expand to include cradle-to-grave assessments to capture long-term impacts and support broader adoption in sustainable infrastructure.

Comments

This thesis presents a comparative life cycle assessment of thermoplastic and conventional rebars (Chromium, stainless steel, and thermoset) used in reinforced concrete bridge decks. It uses real bridge design data from MaineDOT and models environmental impacts using OpenLCA and the ecoinvent database.

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