Theses and Dissertations

ORCID

https://orcid.org/0000-0003-0393-133X

Issuing Body

Mississippi State University

Advisor

Howard, Isaac L.

Committee Member

Burcham, Timothy N.

Committee Member

Cisko, Abby

Committee Member

Freyne, Seamus

Date of Degree

12-13-2024

Original embargo terms

Worldwide

Document Type

Dissertation - Open Access

Major

Engineering (Civil Engineering)

Degree Name

Doctor of Philosophy (Ph.D.)

College

James Worth Bagley College of Engineering

Department

Richard A. Rula School of Civil and Environmental Engineering

Abstract

A global plastics crisis exists with around 400 million metric tons (MMT) of plastics production and 350 MMT of plastics waste generated annually around the globe. Plastics are durable and essentially non-biodegradable, so they accumulate in both terrestrial and marine environments as pollution and within landfills without breaking down over time. Plastics are ubiquitous in 21st-century society and culture, comprising essential elements in most industries including packaging, transportation, electrical/electronics, and building/construction. The role of civil engineering and infrastructure in addressing the plastics crisis was specifically explored. Responsible plastics recycling yields products with improved engineering properties, performance characteristics, marketability, and/or manufacturing costs, and it doesn’t force plastics recyclate into products at the expense of reliability, durability, safety, or usability. Military rail infrastructure was extensively explored, and performance challenges with recycled plastic (RPL) crossties (i.e. ties or sleepers or railroad ties) were documented. The biggest weaknesses of RPL ties identified were their insufficient high temperature lateral stability and thermal expansion, vertical stiffness, inherent ductility, and variable strength. Noted problems with maintaining gage, center cracking, and deformation of the recycled plastic ties are manifestations of these weaknesses. Other infrastructure items identified included pipes, lumber, and asphalt, and the potential impact of all these items on the plastics crisis was quantified. Absolute (and unrealistic) best-case scenario incorporation of recycled plastics into all these infrastructure elements would result in the consumption of 2.1% of the annual global plastics waste. This limited impact reveals that the global plastics crisis is larger than many seem to have comprehended, and it reveals the fact that civil engineering and infrastructure elements are not able to provide an avenue by which society can recycle its way out of the crisis. Market-driven solutions to the plastics crisis will incentivize all parties involved to address the crisis from production through applications and usage to re-use and recycling to waste disposal. A holistic approach to solving the plastics crisis is necessary to produce sustainable solutions, and responsible recycling in civil engineering and infrastructure will be only one of several crucial elements to that successful approach.

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