Date of Award
2026
Degree Type
Dissertation
Degree Name
Doctor of Philosophy in Civil and Environmental Engineering
Department
Civil and Environmental Engineering
First Advisor
Vinka Oyanedel-Craver
Abstract
The rapid escalation of plastic waste production remains a significant environmental concern globally and has prompted researchers to seek innovative and sustainable methods for recycling plastic waste to prevent its accumulation in the environment and mitigate its adverse effects on the environment and human health. One way is by incorporating plastic waste into construction materials, however, mechanical performance and most especially the environmental performance of these bricks during the manufacturing and usage stage have not been fully explored. Methods for investigating the mechanical and environmental performance of the plastic blocks being produced are presented in the studies included here. The objective of this dissertation is to investigate the mechanical performance, environmental performance and the influence of ultraviolet (UV) weathering on the manufacturing and usage of plastic bricks produced from plastic waste and aggregates.
The research presented in this dissertation consisted of four interrelated studies. The first study provided a critical review on the primary manufacturing processes used to produce bricks using plastic waste to ultimately identify the emissions associated with manufacturing process, and to evaluate the occupational health and environmental risks associated with the use of plastic waste in construction bricks. This included the extrapolation of potential adverse impacts from comparable plastic mechanical recycling activities due to a lack of literature on these plastic block recycling processes. The review concluded that the extrapolated likely health and environmental hazards from comparable mechanical recycling activities, included the release of heavy metals, POPs, phthalates, particulate matter, microplastics, VOCs, and airborne fungi from sorting, washing, shredding and melting/extrusion processes, with the washing stage that may constitute the largest environmental risk due to the threat of microplastics in effluent and the leaching of heavy metals. These pollutants are well known to be acutely and chronically hazardous to human health and pose a risk to the environment.
The goal of the second study was to evaluate the mechanical properties, environmental performance and the effects of UV weathering on plastic bricks manufactured from plastic waste in Timor-Leste, focusing on: compressive strength, leaching potential of pollutants of organic and inorganic contaminants and the influence of UV weathering on leaching and strength, and the overall environmental performance through a life cycle assessment (LCA). The blocks demonstrated compressive strengths up to 24.3 ± 0.57 N/mm², suitable for paving applications. Mechanical performance improved with lower plastic content, while UV weathering reduced strength, increased porosity, and increased the leaching of inorganic contaminants, including Cr, Pb, Cu, amongst others which are metals of concern. Organic compounds such as PAHs were found below detection limits and PFAS concentrations were reduced after UV aging. The Life cycle assessment identified extrusion as the dominant contributor to climate change (GWP100) and particulate matter formation (PMFP).
The third study investigates the effects of the feedstock type and state used to manufactured bricks on the mechanical and environmental performance and analyzes the particulate emissions from the extrusion process to determine the impact of the process on occupational health. Blocks were produced using UV aged and unaged pristine and recycled High-Density Polyethylene (HDPE) and Polypropylene (PP) plastics, the specific objectives were to (1) assess compressive strength and creep behavior under compression, (2) evaluate the leaching potential of pollutants from these bricks, (3) quantify and analyze particulate emissions during the extrusion process and, (4) determine the effect of UV weathering on leaching, emissions, and strength. The blocks exhibited compressive strengths up to 35.25 ± 1.53 N/mm², with pristine blocks having higher compressive strength, lesser leachate concentrations and less resistant to creep. Aging reduced strength and increased leaching by up to ~80%. Using aged feedstock produced more nano and micro particulates.
The fourth study investigates the use of fishing gear waste and waste seashells as partial replacement for aggregates for making blocks. The mechanical and environmental performance of the manufacturing process and block during usage was also examined. Blocks had a compressive strength of up to 32.15 N/mm², with the blocks containing shells having a better creep resistant, with 3.14% strain. Shredding and extrusion processes released nano and micro particulates and blocks leached metals, with blocks containing shells leaching out lower amount.
Overall, this study summarizes the mechanical performance, environmental impacts and emissions that the plastic block manufacturing process and the usage of the blocks can pose, and how the type of feedstock used and UV exposure can affect their performance.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Recommended Citation
Neba Nforsoh, Sirri Akongnwi, "ENVIRONMENTAL IMPACTS OF RECYCLED PLASTIC BRICKS DURING THE MANUFACTURING PROCESS AND USAGE PHASE" (2026). Open Access Dissertations. Paper 4567.
https://digitalcommons.uri.edu/oa_diss/4567