Date of Award

2021

Document Type

Dissertation

Degree Name

Ph.D.

Department

Mechanical Engineering

First Advisor

Matt Gordon

Second Advisor

Brian Majestic

Third Advisor

Yun-bo Yi

Fourth Advisor

Ali Azadani

Keywords

Materials science, Cement, Recycling

Abstract

Recycling options for fiber polymer matrix composite waste materials are limited because they typically cannot be reused, reprocessed for down-cycling, and are generally environmentally unfriendly. The utility industry, specifically electrical distribution, has been increasingly using hybrid carbon, glass fiber, and epoxy resin composite rods for high-voltage (HV) conductor transmission lines. The high-voltage conductor core (HVCC) used in the transmission line can have an optimal in-service-life of roughly several decades, in which the material is then retired to a waste landfill. Currently, there is limited research and recycling methodology for these hybrid composite rods. In this research, powder carbon fiber, glass fiber, and epoxy admixture filler material were used in cement to improve the durability and reduce aging effects in hardened Portland cement materials.

This research also attempts to determine a method of processing the HVCC material for an admixture of recyclable filler material in cementitious construction building materials as an alternative to disposal in landfills. The corrosive aging effects of moisture and saltwater environments on low- and high-pressure compacted hardened neat Portland cement material were found to decrease average compression strengths by approximately 30% and 8% respectively. Salt-aged OPC neat low-pressure maximum average compression strength decreased from 75 MPa to 52 MPa, while OPC with particle fiber powder admixture at 6.0 wt% only decreased from 55 MPa to 52MPa. Recycled HVCC filler in cement at high-pressure compaction was a significant factor reducing degradation of mechanical compression strengths after saltwater aging by approximately 93% in high pressure compacted Portland cement. Salt-aged high-pressure compacted OPC maximum average compression strength decreased from 59 MPa to 41 MPa, and OPC with particle fiber powder admixture maximum average compression strength decreased from 44 MPa to 41 MPa. The OPC with HVCC crushed rod chips admixture at 6.0 wt% had the poorest maximum average compression strength at low- and high-pressure compacted at 34 MPa and 32 MPa respectively. Therefore, particle fiber powder consisting of carbon/glass fibers and epoxy resin was shown to have substantial qualitative benefits as an admixture filler in cement.

Additional numerical approaches were developed for low-pressure and high pressure molecular diffusion analyses. The numerical models were used to expand the understanding of low-diffusive particle inclusions such as fibers can act as retardants of water transport, which can contribute to carrying charged ions, Cl- through porous cement. Molecular dynamics mean squared displacement simulation of water transport decreased by roughly 85% in high-pressure compacted cement with carbon/glass fiber and epoxy. Concentration transport of chemical species had decreased saturation in by 57% in low porosity (0.02) cement compared to high-porosity (0.05) with fibers. The research presented in this dissertation was enhanced using molecular dynamics analysis, 2D finite element concentration diffusion analysis, and experimental methods.

Publication Statement

Copyright is held by the author. User is responsible for all copyright compliance.

Provenance

Received from ProQuest

Rights holder

Edward Patton Clark

File size

156 pgs

File format

application/pdf

Language

en

Discipline

Materials Science

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