Author ORCID Identifier

https://orcid.org/0009-0006-0413-4868

Semester

Summer

Date of Graduation

2025

Document Type

Problem/Project Report

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Hota V.S. GangaRao

Committee Co-Chair

Rakesh Gupta

Committee Member

Chao Zhang

Abstract

Over four billion pounds of carpet are discarded annually in the United States, making carpet waste a significant environmental concern. Calcium carbonate (CaCo₃) constitutes up to 45% of the mass of most synthetic carpets. Reusing this CaCo₃ as a filler in the rapidly growing fiber-reinforced polymer (FRP) industry, which is projected to reach USD 10.38 billion, presents a low-cost, practical approach to developing a market-based solution to post-consumer carpet waste.

This study investigates the reuse of CaCo₃ recovered from discarded carpet backing as a filler in FRP composites, focusing on its mechanical viability in comparison to virgin CaCo₃. The methodology involves a structured sieving process to isolate usable fractions, followed by resin mixing, viscosity measurement, and mechanical testing of both resin systems and glass fiber–reinforced polymer (GFRP) composites. Tension, compression, flexural, and short-beam shear tests were conducted on specimens fabricated via lab-scale hand lay-up and industrial pultrusion.

Three categories of GFRP coupons were prepared using virgin, #80-below, and #120-below CaCo₃ fillers, each tested with 20% and 30% filler content by total resin weight. The mechanical test results indicated that reused CaCo₃ can be used in GFRP fabrication, with less than a 30% reduction in tensile and flexural strength, and up to an 11% increase in stiffness compared to virgin-filled specimens.

To assess industrial applicability, the lab-scale process was replicated in collaboration with a major U.S. pultrusion manufacturer. Coupons extracted from these pultruded plates were tested and showed comparable mechanical behavior to virgin-filled composites.

Overall, the findings confirm that up to 20% by total matrix weight of sieved, recycled CaCo₃—particularly particles passing ASTM No. 80 sieve—can be effectively reused without significant compromise in structural performance. This research supports a scalable and sustainable open-loop recycling method for CaCo₃-rich carpet waste in FRP manufacturing, offering both environmental and economic benefits.

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