Theses and Dissertations

Brian Giltner

Issuing Body

Mississippi State University

Advisor

Freyne, Seamus F.

Committee Member

Mohammadi-Aragh, Mahnas J.

Committee Member

Gullett, Phillip M.

Committee Member

Lamanna, Anthony J.

Date of Degree

11-25-2020

Document Type

Dissertation - Open Access

Major

Civil Engineering

Degree Name

Doctor of Philosophy

College

James Worth Bagley College of Engineering

Department

Department of Civil and Environmental Engineering

Abstract

The commercial use of hemp fiber in the construction industry within the United States is non-existent. This lack of use is because of State and Federal laws forbidding the growth of hemp in the United States, which has led to a lack of research. Not having an established supply chain for hemp and coupled with limited research has put the United States behind other countries in finding viable options for these renewable resources. This is a study of the performance of raw hemp fibers and processed hemp twine in a cement past mixture subjected to tensile loading. Three water/cement ratios (0.66, 0.49, 0.42) were considered. Replacement of cement with fly ash is also part of the program to see if it affects the performance of the system. A detailed description of the method of applying the tensile load to the micro/macro fibers along with the fixture setup is part of this article. The results of this investigation show the hemp twine and fibers will bond to the cement matrix and they can carry higher tensile loads at higher w/c ratios. This study shows that 30 mm embedment length is best for hemp macro fibers and 20 mm embedment for hemp micro fibers. This study also includes a comparative investigation of the performance of hemp fibers to synthetic and steel fibers added to a concrete mix. This investigation examined the compressive strength of the fiber-reinforced concrete mixes, flexural capacity, ductility, flexural toughness and the effects the fibers have on Young’s modulus of elasticity. All fibers were introduced to the same mix design (w/c = 0.49) with replacement of 25% of cement with fly ash. Hemp micro fibers at the same dosing rate a synthetic micro fibers has a slightly higher toughness and equivalent flexural strength. Hemp macro fibers at a higher dosing rate as compared to synthetic fibers will have similar toughness and equivalent flexural strength. Steel fibers performed better than the synthetic and natural fibers at 28-day compressive strength.

URI

https://hdl.handle.net/11668/20830

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