Date of Award

Fall 12-15-2023

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Eric Landis

Second Committee Member

Bill Davids

Third Committee Member

Jameson Shannon

Abstract

Ultra High Performance Concrete (UHPC) and High Performance concrete (HPC) is characterized by high compressive strength and high toughness. This is achieved through maximizing the particle packing density in the matrix and the use of fibers to reinforce the matrix, increasing the materials toughness. The interactions of fibers and the matrix during loading is quite complex and involves several different energy dissipation mechanisms. The goal of this work and this thesis is to investigate these interactions and identify any changes in material response, and hope that these changes may be useful for the design of UHPC moving forward.

In this thesis two different reinforcement types, Steel Wool/Steel Fiber and purely Steel Fiber, are tested in a split cylinder tensile test using a quasi static load rate and a high loading rate to investigate changes in the material response. The fracture response is evaluated for loading rate, fiber orientation, and reinforcement type individually. This is done using Digital Volume Correlation, and Image processing Analysis to determine surface area generation and volumetric strain production by both macro cracks and micro cracking.

This study found that when loading rate increases the amount of micro cracking in the specimen also increases, this trend was seen for 75% of the data. It was also found that for 75% of the optimum fiber oriented specimens, less volumetric strain was produced per joule of absorbed energy then in the pessimum fiber oriented specimens. This means that the optimum fiber oriented specimens were performing better than the pessimum. The optimum fiber oriented specimens showed another trend which was an increase in the amount of volumetric strain made up of micro cracking per joule of absorbed energy than the pessimum fiber oriented specimens, this was again seen for 75% of the data. The Steel Wool and Fiber reinforced specimens performed the best, with lower amounts of volumetric strain per joule of absorbed energy then in the purely Fiber reinforced specimens this again was seen for 75% of the data

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