Investigation of fiber and cracking behavior for conventional and ultra-high performance concretes using x-ray computed tomography

Oesch, Tyler Scott

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Description

Title

Investigation of fiber and cracking behavior for conventional and ultra-high performance concretes using x-ray computed tomography

Author(s)

Oesch, Tyler Scott

Issue Date

2015-04-20

Director of Research (if dissertation) or Advisor (if thesis)

Kuchma, Daniel A.

Doctoral Committee Chair(s)

Spencer, Billie F., Jr.

Committee Member(s)

• Landis, Eric N
• O’Daniel, James L
• Lange, David A.
• Cusatis, Gianluca

Department of Study

Civil & Environmental Eng

Discipline

Civil Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• X-Ray Computed Tomography (CT)
• Double Punch Test (DPT)
• Fiber Reinforced Concrete
• Ultra-High Performance Concrete (UHPC)
• Anisotropic Fiber Orientation
• Digital Image Processing

Abstract

To make significant advances in concrete engineering, understanding the behavior of cementitious materials at the micro-scale will be necessary. To reach this goal, the location and orientation of constituent materials within concrete members, as well as the nature of damage initiation and growth, need to be understood at very small scales. This dissertation sought to increase that understanding through the collection of micro-scale data using x-ray computed tomography (CT). The quasi-static phenomena investigated included the tensile, compression, and reinforcing bar pull-out behavior of both ultra-high performance concrete (UHPC) and conventional concrete. Ballistic damage of UHPC samples was also investigated. These testing efforts yielded a number important results. First, relationships were identified between mechanical performance and cracking parameters that could be quantified mathematically and implemented into future finite element analysis models. Second, these test results demonstrated that the cracking structures of UHPC samples subjected to the double punch test (DPT) are heavily influenced by fiber anisotropy. This can lead to actual crack structures that are significantly at variance with the theoretical crack structure, which may decrease DPT accuracy in predicting tensile strength. Third, fiber orientations within both small and large samples of UHPC were demonstrated to be highly anisotropic. Thus, the assumption of a uniform distribution of fiber orientations within UHPC could lead to significant over-predictions of strength in some structural members. The results of this dissertation have the potential to both improve the accuracy and resiliency of numerical models as well as provide insight to the materials engineering and structural design communities about the optimal use of UHPC.

Graduation Semester

2015-5

Type of Resource

text

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Copyright and License Information

Copyright 2015 Tyler Oesch

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