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

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Civil Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Oesch, Tyler Scott

Contributors dc:contributor

• Kuchma, Daniel A.
• Spencer, Billie F., Jr.
• Landis, Eric N
• O’Daniel, James L
• Lange, David A.
• Cusatis, Gianluca

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

Statement dc:rights

• Copyright 2015 Tyler Oesch

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/78353

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/78353