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Kuchma, Daniel A. Spencer, Billie F., Jr. Landis, Eric N O’Daniel, James L Lange, David A. Cusatis, Gianluca Oesch, Tyler Scott 2015-07-22T22:16:31Z 2015-07-22T22:16:31Z 2015-05 2015-04-20 2015-5 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. Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2015-07-22 without embargo terms The student, Tyler Oesch, accepted the attached license on 2015-04-06 at 19:01. The student, Tyler Oesch, submitted this Dissertation for approval on 2015-04-06 at 19:07. This Dissertation was approved for publication on 2015-04-20 at 16:56. DSpace SAF Submission Ingestion Package generated from Vireo submission #7794 on 2015-07-22 at 10:31:30 Made available in DSpace on 2015-07-22T22:16:31Z (GMT). No. of bitstreams: 2 OESCH-DISSERTATION-2015.pdf: 12469294 bytes, checksum: 77dc907411789dbad295950dc6920248 (MD5) LICENSE.txt: 4208 bytes, checksum: 53599fa525bef5ffebedac15a2fe6ff5 (MD5) Previous issue date: 2015-04-20 application/pdf http://hdl.handle.net/2142/78353 en Copyright 2015 Tyler Oesch X-Ray Computed Tomography (CT) Double Punch Test (DPT) Fiber Reinforced Concrete Ultra-High Performance Concrete (UHPC) Anisotropic Fiber Orientation Digital Image Processing Investigation of fiber and cracking behavior for conventional and ultra-high performance concretes using x-ray computed tomography text text Civil & Environmental Eng Civil Engineering University of Illinois at Urbana-Champaign Dissertation Ph.D.