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Fiber-reinforced concretes (FRCs) offer significant improvements in tensile strength and durability compared to most other concrete mixes.
However, for safe and efficient use of FRC in large structures, anisotropy of fiber orientation needs to be understood and properly controlled. In this project, both cored samples extracted from a FRC slab and FRC samples cast individually in molds were assessed using X-ray computed tomography (CT) and measurements of fiber orientation were extracted from the resulting CT images. These results showed that fibers within the slab were highly anisotropic in orientation while fibers in individually cast samples showed a much more heterogeneous distribution of orientations.
This indicates that fiber orientation is highly dependent on the casting process and suggests that FRC can only be safely and efficiently utilized if anisotropic fiber orientation is properly accounted for during design and optimized casting methods are used during construction.
Conventional concrete and UHPC performance-damage relationships identified using computed tomography
(2016)
To make significant advances in concrete engineering, it will be necessary to understand the behavior of cementitious materials at the microscale. To achieve this goal, the nature of damage initiation and growth needs to be understood at very small scales. This Research program sought to increase that understanding through the collection of microscale data using X-ray computed tomography (CT). The tensile and compression behavior of both ultra-high performance concrete (UHPC) and conventional concrete were investigated as a part of this
program. Relationships were identified between mechanical performance parameters, such as stiffness degradation and work of load, and cracking parameters, such as crack volume and crack surface area, that could be quantified mathematically and implemented into future finite element analysis (FEA) models. The results of this Research program have the potential to improve the accuracy and resiliency of numerical models and to provide insight to the materials engineering community concerning the optimal use of UHPC.