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Performance and Design of Extruded Fiber-Reinforced Mortar with Preferentially Aligned Fibers

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dc.contributor.authorAlarrak, Rasheden
dc.contributor.committeechairBrand, Alexander S.en
dc.contributor.committeememberRoberts-Wollmann, Carin L.en
dc.contributor.committeememberKing, Jonathan Leeen
dc.contributor.committeememberAidi, Bilelen
dc.contributor.departmentCivil and Environmental Engineeringen
dc.date.accessioned2024-05-04T08:00:47Zen
dc.date.available2024-05-04T08:00:47Zen
dc.date.issued2024-05-03en
dc.description.abstractThis dissertation presents a comprehensive investigation into the mechanical properties of fiber-reinforced concrete (FRC), focusing on fracture and flexural toughness properties, the impact of fiber orientation and distribution, and the evaluation of flexural models for predicting the behavior of functionally graded FRC. It embarks on a critical investigation aimed at bridging a significant gap in the understanding of FRC materials' behavior, particularly in terms of fracture and flexural performance. Across five distinct manuscripts, this work employs a variety of experimental methodologies, including three-point bend tests, four-point bend tests, digital image correlation, X-ray computed tomography, and the implementation of the two parameter fracture model and then size effect fracture method to explore the effects of different casting techniques – namely, conventional casting and pump-driven extrusion – on the performance of FRC. The core hypothesis tested throughout these studies suggests that the extrusion process, by aligning fibers parallel to tensile stresses, significantly enhances the concrete's ductility, post-peak behavior, and overall fracture and flexural properties. This hypothesis was corroborated across various experiments, which demonstrated that fiber alignment via extrusion not only enhances the concrete's mechanical properties but also leads to more effective crack propagation control, increased toughness, and enhanced residual strengths. The research encompasses a series of systematic investigations into the effects of fiber alignment on the mechanical properties of FRC, revealing that the extrusion process significantly enhances fracture and flexural properties and maintains residual strength after peak stress. Utilizing both extrusion-based and conventional casting methods with varying dosages of polyvinyl alcohol fibers, the study demonstrates notable improvements in fracture properties, deflection at failure, and equivalent flexural strength ratio for extrusion-based specimens compared to their conventionally cast counterparts. Moreover, the dissertation explores the impact of casting methods and fiber orientation on fracture energy, offering a size-dependent improvement in extrusion-based methods. The strategic distribution of steel fibers, employing an innovative targeted fiber injection for creating Functionally Graded FRC (FG-FRC), is shown to significantly enhance the structural integrity and resilience of the material. The analysis of flexural models applied to FG-FRC specimens, proposing a novel functionally graded factor to improve model predictability, further advances the understanding of the predictability and reliability of these models in assessing FRC's structural behavior. This dissertation advances academic knowledge in the field of FRC casting and offers significant implications for the construction industry, demonstrating a profound understanding of the challenges and opportunities in extrusion-based FRC casting. Through its innovative approach and detailed investigations, this work contributes significantly to the advancement of the FRC casting field, paving the way for the development of more resilient and efficient construction materials.en
dc.description.abstractgeneralThis research explores the enhancement of concrete's strength and flexibility through the incorporation of individual fibers, with a special focus on the integration and alignment of these fibers. The study examines how concrete can be made more resilient by mixing in fibers in specific ways. A variety of tests, including bending beams and employing advanced imaging techniques, were conducted to observe the effects of mixing fibers using traditional methods versus a novel extrusion-based technique that aligns the fibers in the desired direction in the concrete. The research hypothesized that this innovative alignment method would improve the concrete's ductility and enhance its ability to resist crack propagation. The findings confirmed this hypothesis, revealing that aligned fibers significantly improve concrete's bending capacity, reduce sensitivity to cracking, and retain residual strength even after cracking. Further investigation into varying methods of fiber addition, such as a targeted approach for placing fibers in strategic locations, demonstrated a marked enhancement in the material's ductility. Additionally, the study evaluated mathematical models for predicting the behavior of fiber-reinforced concrete, aiming to improve the understanding and reliability of these models for practical construction applications. In short, the research underscores that adjusting the method of fiber integration into concrete can lead to the development of structures that are both stronger and more durable. This advancement holds promising implications for the future of construction, offering pathways to create more resilient and efficient building materials.en
dc.description.degreeDoctor of Philosophyen
dc.format.mediumETDen
dc.identifier.othervt_gsexam:40302en
dc.identifier.urihttps://hdl.handle.net/10919/118752en
dc.language.isoenen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectFiber-reinforced concreteen
dc.subjectMortaren
dc.subjectFractureen
dc.subjectFlexuralen
dc.subjectFiber alignmenten
dc.subjectExtrusionen
dc.subjectDigital image correlationen
dc.subjectX-ray computed tomographyen
dc.subjectCrack propagationen
dc.subjectStrain localizationen
dc.subjectInjectionen
dc.subjectFlexural modelen
dc.titlePerformance and Design of Extruded Fiber-Reinforced Mortar with Preferentially Aligned Fibersen
dc.typeDissertationen
thesis.degree.disciplineCivil Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.nameDoctor of Philosophyen

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