UTC 2022 Funding - Cycle 1 Research Projects

Project No.: CY1-OU-03
Title: Durability Assessment of Binders with Interlayer Reinforcement for 3D Printed Elements
Performing Institution: University of Oklahoma, University of New Mexico (consulting collaborators)
Principal Investigator: Shreya Vemuganti, University of Oklahoma
Start and Anticipated Completion Dates: 10/1/2023-09/30/2024
Abstract: 3D Concrete Printing (3DCP) is one of the fastest emerging technologies and involves layerby-layer building of a binder material with additives without the use of formworks while enabling the design freedom to produce complex structural geometries. To enable this technology to reach end-use applications in construction such as printing large-scale, fail-safe concrete structural elements, the low tensile strength of concrete is to be overcome. Incorporating reinforcement such as steel between printed layers to carry tensile stress is at the risk of exposure to environmental degradation mechanisms such as chloride ingress and freeze-thaw which affect their durability due to lack of formwork and the weak morphology of the interface. In this study, it is hypothesized that the intrusion of chlorides and exposure to freeze-thaw cycles will decrease the flexural strength and interlayer strength of reinforced 3DCP elements. In addition, 3DCP elements with fiber-reinforced polymers may show increased resistance to deterioration mechanisms while improving flexural and interlayer strength. This project aims to assess the durability properties of cementitious binders with interlayer reinforcement to aid in the design and development of 3DCP elements for transportation infrastructure. The objectives of the proposed study are to answer two issues: the effect of deterioration mechanisms such as chloride ingress and freeze and thaw on the mechanical performance and flexural strength capacities of (a) cementitious binders with successive layers representing 3D printed elements and (b) cementitious binders with different types of reinforcement incorporated at the interface between successive layers. The following tasks will be pursued to achieve the aforementioned objectives: (1) developing a database of mix design for 3D printed concrete by targeting the specific workability requirements; (2) preparing specimens with steel, glass fiber (GF), and carbon fiber (CF); (3) subjecting specimens to deterioration mechanisms including freeze-thaw and chemical ingress; (4) testing specimens without exposure, with freeze-thaw exposure and chemical ingress exposure in flexure, and analyzing results including load vs displacement behavior; (5) investigating failure interfaces using microscopic analysis; (6) performing a training session for rural STEM high school teachers; and (7) identifying large-scale structures for 3D printing of durable elements. The outputs of this project include: (1) mix designs based on the existing literature review of 3D printed concrete by targeting the specific workability requirements, fresh properties, and hardened properties; (2) load vs displacement graphs, average strengths, and failure mechanisms from flexural testing of 3DCP elements with three types of interlayer reinforcement and two types of deterioration mechanisms. This work offers solutions to using 3DCP with reinforcement for large-scale structural and non-structural elements that could save 35% to 60% of the total cost of concrete construction because no formwork is needed. Also, 3DCP shows promise for reducing global energy usage significantly.
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