The Longitudinal Shear Behavior of Carbon Fiber Grid Reinforced Concrete Toppings

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Title: The Longitudinal Shear Behavior of Carbon Fiber Grid Reinforced Concrete Toppings
Author: Grimes, Hartley Ray
Advisors: Dr. Rudolf Seracino, Committee Chair
Dr. Emmett Sumner, Committee Co-Chair
Dr. Sami Rizkalla, Committee Co-Chair
Abstract: Precast double-tee (DT) floor systems with cast-in-place concrete toppings reinforced with welded wire fabric (WWF) often suffer from durability problems along the longitudinal joints of adjacent DTs. The high strain demand along these joints leads to cracking of the concrete topping, exposing the steel reinforcement to an aggressive environment resulting in corrosion. Carbon fiber grid (G-Grid) reinforcement is proposed as a replacement for the WWF to address this problem. This thesis presents an experimental program designed to investigate the longitudinal shear behavior of C-Grid reinforced concrete. Twenty-two single-shear test specimens were designed to simulate the joint of adjacent DTs with topping. The objective was to obtain the fundamental shear-slip behavior and compare it to that of WWF reinforced specimens. Parameters included the reinforcement ratio and grid orientation. In addition, this thesis also looks at, through direct tension tests, C-Grid’s potential to interfere with the bond between the DT and the topping. It was found that, at least in the small-scale tests, steps should be taken to prevent this premature cold joint debonding. Two methods – chairing the C-Grid, or significantly roughening the DT surface – were shown to be adequate to prevent this phenomenon. The results of this investigation demonstrate the suitability of C-Grid as reinforcement in cast-in-place toppings. The longitudinal shear behavior observed in C-Grid and WWF reinforced concrete were similar to the point that shear-friction models, intended to be used with steel reinforcement, were able to predict and design the longitudinal shear capacity of C-Grid reinforced toppings with slight modifications. Shear-friction design models from the 6th Edition of the PCI Design Handbook, ACI 318-08, and other published models were used in this comparison.
Date: 2009-12-04
Degree: MS
Discipline: Civil Engineering

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