Date of Award

2020

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering (PhD)

Administrative Home Department

Department of Civil and Environmental Engineering

Advisor 1

Qingli Dai

Advisor 2

Zhanping You

Committee Member 1

Jacob Hiller

Committee Member 2

Trisha Sain

Abstract

With the accelerated accumulation of scrap tires, the landfill becomes unacceptable due to limited space and its environmental pollution. The rubberized concrete materials containing scrap tire rubber particles as partial replacement of aggregates have been considered as one applicable method to recycle waste tire. However, the mechanical and durability properties of concrete materials can be significantly affected by adding rubbers without optimized designs. The main objective of this research is to develop the optimized designs for fiber-reinforced rubberized normal concrete and rubberized self-consolidating concrete through experimental evaluation of fresh performance, mechanical property, and durability resistance. For fiber-reinforced rubberized normal concrete, steel fibers and plastic fibers were added along with recycled rubber aggregates. The results showed steel fibers could improve compressive strength, splitting tensile strength, and flexural strength of rubberized normal concrete. In the case of plastic fibers, reduced compressive and flexural strength were found by comparing with that of control specimens. However, the fracture energy and post-crack extension were significantly improved by comparing that of control specimens in fiber-reinforced rubberized normal concrete samples regardless of fiber types, especially the fracture energy was increased about 10 to 50 times.

The steel fiber-reinforced self-compacting rubber concrete (SRSCC) was also designed by introducing steel fiber and recycled rubber aggregates into self-compacting concrete (SCC). The experimental results showed the SRSCC can meet most requirements of fresh performance (flowability, filling ability, and passing ability) in terms of field applications. Regarding hardened properties, the compressive strength was reduced with the added rubber aggregate and steel fiber. However, SRSCC samples with 10% rubbers showed higher splitting tensile strength than that of plain SCC samples. The Load-crack mouth opening displacement (Load-CMOD) curves showed the increased flexural strength and total fracture energy of SRSCC samples with added steel fiber by comparing that with plain SCC. The critical fracture parameters, including initial fracture energy (Gf) and stress intensity factor (KІc) were increased with added rubber aggregate and steel fiber. With these properties, the bilinear strain-softening model (aggregate interlock effect) and trilinear strain-softening model (aggregate interlock and fiber-bridging effects) were calibrated. The strain-softening curves were utilized in the ATENA finite element model (FEM) to predict the flexural-fracture behaviors of corresponding specimens, and the simulation showed reasonable agreement with experiments. Also, the SRSCC specimens showed excellent freeze-thaw resistance after 600 F-T cycles. In the future, the success of applying fiber-reinforced rubber concrete materials could be an environmental-friendly utilization for recycling solid tire rubber waste and improve the mechanical and durability performance of conventional concrete materials.

Available for download on Tuesday, June 01, 2021

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