Author

Kevin Trainor

Date of Award

8-2011

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Eric N. Landis

Second Committee Member

William G. Davids

Third Committee Member

Andre Khalil

Abstract

3-D images of plain and steel fiber reinforced reactive powder concrete generated by X-ray Computed Tomography were analyzed in conjunction with mechanical testing results to determine their fracture toughness. In addition to fracture toughness measurements, analysis of X-ray CT images yielded fiber reinforcement and orientation information for those specimens reinforced with steel fibers, specifically fiber volume fraction and local reinforcement orientation. Phase and fiber segmentation made it possible to identify and quantify individual toughening mechanisms, including matrix cracking and fiber pullout, debonding, and bending on a fiber by fiber basis. Measured reinforcement ratios ranged from 3.1 - 4.2%, compared to a target ratio of 3.6%, and fracture toughness of unreinforced specimens ranged from 0.021 - 0.028 N/mm2. Analysis of toughening mechanisms revealed that fracture toughness in steel fiber reinforced reactive powder concrete is dictated by a combination of fibers engaged in toughening and the orientation of the reinforcement. Results showed that matrix cracking and fiber pullout are the principle toughening mechanisms at work

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