Semester

Fall

Date of Graduation

2002

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Julio F. Davalos

Committee Co-Chair

Indrajit Ray.

Abstract

The continual degradation of civil infrastructures worldwide has prompted the need for effective solutions, posing major challenges to those involved with reinforced concrete structures. Externally bonded fiber reinforced polymer (FRP) composites have proven to be an efficient means of rehabilitation and enhancement to both existing and new structures alike. An important issue regarding this technology that needs further exploration, however, is the strength and integrity of the interface bond---the inadequacy of which can result in premature failure of the reinforced member.;Until now, there were no available methods to rigorously evaluate the interface bond strength and integrity for concrete structures externally reinforced with FRP materials. Existing large-scale tests of structural components used for stiffness and strength evaluations, on the one hand, are ill suited for detecting delamination effects. On the other, small-scale tests only provide average interface strength properties that neither describe failure mechanisms nor provide fracture toughness data.;In an effort to resolve this dilemma, a new test methodology, referred to as the Single Contoured-Cantilever Beam (SCCB) specimen, conceived and fashioned after the established double cantilever beam (DCB), is implemented. Using this newly developed experimental fracture approach, insights have been gained into the elusive fracture toughness of the CFRP-concrete interface. This methodology is then extended to evaluate the fracture toughness of the same interface as subjected to one of three commonly encountered field exposure-conditions: (1) wet-dry cycling under sodium-sulfate (Na2SO4), (2) wet-dry cycling under sodium-hydroxide (NaOH), and (3) freeze-thaw cycling under calcium chloride (CaCl2) attack. Considerable degradation of the interface bond integrity is found to have resulted in each case, when compared with companion specimens of the same age. This new test method can therefore serve both to qualify existing products as well as in developing new formulations of adhesives and FRP systems.

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