Doctoral Dissertations

Date of Award

5-2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Civil Engineering

Major Professor

Z. John Ma

Committee Members

Richard M. Bennett, Timothy Truster, Yann Le Pape

Abstract

Alkali-silica reaction (ASR), which was recently discovered in nuclear power plant structures commonly without shear reinforcement, has previously been shown to induce anisotropic expansion in confined concrete. A large-scale testing program on alkali silica reaction (ASR)-affected concrete structural members without shear reinforcement representative of structural members found in nuclear power plants is presented. Three large concrete specimens with ASR and varying levels of confinement were monitored in accelerated testing conditions.Strong anisotropic expansion and oriented ASR-induced cracking resulting from the confinement effect caused by the reinforcement layout and additional structural boundary conditions were observed. Surface cracking is not indicative of internal ASR-induced damage/expansion.The fracture properties (strength, stiffness, and specific fracture energy) of ASR-induced anisotropically-damaged concrete specimens were quantified by varying both the damage level and relative direction of the ASR-induced cracking orientation against the loading direction corresponding to the fracture propagation. The effect of different orientations (0, 45, and 90 degrees relative to the notch of the specimen) of expected ASR-induced cracks on the fracture properties was investigated using a wedge-splitting test (WST). Specimens without ASR expansion generally showed the highest fracture properties; however, the specific fracture energy was highest for ASR-affected specimens in which the expected orientation of ASR-induced cracks was perpendicular to the WST specimen notch. Specimens in which the ASR-induced cracks were parallel to the notch exhibited the lowest strength and fracture energy.A new model was developed for predicting the expansion of concrete structures affected by alkali-silica reaction. The model includes a novel combination of existing models as a alkali-silica reaction advancement model, a novel casting direction anisotropic expansion model, a novel stress-dependent anisotropic expansion model, and a novel material property evolution model dependent on the degree of ASR expansion. The calibrated model was validated in predicting the ASR-expansion of the large-scale reinforced concrete specimens with confinement of this study. The results of this study highlight the need for additional research to be conducted to investigate a possible size effect for very-large concrete specimens affected by ASR and the need for additional research on multi-axially loaded concrete specimens with ASR.

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