Effects of Alkali-Silica Reaction on the Fracture Behavior of Concrete

With the majority of nuclear power plants in the United States approaching their operational life span, it has become important to reevaluate their durability. In partnership with other research institutions, Oak Ridge National Laboratory (ORNL) has allocated resources to identify mechanisms for degradation of structural components in these power plants. Among these degradation mechanisms, alkali-silica reaction has proven to be common. The University of Tennessee–Knoxville has partnered with the Fusion and Materials for Nuclear Systems Division of Oak Ridge National Laboratory to evaluate the effects of this reaction.Alkali-silica reaction in concrete structures has become a subject of interest in the research community as well as in the field of structural engineering. Alkali-silica reaction (ASR) is a chemical process in concrete that involves the reaction of alkaline solution with amorphous silica present in many aggregates. The alkaline solution dissolves the silica within the aggregates and forms an expansive gel product. In the presence of water, the gel expands, which can cause internal stresses and subsequent cracking within concrete. This poses long term risks on the structural integrity of reactive concrete.At the University of Tennessee–Knoxville, a controlled environment was constructed to cure and monitor alkali-silica affected concrete specimens. This environment was used to develop specimens for testing of mechanical properties and monitor gel formation and expansion over time. Traditional testing was performed to evaluate the mechanical properties and the wedge-splitting test was performed to characterize fracture behavior. This thesis also investigates the effect of micro-crack orientation on the mechanical behavior. Additionally, a computer model was developed to simulate alkali-silica formation and loading of affected specimens.