Dynamics Testing for Alkali-Silica Reaction Diagnosis in Concrete.

This research is investigating a probabilistic framework for health diagnosis and prognosis of aging concrete structures in nuclear power plants. The current work focuses on degradation caused by ASR (alkali-silica reaction), which is a chemical reaction between the cement and certain aggregates containing amorphous silica – in the presence of water the ASR gel will expand causing damage to the concrete structure. Several different monitoring techniques — infrared thermography, digital image correlation (DIC), mechanical deformation measurements, nonlinear impact resonance acoustic spectroscopy (NIRAS), and vibro-acoustic modulation (VAM) —are being studied for ASR diagnosis of the specimen. This paper reports on the VAM study, which uses two simultaneous excitation frequencies; the interaction of these frequencies indicates damage through the presence of sidebands. Multiple resonant frequencies are considered along with their corresponding mode shapes. The possibility for damage localization is investigated.