Dynamics-based testing to localize macro cracking due to alkali-ailica reaction in concrete

Abstract

This work focuses on the diagnosis of degradation in concrete structures caused by the alkali-silica reaction (ASR): a chemical reaction between the cement and certain aggregates containing amorphous silica. The suitability of vibro-acoustic modulation (VAM), is investigated for the detection and localization of cracks caused by ASR. In a VAM test, the structural component is excited using two frequencies. The frequency modulation appears as sidebands around the higher (probing) frequency in the power spectral density (PSD) of the measured response in the neighborhood of the damage zone. A map of the magnitude of such sidebands can be used to detect and localize the damage. We conduct laboratory experiments on four concrete blocks with varying levels of reactive aggregates and different amounts of steel reinforcement, and show that VAM-based testing with optimized test parameters and suitable sensor density can potentially be used to detect and localize cracks in thick concrete structures.