Vibro-acoustic modulation to detect and localize alkali-silica reaction (ASR) induced macro-cracking in concrete structures

In this work, we investigate the suitability of a novel dynamics-based method, namely vibro-acoustic modulation (VAM), for the detection and localization of cracks caused by the alkali-silica reaction (ASR). ASR is a chemical reaction between the cement and certain aggregates containing amorphous silica. In a VAM test, the structural component is excited using two frequencies. The frequency modulation (and hence the nonlinear structural behavior) appears as sidebands around the higher (probing) frequency in the linear spectrum (LS) 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 [1]. We perform laboratory experiments to investigate VAM-based damage diagnosis in thick concrete components. We describe laboratory testing on a cement slab containing four pockets of reactive aggregates placed at known locations. Our experiments 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.