Assessment of ASR-induced development in concrete with natural and recycled reactive aggregates via resonant ultrasound spectroscopy coupled with imaging techniques

Numerous characterization techniques have been used to assess ASR-induced development (i.e., the formation of ASR products and cracks during expansion). Amongst those, scanning electron microscopy (SEM), coupled with energy dispersive X-ray spectroscopy (EDS), is a well-recognized technique enabling assessing the presence, morphology, and composition of ASR products. However, the correlation between ASR products' amounts and physicochemical features with induced damage (i.e., crack formation and impact on the mechanical performance of the affected concrete) via SEM is purely qualitative. Preliminary results showed that resonant ultrasound spectroscopy (RUS) could be a suitable technique to evaluate ASR-induced damage because it allows assessing the corresponding changes in the linear viscoelastic properties. Nonetheless, a systematic study fully demonstrating its potential to appraise ASR-induced expansion and deterioration, especially from ASR originating both from natural and from recycled aggregates, is still lacking in literature. This work aims to quantitatively appraise ASR-induced products and associated deterioration by the coupling of SEM-EDS and RUS, particularly a version thereof called SIngle MOde RUS (SIMORUS). Concrete mixtures incorporating highly reactive natural and recycled fine and coarse aggregates were cast and stored in conditions accelerating ASR development. At 4, 11, 16, 24 and 36 weeks, the samples were characterized by the abovementioned techniques. Quantifications of ASR-induced damage proxy parameters (i.e., Young’s, E, and shear, G, moduli), and the respective quality (Q-)factor, were performed over time. The results reported here suggest that SIMORUS is a promising technique to describe the impact of the ASR-induced development on the linear viscoelastic properties of an affected concrete. However, as shown, such an impact depends on the reactive aggregate type used in the mixture.