The alkali-silica reaction (ASR) is the source of one of the most deleterious durability issues of the worldwide concrete infrastructure. It consists of chemical reactions between aggregates and the alkaline pore solution. The ASR products lead to deformations and cracking and, consequently, extensive structural damage, causing major safety, economic and environmental issues. Since the first investigations (eight decades ago), some basic ASR (cracking) mechanisms have been discovered. However, a comprehensive understanding has not been achieved yet, due to its complex multiscale nature.
One of the major knowledge gaps stems from lack of characterization of the deformations and crack propagation at the mesoscale (few µm- few cm). Results from systematic non-destructive studies have been lacking, although they are necessary to track the ASR cracking. That is because the typical petrographic characterization techniques rely upon 2D microscopy (electron and optical), which require destructive
specimen preparations. X-ray tomography (XT), as a non-destructive technique, has been recently adopted, although, so far only in limited cases, mainly for simplified model systems and exploited only for qualitative analysis. [...]