Understanding of ASR-Induced Development Caused by a Highly Reactive Fine Aggregate Through Advanced Imaging Techniques

Over the recent decades, numerous research projects were developed to better understand the alkali-silica reaction (ASR) development as a function of time, especially the formation of reaction products and its association with induced deterioration. Several imaging techniques were used in this regard, such as scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS). Although SEM/EDS has been ever since well recognized as a powerful tool to detect the presence and to characterize the morphology and composition of ASR-products in concrete, the appraisal of ASR-induced damage development and degree via SEM alone is not fully possible, because of the intrinsically altering nature of the respective specimen preparation. This work aims at appraising ASR-induced products formation and the associated deterioration through a coupled SEM/EDS and X-ray micro-tomography (XMT) analysis. Concrete mixtures incorporating a highly reactive fine aggregate were fabricated and stored in conditions enabling ASR development. At 3–4, 11, 16, and 24 weeks, the samples were prepared and tested with the three techniques. Preliminary evaluations show quite promising results in terms of ASR-secondary products formation and composition along with cracks generation and propagation. Further quantitative analysis will help to fully describe ASR-induced deterioration mechanisms triggered by highly reactive fine aggregates.