In the framework of the design and production of concrete building materials, Alkali Silica Reaction (ASR) damages are amongst the most commonly diagnosed durability problems for aged infrastructures; but, despite years of study, the mechanism of ASR is still not completely understood.
To gain insights into the effect of ASR on the mechanical performance in commercially-produced high-strength concrete samples submitted to different environmental and life service conditions, in-situ X-ray computed microtomography measurements have been performed under compressive strength tests. This approach allowed for the investigation of the microstructural properties and to follow the formation and evolution of cracks within the imaged volume, in order to disclose the failure mechanisms.
Automated crack detection algorithms and digital volume correlation analysis enabled the description of the sample microstructure and describe the deformation mechanisms. The sample microstructure evidenced patterns of cracks which were more developed in the samples affected by the deterioration process. The crack propagation resulted similar in all the samples with the large prevalence of vertical cracks, as expected in this type of concrete undergoing compressive uniaxial strength test, sometimes following pre-existing microcracks and running at the interface between matrix and aggregate grains.
This study, complemented by optical microscopy, micro-Raman mapping, SEM/EDS and X-ray diffraction, allow to propose a weakening mechanism related to the expansive reactions, which further reduces the strength at the interface between reactive aggregates and cement matrix, and to the number of newly formed cracks.
A thorough understanding of the dynamic of the process can be relevant in the framework of new building solutions and durability of materials under severe life service conditions enabling a more reliable prediction of their remaining life service.