Modelling of alkali–silica reaction based on time-resolved micro-computed tomography imaging

The progress of alkali–silica reaction (ASR) in specimens consisting of reactive glass aggregate in a cement matrix was monitored using X-ray micro-computed tomography. The technique was used to study the formation of cracks in both aggregate particles themselves and the matrix, as well as to measure expansion. A model, based on the progressive formation of cracks in concrete, is developed and used to further examine the process of ASR, and the manner by which approaches used to control ASR expansion function. It is concluded that ASR-controlling measures work by reducing available alkali ions, but also by weakening the cement matrix. This means that a similar number of cracks forms in both highly expansive instances of ASR and instances where expansion is limited by the use of controlling measures, with only crack width differing.