Evaluating concrete affected by internal swelling reactions (ISR) using the extended version of the damage rating index (DRI)

Internal swelling reactions (ISRs) are distress mechanisms that compromise the service life of critical concrete infrastructure. The initiation, propagation, and cracking patterns associated with ISR can be analyzed via the damage rating index (DRI), a semi-quantitative microscopy procedure used to assess concrete deterioration. Although the DRI provides a systematic method for evaluating the causes and extent of deterioration, subjectivity and variability often hinder its application. This study depicts the distress features within the DRI analysis to understand their effects on expansion and mechanical responses. The findings indicate that each of the distress features, specifically the presence of closed and opened cracks within the aggregate, along with cracks in the cement paste and debonded aggregates, exerts distinct influences on the mechanical responses of the material. Furthermore, this research's key findings show that the average counts of distress features and the interquartile ranges of the count distributions for the various distress features and mechanisms resulted in predictions of expansion with R 2 values greater than 0.83. Variability in determining the extent of deterioration was then addressed using convergence plots, validating a sample size of 75 ± 25 cm 2 for laboratory-made specimens as sufficient. Finally, the deconstruction of the distress feature counts enabled the creation of reference distress feature count ranges based on each expansion level and distress mechanism.