Appraisal of visual inspection techniques to understand and describe ASR-induced development under distinct confinement conditions

Conventional visual inspection techniques are generally qualitative and therefore unable to provide accurate information on the extend of alkali-silica reaction (ASR)-induced damage development in concrete. Therefore, improving and finding more accurate visual procedures is extremely important for a better condition assessment and development of management protocols of ASR-deteriorated infrastructure. This work intends to assess ASRinduced damage development on distinct surfaces of thirty-two concrete blocks displaying various confinement configurations (none, 1D and 2D) and incorporating different aggregate types (reactive fine and coarse) through the use of distinct visual and microscopic techniques. Three expansion levels were selected for analysis (0.08%, 0.15% and 0.25%) and once reached, various visual inspection techniques (qualitative, semi-quantitative and quantitative) along with the Damage Rating Index (DRI), a semi-quantitative petrographic analysis, were conducted on the surface of the affected members. Moreover, cores were extracted from the three different directions (longitudinal, transverse, and vertical) of affected blocks at selected expansion levels, and the DRI was performed on those with the aim of comparing the damage on the surface and core of the affected blocks. Results show that the higher the confinement, the higher the surface damage on the affected members. Furthermore, the DRI results obtained from the cores and surfaces of the blocks demonstrate that the surface of the members experienced significantly higher amount of damage than the core specimens. Finally, a qualitative model is proposed to describe ASR-induced surface deterioration in concrete under distinct confinement configurations.

Automated summary

Conventional visual inspection techniques are unable to accurately assess the extent of alkali-silica reaction-induced damage in concrete. This study aims to evaluate the development of ASR-induced damage on different surfaces of concrete blocks using visual and microscopic techniques. Results show that higher confinement leads to increased surface damage in affected members.