Classification of alkali–silica reaction damage using acoustic emission: A proof-of-concept study

• Acoustic emission (AE) was used to monitor alkali–silica reaction (ASR) damage in concrete specimens.
• The rate of AE activity showed a good correlation to the rate of expansion from ASR damage.
• ASR damage was assessed using petrographic examination and related to AE parameters.
• An AE based chart was developed to classify ASR damage.

Alkali–silica reaction (ASR) is a concrete degradation mechanism that generates internal cracks in concrete material as a result of volumetric expansion. This mechanism is currently affecting many structures throughout the United States, especially in Texas and the Pacific Northwest. In this study, an accelerated ASR test was implemented at the University of South Carolina Structures and Materials Laboratory on twelve specimens with dimensions of 3 × 3 × 11.25 in. (76 × 76 × 286 mm). The specimens were cast using reactive aggregate and mortar with a high alkali content and placed in a controlled environment with high humidity and temperature to accelerate the reaction, while being continuously monitored with acoustic emission. Length change measurements and petrographic examination were conducted periodically to serve as benchmarks for ASR damage detection. Micro-cracking associated with ASR damage was detected by AE and the rate of AE activity was correlated to the rate of ASR damage. An AE based Intensity Analysis chart that enables ASR damage classification in correlation with petrographic analysis was developed.