Ultrasonic-acoustic emission hybrid system for monitoring concrete structures affected by alkali-silica reaction

Alkali-silica reaction (ASR) in concrete can cause internal cracks resulting in structure deterioration. Current ASR assessment and monitoring programs still rely on visual inspection of the concrete surface cracks or measuring the concrete expansion. These methods cannot provide a comprehensive assessment or the mechanical information needed for a lifetime prediction. In this work a hybrid health monitoring system using active ultrasonic testing and acoustic emission testing for monitoring ASR damage in concrete is proposed. The two systems share the same sensors and work independently without mutual interference. This system was deployed on three large concrete beams: control, ASR unconfined and ASR 2D-confined samples. The relative velocity change is extracted from the ultrasonic signals, and have a good agreement with the AE results, number of cumulative hits. These results are also confirmed by the volumetric expansions. The initiation of rapid alkali-silica reaction inside the two ASR samples is detected by the ultrasonic method and expansion measurement and is confirmed by the AE results. The proposed hybrid monitoring system can provide a comprehensive solution for long-term monitoring of ASR damage in concrete.