Assessment of anisotropic damage in ASR-affected concrete structures by utilizing acoustic emission

Assessing ASR damage through the elastic modulus (E-mod) is complicated due to the non-linear behaviour of cracked concrete, which can introduce testing artifacts. To address this, acoustic emission (AE) monitoring was applied during cyclic compression tests. AE data was used to define a critical load level, i.e. the maximum load at which no additional cracking occurred. By tracking high peak frequency events, it was possible to prevent high-energy AE signals associated with cracking. Limiting the loading below this threshold minimized test-induced damage. The stabilized secant E-modulus was then determined from subsequent cycles. This method resulted in E-modulus values 5–10% higher than after conventional testing. The load threshold varied with damage degree and crack orientation and is considerably lower than the commonly used load level at 40% of the compressive strength. These findings highlight the importance of AE-guided, damage-controlled testing protocols for reliable concrete mechanical performance assessment.