Dynamic elastic properties of hardened experimental mortar bars affected by accelerated alkali–silica reactivity test: a laboratory approach

The evaluation of ASR sensitivity of aggregates is of utmost importance due to durability and safety of structures and also due to economic reasons related to repairs or replacements of ASR-affected concrete. Laboratory tests for ASR detection rely mostly on petrographic examination and on laboratory expansion tests. The latter are mostly expressed in terms of length change (expansion) of experimental mortar bars subjected to the effect of alkaline environment. Along with this, recording of the propagating ultrasonic wave signal can increase reliability of test results. In the recent study, dynamic elastic properties of experimental mortar bars were recorded in both normal setting/hardening state (first 28 days) and in the conditions of accelerated ageing conditions in alkaline solution with elevated temperature (another 37 days). Setting/hardening of the studied materials under normal conditions was manifested by quasi-exponential P- and S-wave ultrasonic velocity increase. However, alkaline solution resulted in the rapid development of ASR phenomena in reactive aggregates and significant change of elastic wave velocities and other dynamic elastic parameters. Comparing various ultrasonic characteristics, dynamic ones (amplitudes, frequencies) proved significantly higher sensitivity and tighter correlation to length changes (expansion) cause by ASR than did the kinematic ones (elastic wave velocities, dynamic elastic moduli).