ABSTRACT
Mechanical properties of concrete are generally evaluated by compressive strength, which is only an index at ultimate failure. Since compressive strength does not provide information about the internal state or fracture process, it is not appropriate for evaluation of concrete at lower stress levels, the levels at which concrete structures are actually used. For this paper, the use of acoustic emissions (AE) for evaluation of the condition of the bond between aggregate and mortar was investigated. The results show that AE hits measured at load levels between 20 and 40% within cylindrical concrete specimens depend mainly on bond crack occurrence, and that the influence of the state of the transition zone on bond crack occurrence can be evaluated by the relationship between the AE hit ratio and the load level.
