<![CDATA[Acoustic emission (AE) a non-destructive testing technique that is specially used to detect active cracks. This technique was employed to evaluate crack propagation in the reinforced concrete specimens during static loading in the four-point bend test. Cracks were detected by an array of AE sensors which were fixed on the surface of a specimen. AE signals from crack activities were then recorded and analysed by the AE computerised system. The AE results from crack activities during static loading were classified into three stages of crack mechanisms. In the first stage, the AE sources were expected to appear from micro and macro cracks in the presence of pores, voids, mortar, sand, etc. in the concrete part. In the second stage the steel bars were deformed elastically. Here AE sources were attributed to continuously macro cracking in the concrete part and slip between steel reinforcing bar and concrete. In the third stage, when the steel bars were deformed plastically, AE sources were generated by large crack in both longitudinal and shear cracks due to high level of applied loading. This experimental work showed a very sensitive AE technique to detect crack growing in the reinforced concrete structure.]]>
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