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Catastrophic failures due to corrosion are among the most common phenomena in pre-stressed concrete pipeline, which has been reported in Iran, as well. Structural health monitoring, quick assessment and timely detection of corrosion in its early stages with active in-situ sensors is could prove vital in avoiding such hazards. Acoustic emission is a non-destructive technique that can be used to give a better insight on the structural state of such concrete structures. However, the interpretation of the AE measurements is quite challenging and may actually be even more difficult when the concrete is cracked, which would affect the material and structural properties of concrete pipes. The amplitude distribution of the acquired signals is very sensitive to micro-cracking. This paper presents the results of an experiment conducted in the laboratory of Middle East Technical University on pre-stressed concrete pipe for determining the amplitude attenuation and path of acoustic wave propagation and frequency spectrum before and after corrosion using Hsu-Nielsen pencil-lead break source and applying accelerated corrosion. The results from the laboratory tests indicate that since the changing in amplitude and wave propagation path is negligible before and after corrosion, the AE measurements can be used as an accurate method for tackling the problem mentioned above. Then the performed AE measurements are reported and results discussed.

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Corrosion in spiral steel prestressed wires tensioned around core are one of the major weaknesses of prestressed concrete pipes which their untimely detection can cause sudden failure and damages. To date, these kinds of pipes are used and produced in Iran and their abrupt failure due to corrosion has been experienced. In this study acoustic emission monitoring in prestressed concrete was used to investigate the corrosion. An approximately full-scale experimental sample pipe is made in Middle East Technical University laboratory. The pipe is loaded by internal water pressure and accelerated corrosion applied to the sample and the resulted acoustic emission signals are recorded using piezoelectric sensors during corrosion. The sample is tested under wetting and drying cycles frequently for corrosion detection in which during the experiment, pipe inside pressure was fluctuated and Kaiser Effect was studied in different conditions. Experimental results show significant changes in some gained acoustic emission parameters as the pipe work pressure increases to higher amounts. It is shown that the changed AE parameters can be used for damage prediction, condition assessment and corrosion detection of prestressed concrete pipelines.