The corrosion of reinforcement is a well-recognised problem in the maintenance of concrete structures that can lead to reduction of the cross-section of the rebar, thus weakening the load-carrying capacity of the structure. Under ordinary design conditions, cracks are allowed to appear in concrete beams. However, the existence of cracks can speed up the corrosion rate of reinforcement significantly. In this study, the corrosion activities of reinforcement in concrete beams with or without cracks under accelerated corrosion conditions were monitored using embedded cement-based piezoelectric composite sensors and the acoustic emission (AE) technique. The AEs generated by the initiation of localised corrosion and subsequent concrete cracks were successfully detected and recorded by a homeprogrammed DEcLIN monitoring system. Based on frequency domain identification, useful information was extracted to explain the process of deterioration of concrete structures. It was found that cement-based piezoelectric sensors show a good capability in AE detection and the beam with cracks corroded much earlier than the case without cracking, consequently resulting in early deterioration.