Abstract. An experimental study was performed to utilize acoustic emission (AE) intensity analysis for the assessment of the concrete-to-steel bond behaviour of reinforced concrete structures. A total of 18 reinforced concrete unconfined prism samples were tested in a direct pullout test setup under incrementally increasing monotonic loading as being constantly monitored with attached AE sensors. The samples were cast using variable bar diameter (10, 20, 35 mm) and bar embedded length (50, 100, 200 mm). Different AE signals parameters were recorded throughout the tests until failure including rise time, counts, number of hits, signal strength, energy, amplitude, duration, and frequency values. Moreover, an AE intensity analysis was applied on AE signal strength results to produce two additional AE parameters: historic index (H (t)) and severity (Sr). Results demonstrated that cumulative signal strength (CSS) correlated well with different degrees of loss of bond from micro-cracking till bond splitting failure, which resulted in cover cracking or delamination. The review of CSS, H (t), and Sr curves allowed the detection of two progressive stages of bond deterioration (micro-cracking and macro-cracking) in all tested specimens. Intensity analysis parameters (H (t) and Sr) were employed to create bond damage classification chart to evaluate the concrete-to-steel bond condition in reinforced concrete structures.