Study On Deterioration Of Band Behavior In Concrete Elements With Corroded Rebar Based On Acoustic Emission Technology

Favorable bond strength supplies insurance to resist loads and deformations for concrete combined with steel bar in reinforced concrete. Bond deterioration, caused by corroded rebar, is one of the main reasons for the decrease of durability in reinforced concrete construction .Acoustic emission(AE) technique, a useful method for the investigation of damages in metal and composite materials, is extensively applied to a variety fields in civil engineering. This paper carries out pull-out tests on different degrees of corroded specimens ,and uses the AE technique to detect damaging specimens during loading, and applies micro-analysis method to explain and evaluate the bond deterioration process of the specimens . Several results has been gained as follow:1,Through lead-breaking and stimulant loading tests, reasonable detecting parameters, such as threshold ,time parameters, velocity of signal, attenuation are gained .These tests also supply some important and available ways to chose detecting parameters in concrete AE detection.2,The bond strength of different degrees of corroded specimens are studied through pull-out tests. The pull-out tests revealed the following varied degrees of bond strength in corroded specimens: the law of average bond resistance coinciding with the slipping quantity of rebar ;the law of bond strength coinciding with corrosion degrees ,and the law of slipping quantity at the ultimate bond strength coinciding with corrosion degrees as studied in post-corroding , post-cracking and cracking stage.3,Based on the traditional analysis of basic issues in pull-out tests, this paper also considers AE parameters .Through parameter analysis, characters of AE parameters coinciding with the changing of stress level is studied. In addition, inner damages and its intensities in samples were identified during the loading process through correlating graph ,risetime, duration, amplitude and frequency analyses. By means of AE source location technique ,the position of cracks and their progress tendency was ascertained. At last, the Kaiser effect in concrete material during bond destruction was proven.