Uniaxial compression failure characteristics of 60-year-old bridge concrete under different loading rates

In order to study the failure characteristics of old age concrete, five different loading rates (0.02 mm/min ~ 1.5 mm/min) were used to carry out uniaxial compression tests on 60-year-old bridge concrete cores. The Digital Image Correlation (DIC) method was used for non-contact full field deformation observation of crack evolution. At the same time, the cumulative counts, event number and amplitude were used as the characterization parameters of Acoustic Emission (AE) technology to monitor the concrete damage process. The results show that the ultimate strength, the number of cracks, and the severity of failure of aged concrete increased with the increase of loading rate, while the number of AE events decreased with the increasing loading rate. And the compressive strength of the old bridge concrete is 26.3 MPa, which is 24.5% lower than the design strength of 35 MPa.There is an obvious compaction stage of aged concrete under different loading rates compared with early age concrete, and the slope of the stress-strain curve in this stage increased continuously. When the specimen was damaged, the initial cracks developed vertically and then obliquely, the overall failure of the specimen is caused by tensile cracks.