Abstract: Initial defects of concrete material play a great role in its deformation and failure properties. We conduct a series of uniaxial compression tests on the initial defects of different sizes and different inclination angles to explore their influence on the deformation behaviors and failure mechanism of concrete, and analyze stress-strain curves, acoustic emission characteristics, and images of crack propagation. The test results show that: (1) Compared with an intact specimen, the peak stress and peak strain in a concrete specimen with initial defects are reduced; the stress-strain curve shows a more obvious concave trend in initial loading stage, and a gentler slope in unloading stage. However, the influence on residual strength presents no obvious pattern. (2) The failure process of concrete with initial defects has four stages of crack development: initiation, propagation, coalescence, and through crack failure. (3) Tensile failure dominates at inclination angles of 0° and 90°, while initial defects at 30°, 45° or 60° cause shear failure along their paths.

Key words: concrete, initial defect, acoustic emission technology, failure properties, uniaxial compression