Abstract: The strength and damage patterns of no-fines concrete are investigated with the help of PFC3D. The three-dimensional structural models of no-fines concrete composed of two typical shapes of pebble aggregate are established with varied porosity (0.26, 0.28, 0.30, 0.32, 0.34, 0.36, and 0.38). The stress and deformation of each test block under uniaxial compression test are simulated. In the meantime, the development of internal fractures during the uniaxial test is monitored. Research results reveal that (1) with the increase of porosity, the number of particles and the number of particles in contact decrease gradually, and the uniaxial compressive strength of the model decreases also. (2) The stress-strain curve of no-fines concrete obtained from numerical simulation is consistent with that of porous concrete obtained by previous tests by other scholars, indicating that PFC could well simulate the stress-strain features of no-fines concrete. The uprising segment of stress-strain curve of no-fines concrete is more linear than that of conventional concrete; in the downward segment, unloading gets more swiftly, implying that no-fines concrete is highly brittle. (3) Mostly found in the vicinity of corners and loading surface, fractures of no-fines concrete intensifies with the increase of loading, and even expands dramatically until penetration after peak strength is reached. (4) In accordance with the locations of fractures at peak strength, the vulnerable zone of no-fines concrete is defined as the part left when inscribed sphere is removed, which accounts for 47.6% of the total volume of test block, and in which fractures takes up over 69%. The research findings offer reference for the study of mechanics and damage mechanism of no-fines concrete

Key words: no-fines concrete, PFC3D, uniaxial test, damage pattern, vulnerable zone