Effect of aggregate size on concrete behaviour under lateral confinement : test

This paper presents an experimental study on the effect of coarse aggregate size on the mechanical behavior of passively confined concrete. In total, 32 concrete cylinders with different aggregate sizes and thicknesses of fiber reinforced polymer (FRP) jacketing were tested under monotonic axial loading. From the test results, it is shown that the aggregate size does not affect behavior of unconfined concrete and the beginning stage of stress-strain curves of FRP confined concrete. However, in the transitional stage of stress-strain relationship of FRP-confined specimens, the concrete with larger aggregates has a higher stress. The second stiffness of stress-strain relationship is not affected by the aggregate size. Furthermore, at the ultimate stage, larger aggregates cut FRP to failure more easily and earlier. Hence, the ultimate strain has a decreasing trend with increasing aggregate size. Meanwhile, the ultimate strengths are similar for the specimens with different aggregate sizes because of the two aspects with increasing aggregate size: enhancing effect on stress in the transition stage and decreasing effect on strain in the ultimate stage.