Bond between epoxy-coated reinforcing bars and concrete under impact loading

Abstract
The bond between epoxy-coated reinforcing bars and concrete under static, high strain rate, and impact loading was studied for plain concrete, polypropylene fibre reinforced concrete, and steel fibre reinforced concrete. The bond stress, slip, crack development, the bond stress–slip relationship, and the fracture energy during the bond-slip process were investigated experimentally. The results were compared with those for uncoated reinforcing bars. It was found that for epoxy-coated rebars, the bond resistance decreased, in terms of the maximum local bond stress and the average bond stress; wider cracks developed during the bond process; and the fracture energy during bond failure decreased. It was also found that the influence of epoxy coating on the bond behaviour for push-in loading was much more significant than for pull-out loading. However, steel fibre additions at a sufficient content, and higher concrete strength, can mitigate the above effects to a considerable degree. Polypropylene fibres were much less effective in this regard than steel fibres. Key words: epoxy-coated rebars, bond, fibre concrete, strain rate, impact steel fibres, polypropylene fibres, concrete, high strength concrete.