Bond performance of reinforcing bars in fly ash-based engineered geopolymer composites under uniform and nonuniform corrosion conditions

While concrete is the most popular building material in the world, corrosion of the steel reinforcement in reinforced concrete (RC) structures poses ongoing durability issues. In this study, the effects of alkali activator modulus, concentration, and different corrosion periods are rigorously investigated utilizing accelerated electrochemical corrosion techniques under both uniform and nonuniform corrosion conditions. Bond stress and bond stress deterioration are evaluated to provide a thorough examination of corrosion-induced fracture formation through pull-out experiments. X-CT 3D imaging is also used to understand the spread of rust in both corrosion scenarios. Results show that mixes with lower alkali activator modulus and higher alkali activator concentration might result in better bond stress preservation and higher ultimate bond stress under corrosion. High bond stress, however, usually corresponds to a more brittle failure when subjected to pull-out force. Nonuniform corrosion treatment can result in differential rust formation and a quicker bond breakdown between steel bars and engineered geopolymer composites (EGCs) than uniform corrosion. Furthermore, under corrosion, EGCs with high alkali activator modulus tend to form more penetrating cracks with limited width and depth. Both narrow and deep penetrating fractures can arise from EGCs with low alkali activator concentration.