Investigation of adhesion-reinforcement shear behavior in perlite-substituted concretes based on axial tensile tests under high temperature conditions

Reinforced concrete structures are exposed to various external effects throughout their service life, which may cause deviations in structural performance from the intended design criteria. One of the most common and critical external factors leading to damage in reinforced concrete structures is high temperature. Elevated temperatures adversely affect structural performance by degrading the mechanical properties of both concrete and reinforcement, which are the two main components of reinforced concrete systems. One of the most critical parameters governing this performance degradation is the bond relationship between reinforcement and concrete, which constitutes the fundamental mechanism of reinforced concrete behavior. Micro- and macro-cracks that develop within the concrete matrix due to high-temperature exposure lead to significant reductions in bond strength. In this context, the present thesis investigates the variation of bond behavior in reinforced concrete elements under the influence of elevated temperatures through pull-out tests. The study compares reinforced concrete specimens with compressive strengths of 25 and 40 MPa produced using perlite aggregate—known for its superior thermal properties compared to conventional aggregates—with their conventional aggregate counterparts (control specimens). All specimens were tested under temperature exposures of 25 °C (reference), 200, 400, 600, and 800 °C. The results indicate that although perlite aggregate concretes exhibit greater mass loss under high temperatures, they demonstrate a more advantageous and stable performance in preserving the reinforcement–concrete bond compared to conventional concretes.