High-temperature bond performance of carbon and stainless steel reinforcement in concrete: A material-level experimental study with functional, economic and environmental approaches

The structural integrity of reinforced concrete structures is highly conditioned under extreme conditions depending on the adherence between steel and concrete. This research studies the behaviour at high temperatures (200 °C and 400 °C) and different cooling techniques, rapid (in water) and slow (in air) of two types of steel, austenitic stainless steel (EN 1.4301) and carbon steel (B500SD). For this purpose, compression and indirect tensile tests were carried out on concretes of characteristic types, C30 and C50, evaluating the thermal and cooling impact on the mechanical properties. Experimental tests indicate a significant loss in the strength capacity of the concrete as a function of increasing temperature, ranging from 70% for compression to 50% for tensile in case of rapid cooling. For the adherence test, stainless steels showed a better compromise than carbon steels, both for C30 (5.93 MPa) and C50 (6.88 MPa) concretes. However, its higher unit cost and carbon footprint limit its competitiveness against carbon steel, especially in conventional structures. Nevertheless, there is an opportunity for its application in structures used in environments with a risk of high temperatures, provided that its production processes are optimised. This study adds to the knowledge about the behaviour of reinforcement in extreme conditions and provides important data for optimising structural design, together with a critical analysis of sustainability for material selection.