Post-fire Structural Properties of Hot-Rolled and Cold-Rolled Duplex Stainless Steel Reinforcing Bar

This paper is concerned with the behaviour of duplex stainless steel reinforcing bar following exposure to elevated temperatures from a fire followed by subsequent cooling. The study focuses on duplex grade 1.4362 reinforcing bar, and includes both hot-rolled and cold-rolled variants. Grade 1.4362 duplex stainless steel reinforcement has become a popular choice for reinforced concrete owing to its excellent combination of outstanding mechanical behaviour and corrosion resistance as well as cost-effectiveness. There is no information on the post-fire performance of duplex 1.4362 reinforcing bar available, despite being necessary for an engineer that may wish to study the structural integrity of a relevant structure following a fire. To address this gap in the existing knowledge, this paper presents a detailed discussion and analysis based on a series of laboratory experiments comprising mechanical and metallurgical testing. It is shown that grade 1.4362 duplex stainless steel reinforcing bars perform unlike any other types of carbon steel or austenitic stainless steel rebars, owing to the austenite-ferrite grain boundary, and the associated instabilities. Based on the results presented in this paper, a series of recommendations are proposed for the post-fire mechanical property retention factors that can be used in assessment and design. Finally, this paper aims to highlight the potential for rehabilitation and salvage of existing reinforced concrete structures following a fire, and aid in the prevention of unnecessary demolition and replacement.