Flexural behaviour of one-way slabs with stainless steel and fibre reinforced concrete under elevated temperature

• Experimental study of post-fire RC slab behaviour at 700°C. • First flexural test on stainless steel reinforced slabs after fire. • Steel fibres enhanced strength, ductility, and fire resistance. • Plastic wire concretes showed poor post-fire capacity and stiffness. • Finite element modelling and ACI 318-19 predictions agreed with experiments. This study investigates the post-fire flexural performance of reinforced concrete (RC) slabs, with novelty in evaluating the combined effects of reinforcement type, hybrid fibre concretes, and thermal exposure at 700°C for two hours. An experimental program was conducted on eight one-way simply supported slabs (2,200 mm long) tested under two-point loading. Key variables included reinforcement type (steel vs. stainless steel), mix composition (ordinary Portland cement, 1% steel fibre concrete, or a combination of 2% plastic wire and 1% steel fibre concrete), and thermal exposure (heated vs. unheated). Experimental results were compared with finite element simulations in ABAQUS and predictions from ACI 318-19. The results showed that plain stainless-steel reinforcement experienced severe bond deterioration, reducing load capacity by 67.3% and initial stiffness by 71% relative to conventional steel. Incorporating 1% steel fibres enhanced ultimate strength by 6.5% and ductility by 0.5%, while heated fibre-reinforced slabs achieved 2.6 times the stiffness of a heated ordinary concrete slab. In contrast, plastic wire mixes reduced load capacity by 19–20.5% and stiffness by up to 72%. ACI 318-19 equations accurately predicted ribbed carbon steel performance but underestimated that of plain stainless steel due to a weaker bond with concrete. Experimental results were validated by numerical simulation, and overall findings highlight the potential of steel fibres to enhance fire resistance and support the design of safer, fire-resilient RC slabs, offering practical guidance for future structural applications.