The Fire Performance of Polymer Fibre Reinforced Composite Concrete Slabs

Dispersed polymer macro-fibres have recently started to be used within steel-concrete composite slab floors to reduce the need to lift, position and fix steel reinforcing fabric. Polymer fibres can be used to replace light reinforcing meshes required for crack control. This paper investigates the performance in fire of a macro-synthetic polymer-fibre-reinforced composite slab system. The performance-based fire design of a composite floor slab can take advantage of secondary load carrying mechanisms that develop during a fire, the most significant of these being catenary (tensile membrane) action. For a slab to act in tensile membrane action, it must contain sufficient reinforcing to provide the required tensile capacity. The polymer macro fibres used to reinforce concrete typically soften with increasing temperature and melt by around 160 degrees C. There is therefore a concern that by replacing a steel reinforcing mesh with the polymer fibres, there will be no secondary load-carrying mechanism and the slab may be more vulnerable than a traditional slab exposed to the same fire condition. However, the interaction between the thermal gradient in the slab, the thermo-mechanical properties of the concrete including the fibres, and the restraint condition at the slab boundary is far from clear. This paper presents preliminary results from computational research into the performance of polymer fibre reinforced concrete slabs. It focuses upon model slabs designed to capture the underlying mechanisms that govern their thermal and structural behaviour during a fire, and demonstrates that the introduction of polymer fibres into concrete enhances the ability of a floor slab to carry load during a fire. The performance of the polymer fibre-reinforced concrete slab considered is comparable to that of an equivalent slab with traditional steel fabric reinforcement.