Strength and serviceability of continuous composite slabs with deep trapezoidal steel decking and steel fibre reinforced concrete

► Tests presented on two-span composite slabs with steel fibre reinforced concrete. ► Describes the effects of steel fibres on in-service and ultimate load response. ► Steel fibres provide effective negative moment crack control at interior supports. ► Steel fibres enhance the strength and deformation capacity of composite slabs. An experimental study is described of the behaviour of short-term static load tests on two-span composite slabs fabricated with deep trapezoidal decks and steel fibre reinforced concrete. The aim was to study the effects of varying the steel fibre dosage on the cracking behaviour at the negative moment region, on the redistribution of moments, on the end slip between the decking and the concrete, and on the load carrying capacity of the slabs. In total, 8 two-span composite slab specimens were cast and moist cured for a period of 14days and then loaded monotonically to failure at an age of at least 28days. In addition to the steel decking, one of the specimens contained no reinforcing steel and no steel fibres, four of the specimens were reinforced only with steel fibres in the concrete (with nominal fibre contents of either 20, 30 and 40kg/m3). In the other three specimens, welded wire-mesh was included over the interior support, one with plain concrete and two with steel fibres in the concrete. The concrete properties, including compressive strength, tensile strength, modulus of elasticity and fracture energy, were measured on companion specimens for every test slab. Compared to the plain concrete composite slab and the slab containing SL62 welded wire mesh in the negative moment region over the interior support, the slabs containing steel fibres in excess of 20kg/m3 provided significant improvements in the slip load and the peak load. In addition, at service load levels the fibres provided crack control that was of similar effectiveness to that provided by the SL62 mesh.