Flexural Behaviour of Precast Steel Fibres Reinforces Concrete Composite Slabs with Different Shapes

This paper aims to disclose the flexural behaviours of concrete composite slabs (CCSs) with different materials and shapes. For this purpose, eight types of CCSs were prepared with three kinds of materials (i.e. natural concrete, steel fibre-reinforced slit ceramic aggregate concrete (SFRSCAC) and steel fibre-reinforced recycled aggregate concrete (SFRRAC)) and five different shapes (i.e. rough surface, rectangular-rib, cross-rib, bar truss and bar truss with rectangular-rib). Thus, eight full-size CCS were established and subjected to static load tests. Then, the load-deflection curves, load-rebar strain curves, load-concrete strain curves and strain-depth relationship were analysed in details. Finally, the calculation methods were proposed for the cracking and ultimate bending moments of the CCS. The results show that: (i) under the vertical load, the eight specimens shared similar flexural behaviours and all underwent the elastic phase, elastic-plastic phase and failure phase; (ii) the crack resistance of both SFRSCAC and SFRRAC were greatly improved through the addition of steel fibres; (iii) the shape of the bottom plate has a major impact on the flexural performance of the CCS, especially in the elastic-plastic phase and the failure phase; (iv) the effect of the bottom plate should be considered in the calculation of the cracking moment, and the contribution of steel fibres to the tensile zone should be taken into account for the calculation of ultimate bending moments of the CCSs fabricated by SFRSCAC or SFRRAC.