Steel fiber reinforcement for extruded prestressed hollow core slabs

An experimental investigation was conducted to assess the potential of steel fibres as secondary reinforcement in prestressed hollow core slabs. Following a brief laboratory study and a feasibility trial, a series of fibre reinforced extruded slabs were made at the premises of a local manufacturer and subsequently tested in shear: one of a number of potential modes of failure which cause concern in this type of slab because of the lack of shear or secondary reinforcement. The addition of the fibres increased both the ultimate strength and toughness of the slabs leading to safer and more controlled failures. The predictive equations of other researchers were shown to accurately estimate the shear strength in the case of plain hollow core slabs, but to overestimate the shear enhancement clue to adding steel fibres. Additionally, the effect of the manufacturing process, in which the concrete is compacted by rotating augers, on the fibre distribution and orientation was investigated. Whilst fibres were found to be randomly distributed within the cross-section, a tendency to align vertically within the webs was observed. This has particular relevance to the vertical shear performance.