Toughness properties and fiber dispersion in vibrated and self-consolidating fiber reinforced concrete

The connections between mechanical properties of fiber reinforced concrete and fiber dispersion, as influenced by fresh state properties of the material and casting modalities, are investigated in this work with reference to mostly two-dimensional structural geometry, selected as representative of significant potential applications in precast construction industry (folded plate roof elements, structural topping in precast slabs etc.). Square plates 600 mm wide and 60 mm thick were cast with three different fiber reinforced concretes featured by different fresh state properties. Specimens were cast in different ways, allowing for either a radial spreading or a prevalent one-directional flow of the fresh mix in the moulds. After analyzing fiber dispersion through Alternate-Current Impedance Spectroscopy, beam specimens have been cut from the plates with their axis differently oriented with respect to the flow direction, and tested in 4 point bending, either according and upside-down with respect to the casting. The thus measured mechanical properties are going to be correlated to the detected fiber dispersion.