Non-destructive monitoring of fiber dispersion in fiber reinforced concrete: a comparison between different methods

The major advantage of incorporating fibers into self-consolidating concrete (SCC) is the achievement, thanks to the elimination of compaction and vibration and to the rheological stability of the SCC matrix, of a randomly uniform dispersion of fibers within structural elements. Monitoring of fiber dispersion related issues through a non destructive either time- and cost-effective method becomes hence a crucial need in the sight of developing “ad-hoc” quality control procedures. These have also to be meant as instrumental to anticipate undesired scattering of expected mechanical properties due to poor fiber dispersion. In this paper fiber reinforced concrete self-compacting (FRSCC) cylinders, cored from beams cast for material characterization according to Model Code recommendations, have been monitored by means of different non-destructive and destructive techniques. The reference ND method, recently developed by the authors, is based on magnetic inductance properties of fiber reinforced cementitious composites (FRCCs). For the sake of comparison X-ray imaging and fiber counting after specimen crushing have also been employed. The quantitative prediction that can be garnered by each method will be cross-compared and finally compared with destructive measures, also in order to address an evaluation about their effectiveness and address the use of either method for quality control of the actual fiber dispersion in existing FRCC structures.