Direct tensile self-sensing and fracture energy of steel-fiber-reinforced concretes

Based on the experimental tests, the tensile self-sensing and fracture energy of steel-fiber-reinforced concretes (SFRCs) were focused to investigate. Firstly, the plain mortar matrix of SFRCs produced the strain-softening behavior and no self-sensing ability. Secondly, among six fiber types with same amount 1.5 vol.-% as follows: macro twisted (T30/0.3), macro smooth (S30/0.3), macro hooked (H30/0.375), meso twisted (T20/0.2), meso smooth (S19/0.2) and micro smooth (S13/0.2), the T20/0.2 revealed the highest first gauge factor (GFcc) and first-cracking strength whereas the S30/0.3 produced the highest first-cracking strain. Thirdly, the strain-sensing capacity of SFRCs using macro twisted fiber was observed to increase with increasing of fiber content in range of 0–2.0 vol.-%. Fourthly, in evaluating three SFRC matrices with same amount 1.5 vol.-% macro hooked fibers including M1 (control), M2 (added CB), M3 (added GGBS), M2 produced a significant enhancement in both self-sensing capacity and tensile strength while M3 produced a slight enhancement of them, in comparison with M1. Finally, the fracture energy of the investigated SFRCs were comparatively evaluated as follows: the ratio between elastic fracture energy and total fracture energy was the lowest, from 0.02 to 0.08 while the ratio between localized fracture energy and total fracture energy was the highest, from 0.38 to 0.82.