The effect of tensile and bond characteristics of NiTi shape memory alloy, steel and polypropylene fibres on FRSCC beams under three-point flexural test

Abstract

This paper reports a study on the use of nickel-titanium (NiTi) shape memory alloy (SMA), steel and polypropylene (PP) fibre as reinforcement in self-compacting concrete (SCC) to improve its load bearing capability and fracture resistance. The fibre’s type and its property between fibre and concrete matrix significantly influence the flexural performance of fibre-reinforced SCC (FRSCC), thus, the single fibre tensile property and the pull-out property between fibres and concrete matrix were studied prior to flexural strength test. In addition, in order to trace the failure and fracture development easily during the flexural strength test, the specimens tested in this study had a 25 mm notch. It is found that the NiTi fibre had 189 MPa tensile strength and 105 N pull-out strength, respectively. This is attributed to the smoth surface and the geometry of the NiTi fibre used (no hooked-end). The flexural strength and fracture development of FRSCC depend on the fibre type and fibre volume fraction used. It is found that the flexural strength of NiTi SMAFRSCC increased from 15 kN to 17.5 kN and NiTi SMAFRSCC specimens showed a considerable flexural residual performance without any fibre deformation and rupture. The steel and PPFRSCC samples also showed increased flexural strength with increase of fibre volume fraction but steel FRSCC has the larger values due to its higher fibre tensile strength.