Dynamic compressive behaviour of recycled tyre steel fibre reinforced concrete

This paper presents a systematic experimental study on dynamic compressive behaviour of recycled tyre steel fibre (RTSF) reinforced concrete. The use of RTSF can not only enhance the mechanical properties and sustainability of cementitious materials but also reduce the environmental impact of waste tyres. A series of tests were conducted to investigate the effect of RTSF content (0.5%, 0.75%, 1.0% and 1.25%) on workability, air content and compressive strength of concrete as well as the dynamic compressive behaviour under various impact velocities (35, 55, 75, 95, 110 and 125 s−1). For comparisons, plain concrete without fibre and concrete reinforced with 1.0% industrial steel fibre (ISF) were regarded as the reference mixtures. The split Hopkinson pressure bar (SHPB) was adopted to study the dynamic failure pattern, dynamic compressive strength, dynamic increase factor (DIF), energy dissipation and toughening mechanism. Results indicate that with increasing RTSF content, the slump of concrete was reduced while its air content was increased. At the same fibre content (1.0%), RTSF reinforced concrete exhibited a higher workability and air content than ISF reinforced concrete due to the different fibre shape and aspect ratio. The compressive strength of concrete at various strain rates went up with the increase of RTSF content from 0 to 0.75% but reduced with the further increase of RTSF content from 0.75% to 1.25%. DIFs of all mixtures were closely related to strain rate. The optimal dosage of RTSF for concrete was found to be 0.75%, considering workability, compressive strength, and dynamic compressive performance