Experimental investigation on axial compressive and splitting tensile behaviour of reinforced concrete with a low content of hybrid steel fibres

This study intends to explore how the hybrid steel fibre reinforcement with a low content affects the mechanical characteristics of concrete. The axial compression properties of hybrid steel fibre-reinforced concrete (HSRC) were systematically investigated regarding stress-strain curves, failure modes, elastic modulus, and toughness. The crack propagation and fracture process of HSRC were analyzed based on the cumulative crack width and horizontal strain field. The results showed that the micro-straight steel fibre (mSF) demonstrated a more pronounced influence on post-peak stress retention in the axial compression test, whereas macro hooked-end steel fibre (MHF) positively affected the peak strain enhancement. The average peak stress of the HSRC increased by 8.6 % higher than that of H 40 and 16.4 % higher than that of S40. 40 . It is noteworthy that the mixing of steel fibres at a low fibre content was detrimental to the compressive toughness. The splitting tensile test showed a transitional stage before the HSRC reached its peak load, during which the load steadily increased and crack propagation slowly occurred. Moreover, the digital image correlation (DIC) measurement results suggested that mSF can enhance the internal quality of concrete. The study contributes to a deep understanding of the synergistic reinforcement mechanism and the fracture processes in HSRC.