Comparative study on fracture evolution in steel fibre and bar reinforced concrete beams using acoustic emission and digital image correlation techniques

In recent decades, the demand for sustainable construction practices has increased, but raw materials such as reinforcing steel remain scarce. Therefore, steel fibres have emerged as a popular and sustainable choice in the construction industry, offering a cost-effective alternative to traditional steel bar reinforcement for both flatwork and elevated structures. The purpose of this study is therefore to compare the performance of fracture behaviour between steel fibre-reinforced concrete (SFRC) and steel bar-reinforced concrete (SBRC) beams subjected to three-point bending. The fracture process was monitored by using two non-invasive techniques: acoustic emission (AE) and digital image correlation (DIC). The damage level was identified by characterizing the parameter-based AE data such as hit rate, energy release, count, rise time, amplitude, and signal strength. DIC images were employed to visualise the crack propagation in parallel with the AE data. To further understand the fracture characteristics, the integration of 2D source localization of AE events (based on local AE fracture energies) with DIC results was investigated. The parameter-based AE results showed that SBRC beam experienced a high density of AE hits with large peak amplitude events that were accelerated during the pre-peak loading phase. The Ib-value analysis revealed that SBRC beam exhibited a higher degree of fracture magnitude during the primary crack development process than SFRC beam. Following the main cracking stage, SFRC beam demonstrated an improved post-cracking softening behavior and superior ability to arrest crack propagation compared to SBRC beam. The integration of local AE fracture energy and DIC results provided a novel approach for a better understanding of the fracture behaviour in both SFRC and SBRC beams. This study’s findings contribute to more precise monitoring of fracture evolution in SFRC and SBRC beams, ultimately improving the selection process for primary reinforcement in flatwork and elevated structures.