Optimization of fibre orientation and distribution for a sustainable Ultra-High Performance Fibre Reinforced Concrete (UHPFRC): Experiments and mechanism analysis

This study addresses an optimization of fibre orientation and distribution for a sustainable Ultra-High Performance Fibre Reinforced Concrete (UHPFRC). The purpose of this research is to propose an efficient method that can improve the fibre efficiency in the UHPFRC and understand the intrinsic mechanism. The UHPFRC skeleton is designed by employing particle densely packing model (Andreasen & Andersen model). Based on appropriate application of superplasticizers and fibres, a UHPFRC with high flowability is firstly produced, and two cast methods are utilized in this study. Furthermore, to minimize the error, two image analysis tools are parallelly employed to evaluate the fibres distribution and orientation in the hardened UHPFRC. The obtained results show that the fibres orientation and distribution can be significantly influenced by the fresh UHPFRC flowing parameters, (e.g. flowing direction, flowing distance and wall effects), and the flowing process of fibres in the fresh UHPFRC can be generally divided into: disorder period, stable period and re-disorder period. Additionally, the added fibre dosage is also a key factor for obtaining an optimized UHPFRC, since the interactions between single fibres have close relationship with their dynamic movement during the UHPFRC flowing process.