Optimized design of steel fibres reinforced ultra-high performance concrete (UHPC) composites: Towards to dense structure and efficient fibre application

This paper presents a method for designing steel fibre reinforced Ultra-High Performance Concrete (UHPC) composites with dense micro/meso structure and efficient fibre application. Based on the modified Andreasen & Andersen packing model, the UHPC skeleton is first designed. Then, the effects of steel fibre shape and content on particle packing of UHPC are evaluated, which depicts that the hooked-end fibres have the most obvious negative effects on this system compared to other shaped fibres. Hence, to minimize the negative effects of fibres, the D-Optimal Design (DOD) method is utilized for the theoretical optimized design of UHPC via modelling of wet packing density with hybrid fibres. Meanwhile, an aided design model called Artificial Neural Network (ANN) is built for the prediction of wet packing density against different fibres, which shows very satisfactory accuracy, convenience and practicability. Finally, the basic properties of the developed UHPC are evaluated in detail to prove the feasibility and advancement of the proposed design method. In general, based on the approach proposed herein, an optimized UHPC composite with dense structure, high fibre efficiency and admirable mechanical properties could be produced.