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To overcome the drawbacks caused by the intrinsic brittleness of cementitious materials, various types of fibres were incorporated as reinforcements. Extensive research on Ordinary Portland cement indicated that compared with the use of a single type of fibres, the mixed-use of multiple fibres can significantly improve both strength and toughness of the cementitious composites, which is referred to as the hybrid effect. However, such hybrid effect in multiple fibre-reinforced magnesium phosphate cement-based composite (HFRMC) still lack quantitative understanding. Therefore, this study conducted a series of experiments, including slump flow tests, compression tests, four-point bending tests and microstructure analysis, to investigate the hybrid effect of micro-steel fibres (MSF) and polypropylene (PP) fibres in HFRMC. Two types of mixed designs of HFRMC were conducted: 1. total fibres fraction (including both PP fibres and MSF) was fixed to be 1.6%; 2. PP fibres fraction was fixed to be 1.6% with different addition of MSF. Our results indicated that the slump flow of magnesium phosphate cement mortar varied around 7.6–8.8% with the hybrid use of MSF and PP fibres, while the flexural strength and toughness increased around 13.7–23.1% and 1.6–45.9%, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a semi-discrete model based on peridynamics (PD) for engineered cementitious composites (ECCs) is applied to simulate the fracture behavior of functionally graded ECC (FGECC) beams. This is a new application of PD in ECC. Prior to simulating the crack behavior, the convergence of the PD model for ECC is discussed and the appropriate horizon size δ and nonlocal ratio m are obtained, i.e., δ = 1.6 mm and m = 4 . In addition, when the bond strain exceeds the elastic limit, a damage variable is introduced into the model, and the model is validated using a simple numerical algorithm. Finally, the dynamic fracture behavior of a two-dimensional FGECC beam under four-point bending is investigated, and the effect of the initial crack location on the fracture behavior is analyzed. Simulation results show that the initial crack location can affect the crack propagation pattern, thereby enabling one to understand the dynamic fracture behavior of ECC structures and guide the engineering practice. [ABSTRACT FROM AUTHOR]