Testing and modelling of fibre-matrix interface by microcube splitting

This study examines the impact of microfibre inclusion on the tensile properties of cement paste at the microscale through both experimental and simulation approaches.Micro-cubes containing vertically aligned microfibres were fabricated using cement pastes with varying waterto-cement (w/c) ratios, ranging from 0.3 to 0.5.These specimens underwent a splitting test using a nano-indenter with a wedge tip, and the results were compared to those of micro-cubes without fibres.Mechanical properties, including load capacity, peak deformation, stiffness, and fracture energy, were analysed.The findings indicate that fibre inclusion reduced the splitting tensile stress and modulus of the micro-cubes across all w/c ratios.Additionally, the influence of fibre inclusion became more pronounced with higher w/c ratios, likely due to a more porous interfacial transition zone (ITZ) at these higher ratios.To complement the experimental work, a lattice model with a simplified microstructure, comprising paste, fibre, and ITZ, was developed to simulate the fracture behaviour of the micro-cube under indentation splitting.The simulation results were in strong agreement with the experimental data, facilitating the determination of the mechanical properties of the ITZ.