Combined experimental and numerical study of fracture behaviour of cement paste at the microlevel

The aim of this paper is to investigate the fracture performance of cement paste at the microlevel. An experimental procedure for micromechanical testing of consecutive layers in cement paste is developed. Every layer is tested by nanoindentation and subsequently imaged in ESEM to link the phase distribution with the measured micromechanical properties. The obtained micromechanical properties were used directly as input for numerical simulation of fracture behaviour of cement paste. A comparison is made between simulated 2D fracture response from individual slices and simulated fracture response of 3D structure, which is reconstructed from the 2D slices. In addition, the influence of heterogeneity on fracture response was studied. 3D microstructure enables more stable crack propagation, branching and crack trapping, which is attributed to more restrain and phase connectivity. Neglecting heterogeneity and original phase distribution in numerical simulations of cement paste leads to overestimation of both tensile strength and fracture energy.