Geometrical model for tortuosity of transport paths in hardened cement pastes

Tortuosity is an important parameter for characterising the transport behaviours of cement-based materials. Based on some basic assumptions obtained by scanning electron microscope observations, this paper presents a two-dimensional geometrical model for the tortuosity of transport paths in hardened cement pastes. The proposed model is expressed as a function of porosity, cement hydration degree, shape factor of cement particles and water/cement (w/c) ratio. In order to validate the proposed model, mercury intrusion porosimetry (MIP) tests on 30-day-cured cement paste samples with different w/c ratios were conducted to determine microstructure properties such as porosity, tortuosity and pore size distribution. The tortuosities of the samples from the proposal model were compared with those from the MIP tests and the results show good agreement. The present work can provide a basis for modelling the tortuosity of transport paths in mortar and concrete in order to numerically analyse the transport behaviours of concrete materials and structures.