AbstractAccurate prediction of transport properties for cementitious materials remains a challenge since it is difficult to experimentally obtain the realistic three-dimensional (3D) pore network of cement paste. In this study, the 3D pore network of cement paste is quantitatively characterized using nano X-ray microtomography coupled with the metal centrifugation porosimetry (MCP). First, the MCP technique is carried out to impel the liquid metal into the pore network of cement paste. Subsequently, the 3D pore network of cement paste with the intruded metal is reconstructed using high-resolution X-ray microtomography. Finally, based on the X-ray microtomography images, the transport properties of cement paste including ionic diffusivity and fluid permeability are simulated using a set of lattice Boltzmann transport models. The results show that the metal alloy can significantly enhance the contrast between the pore network and solid phase, and the realistic 3D pore network can be successfully reproduced. For the cement pastes with water-to-cement (w/c) ratios of 0.5 and 0.6, the transport properties are dramatically increased with the improving w/c ratio. A similarly dramatic growth evolution of transport properties also occurs when the effective porosity of cement pastes raises from 27.56% to 36.11%.