Characterizing connectivity and tortuosity of pore network based on LF-NMR method to assess the water permeability of white cement mortar

To better understand the macro transport properties and durability of cementitious materials, their microstructure should be characterised more accurately. This study investigated white cement mortars with different water-cement ratios, sand volume fractions, and curing ages. The water permeability was measured using a self-manufactured facility. The low-field nuclear magnetic resonance (LF-NMR) technique combined with the displacement method was used to test the pore size distributions (PSD) of total pores and connected regions. Two-dimensional mortar and pore-based matrix models were established to obtain the tortuosity of the transport path. The results show that the pore connectivity of the mortar ranges from 32 % to 52 %, and the tortuosity ranges from 1.428 to 1.542. The pore connectivity was spatially sensitive, and small pores were densely connected, linking large pores to form a pore network. Although capillary pores dominate the permeability, the role of gel pores cannot be ignored. Considering gel pores can improve the accuracy of the predicted water permeability by 80 %. The relative error of the modified model is [-23.76 %, 37.19 %], which shows a significant improvement.