Gas permeability characteristics of granite-manufactured sand concrete and its numerical simulation using NMR-MIP modified method

Abstract

Natural sand resources are becoming increasingly scarce with the rapid development of infrastructure. Therefore, manufactured sand usage is inevitable. However, the significant differences in granite powder content between manufactured- and natural sand have a remarkable impact on the pore structure and permeability of cement-based materials, which are crucial for material durability. In this work, several granite powder dosages (0–32 %) of granite-manufactured sand were considered for preparing manufactured sand concrete, and a suitable physical filling model was chosen to quantify the material particle filling for characterizing the overall pore-filling effect. Mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR) were used to examine the pore structure of the specimens. The quasi-stationary flow method was used to test the gas permeability of concrete. Finally, a random hierarchical bundle model using the NMR-MIP method is proposed to predict the gas permeability of cementitious materials based on their pore size distribution. The results show that granite-manufactured sand and an appropriate amount (i.e., 8 %) of granite powder can improve the filling effect and anti-permeability performance of concrete. There is a good correlation between the pore structure parameters and gas permeability, where the physico-mathematical relationships can be modeled. The maximum relative difference between the predicted and experimental values of the random tube bundle model was reduced to 30.93 % using the NMR-MIP method compared to 70.87 % with the traditional MIP method.