An Investigation into the Compressive Strength, Permeability and Microstructure of Quartzite-Rock-Sand Mortar

River sand is an essential component used as a fine aggregate in mortar and concrete. Due to unrestrained exploitation, river sand resources are gradually being exhausted. This requires alternative solutions. This study deals with the properties of cement mortar containing different levels of manufactured sand (MS) based on quartzite, used to replace river sand. The river sand was replaced at 20%, 40%, 60% and 80% with MS (by weight or volume). The mechanical properties, transfer properties, and microstructure were examined and compared to a control group to study the impact of the replacement level. The results indicate that the compressive strength can be improved by increasing such a level. The strength was improved by 35.1% and 45.5% over that of the control mortar at replacement levels of 60% and 80%, respectively. Although there was a weak link between porosity and gas permeability in the mortars with manufactured sand, the gas permeability decreased with growing the replacement level. The microstructure of the MS mortar was denser, and the cement paste had fewer microcracks with increasing the replacement level.