The possibility of utilizing magnetic water for improving the properties of OPC mortars containing blast furnace slag (GGBS) was investigated. The effect of magnetic field strength of tap water on the various properties OPC mortar was extensively studied, using magnetic water device that developed herein this study for producing magnetic water. This research investigates the fluidity, strength and durability related characteristics, of mortar made with or without magnetic water and contained GGBS. The test variables included the magnetic strength of water (0, 0.5, 0.8, and 1.2 tesla (T)) and different content of slag (20, 35 and 50% by weight of cement). It was found that using of magnetic water has led to improve the fluidity and notable enhancement in the microstructure, mechanical properties and sorpativity of OPC matrix, when compared with corresponding properties of OPC matrix made with tap water. However, these enhancements are mainly dependent on the magnetic strength of water and the content of slag.