Experimental study on cement mortar with magnetized water treated by composite time-varying electromagnetic fields

The present study investigated the effects of composite time-varying electromagnetic fields on the microstructure and macroscopic mechanical properties of cement-based composites. Fourteen magnetized water samples were prepared using direct current (DC), sinusoidal/triangular/rectangular alternating currents (AC) and their combined electromagnetic field configurations. Comprehensive characterization was conducted to elucidate the evolution of physicochemical properties and their subsequent effects on the compressive strength of M20 cement mortar. The experimental findings demonstrated that critical parameters of magnetized water, the maximum increases in pH value, conductivity and viscosity of water, were 30.9%, 32.3% and 24.3% respectively. Conversely, surface tension displayed an inverse relationship with frequency elevation. Studies have shown that the application of magnetized water treatment technology can significantly enhance the compressive strength of cement mortar. When treated with a DC-sinusoidal combined electromagnetic field of 5 kHz, the 7d compressive strength of cement mortar can reach a peak of 19.39 MPa. This strength value represents an 11.4% increase compared to the control group. The DC-triangular combined electromagnetic field (1 kHz) exhibited a substantial 32.5% enhancement in 28d compressive strength. A comparative analysis was conducted, which confirmed that the synergistic effects of combined time-varying electromagnetic fields were superior to those of individual magnetic field applications. These findings provided significant implications for optimizing electromagnetic processing parameters to improve the performance of cementitious materials and for construction material engineering.