<p>This research aimed to both retard and accelerate hydration reactions at the first stage of hydration in mortars. For this purpose, mortars were subjected to stress intensities of 0&#xa0;V and 20&#xa0;V direct current (DC) via a DC power supply for two days. The mortars were prepared by replacing cement with blast furnace slag (BFS) at 0%, 10%, 20%, and 30% by weight. Additionally, the impact of nano zinc oxide (nZnO) and BFS on hydration reactions was investigated when combined in the mortar. The findings indicated that while nZnO and BFS decelerated hydration reactions in the mortar, they notably accelerated the reactions when combined with DC application. When the 20&#xa0;V DC was applied to the mortars with 0%, 10%, 20%, 30% BFS and 20% BFS-0.50% nZnO modification, the final setting times occurred approximately 748, 715, 687, 648, 780&#xa0;min earlier than the reference mortar, respectively. This means that by increasing the internal temperature of cement-based materials, C-S-H gels form more quickly, which is the most critical factor in their strength. According to microanalysis examination, it was observed that the C-S-H gels formed firmer as a result of DC application, especially in mortars containing 20% ​​BFS-0.50% nZnO. Additionally, it was observed that the addition of 20% BFS and 0.50% nZnO, along with DC application, resulted in a 79.20% improvement in compressive strength (CS) on the 7th day compared to the reference mortar. This study is critical for slowing down the hydration reactions in hot weather conditions and increasing the hydration reactions in cold weather conditions in cement-based materials.</p> Graphical Abstract <p></p>