At the early maturity stage, the curing temperature has a significant impact on the mechanical properties of concrete. Concrete cubes are cured in water baths at different temperatures—5 °C, 20 °C, 35 °C, and 50 °C—in order to measure their compressive strength. This method is predicated on the knowledge that the pace of cement hydration is strongly influenced by the curing temperature. Then, the realistic curing temperature regime was imposed where the temperature of the curing water was modified based on the temperature patterns obtained from semi-adiabatic testing of concrete mixes to simulate curing conditions in the core of massive concrete structures. Ordinary Concrete: Compared to specimens cured at an isothermal curing at 20 °C, those cured in water baths at realistic curing showed an increase in compressive strength of 48% at seven days and 18.5% at 28 days. Fly Ash 18% Replacement: Compared to specimens cured at at 20 °C, the compressive strength of those cured at realistic curing increased by 45% at seven days, with a modest rise of 0.2% by the 28th day. Slag 18% Replacement: Compared to specimens cured at 20 °C, the compressive strength of those cured at realistic curing increased significantly by 121% at seven days and by 21.7% at 28 days.