The addition of granulated blast furnace slag (GBFS) to cement compositions represents a significant potential for enhancing the economic efficiency of cement mixes in terms of both cost and consumption of cement, as well as for improving their technical properties. In particular, when fine GBFS is used in concrete mixtures, it may be beneficial to employ water-reducing additives. However, given the superplasticizing effect of these additives on the setting time of the cement paste, the impact of such additives on parameters of heat curing, such as exposure duration and temperature rise rates, becomes crucial. This paper presents the findings of a study investigating the early compressive strength development kinetics of concrete containing ground-granulated GBFS, with a focus on the influence of GBFS content and additives in Portland cement-GBFS mixtures. The most effective additive for enhancing the strength of concrete produced from 70% cement and GGBFS is a two-component additive containing sulfo naphthalene formaldehyde-based superplasticizers at a concentration of 50% and Na2SO4 at a concentration of 5%. When subjected to heat-steam curing at 60 ℃, both this two-component mix and the polycarboxylate superplasticizer resulted in an early strength increase of up to 80%. As the quantity of a water-reducing additive based on polycarboxylate increases, the start and end times of setting are prolonged, while the amount of water in the paste with equivalent fluidity decreases. Factors that contribute to increased strength in GGBS concrete include the steam curing temperature, the use of water-soluble additives, hardening accelerators, and the size of the slag particles.