Alkali activated slag cement (AASC) mixed with two types of ground granulated blast furnace slag (GGBFS) is studied. Two slags, GBFS-A and GGBFS-B, were replaced in 10 % increments and blended into 11 cases. The alkali activator is a 5 % activator (5 % NaOH + 5 % Na2SiO3) and a 10 % activator (10 % NaOH + 10 % Na2SiO3) and the W/B ratio is 0.45. Experiments were performed on compressive strength, and XRD, MIP, and SEM/EDS analyses were conducted. The results showed that the strength change according to the mixing ratio in the 5 % activator was less than 5 %. However, in the 10 % activator, the strength of R10 (GGBFS-A 100 %) was 20.9 % higher than that of R0 (GGBFS-B 100 %). The XRD results showed that the 5 % activator samples had little difference in peaks from the reaction product. The 10 % activator decreased the amorphous phase as the GGFBS-A ratio increased, indicating that GGBFS-A hydration was higher in the same conditions. The MIP results also showed that the 10% activator specimens had porosity and pore size lower than those with the 5 % activator. The SEM/EDS analysis showed that a high density of C-S-H with a high Ca/Si ratio was produced as the concentration of activator increased. The strength properties of the AASC of the two types of GGBFS blends are affected by the composition and ratio of each GGBFS and the concentration of alkali activator has a major influence. In the 10% high activator environment, with higher basicity and a higher hydraulic modulus, the increase was accordingly stronger, whereas the 5% lower activator did not show this trend. Therefore, it is considered that the strength characteristics by the basicity and hydraulic modulus are affected by the degree of hydration of GGBFS due to the high activator concentration.