This article reports on research into the use of solid alkalis (Na2CO3 and K2CO3) as activators to obtain hybrid cement (cement whose hydration generates a mix of C-A-S-H and (N,C)-A-S-H gels) from a blend of 20% clinker+40% blast furnace slag+40% metakaolin. More specifically, the study aimed to determine the effect of activator dosage (5 and 8wt%) and type of alkaline cation (Na+ or K+) on the 2- and 28-d mechanical strength of the end materials. The findings showed that the highest mechanical strength values were obtained with 5% Na2CO3. According to the XRD, NMR, and SEM/EDX analyses conducted on the reaction products, the alkalinity and solubilized chemical species generated by adding 5% Na2CO3 to the system yielded a mix of (N,C)-A-S-H and C-A-S-H cementitious gels as the main reaction products. The secondary reaction products included metastable (3CaO center dot Al2O3 center dot CaCO3 center dot 11H2O-type) carboaluminates that evolved into the calcite or vaterite forms of calcium carbonate. When K2CO3 was used (instead of Na2CO3), a (3CaO center dot Al2O3 center dot 0.5Ca(OH)2 center dot 0.5CaCO3 center dot 11H2O-type) hemicarboaluminate also formed. The study also revealed that Na+ favors coagulation/precipitation more effectively than K+, generating gels with a wider range of Qn species.