Carbonation on waterglass‐ and NaOH‐activated slag pastes was analyzed and compared with carbonation in Portland cement pastes to determine possible differences. Thermogravimetry‐differential thermal analysis (TG/DTA), Fourier‐transform infrared spectrometry, and nuclear magnetic resonance were used to determine the effects on the main reaction products. According to the TG/DTA results, carbonate precipitation following carbonation is much more intense in Portland cement pastes than in alkali‐activated slag pastes. This may be attributed to the fact that in Portland cement paste both the portlandite and the C–S–H gel can be carbonated, whereas in alkali‐activated slag pastes, only the C–S–H gel is carbonated directly. In both systems, carbonation leads to the formation of CaCO 3 , Si‐rich C–S–H gel, silica gel, and alumina. The carbonation of waterglass‐activated slag pastes is not altered by the presence of either of the organic additives used in the study.