The present study aims to investigate the performance of alkali-activated fine slag under water curing condition. Ground granulated blast furnace slag (GGBFS) with a fineness of 6000 cm2/g was alkali-activated by the premixed alkaline solution from sodium hydroxide and sodium silicate liquid with the constant Na2O concentration at 5% and the modulus ratio of SiO2/Na2O at 0.5. Water-to-solid (w/s) ratio varied from 0.3, 0.4 and 0.5 to examine the effect of w/s ratio on the strength development and cracking performance of the AAS specimens. The compressive strength test, crack observation, and thermal conductivity test were conducted. The compressive strength results showed that this property was adversely affected by the w/s ratio, and the strength slowly increased after 7 curing days. Macro-cracks occurred in watercured AAS cubes and they were more server in the specimens with lower w/s ratio. Besides, as the w/s ratio decreased, these AAS performed higher thermal conductivity.