The hydration and hardening process of lime is briefly described
Because lime is hardened in air. So it's called gas hardening material. Some lime burns too far and put it in the water for a short time, it can not be converted into calcium hydroxide. This lime won't work. Lime must be digested completely and thoroughly before use. If the use of incompletely digested lime, there will be quality accidents. If the wall must burst.
This is an exothermic chemical reaction called digestion, not hardening. Calcium hydroxide reacts with carbon dioxide in the air. Calcium carbonate is produced, and calcium carbonate is hard.
Lime is a hard material, not a hard material. Lime is calcined. It's called calcium oxide. Calcium oxide is called quicklime, and when lime is placed in water, it becomes calcium hydroxide.
