the concept is very difficult to understand wat is happening in the hydration of cement....its difficult catch up the points
In the hydration of cement, chemical changes occur slowly, eventually creating new crystalline products with heat evolution Tricalcium silicate + Water ---> Calcium silicate hydrate+Calcium hydroxide + heat
To simplify and expand upon what the other answer said: Concrete becoming a solid isn't a matter of the mixture simply drying out. It is a chemical reaction between the water and the cement. The chemical reaction gives off heat during the process. We keep adding water to concrete during the curing process so that there is enough water in the mixture to completely react all of the cement, rather than allowing the heat to cause some of the water to evaporate before it gets a chance to react. The heat of hydration is the amount of energy given off (as heat) during the reaction.
