I think we have been already taught how this goes, butIf you mix water and cement, and you record the mass while it's still wet, then if it dries, will you also get the same mass? if not, much percent do you think will be lost?
The problems with cement is that it's a very Thirsty molecule. Could be all the water remains in the concrete. Concrete doesn't harden because it loses it's water - it hardens because of a chemical change (it's hot). Portland cement can harden under water - and the Romans understood this. Some of their bridges are still in use. Then the idea was lost until the end of the 18th century, I think.
Water requirement for chemical reaction for cement is less than 30% Therefore excess water is evaporated on drying.
