Concrete is mixture of binding material and filler material. Binding process is completed by the action of hydration reaction. this reaction involves cement reacting with water, which forms gel and releases heat of hydration. The amount of water added during preparation of concrete is fixed and depends on type of MIX(Compressive strength), the client requires in its construction.
So to complete this reaction , we need frequent curing(process of adding water to cement and concrete surface) to be done after 24 hours of placing fresh concrete. This imparts strength and durability to strength.
the process of curing depends on type of structure like walls, roofs,flooring,beam and columns. This is done usually till formwork is not removed. Formwork means the mechanical shuttering provided to give the concrete appropriate shape. Mainly these structures require 10-12 days of proper curing.