Concrete is a construction material which is a viscous liquid mix of aggregate, cement and water at the beginning and needs a certain time period to get hardened and gain strength.The process of hardening and gaining strength is an exothermic chemical reaction and known as “setting of concrete".The more sound setting process is the more quality concrete. So you should cure( look after) fresh concrete to ensure that its setting process continues in a healthy way.As mentioned above, setting is a chemical process and originates from cement and water that come in-contact each other. Cement starts hydration process ( takes more and more water to get hardened) and this produces heat. As the heat increases in fresh concrete it causes some of the water evaporate. As water evaporates there occurs air voids which is not good for concrete. ( In outdoor concrete pavements such as aprons, roads, runways, etc. tiny air voids of same size are distributed in an orderly pattern ( not random sized, or randomly distrubuted) concrete intentionaly to make it more resistant against some environmental effects, especially freezing and thawing. This is, of course, nothing to do with the unintentionally left air voids.) And besides, as the water decreases the cement particles can not get enough water to be completely hydrated, thus making a sound setting impossible.So, the most important way of curing a concrete is to give water, to wash it just after it is hard enough to step over it without leaving any foot step. It is very important to wash your just-hardened concrete in a sound way during the first 3 day after pouring. If possible, leave your hardened concrete completely in a mass of water, submerge it. :) Your new hardened concrete is burning due to the heat relased and is very thirsty since cement in it wants more and more water. So, after your newly poured concrete hardened, regardless of the time of the day it is very important to give it water as much as possible.The need for washing your hardened concrete decreases through time. So, first 3 day-->submerge it, following 7 days-->at least 4 to 5 times a day give it long showers, next 20 days--> 2 to 3 times a day wash it.The time periods needed can change according to the local conditions ( weather, type of structure, etc.) But, since concrete gains 50% of its max. strength in 3 days, and 70% in 7 days these are critical days for water curing. Concrete continues to gain strength for years, but after 28 days it almost reaches 90% of its max expected strength so the water curing is no longer needed after 28 days.Fresh concrete can also be protected against wind, very low temperatures, very high temperatures etc. All these precautions/actions ( curing of concrete) are to ensure that the hydration of cement, thus the setting of concrete takes place in good condition.