2 questions really
Sometimes it has to be kept wet, other times not. Does the atmospheric temperature & humidity affect how long it takes to cure, and how strong it will be?
I remember needing to wet down a new patio regularly as it set up, but this isn’t done with streets, sidewalks, or poured buildings.
In: Chemistry
Temperature, humidity, and wind affect evaporation. The cement in the concrete needs to keep moisture in so that a chemical reaction can take place for it to become strong. If the water on the surface evaporates before the concrete “cures” it will result in surface cracking.
It is always better for concrete to be cured properly so that the cracking is minimized. Many organizations like your state or countries department of transportation require concrete to be covered, watered, or sprayed with compounds that block evaporation. If freshly placed concrete appears very white in color and is not covered, that usually means it has one of those compounds sprayed on the surface that are supposed to seal moisture in. These are used so that it does not need to be covered or watered.
Large flat areas like bridge decks or big slabs have wide areas where evaporation and cracking are more likely to happen and these absolutely need to be cured properly. The compounds only work so well so these wide areas are better sprayed with water (sometimes they even do both). If you poured a column it usually has forms around the sides and is only exposed at the top. The forms should hold in most of the moisture and it’s really only the top where evaporation would happen, so the evaporation is reduced.
It’s also important to remember that all concrete will crack. The best thing you can do is try to control where it cracks. This is why sidewalk has that groove about every 4-5 feet. This is a weak spot made on purpose so that the concrete’s more likely to crack along that groove rather than somewhere else.
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