Spray new concrete, gunite pool shells or concrete decks, with water. Spraying water on concrete is one of the oldest and best ways to cure concrete.
The chemical reaction that binds the sand and gravel together to form hardened concrete can take up to 28 days to fully complete.
Concrete curing and hardening is a chemical process that is exothermic that generates heat. You want concrete to be cured slowly, uniformly, and evenly from top to bottom.
During the summer months, the outside temperature can become hot. By keeping the surface wet, you are keeping the concrete temperature low. Be sure to start watering the concrete in the morning and keep watering throughout the hottest part of the day. Do not start watering during the hottest part of the day because it could shock the concrete into developing surface crazing (similar to a hot glass breaking when filled with cold water).
Spraying water on the surface prevents the surface of the concrete slab from drying faster than the bottom.
Finished Surface
Is this a finished surface, i.e. final decking with no stone going over top? If so, yes, stay off it the day it's poured. By the next morning, stay off if you can, or walk gingerly (no twisting boots), and keep it wet by misting, or if you need to leave, cover with wet burlap, old sheets, towels, etc. You only need to do that for a day or two, after which occasional misting is good for around a week.
If it's a finished surface, be careful not to cool it really fast by flooding it after it dried out and got hot in the sun - just mist it to cool it slowly, after it's stayed wet for an hour or so, you can flood it if that's helpful for keeping it moist. Gentle temperature change allows the cracks to develop more slowly, and more likely follow the intended control joints. Rapid cooling induces cracks. This is the worst risk when people are advised to mist twice a day. That's way too long between drinks in the sun (for a finished surface), and ineffective if it's concrete that will be surfaced with something else.
Pool Shell
If it's a pool shell (that will be plastered) and surrounds that will be finished with stone or other material, you can't hurt it by walking on it the next day. I would not walk down any bulking such as steps or ledges on the same day it was put in (this could be why they advise 1.5 days).
How to Water
As soon as the concrete is set enough to walk on (which with shotcrete, that's quick...) you can start watering it. Do it several times a day 3-4 times or more. If it starts to rain you don't need to add to that. If you are unsure start early the morning of the day after it is poured.[1]
Avoid shooting a jet stream of water at the concrete at first. It won't matter by the second day after finishing, but contractors don't know how well their customers absorb instructions, so they perhaps find it safer to just say 1.5 days.
How long to Water Concrete?
The most critical time is in the first 3-4 days. There really isn't a great reason to go more than 14 days with this process. Even stopping at 7 is like a 95% job.
The benefit of keeping concrete from drying too quickly mostly happens at the surface and in the early stages of curing. After the first few days the surface has settled in, and the rest of the curing is going on deeper, and misting has little to no effect. Misting for longer doesn't hurt anything, and can give you something to do while you're anxiously waiting for the next steps
