Concrete needs the right amount of water per application. Rule of thumb is just enough water to completely saturate the dry cement with the sand and or rock as with hand mixing. I would rather see a little over water, then not enough. As for cracking, both over and under water can cause a crack. I am a old time tile setter and know a little about concrete and concrete mix. We use to "DRY PACK" (what it was called) our floors before laying tile before they came out with "Thin-set" (thank God). We would dampen our mix, not wet (sand and cement only) pack the layment and screed. Sprinkle dry cement than lay our flooring. Next was the Key part. We than soaked the floor with water, to harden the cement base and bond the tile. Grouting was also down the same day (more water). Again, with just the right amount of water. As for screeding poured concrete, too dry or too wet is not recommended. Pour, rake, juke, screed and then finish with a smooth or ruff surface depending on the application. I have seen dry lumps of concrete coming out of a concrete truck before and stopped them to add water and remix. Note: If a vapor barrier (plastic sheeting) is used, less water is needed and a dry soil you would add extra water. I wet the soil before pouring if no vapor barrier is used. Reason is it gives more time to finish the slab. Adding water to the top of the slab for a couple days adds to a better cure and a harder surface.
