· Michael Blair
Concrete does not dry, it cures — a chemical reaction needing moisture and a reasonable temperature. Middle Tennessee delivers conditions that interfere with that at both ends of the year.
Hot weather
A Nashville July pour sets fast, which gives finishers very little working time and encourages adding water at the site to keep it workable. Added water weakens the mix permanently.
Rapid surface drying also causes plastic shrinkage cracking — fine random cracks appearing while the slab is still soft. Evaporation retarders, shading and early morning pours all address it.
Cold weather
Below about 40°F, hydration slows dramatically, and concrete that freezes before it reaches strength is permanently damaged. Middle Tennessee winter pours are workable but need protection.
Blankets, heated enclosures and accelerating admixtures are the normal responses. A pour on frozen subgrade is a mistake regardless of what is done afterwards.
- Very hot: early start, evaporation retarder, no added water on site
- Very cold: blankets, admixtures, never on frozen ground
- Rain soon after: cover, do not work water into the surface
- Windy: wind accelerates surface drying more than heat does
Rain
Rain on fresh concrete before it has set can wash cement from the surface, leaving a weak, dusty finish that spalls later. Once it has set, rain is largely harmless and even helpful for curing.
The wrong response is troweling rainwater into the surface, which raises the water-cement ratio exactly where strength matters most.
Curing is not optional
Keeping concrete moist for the first several days develops most of its strength. A slab left to dry in Nashville sun reaches a fraction of what the mix could have delivered.
Curing compound, plastic sheeting or wet burlap all work. Ask what the plan is — a contractor who has one is telling you something useful about the rest of their work.