The most common misconception about concrete is that it dries. It does not. It hydrates - a chemical reaction between cement and water that keeps building strength for weeks, as long as the water stays available.
That is why Sacramento summers are hard on new slabs. Air in the high nineties, single-digit humidity and an afternoon delta breeze can pull surface moisture out faster than the slab can replace it from below. The result is a surface layer that never fully hydrated: weak, dusty, prone to scaling years later.
What we do about it
- Start at first light so placement and finishing happen in cool air
- Use evaporation retarder when wind and heat conditions call for it
- Apply curing compound, or run a wet cure with covering, immediately after finishing
- Adjust mix and admixtures for the day's actual conditions
- Reschedule rather than pour into an extreme heat event
What you should do in week one
If we have set up a wet cure, keeping it wet matters. If we applied curing compound, leaving it undisturbed matters. Either way, the first seven days determine a large share of the slab's final durability.
- Do not remove covering or barricades before we say so
- Keep sprinklers from blasting the fresh surface unevenly
- Keep vehicles off for the full period we specify
- Do not apply sealer to a slab that has not cured and dried
Why the color keeps changing
New concrete lightens as it cures and continues shifting for weeks. Blotchy appearance in the first month is common and usually evens out. Judging final color at day three is judging an unfinished process.
Cold weather is a different problem
Sacramento winters rarely freeze hard, but hydration slows significantly in cold conditions. That means longer waits before traffic, not a weaker slab - provided the concrete is protected from a hard frost in its first day.
Planning a summer pour and want to know how the heat affects your schedule? Call 877-889-1187.