When the temperature of fresh-mixed concrete hits 77 degrees Fahrenheit, quality is at risk, depending on the site conditions. When you get above 90 degrees in ambient temperature, you’ll have difficulty producing quality concrete without some serious adjustment to the mix. Interestingly, in the recent years, I cannot tell you how many pours we have made in the middle of the summer starting at midnight. Even with this change of cycle, we also do some of this at times:
- Moisten subgrade, steel reinforcement, and formwork before pouring concrete.
- Use cool aggregates with water added (sparingly and within tolerance) to the concrete mix to reduce initial temperature.
- Personally, I like wet cures on slabs even with a curing compound.
- Ensure there is enough labor to minimize the time required to place and finish the concrete.
Be adaptable. Concrete is a strange animal at times and seems to have a mind of its own. Only one chance to get it right the first time.