American Concrete Institute (ACI) committee 305 defines Hot Weather Concrete as "any combination of high ambient temperature, high concrete temperature, low relative humidity, wind velocity and solar radiation."
Problems associated with hot weather concrete include:
- High water demand
- Increased slump loss
- Faster setting
- Higher potential for plastic shrinkage cracking
- Higher difficulty entraining air
- Need for early curing
Tips to reduce the harmful effects of high ambient temperatures include:
- Be ready when concrete arrives
- Unload concrete as quickly as possible
- Use set controlling admixtures (retarders)
- Use a surface evaporation retardant
- Use moist curing when possible
- begin curing immediately
Average Set Time of Concrete at Various Temperatures
| Temperature |
Approximate Setting Time |
| 100° F (38° C) |
1 hour 40 minutes |
| 90° F (32° C) |
2 hours 40 minutes |
| 80° F (27° C) |
4 hours |
| 70° F (21° C) |
6 hours |
| 60° F (16° C) |
8 hours |
| 50° F (10° C) |
10 hours 40 minutes |
| 40° F (4° C) |
14 hours 40 minutes |
