Tight specs for concrete temperature control during hot weather don't have to drive concrete production costs out of sight. With a modest investment in aggregate cooling equipment, producers can reduce mix temperature at a reasonably low operating cost. Under many conditions, aggregate cooling costs less than using ice or liquid nitrogen to get the same results.
EVAPORATIVE COOLING OF AGGREGATE PILES
Simply wetting an aggregate pile cools it by evaporation. But the amount of cooling is limited by relative humidity. Wet aggregate won't cool as much in humid climates because evaporation is less.
COOLING AGGREGATE WITH COLD WATER
Putting cold water directly on the coarse aggregate stockpile brings aggregate temperature quickly to about 5 degrees Fahrenheit to 10 degrees Fahrenheit above the cold water temperature. A properly designed system will effectively cool stockpiles in a relatively short time. When natural water temperature isn't low enough to drop the concrete temperature below specified levels, mechanical water chillers may be needed.
EQUIPMENT REQUIREMENTS
A well-designed aggregate cooling system with chillers will require:
- Adequate water storage capacity--normally about 1 day's total chilled water demand
- Sprinklers for evaporative cooling
- High-volume pumps for moving chilled water to the aggregate piles
- A chilled water system that consistently produces 40 degrees Fahrenheit or colder water
- A water distribution and drainage system
