Cooled gravel can be used to lower the temperature of the concrete mix. The gravel can be cooled with cooled water or with cold air.
Gravel cooling by means of water takes place on a special conveyor belt (wet-belt) between the gravel storage and the mixer. The gravel is sprayed with cooled water during transport on the belt. The used, warmed water is collected and pumped back to the chiller via a precipitation basin. To prevent the gravel from heating up due to ambient heat or the sun, the wet-belt is placed in an insulated housing.
Gravel cooling by means of air takes place in the storage silos for the gravel. Cold air is blown through the filled silo to cool the gravel. The silos are modified to achieve optimum cold air flow and insulated to prevent warming from the environment or the sun. The air is cooled by an air-blast unit, and the warmed air (which is still colder than the environment) is recirculated to increase the efficiency of the system.
If the gravel is cooled 2°C, the temperature of the concrete mix will drop by 1°C.