As discussed in our article about Why Concrete Cooling is Necessary there are several important reasons why cooling concrete is beneficial, particularly in relation to improving its strength and durability. Thus for optimal results many large-pour cement projects require a comprehensive concrete cooling system. The exact specifics of the concrete cooling system will of course vary somewhat depending on the particular application and needs of the project. However, what follows is a general overview of the main components likely to be found in most concrete cooling systems.
Water Chilling Plant
The temperature of the water used in cement hydration is one of the single most important factors in determining the concrete’s temperature. Thus using well-chilled, cool water is an effective concrete-cooling strategy and most concrete cooling systems utilize a water chilling plant. The water chilling plant is a water cooling system designed to lower water temperature from its natural environmental temperature often to near freezing levels.
The water chilling plant itself is likely to contain various pieces of equipment which may vary somewhat depending on the particular system. Common components include compressors, a gauge and control panel, pumps, evaporative condensers, and heat exchangers. The efficiency of the system may vary, but strides have been made in making modern water chilling plants much more power efficient than older plants.
Cold Water Tank
Once the water has been chilled in the water chilling plant it will need to be stored in an insulated tank to maintain its cold temperature. The tank will of course have a pump for circulating the water into and out of other parts of the cooling system. Cold water tanks may themselves be made of concrete or they may be made of steel or other materials. The size of the tank will typically vary depending on the requirements of the cooling system. In all cases it is important that the tank be well insulated to prevent the water from warming up again.
Ice Plant
In addition to cooling the water used in cement hydration, another common and effective strategy for concrete cooling is to add ice, particularly flake ice, into the mixing drum to further lower the concrete’s temperature. Flake ice is an especially good type of ice to use for this application because its small size and high relative surface area ensure that it will pack the most cooling punch while still melting quickly and thoroughly. Rapid melting is important because the cement mixture needs to be uniform.
Thus, the ice plant is responsible for making the ice that will be used in the cooling process. Ice production generally takes place in a refrigerated drum. Water is sprayed onto the drum’s surface where it will freeze almost immediately. Next an ice removal tool will shear the ice off the drum’s surface, allowing it to fall into a storage bin. For the best cooling properties the ice should be relatively thin, roughly about 1.5mm thick. Good ice plants will also make ice that remains crisp and does not stick together or clump into blocks, will melt rapidly, and that is easy to convey to the blowing system.
Ice Storage Bin
Just as the cold water tank holds the chilled water that leaves the water chilling plant the ice storage bin houses the completed flake ice. It is crucial that the ice storage bin be well-insulated and many are thus double-walled. Some systems also include an air-cooling unit designed to keep air temperatures low and prevent the ice from melting. A good ice storage bin will keep the flake ice crisp and maintain its cooling integrity. Just as the cold water tank comes in various sizes to fit the needs of the project, so too are different capacity ice storage bins available.
Ice Delivery and Weighing
The ice delivery and weighing component of the concrete cooling system plays an important role in delivering the correct amount of ice to the mixing drum and batcher plant. It must also do so in a consistent, reliable way that does not freeze up or compromise the integrity of the ice. Typically the ice delivery system will utilize a blower, rotary valve, and cyclone receiver.
Aggregate Cooling With Water
For many concrete cooling projects chilling the mixing water and adding flake ice to the mixer will be enough to sufficiently cool the concrete. However for other projects the application calls for such significantly cooled concrete that it is also necessary to cool the cement aggregates. One effective method is with the use of chilled water. The cooling rate of the aggregate will depend in large part on the size of the aggregate, as well as on the temperature of the water. Depending on these factors exposure to water may accomplish the necessary aggregate chilling in as little as one minute to as long as an half hour or more.
Two methods of aggregate cooling with water include wet belt applications and flooded aggregate silos. With wet belt applications the aggregates are placed on moving conveyor belts and then flooded with chilled water. With the flooded silo method the aggregate silo itself is completely flooded with chilled water. Both methods require a sediment basin and de-watering system to re-separate the water from the aggregates.
Aggregate Cooling With Air
Water cooling the aggregate is an extremely effective method; however, it requires more space to accomplish since it necessitates the use of a de-watering system. Thus for projects with limited space, air cooling of the aggregates may be more desirable. This process involves blowing cool air in a continuous stream through the aggregate silo. Typically the aggregates will be slightly moistened since evaporative cooling holds much greater cooling potential. However, since the moisture is evaporated no net moisture is added to the aggregates.
Other Cooling Systems: Sand Cooling & Post-Cooling
For some projects that need extremely thoroughly cooled concrete they may utilize another cooling method in addition to chilled water, ice, and aggregate cooling: sand cooling. Sand cooling is a much more demanding process that will generally require custom-designed systems specialized to meet the needs of the particular project.
A final option is a post-cooling systems that runs chilled water through a network of pipes throughout the concrete. This process may be used in dam construction to allow for very thorough cooling. These final two options are not as common as other components of a concrete cooling system.
SEMCO/SEMCOLD LLC builds and delivers reliable, efficient concrete cooling systems that are custom-designed for each of our clients with their cooling needs and capacity demands in mind. No matter the size of the project we will create a state-of-the-art concrete cooling system that will get the job done.