The curing and hardening of concrete is a chemical reaction that occurs via hydration as the cement mix forms strong bonds with water. This chemical reaction is an exothermic reaction, meaning that it gives off heat as a byproduct. For large-pour concrete projects this can result in serious problems as the concrete expands, develops a temperature gradient, or experiences reduced tensile strength and cracking. To overcome this problem concrete, particularly for large projects, must typically undergo a cooling process.

One effective method of concrete cooling is aggregate cooling. Let’s take a look at what aggregate cooling is, how it works, and whether or not it is always necessary for concrete cooling systems.

What Is Aggregate Cooling?

To understand what aggregate cooling is, it is first necessary to understand what aggregates are. The term “aggregates” refers to the inert granular materials that are present in the mix. These typically consist of sand, gravel, or crushed stone. When the aggregates are combined with the cement mix and water together these ingredients combine into concrete. Thus aggregate cooling refers to the cooling of these inert aggregate materials. By cooling these materials prior to the mixing process, the temperature rise that occurs due to hydration during the mixing can be partially offset, thereby reducing or eliminating the potential problems discussed above.

How Are Aggregates Cooled?

There are two broad methods of cooling aggregates: cooling by water and cooling by air.

Cooling by Water – Cooling by water involves the use of chilled water to cool the aggregate materials. This is most often accomplished via the flooded silo method or by wet belt applications. In the flooded silo method the silo in which the aggregates are stored is literally flooded with chilled water, thereby cooling the aggregates. However, this necessitates water removal which, depending on the particular setup, system, and resources available might be burdensome. Thus, another alternative is the wet belt method which cools the aggregates with chilled water as they travel along a conveyor belt, thus avoiding full silo flooding and minimizing excess water.

Cooling by Air
– Cooling by air offers the advantage of removing the need for a dewatering system. In air cooling a series of air nozzles are installed in the silo where the aggregates are stored and a defined air stream is established. The aggregates are then moistened and the cold air is blown past them, cooling them with evaporative cooling and removing the moisture in the process.

What Other Concrete Cooling Options Exist?

Aggregate cooling is only one of several broad concrete cooling approaches which include:

  • Aggregate Cooling – As discussed above.
  • Drum or Agitator Cooling – Cooling occurs in the agitator drum or mixing truck during the mixing process itself.
  • Water Cooling – The water used for hydration is cooled separately prior to mixing.
  • Post Cooling – Cooling occurs after the concrete has already been mixed and poured.

Is Aggregate Cooling Necessary?

So is aggregate cooling necessary? The answer is it depends. It depends on the size and requirements of the pouring project and the efficacy of the other cooling approaches used. Often for small- or mid-size pour projects aggregate cooling is not necessary. Ultimately some companies opt to avoid or minimize aggregate cooling by instead focusing on other concrete cooling methods as discussed briefly in the previous section.

Semco Provides Dependable Concrete Cooling Systems

Semco provides dependable, industry-leading concrete cooling systems that may or may not incorporate aggregate cooling depending on the particular client’s and project’s needs. We are committed to helping our clients get the system that best fits their requirements and will discuss their aggregate cooling and other concrete cooling options to ensure the best results. Our clients can count on us for outstanding concrete cooling systems.