(by Mike Sheehan)
Granted, we did not have a harsh winter, but the need to heat concrete and provide accelerators for proper set time and strength gain was still required. The ideal temperature range for delivered concrete is between 60 and 80 degrees. Of course there are many factors that determine what concrete producers see as their daily target, but this is really about a commonsense approach to understanding what some of the factors are that require us to heat the water to control temperatures.
Obviously, cold air temperatures are the driving force. Once temps begin to fall, and it “feels” chilly, that is a good indicator that the concrete will experience the same chill, thereby reducing strengths and increasing set times. We control this with heated water and accelerators. In addition to air temps, the raw materials themselves are affected by the cold, and if not heated, will create a cold batch of concrete. Again, we use hot water in the mix to create the correct temp range for quality concrete.
However, as we transition to early spring, and we experience warmer days, customers who “feel” the warmth might think that there is no longer a need to heat the water or use accelerators. As I mentioned earlier, the same ingredients, specifically the aggregates, are still sitting in the same cold stock piles they were over the winter. It takes Mother Nature time to warm these items up into a range where the concrete supplier does not need to heat water and recommend chemical admixtures. Typically, this happens in late March or early April.
So remember, just because the calendar flips to spring, doesn’t mean winter concrete practices stop. Check with your local Ready Mix Supplier if you have additional questions, especially one with an in-house QC Manager.