ACI Offers Guidance on Placing Concrete in All Weather

Brief

ACI offers guidance on how to place concrete in hot weather, cold weather and windy conditions. Concrete can set faster in hot weather, but care should be taken to avoid placing concrete directly on frozen ground or during high winds.

Insight

According to the ACI, concrete may be affected by, “…one or a combination of the following conditions that tends to impair the quality of freshly mixed or hardened concrete by accelerating the rate of moisture loss and rate of cement hydration, or otherwise causing detrimental results:

High ambient temperature; high concrete temperature; low relative humidity; and high wind speed.” Under fair weather conditions, concrete can take anywhere from 8 to 48 hours to set properly. While concrete can reach its full strength in as little time as a week, it also takes nearly a month for it to cure properly.

However, anyone who has worked in construction before knows that weather conditions are seldom ideal.

While working with concrete may come as second nature to many contractors, it is one of the trickiest substances to work with due to how quickly it can change when exposed to different temperatures, humidity, and wind rates. The American Concrete Institute’s (ACI) technical publications are an excellent resource that provide insights regarding the plethora of effects of environmental factors on concrete.

The ACI covers a variety of subtopics, ranging from extreme temperatures, humidity levels, wind velocity, natural disasters, saltwater, and freshwater’s effects on concrete in order to give contractors and concrete industry professionals accurate and up-to-date information.

Heat

The ACI’s (305.1 – 14 Hot Weather Concreting) specifications for setting and mixing concrete in hot weather suggests contractors should try to limit the maximum concrete temperature to 95º F. Contractors should ideally aim to work with, or pour, concrete when it is anywhere from 50-60º F. Under fair weather conditions, concrete can take anywhere from 8 to 48 hours to set properly. While concrete can reach its full strength in as little time as a week, it also takes nearly a month for it to cure property.