How Environmental Conditions Affect Pouring Concrete Countertops

We talk a lot about timing and curing concrete in “normal conditions” but what should you expect when conditions aren’t so normal? This is usually a concern when pouring outdoor countertops.

It’s generally not recommended to pour outdoor countertops in winter since the temperature needs to stay above freezing for at least 5 days straight to avoid cracking. When pouring in lower temperatures, the cure time is going to be longer. For example, instead of floating the counter 30-60 minutes after the pour, that time may be extended by two or three times longer. It’s important to pay attention to what the concrete looks and feels like, rather than time itself.

On the other hand, if you are pouring in temperatures over 80º F or direct sunlight, the timing can be reduced. When pouring in these conditions, it’s common to have to float more than once. Generally, you will use the magnesium (or Lexan) float when the concrete first starts to set up and looks dull and dry. When it starts to look dull and dry again, it’s usually time to trowel however in these conditions (as well as windy days) the surface will start to look dull and dry after floating but will still be too soft to trowel. In these cases, you will want to float again.  

In warmer weather, we recommend pouring in the early morning, using the coldest water available and wet curing. Wet curing is when you keep the concrete covered with a concrete blanket/tarp/plastic drop cloth and repeatedly spray with water throughout the day. You will want to keep this process going for at least 48 hours. Wet curing isn’t necessary for every countertop however it should be considered in the following conditions:

·      When pouring a piece over 8 feet long

·      When pouring any large section using Euro Forms

·      When pouring in temperatures 80º F or higher

·      When pouring in direct sunlight