Before the Pour
For concrete, the ambient temperature should be over 41°F. This temperature allows the concrete to be able to set without freezing, though it will take longer to reach its proper strength. If the temperature is expected to be 41°F or lower at the time of delivery and the pour itself, extra measures will need to be taken to keep it warm.
Prepare the Concrete Pour Well in Advance
It is ideal to prepare the pour site well in advance of delivery, and this is particularly true during the winter. The time should be taken to insulate your framework. Frost blankets will assist with preventing the subgrade from freezing, so your concrete won’t end up cracking once the subgrade has thawed. In addition, you can utilize frost blankets once the pour is complete to help keep the heat in the concrete as it sets.
A space heater might also be needed for interior projects, as this will keep the pour site heated, which maintains an acceptable air temperature before delivery,during and after the pour.
If the pour site has been kept insulated in preparation of the concrete, the concrete should be poured as soon as possible. This is common practice, typically to avoid premature setting of the mix. In cold weather, pouring it quickly after delivery means the mix will not naturally lose more heat than expected, which assists in maintaining a comfortable temperature for longer.
Concrete should never be poured on a frozen ground. If the pour site has frozen before delivery, make sure it is properly thawed and brought to a acceptable temperature before pouring the concrete. While this might mean delaying the pour until the temperatures have risen, this is definitely preferable to dealing with weak, damaged and unworkable concrete later on.
After the Pour
Once the concrete has been poured, the period directly after the pour becomes critical. As mentioned previously, at around 41°F, the concrete will take longer to set to a suitable strength. This makes it crucial to keep the ambient temperature warm, and not let it drop close to freezing. There will be more chance for the mix to freeze the longer it takes to set, so preventing this is paramount.
The ambient temperature should be monitored and the concrete should be kept covered with a frost blanket for the following two days after the pour. The concrete will develop its strength during this time, so keeping it warms provides the best opportunity to do so unimpeded. Fresh concrete which has frozen during this time will lose significant strength, which renders the pour a failure. This is why it is essential to keep exposed surfaces covered and insulated where necessary.
Accelerating admixtures can help offset the effects of low temperatures as well by increasing the rate of cement hydration. This helps reduce the concrete setting time and the development of early strength in the concrete. The ambient temperature at the job sit will determine dose rates. One example of an accelerator that is often used is calcium, but others accelerators may be used as well.
The final step in the concrete’s strength development is the curing process. The warm temperature should be maintained without the concrete drying too rapidly. It is ideal to leave insulated forms in place for as long as possible, and make use of insulated sheets which help keep the concrete at an optimal temperature so as to prevent freezing.
Our team here at Navasota Concrete supplies high quality concrete for domestic and commercial clients throughout Texas. , including, but not limited to Navasota, Montgomery, Magnolia and College Station. Our highly skilled and knowledgeable team can assist your with finding the perfect mix for your project, no matter the size or scale, and will advise you on pouring techniques in extreme conditions. Don’t hesitate to contact us with the link below for more information!