Protecting Concrete From Freezing

When concrete is being placed below 5 degrees but is not below freezing point concrete will take longer to develop the required strength.

Protecting concrete from freezing.

Salt also lowers the freezing point of water and increases the pressure of frozen water thereby intensifying the effect of the freeze thaw cycle. For flatwork the traditional and still the best way to protect concrete from the cold is to cover it with blankets after it s been finished. The exposure of concrete to cold weather will extend the time required for it to reach initial set which may require finishing crews to be available for a longer period. See sidebar for more about this definition protect from early age freezing.

If the concrete temperature is kept around 50 f this will usually happen in about 48 hours. Depending on the actual ambient temperature protection of a concrete placement may require the use of windbreaks enclosures or supplementary heat. All necessary precautions should be taken in order to to alleviate the negative impacts of cold weather. Note that removing formwork when concrete is too cold or hasn t reached desired strength could damage concrete strength and surfaces and concrete might collapse.

This leads to increased salt damage to concrete driveways which is further amplified by the effect of the freeze thaw cycle. The protection period is the time required to prevent concrete from being affected by exposure to cold weather. Protect the sub grade and the concrete from freezing i ve had concrete floors where the entire surface has peeled off top 1 8 because the general contractor refused to protect and insulate the concrete after we troweled it and the temperature dropped into the 20 s overnight. At this point it is strong enough and dry enough to avoid damage by a single freezing cycle cyclic freeze thaw protection requires air entrained concrete and strength closer to 3500 psi.

Protecting concrete in cold weather is a continuous challenge for concrete contractors and site supervisors. Since the ground is a bit warmer and the concrete generates its own heat blankets will keep it warm even if the temperature goes below 20 f. Concrete absorbs moisture when. When ice melts it carries approximately 10 more water than normal.

Using frost blankets and insulated formwork could be necessary to protect concrete. Concrete is one of the most durable building materials known to man but it can be vulnerable to deterioration from weather salts and the freeze thaw cycle. Modify the mix design so the concrete will gain the necessary strength before freezing or. For more information see concrete basics on page 945 of this issue or the article cold weather finishing in the november 1993 issue of concrete construction.

Special curing and protection is.