When working with concrete below 39°F, there is a fine line between setting and freezing that must be managed. Water is an essential component in concrete curing, and the reaction maintains the slump at a reasonably warm temperature under typical circumstances.
Water expands at 32°F and 40°F while forming ice, which increases its volume. Snow may be a no-show in Denton, but temperatures can drop as low as 33F, definitely undesirable when curing poured concrete. Here is what Action Construction has to say that warrants an expert’s touch in concrete paving.
- It’s critical to heat your concrete mix with hot water. A mixing temperature of 65°F is appropriate for the consistency of the concrete mix.
- Remember, the air is an excellent insulator. To this end, the concrete is passed through air-entraining equipment that introduces air bubbles into the mixture. This keeps the concrete mix warm for longer and also helps to dissipate any freezing or thawing as the concrete hardens by utilizing the air bubbles as stress relievers.
- Add more science: impurities in a pure mix will lower its melting point (while raising the boiling point – but that’s not our topic!). To this benefit, add some calcium chloride to a whole batch at two parts to one. The salt will serve as an accelerator for the concrete setting as a nice bonus.
- Consider that if you’re using calcium chloride on a pre-fabricated rebar reinforced project, the calcium chloride will erode the rebar in the concrete over time. If you have a picky customer who insists on having things their way despite being informed of excessive accelerant usage, get them to make it part of the contract so that you are not held responsible for the client’s lapse in judgment.
- While the concrete is curing, water is released to the surface, freezing and damaging the top layer. When the surface is sturdy enough, this ‘bleed’ water should be sponged up or vacuumed immediately. Else, it will create spalling issues in the concrete by spring.
- Now that the concrete has settled, it’s time to turn up the heat! Concrete takes 48 hours to cure, and during this time, it must be kept at a constant minimum temperature of 50 degrees Fahrenheit or higher. In harsh winters, insulation blankets with induction coils or ventilated heating containment units can sustain temperatures at a pleasant 50F until your pavement is ready.
There are many occasions where the professionals from Action Construction Asphalt & Concrete have used their experience to benefit several winter customers. Unless you can handle a paving project with equipment to create artificially warm conditions, please don’t risk it; let your reliable concrete paving professional deal with it.