A lot of us live in places that are not always optimal for concrete working. In fact, for those living on the north side of the earth most optimal time might be as little as 4-5 months or even less. Still, we run into situations where the job has to be done anyway and this article is for that purpose.
After making a decision about pouring concrete in an environment that has cold weather, there are a few things to keep in mind if you would like to be successful in doing this. You need to follow a few pointers to have long-lasting slabs of concrete.
When done correctly, you will be able to avoid the adverse impacts of cool weather temperatures. For hot weather concreting, here is a guide on the link.
Recently poured, fresh and new concrete slabs lose heat and moisture fast in conditions of cold weather. It is important to keep concrete poured and placed in cold weather from freezing early to make sure concrete develops its strength early while curing.
You need to plan carefully when working with concrete in cold weather. In order to achieve long life from the concrete you are working with, you need to follow the correct aggregate production, correct mix design, proper Jobsite transporting, and adequate mixing to the venue, as well as correct finishing and placing practices with special protective care.
The methods that guarantee correct cold weather concreting are planning, preparing for concrete pour, the actual pouring and after care. I’ll open these up next.
1. Planning is the key for better success rate
Prepare the proper equipment and the workforce for putting into place before pouring. You need to have protective weather gear ready to maintain a consistent kind of working environment and for helping maintain the correct temperature for the concrete to be finished and placed correctly.
Use a low slump concrete for flatwork in low temperatures. This reduces the time of setting and cuts bleed water because cool air inhibits the evaporation rate and set times of concrete.
Use concrete mixes that have admixtures acceleration or Type 3 Hi Early cement that requires a shorter time of protection from freezing.
Use mixes of concrete that contains fly ash if the projects is to be protected from becoming frozen for longer periods of time.
From your company of ready mixing, ask for a heated mix or order one hundred pounds of cement extra in each concrete cubic yard to help develop its early strength.
2. Before you start remove ice and snow
All the ice and snow needs to be removed from the concrete formations and the sub-base before concrete placement.
Make sure that the temperature of the sub-base is not lower than thirty-two degrees Fahrenheit and in the event that it is, you need to heat the sub-base with heating devices such as torches.
3. When you pour the concrete keep the temperature proper
Ensure that the concrete minimum temperature is consistent or exceeding fifty-five degrees Fahrenheit. Do not let the temperature of the concrete become higher than seventy-five degrees Fahrenheit.
Now there are many ways to heat and the correct one depends on the temperature and the provided protection from the weather. Also, one thing to consider is back up if you run out of electricity or gas/whatever is the power source.
When it’s really cold, proper insulation from the outside becomes more and more important as the heat will escape very fast. In those kinds of conditions, the whole thing should be planned out very well.
4. After the concrete starts curing you need to keep the heat
Do not begin the final operations of finishing while the bleeding water exists. Properly finish your concrete with no excess bleed water or extra water that is worked on the surface. Do not do over-finishing.
Do not overwork a slab that has been cooled since this delays characteristic of setting. Ensure that the concrete for cold weather has cured properly. Do not let hardened concrete become dry.
Do not let ice form on the concrete. When ice forms, hydration halts, and the development of strength is impaired seriously. Concrete that has frozen in twenty-four hours can have a fifty percent loss of its twenty-eight day cured strength.
Maintain a temperature of above fifty degrees Fahrenheit using insulated blankets or heat enclosures for 3-7 days after pouring. Use a compound with high-quality cures if you think you won’t be able to keep the concrete temperature higher than fifty degrees Fahrenheit for 3-7 days at a time.
Maintain concrete temperatures higher than forty degrees Fahrenheit for four more days after the use of heated enclosures or insulation blankets. Do not do a sealer application to concrete that has been freshly placed in cool weather.
Remove the heating protection in a method that doesn’t let the concrete temperature to drop lower than forty degrees Fahrenheit for another twenty-four hours.
With these recommendations, you will be able to successfully finish, place and cure concrete to its proper strength capability in conditions of cold weather. Make sure correct care and planning are done before and after the placement of the concrete.
Also, make sure that the time you need for heating is proper, this was just an example case. The time might go as long as 20 days. Remember that even in optimal situations it might take up to 28 days for the concrete to completely cure.
Cold weather concreting can be hard, but it’s not impossible. Of course, it’s always best to leave this kind of work for proper weather. Well, that’s still not always possible and then we need a “can do” attitude.
Most of the time it’s not even about if it is possible, but more about how much it will cost. That, of course, depends on the size of the project and how long and how much it will be heated.
If you’re interested in reading more about climate conditions, and hot places at that, here is also another guide on using ice concrete.