Cold weather concreting
Cold weather concreting By Pat Cantin, PQS
AUTHOR’S NOTE: The following article has been assembled in the hopes of summarizing a plethora of winter concrete placement ‘do’s and don’ts’ as a result of my personal experiences from across Northern Ontario in the past 20 years. Some projects went really well, while others were not so well. In the end, the contents of this article are designed to educate and enlighten the reader from my experiences.
What is cold weather concreting? All the reports and articles I have come across essentially provide the following definition of cold weather concreting: A period when, for more than three consecutive days, the following conditions exist: 1. The average daily air temperature is less than 5°C; and 2. The air temperature is not greater than 10°C for more than one-half of any 24-hr period.
EDITOR’S NOTE: The photograph shown to the right was actually taken from the author of this article, while driving to a construction jobsite in lovely Northern Ontario. The noted outside air temperature (-39°C) does not take into consideration the dreaded wind chill factor, which probably ended up feeling more like -212°C!!!
10 | CONSTRUCTION ECONOMIST | www.ciqs.org | Winter 2014
Main objectives to attain during cold weather concreting If you are a contractor, the last thing you want to hear during the early days of any project are the dreaded words of your Site Supervisor saying to you on a Monday morning that the heaters ran out of fuel over the weekend, or that the site lost power and that the heaters were off-line! What you are essentially trying to avoid are situations such as: 1. Preventing damage to concrete due to freezing at early ages (within the first 48-72 hours after pouring); 2. Assuring that the concrete develops the required strength for safe removal of forms, for safe removal of shores and re-shores and for safe loading of the structure during and after construction; 3. Maintaining curing conditions that promote normal strength development without using excessive heat and without causing critical saturation of the concrete at the end of the protection period;
