Cold Weather Concreting
According to the American Concrete Institute, Cold Weather Concreting requires special practices in order to prevent damage to concrete due to freezing at early ages;
- Ensure that the concrete develops the recommended strength for the safe removal of forms;
- Maintain curing conditions that foster normal strength development;
- Limit rapid temperature changes;
- Provide protection consistent with the intended serviceability of the structure.
Basically, concrete placed during cold weather will develop sufficient strength and durability to satisfy intended service requirements when it is properly proportioned, produced, placed, and protected.
The good casting of concrete in cold weather is obtained when the concrete is secured against damages because of early frost, temperature stresses and when the concrete curing process is managed and under control before, during and after casting.
Why Is It Important?
- Prevent damages against early frost in concrete
- Prevent damages relating to temperature stresses across the concrete structure
- Ensure the best possible hardening process under your conditions
Then you are in overall terms safe to pour and harden your concrete even under severe cold conditions.
Financial considerations
There will, of course, be some cost added to enable a safe winter casting and to prevent you from taking any additional risk when doing winter concreting. But the cost of taking the required precautions shouldn’t be excessive compared to the risk of the additional cost of damages and unexpected delays.
Temperature monitoring with sensors
Monitoring the concrete temperature development inside the structure and follow the temperature distribution in e.g. cross-sections provides you with insights: You can see, if your precautions are correct or need to be adjusted. Following the differences between the real and the expected temperature curve from your simulations, supports you in your decision making. If you have done a reliable calibration of the maturity-strength relation for your specific concrete mix design, then you can take decisions and actions based upon the data from the measurements inside the concrete structures.
Insights you get by monitoring
- Know when you can remove the formwork safely
- Get the optimal starting point for post-tensioning
- Know when to prestress a prestressed lane (e.g. precast)
- Gain insights if and when to cover or uncover your concrete element
- Prevent early frost in your concrete
- Optimise the required compression strength tests (e.g. high-rise buildings)
- Check the maximum allowed concrete temperature to prevent cracks
Decisions before choosing a monitoring solution
- What is the aim of my monitoring? Is it for documentation? Optimal formwork removal time? Temperature variations in cross-sections?
- How much is my allowed cost for the monitoring?
- What system and method do I want to use?
- Where do I want to measure?
- How often do I need temperature readings?
- How do I want my data to be collected (manually vs. wireless vs. remote wireless)?
- How do I want to process my data (choice of maturity function etc.)?
Having a clear answer to the question on top makes it easier for you to choose the optimal system. In this way you avoid choosing a system, that does not fit to your needs or on the other hand, might be too extensive and expensive.
Checklist for Cold Weather Concreting
1. Plan your concreting
- Do you know your concrete structural design?
- Do you know your formwork type?
- Do you know your insulation precautions?
- Do you need any post treatments of concrete?
- When would you like to strip your concrete (formwork/scaffolding removal)?
2. Calculate your expectations and control standards
- What is your expected concrete pouring temperature?
- Check internal temperature differences in the cross section
- Set maximum temperature
- Follow maturity (and strength) development
3. Control your pouring
- Check product quality
- How was your concrete pouring temperature compared to your expected?
- Expected weather (temperature, humidity and wind speed)
- Insulation needed?
4. Control your curing
- Take insulation precautions if needed
- Follow the weather
- Check concrete temperatures
- Follow concrete maturity
- Check concrete quality
