Fluctuating humidity, abundant rain and days with frost characterises the environment for winter concrete in many geographical regions. Challenges with sudden frost leads to concrete crumble, peeling and cracks occur every year in most regions. These problems result not only in costly repair and maintenance costs even years after casting, but also damage the structural properties of the concrete.
If you want to do an appropriate and secure cast of concrete under cold conditions, it sets some requirements for you and your work. We hereby provide you with basic knowledge of how to plan and monitor your castings of simple concrete designs.
It is recommended to do additional research, as the aim here is to showcase opportunities. Winter concreting in practice requires further concreting and hardening knowledge, which this paper does not provide!
Concrete curing and temperature conditions
Concrete can be named a man-made stone but its strength development is fairly sensitive to many external conditions, in particular external temperatures. Besides the proportions of the mixture, which is controlled by the quantity and combination of the rock, sand, gravel or other components, the weather is a factor that cannot be predicted.
Temperature changes can cause cracks or sapling, distress, and aggregate expansion which leads to concrete strength deterioration and overall reduce the product quality.
It is not a secret that concrete strength is extremely important for each construction project. Since concrete is used in key places like foundations or flooring, it is important that the concrete is strong enough to carry the required load.
The main process in concrete hardening is called hydration. Hydration is a chemical reaction in which the major compounds in cement form chemical bonds with water molecules and become hydrates or hydration products. This leaves us with zero control over the external factors such as wind, weather and humidity, that strongly affect the curing of the concrete. Casting concrete in extreme temperatures, either cold or hot weather conditions, requires special attention.
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?
Then you are in overall terms safe to pour and harden your concrete even under severe cold conditions.
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 Winter 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
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
Have a question about using Maturix™ for cold weather or winter concreting?
Send us a message and we will get back to you.