Pouring, setting, finishing, and curing concrete can be a very delicate process contingent on environmental factors. Temperature, humidity, and surface conditions are critical elements in ensuring that concrete sets and cures properly. When extreme weather and other environmental issues come in to play, concrete manufacturers must employ special techniques to avoid cracking and crusting, while also ensuring that the concrete develops the proper strength necessary for its desired purpose. Because of the additional planning, the likelihood of extra costs, and the added investment in materials, companies must decide whether pouring concrete in cold weather conditions makes sense overall and is a worthy investment.
Preparing Employees and Materials for Working in Winter Months
At MCR Safety, we understand that being prepared is key to successfully working with concrete in the winter months. Part of that preparation rests around knowing what employee gear will be needed at a jobsite and which safety gear is critical to avoiding any wasted time. In this article, we will highlight concrete winter pouring and the safety gear one will need, making you prepared for your next winter job.
Before a job even gets started, developing strategies for pouring, temperature control, and testing are essential. Many manufacturers keep temperature-recording charts, which manage the temperatures of the concrete itself. This temperature recording is on top of external temperatures. In addition, utilizing a schedule in conjunction with weather reports can be very helpful in keeping up with the protection and maintenance of the concrete temperature.
Concrete Specific Planning
It is important to take into consideration the specific type of concrete you are working with and whether it requires any special considerations to develop the strength requirements. Experts recommend that concrete poured in cold weather should have a specific amount of air entrained voids to resist freezing and thawing issues. In our article, “An Overview of the Concrete Manufacturing Process,” we highlight the different concrete types.
Understanding Hydration and Curing
In order to effectively manage pouring concrete in cold weather, concrete companies must have a thorough understanding of hydration, also commonly known as the curing process. This process is a chemical reaction that must take place in order for concrete to hold up over time and to develop the appropriate strength and durability. Because temperature affects the rate at which concrete sets and affects how these chemical reactions take place, the concrete itself must be kept at = 40ºF (=5ºC). Concrete curing at less than 40ºF (5ºC) can completely halt the hydration process, which may cause freezing and ultimately lead to cracked concrete.
Maintaining Concrete Temperatures During Cold Weather Conditions
Guidelines for temperature management, as well as placement and protection of concrete in cold weather are established and mandated under the Guide to Cold Weather Concreting - ACI 306. Contrary to popular belief, the guide suggests that if managed properly, concrete set in low temperatures can be more durable in the long term than concrete set in higher temperatures.
The Guide states, “Concrete placed during cold weather, protected against freezing, and properly cured for a sufficient length of time, has the potential to develop higher ultimate strength (Klieger 1958) and greater durability than concrete placed at higher temperatures. It is susceptible to less thermal cracking than similar concrete placed at higher temperatures.”
Some recommendations for maintaining the right temperatures to achieve these results:
- For the first 48 hours, it is critical to keep concrete warm (over 40ºF[(5ºC)]).
- Do not remove formwork before concrete has reached desired strength. This could lead to collapse or to damaged surfaces.
- Edges and corners are particularly vulnerable to freezing and should be watched closely for temperature maintenance.
- There are a wide variety of curing blankets available on the market that can be used to control and maintain concrete temperatures.
Clearly, due to the delicate nature of managing cold weather concrete production, extensive planning is involved in managing concrete temperatures to ensure proper curation.
Successful Tips for Working With Concrete in Cold Temperatures
Although working with concrete in cold temperatures can be tricky, it is not impossible. Here are some basic tips for working with concrete in cold temperatures.
- Concrete should always be poured on a clean surface, free of snow, ice, water, or any other debris or materials.
- Keep tools in trucks or trailers and heat them up if necessary before using them to interact with concrete.
- Concrete should never be poured on frozen ground, as thawing and settling will crack the concrete.
- Pouring concrete on cold or frozen ground and thus slowing the hydration process can cause crusting, where the top portion of concrete sets while the bottom remains soft.
- Sometimes it is possible to thaw the ground or surface on which the concrete is being poured by using heated pipes or electronic blankets.
- It is important to avoid final finishing operations if bleed water is present.
- Because extra cement helps develop early strength, some experts recommend ordering 100 lbs. of extra cement for each cubic yard of concrete.
Successful Tips for Choosing the Right Insulated Gear
Preparing employees for cold weather conditions is equally as important as preparing for different materials and environmental factors. The more comfortable employees are, the more focused they can be on their work. Best practices for working in extreme weather conditions include:
- Dressing in multiple layers of light fabrics
- Using insulated vests and hoodies, such as the SSCL3LZ shown to the right
- Wearing a combination of buttons and zippers, allowing for versatility in controlling temperatures
- Using wind resistant, synthetic fabrics as outer layers
Protecting Employees from Extreme Weather Conditions
Cold and wet weather conditions are a liability disaster for employers managing employees working in these conditions. The best way to manage these risks is to invest in the right equipment to ensure employees are safe and comfortable. In our article, “How to Choose the Right Insulated Gear for Concrete Production,” we cover the basics of selecting the appropriate gloves and body gear for laborers managing production in the colder months. We emphasize the importance of selecting the right gear because frostbite can occur in extreme temperatures.
One of MCR Safety’s most popular insulated glove is the Ninja Ice, which comes in a variety of coated options, such as fully coated, ¾ coated, and palm coated. The Ninja Ice is great because its coating repels water, a nice feature in wet and cold conditions!
We are here to help!
We highly recommend that any employer looking for concrete production safety gear for use during cold winter months register for The MCR Safety 360° Protection Program and schedule a thorough assessment of their safety gear needs.
Be sure to also check out our insulated information covering a full range of insulated safety gear options.
For more details on MCR Safety’s cold weather gear for concrete production you can request a catalog, find local distributors, or give us a call at 800-955-6887.
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