Concrete in Cold Climates

Concrete has many advantages over other building materials. It is low maintenance, durable, and forms the foundations of our man-made world. In order to enjoy the strength and versatility of concrete year-round, extra precautions must be undertaken.

Why are Cold Climates a Problem for Concrete?

Cold weather presents a slew of concrete complications.

Cold Weather Concreting

Frozen Ground

During cold weather, there are additional steps in the concrete pouring process when the ground has frozen. Manpower, time, and resources must first be diverted to ground thawing to ensure concrete is not poured onto frozen ground. The hydration process of concrete curing is an exothermic process and does generate some heat. However, the little heat that is generated will be quickly lost into the frozen ground, and the concrete will not stay warm enough to achieve a strong cure. Frozen ground will also settle when it thaws, causing the slab to shift and crack.

Excess Moisture

Standing water due to snow and ice melt are common on building sites during the winter.  Pouring concrete onto soggy ground introduces excess moisture into the mixture which affects cure duration and compressive strength.

Slow to No Cure

For starters, concrete curing time is always longer when the weather is cold. If temperatures fall below 50° F, the curing process slows dramatically. If temperatures fall below 40° F, the hydration reaction essentially stops and the concrete will not cure to the needed strength requirements. Since concrete is mostly poured during the early stages of a building project, these delays can be costly.

Freezing Defects

There are also a number of concrete defects that are caused by cold temperatures. Concrete should not be allowed to enter a freeze cycle during the first 24 hours after it has been poured. The early formation of ice crystals jeopardizes concrete strength and will result in spalling, pop-outs, and uncontrolled cracking.

Exposed Transportation

Even if concrete is mixed with warm water at the plant, it will continually lose heat as it is being transported. According to Bergen Mobile Concrete, during winter conditions, concrete can lose 5 degrees or more every hour it is on the road.

Tips For Cold Weather Concreting

Planning can help you protect your concrete throughout the preparation, pouring, and curing stages.

Prep The Ground

For faster and more thorough curing, use ground thawing blankets to prepare the ground before pouring. This will help your concrete cure evenly. As snow and ice melt, ensure your pour site has a minimum slope of ¼ inch per linear foot to drain excess water.

Go Easy on the Water

The more water you add when you mix, the longer it will take to cure. While adding water to concrete makes it easier to pour, it can also weaken the concrete and prevent chemical reactions from finishing. Maintaining a low water to cement ratio prevents the water from icing up in freezing conditions.

Refine Your Slump Test

The slump test measures the consistency of fresh concrete.  A concrete mixture is poured into a cone and turned over. The cone is removed and the tester measures how far the mixture slumps down. The lower the number the stiffer concrete is. Different concrete uses require different consistencies. During winter conditions, concrete mixtures should be stiff enough to slump 4 inches or less.

Use a Wintry Mix

Wintry mixes include useful ingredients to help your concrete cure and set properly despite cold conditions. Wintry mixes include accelerators to speed up curing and water reducing additives. These mixtures often have more binding cement powder as well to create a stronger cold mix.

Protect Your Cure

In order to ensure your concrete has cured to the required compression strength, your concrete needs to stay protected and warm during the curing process. Concrete temperatures must stay between 65° and 85° F in order to reach a minimum strength of 500 psi. Once it reaches this compressive strength it will be able to resist the effects of freezing temperatures. The most effective way to protect and warm your concrete is to use concrete blankets after it’s poured.

Stay Up to Date

Keep yourself educated on the continuously advancing world of concrete so you are always aware of the best products, practices, and building codes. The ACI ( American Concrete Institute) offers a wide variety of educational seminars and certifications for every career in the concrete industry.

Cold Concreting Solutions From Powerblanket

Powerblanket offers ideal solutions for cold weather concreting. Our ground thaw blankets provide powerful and even heating to efficiently prepare your ground before pouring. Powerblanket concrete blankets cure 2.8 times faster than conventional insulated blankets and protect your slab throughout the hydrating process. They are heavy duty, weather resistant, easy to install, and are ACI compliant for cold weather concreting. Contact us to find the right concrete solution for your needs 801.506.0198 or [email protected]

Concrete Guide

Take a look at our Concrete Guide for Concrete Industry Professionals. Inside you will learn about:

  • Aggregates
  • Tips for Working with Concrete
  • Weather & Concrete
  • How to Grow Your Concrete Business
Download the Concrete Guide

Curing Cold Concrete: Electric vs. Insulated Blankets

Electric concrete blankets versus insulated blankets. Which one is best and why is it Powerblanket?

Not All Concrete Insulated Blankets Are Created Equal

If you happen to read almost any do-it-yourself guide, you will likely see a sentence that says, “If temperatures are below 40°F, use insulated blankets or straw to keep your freshly-poured concrete from freezing.” Well, that sounds nice and easy, but simply keeping concrete from freezing isn’t enough.

Why Heat Concrete?

The optimum range for proper concrete curing is between 65° – 85° F. When concrete dips below that range, ice crystals can form, cure strength will be compromised, and several temperature based defects can occur. Concrete pouring is a critical stage in any construction project and problems derail progress when it needs to be repaired or re-poured. Solely insulating concrete during curing seems appealing and money-saving, but can lead to costly time delays and expensive re-works.

What is Thermal Insulation?

Simply put, thermal insulation reduces the transfer of heat between objects. There are a myriad of both natural and synthetic materials used to insulate objects in different industries. When thermal insulation is placed on something that is already warm, it will prevent heat from escaping.

The chemical reaction of concrete formation is exothermic and does create some heat. This heat can be trapped (to some degree) with the use of insulating blankets or straw. But if it’s cold enough outside, insulating blankets won’t keep the temperature at an ideal level for maximum curing.

Insulation + Heating

When pouring concrete in cold weather, providing thermal insulation is only half the battle. Most insulated blankets will not provide enough surface contact to effectively insulate your concrete on really cold days. Combining the protective power of insulation plus even heat distribution gives you an advantage over mother nature.

Electric concrete heating blankets provide the protective layer of insulation and an extra boost of heating power to keep your concrete between 65° and 85° F. Concrete blankets have 10x more surface contact than other blankets. They efficiently transfer heat down into your concrete while heavy-duty weather-proof insulation protects it from the elements and heat-loss.

Thaw Before Your Pour

No insulating blanket on its own will thaw frozen ground, and pouring concrete on frozen ground can have serious repercussions.

electric ground thawing blankets

Electric ground thawing blankets are the best way to ensure your concrete pour gets off on the right foot. Using an electric ground thawing blanket prepares the ground before you pour so ambient temperatures above and below your concrete are at ideal levels.

Concrete Curing BlanketsMany factors have an effect on concrete cure time, such as the type of mix used, the size and shape of the slab, and the ambient weather. Of all these factors, weather and temperature is the most unpredictable. The colder the temperature, the longer concrete will take to set and reach its proper strength. During cold weather, a conventional insulated blanket will cause the concrete to take longer to cure and will result in a weaker concrete.

For example, concrete kept at 70°F will set in approximately 6 hours, whereas concrete kept at 40°F will take 14 hours to set. Concrete maintained at 70° F will reach a compression strength of 2,700 psi in 3 days; concrete maintained at 40° F will only reach a strength of 1,200 psi in 3 days.

This disparity in strengths makes a huge difference in whether your construction project can proceed. If concrete takes too long to set, cure, and strengthen, your project can be significantly delayed. Some concrete manufacturers find it too problematic to operate during the winter, creating a costly off season.

Concrete Solutions From Powerblanket

With Powerblanket, there is no off season. The difference between conventional insulating concrete blankets and electric concrete curing blankets is clear, and our electric blankets are a cut above the rest. By combining heavy weatherproof insulation with electric heating components, Powerblanket can cure concrete 2.8 x faster than conventional insulated blankets.

Our ground thawing blankets melt ice and snow and prepare the ground before your concrete is even poured. Our concrete curing blankets then maintain the temperatures you need to more quickly cure your slab to a strong finish. Powerblanket can eliminate costly weather delays, ensure your project proceeds on schedule and that your concrete will be long-lasting and durable. Contact us to find the right concrete solution for your needs 855.440.0208 or [email protected]

Learn More About Concrete Curing Blankets