Concrete pouring in cold weather may require you to take extra measures to ensure the highest quality, most robust finish. If freshly poured concrete is left to cure, or harden, in freezing temperatures it can result in a weaker foundation and even damage to the resulting structure.

Even if the temperature isn’t quite freezing, very cold weather can result in the curing process being drastically slowed down. This means your concrete will not reach its full strength as quickly, resulting in a delay to your project.

To avoid this, hiring a concrete pump will speed up the delivery process. If you’re pumping or pouring concrete in cold weather it’s important to assess the temperature of the air and ground, as well as the temperature of the liquid concrete as it is being poured.

The water in the concrete mix can freeze if the concrete temperature is allowed to drop below 0ºC. This means the mix would expand before it cures, changing the size and shape of the foundation, and could mean that the concrete cracks and is so damaged that it becomes unsafe for further construction. If this happens, it would need to be removed and replaced before the project can continue.

The solution here is to protect the concrete from the cold weather for a period of time, to ensure it is allowed to cure and reach an initial strength of about 2 newtons per millimetre squared (2 N/mm²). This means it will have the strength to resist the expansion of the freezing water. To do this, the concrete needs to be kept above 5ºC for at least 48 hours after pouring, but even after this period of time, the curing process will still be inhibited by the cold, so it’s important to remember that the full strength will take longer to achieve.

There are different solutions that could be considered if you’re pouring concrete in cold weather, depending on how severe the temperature is.

If the outside temperature is less than 5ºC, but it isn’t quite freezing, there is unlikely to be damage caused to the concrete, but it should still be protected for a period of time after pouring as the curing process will still be slower than usual.

In this case, the framework should be left in place for as long as possible, otherwise more vulnerable areas of the structure may be damaged before the concrete sets. For example, a corner could be knocked off or a thinner layer of screed may break down if it is not yet strong enough to support its own weight.

If there is a light frost overnight, newly poured concrete should be covered and protected to stop frost forming on or in the concrete mix. Thick polythene or tarpaulin can be placed over the concrete to achieve this. Whilst timber is a natural insulator, you can also invest in additional insulated formwork and specialist frost blankets if you will be pouring lots of concrete over the winter months. If your concrete structure involves beams or columns, these should be covered or wrapped where possible and if appropriate, space heaters can be used to keep internal structures warmer.

Another step is to ensure that the concrete is above 5ºC when delivered, and check all sub-bases, formwork, equipment (such as wheelbarrows) and reinforcement structures are cleared of frost, ice or snow.

If severe frost is expected, either overnight or during the day, you will need to take all of the above precautions to protect the concrete as it is poured and for a minimum of 48 hours after (longer, if possible). Additionally, choosing a supplier that offers volumetric concrete, where the concrete is freshly batched and mixed on site ready for immediate pouring, will mean the temperature of the concrete has less time to drop.

For more information on how to continue working with concrete in winter, or to discuss effective concrete curing in cold weather, contact the experts at King Concrete in Croydon on 0203 893 2292.

We can offer volumetric concrete mixed on site to your exact requirements, meaning that you only pay for the amount you need, and you get the additional benefit being able to immediately pour your concrete before it has time to freeze.