Does temperature affect concrete curing?

When it is laid and cured correctly, concrete is an exceptionally durable and strong material.

This construction material is used across a huge range of different sectors, applications and industries, thanks to its extraordinary range of properties and advantages.

But, in order to unlock all of these benefits in full, it is vital that the concrete is laid accurately, with sufficient consideration for the conditions that it is being laid in.

So, to ensure that your construction project goes off without a hitch, our team of concrete experts have shared their complete guide to concrete laying and curing in different temperatures, and how each type of condition impacts the concrete.

What effect does temperature have when laying and curing concrete?

Temperature can have a very significant impact on the process of laying and curing concrete.

This includes affecting the concrete’s:

• Setting time – high temperatures reduce the setting time (causing the concrete to set more quickly), while low temperatures prolong the setting time.
• Strength – high temperatures increase the speed of the concrete’s strength development (but, this can actually cause the concrete’s strength to decrease in the long term). In comparison, while low temperatures mean the concrete develops its strength at a slower pace, this can mean that the concrete has higher levels of strength in the long term.
• Cracking – if the concrete experiences rapid changes in temperature whilst it is curing, then this can cause it to crack.
• Freezing – if the temperature drops below freezing point while the concrete is curing, then the water content in the concrete can freeze. This causes freezing and cracking in the concrete.

So, as you can see, it is vital that you both control the temperature conditions during the curing process, and pay careful consideration to the temperature and weather conditions in which you are laying and curing your concrete.

What is the ideal temperature to lay concrete?

In the majority of cases, the ideal temperature for laying concrete ranges from 10°C to 30°C.

However, it is important to note that this is just a ballpark figure, and that it will vary depending on the type of the concrete that you are using, the volume of concrete that you are laying, and a range of other factors.

So, we always recommend that you consult with your concrete supplier, to find out what the specific recommended laying temperature is for your concrete.

What’s more, it is imperative that this temperature remains consistent throughout the laying and curing process. If too much fluctuation occurs, then this can weaken the concrete, cause a flawed finish, or result in cracking.

What is concrete curing?

Concrete curing is the process of ensuring concrete sets and hardens correctly. This involves keeping freshly-poured concrete moist and at the correct, consistent temperature.

By correctly curing the concrete, you can ensure the final product is strong, durable and achieves a flawless, crack-free finish.

Concrete is cured when it reaches its full strength. And it is important to note that, although concrete can be set, it can’t be fully cured. Read more in our how long does it take concrete to cure article.

The length of the curing process varies considerably, based on the temperature of the surroundings, weather conditions, and the type of concrete that you are using. Typically, however, it ranges from between a couple of days to a number of weeks.

Top tips for laying concrete in hot weather or in direct sunlight

When laying concrete in hot weather or direct sunlight, we recommend the following:

• Use hydration stabilisers in the concrete mix (these are designed to slow down the drying and curing process)
• Add a retarding admixture to the concrete mix (similarly, this will also help to slow down the setting time)
• Install shading to cover the concrete, and block direct sunlight. This will help to keep the concrete cooler, and keep its temperature consistent.
• Install windbreaks, protecting the concrete from exposure to hot, dry winds
• Aim to schedule the project during cooler times of the day
• Keep the concrete surface moist, by regularly spraying it with water
• Lay the concrete in smaller sections, so that you can finish each section before the concrete starts to set

Hotter weather or direct sunlight conditions can affect the concrete curing process by:

• Meaning the concrete dries faster
• Increasing the speed of evaporation – thereby causing the surface of the concrete to dry out too quickly. If left unchecked, this can lead to cracking
• Increasing the speed of setting
• Reducing the concrete’s workability
• Increasing the risk of plastic shrinkage
• Reducing the strength of the concrete (due to rapid drying and increased evaporation)

This is why it is so critical to control the temperature during your project, and ensure that your concrete is consistently at the required and moisture content.

Top tips for laying concrete in damp / humid weather

When laying concrete in damp or humid weather, we recommend the following:

• Use dry aggregates to keep the water-to-cement ratio at the required level
• Use a low slump concrete mix (this is less fluid, and so easier to work with in these conditions)
• Add a water reducer to the concrete mix
• Avoid sealing the concrete too early
• Check the weather forecast, and ensure that no heavy rainfall is predicted for at least 24-48 hours after laying the concrete
• Cover the concrete to protect it from rain or excess moisture. We suggest keeping it covered for 24-48 hours (at the minimum) after laying.

Damp or humid weather conditions can affect the concrete curing process by:

• Meaning the concrete takes longer to dry and cure
• Increasing the risk of surface discoloration
• Increasing the risk of mould growth.
• Increasing the risk of scaling or spalling
• Increasing the risk of cracking (as a result of trapped moisture within the concrete).

This is what makes it so important to monitor the moisture content of your concrete, and keep it consistent throughout the curing process.

Top tips for laying concrete in wet / rainy weather

When laying concrete in wet or rainy weather, we recommend the following:

• Use a low slump concrete mix
• Use dry aggregates
• Add a water reducer to the concrete mixture
• Check the weather forecast, and try to avoid any periods where heavy rainfall is predicted between 24-48 hours after laying the concrete
• Cover the concrete to protect it from rain or excess moisture. We suggest keeping it covered for 24-48 hours (at the minimum) after laying

Building on the point above, in extremely wet weather conditions, you may want to install a tent or shelter, to cover and protect the concrete

Wet or rainy weather can also affect the concrete curing process, by:

• Increasing the curing time
• Causing the concrete to wash away
• Causing the concrete to erode
• Increasing the risk of cracking
• Causing the concrete to expand
• Causing discoloration or efflorescence

As you can see, wet or rainy weather does not present the ideal conditions for concrete laying or curing. So, we would suggest that, if possible, you delay your project until the weather is less extreme.

Top tips for laying concrete in cold winter weather

When laying concrete in cold winter weather, we recommend the following:

• Use a low slump concrete mix
• Use aggregates (to help prevent the concrete mix from freezing, before it cures)
• Use a curing compound
• Avoid overworking the concrete
• Protect the concrete with insulation
• Cover the concrete with plastic sheeting, to protect it from frost
• Check the weather forecast, so that you can avoid any particularly cold temperature drops (this is particularly important for the first 24-48 hours after laying the concrete)

Cold winter weather conditions can affect the concrete curing process by:

• Increasing the curing time
• Reduced the strength of the concrete (if it freezes before the curing process finishes)
• Increasing the risk of surface damage
• Reducing the workability of the concrete

So it is critical that, if you do plan a concrete project for the colder months, you ensure that you have the right equipment and measures in place to keep the concrete at a stable, consistent temperature.

If you have any further questions about the best practices for concrete setting or concrete curing, or you would like to enlist the services of professional concrete specialists for your upcoming project, speak to iMix Concrete today.