Although choosing the right concrete mix is vital for the success of any construction project, the site conditions when you pour the mix are just as essential. Temperature plays a key role in this and can determine the longevity and performance of a concrete mix; if conditions are too hot, then the concrete is at increased risk of cracking, too cold and the strength of the mix might be compromised.

But what is the best temperature for pouring concrete? In this article, we’ll explore the ideal site conditions and discover how this can have an impact on the overall end product.

What is the best temperature for pouring concrete?

Concrete should be poured in moderate temperatures to maximise strength and durability, and to cure at a steady pace.

So what do the official recommendations say? BS 8500 is the British standard that everyone should adhere to when using concrete in a construction project. Although this doesn’t specify an exact temperature, it does say that the temperature of fresh concrete at the time of pouring should never be below 5°C or above 35°C. 

Most concrete suppliers agree that the ideal temperature range is between 10°C and 20°C, however, air temperature at the time of batching the concrete should also be taken into account. Concrete should only be batched if the air temperature is above 2°C and rising or below 30°C. All good ready-mix concrete suppliers will inform customers when air temperatures are outside of this range.

What happens if you pour concrete in hot temperatures?

The problem with pouring concrete during a heatwave is that it can cure prematurely because the water in the mix evaporates too quickly. Not only can this cause cracking, but it also greatly reduces the workability of the mix, making it much more difficult to place, compact and finish.

If pouring concrete during hot weather, there are a number of precautions you should take:

• Schedule the work for early or late in the day and avoid peak temperatures between 2pm and 4pm.
• Utilise a concrete pump to ensure the mix can be poured quickly.
• Lightly dampen the sub-base before pouring.
• Use windbreaks to provide some shade.
• Consult an expert, like Tor Multimix, for help.

What happens if you pour concrete in cold temperatures?

If you pour concrete during cold temperatures, this can mean curing takes much longer as the hydration process is slowed right down, meaning the concrete may never reach its intended strength. If the temperature dips below 0°C, also known as the freezing point, then the water in the mix will freeze and expand, causing the concrete to crack and potentially rendering it not fit for use. 

If you have no choice but to pour concrete in cold weather, then there are a few things you should do:

• Never pour straight onto a frozen sub-base.
• Use frost blankets to prevent frost and ice from forming.
• Pour during the warmest hours of the day.
• Use windbreaks or frost blankets to protect the freshly laid concrete.
• Enlist an expert, like Tor Multimix, for advice.

Does weather matter when pouring concrete?

As we’ve covered above, you should ideally be pouring concrete on a mild day with no extreme temperatures. You should also try to steer clear of rainy conditions, as any excess water can affect the ratio of the mix and lead to a weaker final product.

However, sometimes it just isn’t possible to avoid pouring concrete in the rain, particularly when you’re working on a time-sensitive project. Before pouring concrete, keep checking the weather forecast and if rain is predicted, keep the site as dry as possible using tarpaulin or plastic sheets. If it starts to rain heavily during the pour itself, you may have to try and create a makeshift shelter to keep the concrete protected. Be aware of potential problem areas on your site, such as guttering or drainpipes that might direct water onto the surface.

Come rain or shine, the team at Tor Multimix is here to assist with all your concrete needs. We supply a variety of concrete products for customers throughout Glastonbury, Bridgwater, Wells, Somerset, Dorset, West Wiltshire, Bristol, Bath and beyond. With over 40 years of experience, we can help ensure your concrete is poured in the best possible conditions – simply contact us for more information.