9 tips for concreting in hot weather | Converge.io

April 5, 2023

Having to work outside on a very hot summer day is a struggle just by itself. If you are not careful you might leave feeling dehydrated and with a bad sunburn. Even if you can handle the heat, are you aware of the issues it brings when it comes to concreting? 

Concreting in hot weather is not just business as usual. There are a lot of aspects to concreting that change when the temperature rises. To help you figure out how to efficiently and successfully work with concreting during hot days, we have prepared our top 9 best tips. 

But first we are going to learn more about how heat affects the concrete and what problems usually arise when you concrete in hot weather. 

Read more: Learn more about the ideal weather for concreting. Is it concreting in rainy weather, freezing conditions or with high humidity?

What is hot weather concreting?

The main question when defining hot weather concreting is “What counts as hot weather?”. However, the ACI (American Concrete Institute) states that the following conditions seem to be the answer to that question. In other words, it counts as hot weather when these conditions impair the quality of concrete:

  1. High ambient temperature
  2. High concrete temperature 
  3. Low relative humidity
  4. Wind speed
  5. Solar radiation

All of these conditions can provide a set of challenges when it comes to concreting. That is why pouring concrete in hot weather needs to be planned beforehand. That is why it is always a good idea to keep an eye on the weather forecast. If you notice a day with temperatures over 25C you probably have to start planning for hot weather concreting.

Problems with pouring concrete in hot weather 

Many challenges appear when you need to pour concrete in hot weather. The most significant issue that is caused by the heat is loss of moisture. This leads to the concrete setting too quickly. When concrete is setting quicker than it normally would it presents further problems such as:

  1. Difficulty finishing the pouring process in time.
  2. Any breaks in the process could affect the integrity of the concrete mixture. 
  3. Increased risk of cracks in the concrete.
  4. Decreased strength of the concrete

To avoid running into the problems that come with concreting in hot weather we created a list with our most useful tips.

Read more: We explain what happens to concrete when it freezes and how you can protect concrete from rain and frost.

9 tips for concreting in hot weather

  1. Create a well thought out plan
  2. Work during the coolest hours
  3. Keep the tools and machines cool
  4. Remove the concrete from the trucks
  5. Shade the concrete from the sun
  6. Reduce the initial temperature of the concrete mix 
  7. Moisten the surface before contact with concrete
  8. Use curing method that minimises loss of moisture
  9. Remember to take care of the workers

Sun in the sky with some clouds

1. Create a well thought out plan

Laying concrete in hot weather will require some planning. Mainly because there are some extra things you need to consider. For instance, plan to bring in extra staff if necessary to increase efficiency. Working efficiently will help you to minimise the risk of the concrete drying out while you are working. 

You also need to have your equipment ready before the hot weather arrives so you can work fast.

2. Work during the coolest hours

If it is really hot outside we recommend scheduling the concreting during early morning or later in the afternoon. Mainly to avoid the hours in the middle of the day where temperatures are at its highest. It is a better option for both the concrete and the workers. 

3. Keep the tools and machines cool

Let the machines and tools that you use while pouring concrete stand in the shade for as long as possible. Otherwise they might absorb the water from the concrete mix.

4. Remove the concrete from the trucks

It is important to not let the concrete mix sit in the trucks for too long after arrival. If you leave it for too long the temperature will rise in the concrete which will lessen its workability. 

5. Shade the concrete from the sun

If possible you should try to shade the concrete to create a cooler temperature. Direct sunlight will heat up and dry out the concrete a lot faster than if you manage to cover the worksite with sunshades. 

6. Reduce the initial temperature of the concrete mix

Make sure to reduce the initial temperature of the concrete mixture so that you at least have a good starting point. To accomplish a cool starting temperature you must first ensure that the water is cool. The aggregate can be cooled down by sprinkling water on it or keeping it in the shade. 

7. Moisten the surface before contact with concrete

Remember to moisten the surface where the concrete will be placed. If it is not cooled down before you start pouring the concrete, the concrete will instantly be heated. 

8. Use curing method that minimises loss of moisture

To reach its full strength concrete needs to go through the curing process. Unfortunately, the curing will stop if the concrete gets too dry, which means that the concrete will not reach its full strength. To avoid this you need to find a way to keep the water inside the concrete mix from evaporating.

One method that prevents the loss of water is chemical or liquid membranes. There are many different types of membranes but they work by creating a seal that protects the concrete by keeping the moisture in. It can stay on for the full 28 days needed for the curing process to finish. 

9. Remember to take care of the workers

Lastly, let us not forget about taking care of the workers that have to spend all day outside in the blazing sun. Remember to have enough staff so that they can take frequent breaks to rest, drink water and reapply sunscreen. 

Read more: Read up on how to measure the concrete’s temperature, under water concreting and long term effects of cold weather on concrete.

Frequently asked questions

Why does concrete crack in hot weather?

The concrete can crack in hot weather due to loss of moisture. Read more about the long term effects of hot weather on concrete in our article.

What temperature is too hot to pour concrete?

The ideal temperature to pour concrete is around 23C. If the temperature gets a lot hotter than that you might start to experience some problems with concreting and curing. 

Does concrete cure in the sun?

Since direct sunlight can cause the water in the concrete to evaporate, the curing process may be cut short. This leads to the concrete not reaching its full potential strength.

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