Today you’re going to learn the 7 most useful tips for pouring concrete in hot weather.
And these tips actually work.
In fact:
These tips help me pour concrete successfully in hot weather and build defectless concrete structures every time.
So if you’re working in concrete construction I hope you get a lot of value from this post.
Before delving into the list of tips, let’s first address an essential question:
What Temperature Is Really Too Hot For Pouring Concrete?
Before pouring concrete, you must want to know if the temperature is really hot or not.
Whenever I plan to pour concrete I visit websites like AccuWeather to know about the prevailing weather condition of the region.
And it instantly shows me the weather forecasts.
But, you first need to know which weather condition is considered as hot for concreting.
Generally, the ideal temperature is between 10°C (50°F) and 30°C (85°F).
A temperature above 30°C can be considered too hot for pouring concrete.
Additionally, you must consider certain weather-related factors for successful concrete placement. Such as:
- Low Humidity, and
- High wind velocity
In ACI 305R-10, “hot weather” is defined as any combination of high ambient temperature, low humidity, high concrete temperature, and/or high wind velocity that tends to impair the quality of freshly mixed or hardened concrete.
But that doesn’t make any sense to us.
So, I have researched this and found the following recommended range:
- The range of Ideal humidity is 40℅ to 70℅.
- The ideal wind velocity is generally below 16 km/h.
What Happens If You Pour Concrete When It’s Too Hot?
Now that you know about the ideal weather for concreting, let’s discuss what happens when you pour concrete in hot temperatures.
Accelerated Setting Time: Hot weather accelerate the setting time. So, you’ll have less time to place and finish the concrete.
Rapid Moisture Loss: High temperatures cause rapid evaporation of water from the concrete surface.
It can lead to potential plastic shrinkage cracks.
Reduced Workability: The accelerated setting time and fast moisture loss reduce the concrete’s workability.
And, you can’t add water to fresh concrete to increase workability.
Because adding excessive water will weaken the concrete’s final strength.
Surface Defects: Premature drying of the concrete can result in surface defects. Such as crazing, crusting, and uneven texture.
Thermal Cracking: The temperature difference between the concrete’s interior and surface can lead to thermal cracking during the curing process.
Reduced Strength: Rapid drying and accelerated setting can negatively impact the concrete’s long-term strength and durability.
As you can see, too-hot weather can adversely affect the quality and durability of concrete.
So, here are…
7 Useful Tips For Pouring Concrete In Hot Weather
And these tips will help you make defectless concrete structures every time.
Tip-1: Pour In The Coolest Part Of The Day
The coolest part of the day is usually in the morning or night.
So plan to pour either in the early morning or in the night.
In my case, I try to start concreting in the evening, when the sun is set, and continue pouring till the morning.
Tip-2: Block The Sunlight
You might have faced this!
Sometimes, it’s not possible to pour concrete in the coolest part of the day because of certain challenges like neighbors’ sleep concerns or vehicle restrictions at night, etc.
In that case, you need to pour concrete in the daylight.
No worries!
You can plan to pour concrete in the hottest part of the day too.
In that case, the easiest solution is to block sunlight.
You can do so by shading the pouring area.
Tip-3: Use Windbreaks
The excessive velocity of wind accelerates the evaporation of water from the concrete surface.
To get rid of this problem, use windbreaks to protect the concrete.
Tip-4: Be Well Prepared For Hot Weather Concreting
During hot weather, concrete loses water rapidly.
So you need to pour and finish the concrete in as little time as possible.
For that, plan ahead and make sure you have the following three things ready:
1. Manpower:
For mixing, carrying, unloading, vibrating, and finishing the concrete, you’ll need manpower.
Ensure you have a skilled and experienced concrete crew familiar with working in hot weather conditions.
2. Tools:
For pouring and successfully finishing the concrete, you’ll need a set of tools.
Some of the common tools and machinery are:
- Concrete Mixture
- Concrete pump
- Vibrators
- Pumps
- Concrete finishing tools
- Personal protective equipment
- Safety tools and equipment etc.
Based on your project’s requirements, arrange all the tools and make sure they are in working order.
3. Materials:
You’ll need the following materials:
- Cement
- Aggregates
- Admixtures
- Curing materials
- Shading materials
- Windbreaker materials
- Water source.
Make sure you’ve estimated the required materials and gathered them in places. So that you can use them when you need to.
Tip-5: Moisten The Form Before Pouring
It’s a simple yet important technique to ensure successful concrete pouring in hot weather.
By moistening the formwork beforehand you create a damp environment that slows down the rate of water evaporation and absorption.
To moisten formwork just spray water all over. But make sure no excessive water inside the form.
Tip-6: Use Cold Water
This is another excellent tip to apply to pour concrete in hot weather.
It’ll help to:
- Reduce concrete temperature
- Extend the setting time
- Make the concrete more workable and easy to handle.
Use cold water in the following ways:
In the concrete mix: Using cold water during concrete batching will help to reduce the initial temperature of the concrete mix.
For cooling concrete forms: In the above tip (tip-5), I’ve discussed moistening concrete forms.
Use cold water instead of normal water for that.
Tip-7: Prevent Surface Water Evaporation
Hot weather accelerates surface water evaporation.
If the surface water evaporates, the inside water from the concrete tends to come out.
This will hinder the hydration process of cement and make the concrete weaken.
Ultimately the concrete will fail to attain desired strength.
If you somehow prevent the surface water evaporation you’re good to go pouring concrete in hot weather.
Here are some techniques to prevent surface water evaporation.
Use Curing Blankets Or Membrane:
As soon as you finish the concrete, cover the surface with curing blankets or membranes.
It’ll entrap the water and prevent evaporation.
Cover The Surface With Wet Hessian Clothes:
This is another good technique to prevent surface water evaporation.
While using wet hessian cloths, squeeze that properly. So that no water drops on the concrete surface from the hessian cloth. Because the water can increase the water/cement ratio.
Use Curing Compounds:
To prevent water evaporation from the concrete’s surface, apply curing compounds on the surface.
It makes a thin film on the surface that prevents water evaporation.
Start Curing Early:
It’s crucial to start the curing process as soon as possible after finishing the concrete.
It helps to keep the concrete moist and continue the hydration of cement.
But how early can you start the curing?
There is a possibility of increasing the water/cement ratio of concrete by curing water.
In that case, how do you cure and keep the concrete moist?
To understand this, you have to be fully conversant with the concrete curing process.
Fortunately, I talked about this before in the post Curing Of Concrete: The Definitive Guide.
Conclusion:
That’s it for my list of tips for pouring concrete in hot weather.
As someone that works in concrete construction for a living, I really enjoyed putting this list of tips together.
Now I’d like to hear your thoughts:
Which tip from this list you’re going to use?
Or maybe there’s a tip out there that I overlooked (it happens 🙂 )
So go ahead and leave a comment below.