Hot weather concreting

Hot weather concreting

Introduction

Are you residing where the weather remains hot for most of the year, and you might need to pour concrete when the temperature is at its peak? Or it’s a routine hot summer, and you can’t delay your project, and you’re looking for helpful tips. 

We often come across situations where the weather is unfavorable, be it too hot or too cold. However, we must find a way to work through it and make the most out of the situation.

Concrete that overheats and sets too quickly can compromise the quality of the finished product. It may result in a weaker concrete structure, leading to cracking, scaling, or spalling.

Additionally, it can make the concrete challenging to work with, causing problems during the pouring, leveling, and finishing stages. Therefore, keeping the concrete cool and slowing down the setting time in hot weather conditions is essential.

Therefore, here is a guide and tips on hot weather concreting.

Concreting at hot temperatures

When working with concrete in hot weather, you must alter your methods to hot-weather concrete techniques. This is important when freshly mixed concrete may be compromised because of high and rapid moisture loss and accelerated cement hydration.

Only a few who mainly deal with cold weather concreting know about these things. Some factors come into the picture when hot weather is concreting. Such factors as high concrete temperature, high ambient temperatures, wind speed, solar radiation, and low humidity.

Generally, a good thing to remember is to begin thinking about hot weather concreting when the concrete temperature and the air exceed eighty degrees Fahrenheit.

Aggregate use

Ready-mix concrete suppliers take several measures to ensure the concrete they deliver to the job site is as cool as possible. One of the primary factors affecting the temperature of the concrete is the type of aggregate used.

Suppliers typically keep the piles of aggregate in the shade to prevent them from absorbing too much heat from the sun.

In addition to using shaded aggregate, suppliers also use cool water to reduce the concrete’s temperature further. Some suppliers even use chilled water or ice to lower concrete temperatures in hot climates.

By using these cooling measures, the concrete supplier can prevent the concrete from overheating and setting too quickly, which can compromise the quality of the finished product.

Overall, by taking these steps to keep the concrete cool, the supplier can ensure that it is easier to work with and will ultimately perform as intended once it has been poured and set.

Retarding admixtures

During the summer, high temperatures and intense sunlight can cause the concrete to set quickly and become difficult to work with. To address this issue, contractors can use retarding admixtures to slow down the setting time of the concrete. 

Retarders are added to the concrete mix at the job site and work by delaying the chemical reaction that causes the concrete to harden. This gives contractors more time to pour, level, and finish the concrete before it sets.

However, it is essential to note that using too much retarder can cause the concrete to become unworkable and develop a crust.

One type of retarder admixture is the reducing water variety. Water reducers that are mid-range can be used to increase the air content of the concrete while also slowing down the setting time.

This helps prevent the concrete from becoming too burdensome and makes it easier to work with.

It is important to remember that proper curing is critical when using retarders. Curing ensures that the concrete reaches its maximum strength and durability.

The concrete may become weak and prone to cracking and other damages if not cured properly. Therefore, contractors should take special care to follow the recommended curing process when using retarders.

Hydration control admixtures

Hydration control admixtures are chemical additives that help regulate and manage the hydration process of concrete. They offer a distinct advantage over concrete retarders, which only delay the setting time of concrete.

Unlike retarders, hydration control admixtures slow the concrete curing process, even after the admixture wears off. 

When compared to retarders, hydration control admixtures are better suited for hot weather conditions and when concrete needs to start setting at night; this is because retarders tend to develop quickly once they wear off, which can cause the concrete to set too soon, resulting in poor quality and strength. 

These admixtures can be particularly useful in sweltering weather conditions, as they help to prevent the concrete from curing too quickly and cracking.

Additionally, they are ideal for situations where the concrete has to travel a long distance from the supplier to the job site, as they can help delay the setting time of the concrete by up to five hours. 

Overall, hydration control admixtures are essential in modern concrete technology, helping to ensure the quality and durability of concrete in a wide range of applications.

Fly ash

Fly ash is a fine powder that is a byproduct of coal combustion. It is a supplementary cementitious material that can be used in concrete, providing various benefits. When fly ash is combined with concrete, it reduces the amount of Portland cement needed, thereby reducing the overall cost of the construction project.

One of the essential benefits of using fly ash in concrete is that it can help control rising temperatures, making it an excellent choice in hot climates where the risk of concrete cracking due to high temperatures is high.

Fly ash can also help reduce the heat of hydration, which is the heat generated during the chemical reaction between Portland cement and water.

However, when using fly ash, knowing its effects on concrete setting times is crucial. If fly ash is used to slow down definite setting times, it can also change the color of the concrete. Therefore, adjusting the fly ash percentage in your shipment is essential to avoid discolored concrete supplies.

It is also important to note that fly ash is ineffective in higher temperatures. In such cases, using other materials more suitable for the conditions is best. Fly ash is an excellent choice for construction projects requiring cost-effective and environmentally sustainable solutions.

Using too much retarder can significantly affect the concrete’s strength and durability. Retarders are used in concrete to slow down the setting time, which allows for more workability and finishing time.

However, excessive use of retarders can cause the concrete to take much longer to harden, weakening the final product. Additionally, suppose the retarder reacts with other chemicals in the mix.

In that case, it can cause the concrete to become more porous and susceptible to damage from freeze-thaw cycles and other environmental factors. It’s essential to use a retarder in moderation and follow the manufacturer’s instructions to avoid any adverse effects on the concrete.

In addition to cost reduction, there are several other benefits of using fly ash in concrete. Fly ash is a byproduct of coal combustion and is often used as a partial replacement for cement in concrete mixes.

One of the main benefits of using fly ash is that it improves the workability of the concrete, making it easier to pump and place. Fly ash also contributes to the long-term strength and durability of the concrete by improving its resistance to cracking and shrinkage.

It can also help mitigate the effects of alkali-silica reaction, a common cause of concrete deterioration. Furthermore, fly ash is a sustainable material that reduces the amount of waste sent to landfills and conserves natural resources.

Overall, using fly ash in concrete is a cost-effective and environmentally friendly solution with several performance benefits.

Conclusion

Pouring concrete during the early evening of warm summer months is recommended to ensure the best outcome. Ensure your crew and equipment are prepared to begin working when the concrete arrives.

This is because the temperature of the concrete can significantly increase while waiting in the truck. Consider how your soda would be if left in a metal container on a hot summer day.

It is essential to keep the concrete shaded from direct sunlight. Using sunshades can be beneficial to avoid direct sunshine on the wet surface. Additionally, ensure that your equipment and tools are shaded, especially if they come into contact with the concrete directly.

Concrete surface curing too fast might lead to concrete dusting and crumbling. It’s usually something that customers will not be happy about, so if it can be avoided, it should.

If laying concrete for exteriors on a subgrade, spray all the elements using cold water. This includes the different kinds of sub-grades, even before concrete installations. This will protect the forms and the subgrade from water absorption from the concrete.

Once the concrete is set and is bull-floated, utilize a retarder for evaporation or a monomolecular film to slow the evaporation process and retain the water on the surface.