Introductions

Concrete acts as the backbone of any construction structures or foundations be it the laying down of highways or towering high-rise buildings, it lays the foundation of the structures.

But the real challenge arises when this construction is done in hot weather with factors like low humidity, high temperature strong wind.

As it will have a direct impact on the strength, quality & durability of concrete structures.

So special care needs to be taken for working with concrete in hot weather conditions.

What is Hot weather concreting?

When we talk about concreting in hot weather it refers to a condition where there is an acceleration in moisture loss at such a rate that leads to rapid concrete hardening.

In other words, hot weather concreting means working with concrete in high or extremely high temperatures.

The American Concrete institute (ACI)states hot weather consist of mixture of strong wind , high air temperature and low humidity which leads to quick moisture loss in concrete.

It is a really big concern where:

-Where air temperature is above 30 degrees C.

-Humidity falls below 40 degrees C

-Concrete temperature increase above  32 degrees C.

-Wind flow at a speed of 25 km/H.

So it is a complex condition to work with and superior care needs to be taken to prevent the problems like cracks, fast drying and weaker concrete.

Challenges of Hot weather concreting:

To work with concrete in high temperature is really tough and proper care is not taken can impact the durability , quality and longevity of the structures.

The areas that require special consideration are hydration, absorption, and evaporation.

Some of the challenges in hot weather concreting are.

• Slump Loss at an increased rate.
• Higher temperature of the concrete.
• More water demand.
• Decreased setting time.
• Cracking.
• Increased plastic shrinkages.

If the above is not addressed properly it can affect the durability and maximum durability is a key element in many reasons.

1. Hydration

Hydration in concrete is a chemical reaction that generates heat.

The higher the temperature of the concrete the faster the reaction.

In case the chemical reaction happens quickly due to high temperature the compressive strength of the concrete crystals may be reduced.

It is been proved concrete cured in temperature of 18 degree F than normal and result in losing upto 10 % of its 28 days  compressive strength.

2. Balancing slump

In hot weather concreting  there is a reduction in concrete workability, as it make it hardener to finish and place .

TO overcome this extra amount of water is added but this results in weakened concrete and the case of colored concrete adding extra water leads to inconsistent color.

So best solution is to use admixture rather than extra water to balance the slump without impacting strength.

3. Evaporation

Where high temperature exists the existence of strong winds speeds up and low humidity leads to rapid surface drying, which leads to the occurrence of cracking and plastic shrinkage.

• To avoid this risk the following should be done.
• Evaporation control agents should be kept in mind.
• The use of sunshades and temporary windbreaks should be made for the protection of surfaces.
• There should be monitoring of evaporation rates based on wind speed, humidity & concrete temperature.

4. Water absorption

When work is done in hot, dry conditions, the subgrade and formwork absorb water from the concrete, thereby impacting the quality of the concrete.

To prevent this, one can follow the below.

• Pre-wetting of the subgrade should be done before pouring is done.
• Air Content in warm concrete should be maintained to minimize the formation of cracks due to temperature differences between frequent pourings.

5. Proper curing

If fast curing is done in concreting in hot weather, it can lead to the weakening of the concrete.

This is due to concrete curing quickly.

Due to fast curing, the 28-day strength can be reduced by 10 %.

It is better to use curing compounds for consistent hydration.

Even curing blankets, water spray, and plastic sheets can be used to retain moisture.

Measures to be followed during hot weather concrete to get quality concrete:

Some of the best recommendations for successful concreting in hot weather are

1. Proper Preconstruction Planning

To avoid the risk of problems associated with hot -weather issue there should be proper co ordination between contractor, engineers& testing labs.

2. Statergising Concrete production

The use of chilled water, ice, or liquid nitrogen can help in cooling down concrete.

Even wetting and shading of aggregates can help in regularizing temperature.

3. Use of proper transportation

Speed plays a very important role in hot weather

So it is necessary to keep tight delivery schedules.

The forms should be ready to use.

And labor should be such that the concreting is done quickly.

4. Use of Admixtures

It is suggested to use retarders and hydration stabilizers to slow down the setting time, giving more time on site to work with concrete.

5. Techniques to control moisture

By covering the concrete with plastic sheets and the application of evaporation retarders, moisture loss can be prevented.

Impact of using concrete admixture in hot weather

When concreting work takes place in hot weather, it dries and hardens too fast.

This gives rise to low strength, cracks, and rough surfaces.

To fix this, one can use admixtures in the concrete.

The use of admixture helps in reducing the risk of damage occurring due to hot weather.

This is how admixtures help in hot weather concreting.

Locking the moisture

The use of admixtures helps hold the moisture for a longer period.

Thus, avoiding early drying prevents cracks and makes it strong.

Enhances Strength and longevity

By delaying the drying, the concrete can attain the required strength properly.

This helps in achieving a stronger and long-lasting structure

Improves workability

Hot weather concreting involves the risk of fast drying and impacts the strength of the concrete.

However, the use of concrete admixture helps in making the work easy, even with less water.

It helps in improving the workability of the concrete.

In a nutshell, admixtures can be your best friend in hot-weather concreting.

Conclusion

Hot weather concreting is tough to work on, but It is manageable if proper strategies and precautions are taken.

By managing concrete temperature, using effective curing methods and properly fixing the mix design, one can avoid the risk associated with hot weather.

Leading to more durable and high-quality concrete structures.