Introduction:
Hot weather can be defined as any time when the temperature is high enough that extra care must be taken to ensure that concrete is handled, put down, finished, and allowed to cure properly. Most problems with hot weather happen in the summer, but high winds, low relative humidity, and solar radiation can happen at any time, especially in arid or tropical climates. When it’s hot outside, the moisture on the surface of the concrete can evaporate quickly, which can cause several problems. High relative humidity generally reduces the effects of high temperature.
Fig: Hot Weather Concreting
Courtesy: carboncure.com
Hot Weather Concreting:
When planning concrete projects, it is important to consider how hot weather might affect concrete that has just been put down. High temperatures cause the need for water to go up, which raises the ratio of water to cement and lowers the potential strength. Higher temperatures can speed up slump loss and cause trapped air to escape. Temperature also greatly affects how long it takes for concrete to set. Concrete poured when the temperature is high will set faster and need to be finished more quickly. When it is 28 days old, concrete that was cured at high temperatures when it was young is not as strong as the same concrete that was cured at temperatures around 70°F (20°C).
Hot weather greatly affects every step of making and putting down concrete. Hydration is accelerated, and water both within and on the surface of the concrete is relocated. It changes its strength and durability over time. A lot is also affected by how hot it is, how humid it is, and how fast the wind is blowing.
Effect of Hot Weather on Concrete:
i) Higher Water Demand:
When temperatures rise, the moisture content of concrete decreases, making it more difficult to pour. Water is in higher demand to maintain the necessary workability.
ii) Reduction in the Curing Time of Concrete:
When the hydration reaction occurs, the concrete sets quickly, cutting into the time allotted for transporting, laying, and finishing the material.
iii) Rapid Loss of Workability:
Its workability decreases rapidly due to the rapid hydration and evaporation of water from concrete in warm temperatures.
iv) Greater Plastic Shrinkage:
Water will evaporate from the surface of the concrete faster than it will move from the interior to the exterior. Because of this, a moisture gradient will form, leading to surface cracks called plastic shrinkage cracks. Plastic shrinkage is more noticeable when it comes to floors, roads, and pavement, where there is much more surface area than depth.
v) Strength of Concrete:
When the temperature increases, the hydration reaction rate goes up. It makes the concrete stronger at first, but it makes it weaker in the long run. It happens because the soil loses moisture and becomes harder to work with, which makes it harder to pack down.
vi) Durability of Concrete:
As the temperature rises, the workability of concrete decreases; in response, more water is added, leading to pores forming as the water evaporates. It causes the concrete to become porous and less strong.
Setting Concrete in Hot Weather:
Hot weather can cause problems for concrete at some point, usually between 75oF and 100oF. Low relative humidity and high wind speed cause the most problems most of the time. The harsh sun and high temperature, along with these conditions, make it very likely that problems will happen. There are many ways to cool down concrete. The best way is to cool the aggregates, which can be done easily by sprinkling them with water and letting the water evaporate.
You can also use ice or pour liquid nitrogen into the mixer to cool the concrete. Both ways, though, make the concrete more expensive. The contractor should also have sunshades, windbreaks, and other ways to stop the land from drying out too quickly.
Rules for Pouring Concrete in Hot Weather:
1. Make plans and prepare your tools and supplies before it gets hot.
2. Keep the subgrade and forms moist, so they don’t soak up water from the mix.
3. Keep sunshades and windbreaks handy and use them as much as you can.
4. Before the ready-mix truck comes, you should have everything ready. Don’t keep the truck waiting.
5. Keep in touch with the company that makes the ready-mixed concrete. The contractor and the producer need to work together.
6. Concrete should be put down, cut off, and pushed immediately.
7. After screeding, use evaporation retardants, mist or fog with water, or cover with a vapor-proof sheet. It will help stop things from drying quickly, getting crusty, shrinking in plastic, and setting in rubber.
8. Temporary covers, like wet burlap that stays wet, can be put over the new concrete and taken off in small sections right before the finishers come.
9. Other high-risk ways of finishing, like using a smooth trowel, will no longer be needed if a burlap drag or broom finish is used instead.
10. Curing should happen when the surfaces are hard enough to keep from being scratched.
11. After placing and curing, seal with a good sealer for at least 30 days.
12. When the temperature is high, remember to protect the crew. Be careful in the sun, and drink a lot of fluids.
Conclusion:
Hot weather concreting is any time when the temperature is high enough that special precautions must be taken to ensure that the concrete is handled, placed, and moved correctly. In India, most of the land is tropical, but there are also places where it gets very cold. Because of this, we need to be aware of the unique problems when building with concrete in both hot and cold climates.
References:
1. “Pouring Concrete in Hot Weather: When Is It Too Hot? – Concrete Network.” Pouring Concrete in Hot Weather: When Is It Too Hot? – Concrete Network, www.concretenetwork.com/hot-weather-concreting/problem.html. Accessed 31 Jan. 2023.
2. “Hot Weather Concreting | Precautions and Effects.” Hot Weather Concreting | Precautions & Effects, gharpedia.com/blog/hot-weather-concreting-precautions-effects. Accessed 31 Jan. 2023.
3. “Hot Weather Concreting – Maturix I Intelligent Concrete Monitoring.” Maturix, maturix.com/by-challenges/hot-weather-concreting. Accessed 31 Jan. 2023.
4. “What Is Hot Weather Concreting?” Specify concrete, www.specifyconcrete.org/blog/what-is-hot-weather-concreting. Accessed 31 Jan. 2023.
5. “Hot Weather Concrete — What, Why, and How? – Nevada Ready Mix.” Hot Weather Concrete — What, Why, & How? – Nevada Ready Mix, www.nevadareadymix.com/concrete-tips/hot-weather-concrete. Accessed 31 Jan. 2023.
6. “Hot Weather Concreting: Precautions Taken, IS Code, Production and Delivery.” Dream Civil?: Civil Engineering & Construction Informations, 1 June 2022, dreamcivil.com/hot-weather-concreting.
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