At what temperature can concrete work be carried out

Although concrete is a versatile and necessary material for construction, the circumstances in which it is used have a significant impact on its performance. The temperature when mixing, pouring, and curing the concrete is one important consideration. The final product’s strength and durability can be greatly impacted by temperature.

Whether it’s a small do-it-yourself project or a large-scale construction project, knowing the optimal temperature ranges for concrete work is essential. Working in extremely hot or cold temperatures can cause cracks, weaken structures, and cause delays in the completion of construction projects.

This post will discuss the ideal temperature ranges for concrete work and how to control those ranges to produce a durable, robust finish. We’ll also go over the safety measures to take in less-than-ideal temperatures so that your concrete projects last a long time.

Temperature Range	Guidelines
Above 5°C (41°F)	Ideal for most concrete work. Ensure to keep the concrete moist and properly cured.
Between 0°C and 5°C (32°F and 41°F)	Proceed with caution. Use insulating blankets or heaters to prevent freezing.
Below 0°C (32°F)	Not recommended. If necessary, use heated enclosures and add antifreeze additives to the mix.

Advantages and disadvantages of winter work

There are benefits and drawbacks to concrete at below-freezing temperatures that should not be overlooked.

Benefits

1. Ability to pour concrete on loose soil. In the warm season, the soil crumbles, which complicates high-quality laying of the coating.
2. Lower cost of work. Winter is traditionally considered unsuitable for construction, so many stores offer discounts on materials needed to build a house.
3. Expedited provision of services. Unpleasant weather literally forces employees to work faster, which significantly reduces time costs.

Drawbacks:

1. When choosing workers, you should consider craftsmen who are able to pour concrete in winter. This is due to the fact that most builders only work in the summer.
2. There is a high risk that the concrete mixture will freeze, and construction work will have to be suspended until the external temperature reaches positive values.
3. In winter, daylight hours are shorter than in summer, so you need to buy equipment for additional lighting. As a rule, this requires considerable embezzlement.
4. Pouring the foundation on the frozen ground threatens with subsidence and the occurrence of cracks, since the earth sags when the ground.

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How do negative temperatures affect concrete?

As per p. 5.3.15 of SP 70.13330.2012 SNiP 3.03.01-87, it is feasible to lay concrete at negative temperatures solely under specific circumstances that offer the essential characteristics of concrete.

Solution quality at various temperatures

When puton laying occurs at below-freezing temperatures, irreversible structural alterations occur.

In this context, it’s important to keep in mind the characteristics of winter work:

• a solution prepared in the summer heat has a higher resistance and hardens faster than a mixture prepared in winter;
• when working in icy cold, the quality of the solution drops sharply. This is evidenced by the visible deformation of the product. Therefore, the temperature of concrete laying should be above 0 ° C.

Physicochemical processes

Low temperatures make concrete curing more dangerous and time-consuming because they can cause flaws to show up in the completed structure. It is thought that +4 °C is the lowest temperature at which the process can occur naturally.

When the temperature drops below zero, the hydration process of concrete slows down and chemically unbound water turns into ice, increasing the volume of the material by 9.7%. As a result, the mixture experiences stresses that lead to the destruction of its structure. Because frozen water molecules stick to one another, frozen concrete gains high strength, but this is a temporary effect.

The water will start to thaw and rehydrate when the outside temperature rises above zero degrees. However, concrete’s structure cannot be altered to give it the necessary design strength. Research indicates that if the mixture has reached between 30 and 50 percent of its design strength before freezing, the impact of low temperatures has no effect on the chemical and physical properties of concrete.

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Setting and hardening of concrete at low temperatures by day

Take note of the graph that illustrates how concrete hardens at varying temperatures to determine when it’s best to begin construction. Every building material manufacturer includes a table on the packaging that details how concrete hardens at lower temperatures. The ideal time is thought to be when the concrete’s strength is at least 72%. You should review the example, which details the daytime setting of concrete at low temperatures, in order to gain a better understanding of how to calculate the working time.

The right temperature must be chosen for concrete work in order to guarantee strength and longevity. Although a wide range of temperatures can be used to pour concrete, 50°F to 77°F is the ideal range. While hot weather can cause rapid drying and weaken the concrete, cold weather can slow down curing and increase the risk of cracking. In less-than-ideal circumstances, careful planning and safety measures, like the use of additives or protective coverings, can help preserve the quality of concrete.

Winter concreting methods

You should make sure ahead of time that the solution does not freeze if the work is done at a low temperature. Skilled constructors have selected multiple methods that enable concrete work to be produced in below-freezing temperatures.

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Its specificity is what makes working for the mercury column indicators below 0 °C unique. The mixture must be heated to a specific temperature before being laid. The process aims to raise the concrete’s critical strength threshold. This number establishes the minimal strength that concrete must acquire prior to frostbite. Working in the cold makes it more likely that the concrete’s structure will fail and that further ripening will be impossible.

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Heating and insulation of the solution

Scientific advancements provide a wide range of methods for reaching the required temperature.

Among the most well-liked, they emphasize:

1. Internal heating of the building structure. Special wires are laid inside the ceiling. This creates the necessary conditions for the solution to harden.
2. Heating the mixture from the outside. Increase the ambient temperature in a certain area of ​​construction work. For successful concreting, heat guns (construction heaters) and collapsible structures ("teplyaks") are used.
3. Permanent heat-insulating formwork. This method is applicable if the outside temperature is not less than -5°C. This system provides conditions for concrete hardening with the required temperature.

Use of antifreeze additives

Skilled artisans heat the mixture in addition to adding antifreeze additives.

Experts assert that this is a low-cost, straightforward technique for concrete at cold temperatures. Two groups of compositions are distinguished:

1. Inhibiting the process of water crystallization. The compositions contain components that ensure the polymerization of the solution in the cold.
2. Hardening accelerators. Using these components, builders reduce the hardening time of concrete.

Antifreeze components typically account for 2–10% of the cement base. It is possible to perform work at -25 °C when they are used.

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Among the most popular additives for antifreeze are:

• potassium carbonate (potash). This component has gained its popularity due to the fact that it does not provoke the formation of rust on metal structures. The polymerization process continues even at a temperature of -25 °C. The use of potash guarantees the absence of salt traces. However, potassium carbonate has its own peculiarity – the mixture sets quickly. So it is recommended to use the solution no later than 50 minutes after preparation;
• sodium nitrite. This modifier makes it possible to carry out construction work at temperatures down to -19 ° C, and also provides anti-corrosion properties. However, the use of this component leads to the appearance of salt traces on the finished product;
• calcium chloride. Promotes hardening of concrete, even if it is -20 °C outside, and also increases the speed of setting of the mixture. Due to its nature, the composition can leave salt stains on hardened concrete.

Features of pouring concrete under different weather conditions

Pouring concrete in hot weather

For individuals who tend to put things off, pouring concrete in sweltering heat will be an actual challenge.

Since the floor hardens quickly, you have to follow these guidelines:

• mandatory use of waterproofing. Even if it is not required due to weather conditions, its presence will not allow moisture to seep into the soil;
• a larger number of employees will increase the speed of work and ensure high-quality surface coverage;
• finishing the slab in two ways – with an aluminum float and a steel object, will provide a high-quality coating;
• to get a little extra time to complete the work, you should use a wetter mixture;
• you should start moistening the slab immediately after the treated surface has hardened.

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Work in the cool season

When working in a frosty environment, the concrete solidifies gradually. You must wait for at least an hour after the slab is placed before beginning the manual grouting process.

You need to heed the following advice because this stage calls for faster movements than the same movements on a hot day:

• do not moisten the concrete more than necessary;
• if the weather conditions do not require the use of polyethylene waterproofing, you should allow the moisture to escape into the ground. This will speed up the hardening of the concrete;
• you should fill the area with the mixture as early as possible, this will ensure faster readiness of the work, since the air temperature is higher during the day, accordingly, the mixture hardens faster.

Pouring concrete in cold weather

Special conditions must be created in order to pour concrete in below-freezing temperatures. The solution must not freeze in order to prevent the slab’s finely ground surface from getting mushy.

When working in cold weather, keep the following in mind to guarantee the best possible coating:

• you should ask the supplier to mix the solution with warm water on days when the temperature is below freezing. This helps to avoid problems when transporting the mixture;
• addition of quicklime to the mixture accelerates the initial hardening of concrete and will allow it to more reliably resist destructive factors during thawing or freezing. The amount of lime is usually 0.5 – 2% of the mass of the mixture;
• it is important to remember that using a large amount of the mixture is just as problematic as working in hot weather. Addition of lime makes the composition aggressive towards steel, this component cannot be used when working with concrete reinforced with steel structures;
• it is necessary to ensure that the crushed stone bed is not frozen;
• it is necessary to provide additional heating to the building in which the work is being carried out;
• cover the finished slab with polyethylene and cover with a layer of hay or straw, more than 100 mm thick, to provide thermal insulation.

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For any concrete structure to be strong and long-lasting, it is crucial to know the proper temperature for concrete work. Maintaining the proper temperature range helps prevent problems like reduced strength, poor curing, and cracking. Understanding when to use protective measures or additives as additional precautions can have a big impact on the final product’s quality.

Concrete work is particularly challenging in cold weather. It’s imperative to keep the concrete from freezing before it becomes strong enough. This could entail the use of admixtures that speed up curing, insulated forms, or heating blankets. Extreme heat, on the other hand, can quickly evaporate moisture from a material, creating weak spots and cracks. Retarders, misting, and shading are a few strategies that can be used to control these conditions.

In the end, meticulous planning and attention to detail are necessary for successful concrete work in a variety of temperatures. No matter the weather, you can achieve strong, long-lasting results by knowing how temperature affects concrete and using the appropriate techniques. To preserve the integrity of your concrete projects, keep an eye on the environment at all times and be ready to modify your approach as needed.

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