Graph (table) of concrete strength gain by day in summer and at subzero temperatures

Anyone working in construction needs to understand how concrete becomes stronger over time. The chemical process known as hydration causes concrete to gradually gain strength; it does not happen overnight. Temperature is one of the many variables that affect this process and can have a big impact on how quickly concrete hardens and reaches its maximum strength.

Warm summertime temperatures have the potential to quicken the curing process and increase the strength of concrete. This can facilitate faster progress and shorter wait times in a variety of construction projects. It’s crucial to carefully oversee this process, though, to prevent any problems like premature drying or cracking.

On the other hand, concrete encounters distinct difficulties when temperatures drop below freezing. The curing process can be slowed down or stopped by cold weather, which can cause delays and possible weaknesses in the finished structure. It is frequently necessary to use specific methods and additives to guarantee that concrete can cure correctly in these challenging circumstances.

The daily strength gain of concrete under various temperature conditions will be examined in this article, along with a detailed graph and table to show these variations. You can accomplish the best results on your construction projects by knowing these patterns, regardless of whether you’re working in the heat of summer or the depths of winter.

The process of gain

A mixture of water, binder, and filler is used to create concrete, a popular stone material. Its composition includes specialized additives that give it unique qualities and capabilities.

Reliable monolithic compounds are created during the hydration process, and these compounds take on the characteristics of long-lasting artificial stone. Forming a monolith takes several weeks (up to 28 days), and obtaining factory qualities can take up to 6 months.

  1. Setting. Is the initial stage.
  2. Hardening. Final stage.

By understanding all the maturity requirements, you can estimate how long a monolithic structure will last.

Setting

The building material cannot be used right away after pouring. Prior to doing this, you should familiarize yourself with the concrete strength gain schedule and the details of each stage of its development. Since the mixture is frequently transported to the construction site by specialized machinery, automated machinery is used to keep it mobile. Tixotropy technology stops natural maturation and preserves the fundamental consistency parameters until pouring.

However, the necessary working properties will degrade if the mixture is stored for an extended period of time or is exposed to high temperatures. It is mentioned in the concrete strength gain table that the setting time is between 20 minutes and 20 hours. In winter, the term will increase to 6–10 hours if work is done in below-freezing temperatures.

It is imperative to guarantee the presence of warm formwork in order to prevent deformation of the structure. The reinforced elements are defrosted and heated to a high temperature. Warm formwork is useless in the summer.

For winter work, some experts also use heat-insulating materials and specialized additives. You must familiarize yourself with their features and usage instructions before selecting this option.

  1. Steam.
  2. Electric current.
  3. Lime-boiler.
  4. Exothermic cements.
  5. All kinds of accelerators.

It is advised by experts to begin pouring the solution into molds at +20°C. Setting in this instance will take no more than 60 minutes and will happen in an hour. In warm weather, the process happens very quickly.

Setting up will take one hour if the M300 and M200 grades are used and the surrounding temperature is kept at +20 °C.

By understanding the amount of strength that concrete acquires, you can accurately estimate the project’s implementation time and approximate cost.

Hardening

The concrete mixture’s subsequent stage involves it hardening due to hydration. New compounds are created during the process from cement minerals. The absence of moisture in the solution will cause the hardening process to slow down or even stop, which will not give the material the necessary strength and cause it to start cracking.

The strength will steadily rise in the presence of enough liquid and at room temperature. A temperature of +20 °C and an air humidity of at least 90% are considered favorable conditions.

It will take seven to fourteen days to increase strength if these conditions are satisfied. The solution gets 60–70% of its declared strength during this time, after which the process slows down.

Concrete that is kept submerged in water will have stronger properties than concrete that is allowed to dry in the air. A dry atmosphere encourages moisture to evaporate quickly and halts the process. This is because there isn’t enough time for the cement mixture’s grains to hydrate. Preventing premature drying of concrete is therefore necessary to avoid unpleasant consequences.

The volume of the monolith is continuously changing as it hardens. The material likewise contracts; however, it contracts more quickly in the surface regions than in the interior. The concrete will develop shrinkage cracks on its surface if there is insufficient moisture present during the hardening process. Excessive heat generation can also lead to defects.

The temperature outside affects how long it takes for concrete to harden. The process slows down at low levels and speeds up at high ones.

The hardening process must be expedited if the structure being built is going to be subjected to additional loads or if it is necessary to dismantle the formwork quickly. For such tasks, specialized additives are employed. In a construction lab, their concentration is ascertained experimentally.

It is essential to correctly maintain the solution and keep it moist while shielding it from shaking, impacts, and damage in order to quickly reach factory strength. If not properly maintained, the material will deteriorate and become more brittle.

The cold that wintertime concreting contractors experience is the main cause of the weakening.

  1. Slowing down of hydration and increase in the time of setting.
  2. Freezing of liquid from the composition of the concrete mixture, due to which the set of strength properties is suspended.

Special components are added to the raw materials because it takes a lot longer to obtain strength properties at low temperatures.

Engineers utilize antifreeze additives in the winter to initiate the set process and lower the liquid’s freezing point.

The raw material is heated if high temperatures or high humidity are required to speed up the hardening process. The concrete surface needs to be reinforced with mats or shields to prevent temperature hydration and preserve the necessary conditions after the mixture has been poured. It is not permitted to use the filler for additional work if it freezes.

On building sites with access to high-power transformers, there is a demand for electric heating of concrete. Using electrical equipment when working with concrete is the best way to achieve factory strength without sacrificing the material’s performance qualities.

Concrete is covered in the winter to prevent heat loss from the surface.

Features of strength gain

The timetable for concrete hardening is dependent on several variables. The process slows down and stops at the zero mark of the thermometer when the temperature drops because the composition’s liquid starts to freeze and the material’s quality degrades.

The concrete structure cannot achieve factory performance properties without the necessary volume of moisture, and autoclave curing greatly speeds up the process. The interval is shortened when there is moisture in the air.

The composition of B25 concrete dictates the strength gain schedule. Higher grade compositions harden more quickly, requiring workers to begin processing faster. The material needs to be in favorable conditions from the third to the tenth day following pouring. The stone itself is moistened six to seven times a day when the weather is warm, and the solution is coated in a film that repels water.

The mixture needs to be shielded from the sun. The concrete is insulated and artificially heated during the winter. To keep the liquid from freezing and shield the structure from precipitation, specialized heating equipment is used. The SNiP diagrams provide the regulatory and safe period of gain, which must be followed.

What determines the strength gain

  1. Cement mix grade.
  2. Water and cement proportions.
  3. Proportions of other additives.
  4. Compaction method.
  5. Temperature and humidity conditions.
  6. Laying method and speed.
  7. Quality and intensity of moistening.

The final strength properties depend on the component proportions, which must be adjusted as the concrete grade increases.

Higher grades of cement mix foundations are stronger, more dependable, and have longer service lives. The stone’s ability to emit heat makes it stronger during the colder months; however, it is preferable to add specialized additives to the composition to balance the monolith formation schedule. Their purpose is to halt hydration and hasten hardening.

In just two weeks, the composition achieves grade strength with these components. The composition’s component types have an impact on the strength properties gained. Because aluminous cement can release seven times as much heat as traditional Portland cement, it can solidify even in extremely cold temperatures.

It matters how the organic additive grains are shaped and proportioned. Their irregular shape combined with their rough surface improves the adhesion properties and material quality. The mass stratifies as the water content rises.

Sand concrete with a low water/cement ratio works best to expedite the process and shorten the concrete’s curing time. The material will only obtain up to 50% of its declared strength during the maturation process if it is not compacted well. By using manual compacting tools, you can raise the indicator by thirty to forty percent.

Daily schedule

The time interval during which the mixture acquires factory properties is shown in the schedule for obtaining the concrete’s factory strength by day. The composition can "mature" in 28 days in a favorable environment, with the first five days showing the highest hardening efficiency. Seven days after pouring, 70% is shown on the strength indicator. In this instance, additional work can only be started after obtaining 100% of the value, or within 28 days.

However, the graph readings could alter if the surrounding circumstances do. Control tests on samples should be carried out in order to precisely ascertain how long it takes for concrete to fully solidify.

  1. Concrete curing in formwork.
  2. Maturity of the mixture after dismantling the formwork structure.

The structure needs to be further heated and covered with waterproofing materials if the work is done during the winter. The polymerization process will slow down if this doesn’t happen.

Concrete grade M200-M300 (the solution was created on the basis of Portland cement M400-M500) Average daily temperature at which concrete hardens, °C Hardening interval
1 2 3 5 7 14
Concrete compressive strength (% of factory value)
-3 3 6 8 12 15 20
0 5 12 18 28 35 50
+5 9 19 27 38 48 62
+10 12 25 37 50 58 72
+20 23 40 50 65 75 90

Use sand concrete with the lowest possible water to cement ratio to expedite the procedure and shorten the curing period. The terms from the schedule will be reduced by two times if the ratios of cement and water equal ¼. Plasticizers can be added to the composition to dilute it and get a better outcome.

Day Strength Gain in Summer Strength Gain at Subzero Temperatures
1 20% 5%
3 40% 10%
7 60% 20%
14 80% 30%
28 100% 40%

For building projects to be successful, it is essential to comprehend how concrete gains strength over time. Depending on external factors, the rate at which concrete strengthens can vary greatly. Summertime temperatures tend to quicken the curing process, enabling concrete to attain its maximum strength sooner. While this can be helpful for projects with limited time, it also needs to be closely watched to avoid problems like cracking from drying too quickly.

Conversely, concrete’s ability to gain strength can be significantly slowed down by extremely low temperatures. The hydration process, which is necessary for concrete to harden, is less effective when the temperature drops. In order to ensure proper curing, concrete may not reach the desired strength within the typical timeframe, requiring the use of special techniques and materials. For instance, insulating the concrete or adding additives that quicken the curing process can help lessen the effects of cold weather.

Builders and engineers can make well-informed decisions about their construction schedules and methods by consulting a graph or table that illustrates the strength gain of concrete by day under various temperature conditions. The scheduling of formwork removal, load application, and other crucial construction tasks is made easier with the use of this information. When the curing process is appropriately controlled based on temperature, concrete acquires the strength and durability required for long-term functionality.

Any construction project requires an understanding of how concrete strengthens over time, particularly in conditions with fluctuating temperatures. The rate of concrete strength gain by day during summer and below-freezing temperatures is shown in this article’s easy-to-read graph and table. Through a thorough analysis of these variations, architects and engineers can make well-informed choices that guarantee their structures’ longevity and security throughout all seasons.

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Anna Vasilieva

Journalist with a technical education, specializing in construction topics. I can explain complex technical topics in simple and accessible language.

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