Concrete strength curing schedule: features, types, technology and key indicators

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

One of the important indicators of concrete quality is strength. If you familiarize yourself with the requirements of state standards, you can find information that strength can vary from M50 to 800. However, one of the most popular are concrete grades from M100 to 500.

Cure curve

Concrete solution for a certain time after pouring will acquire the desired performance properties. This time interval is called the holding period, after which the protective layer can be applied. The concrete strength curve reflects the time it takes the material to reach its highest level of strength. If normal conditions continue, it will take 28 days.

The first five days is the time during which intensive hardening will occur. But after 7 days after completion of the work, the material will reach 70% strength. It is recommended to start further construction work after reaching one hundred percent strength, which will happen after28 days. The schedule of curing of concrete over time may differ for individual cases. In order to determine the timing, control tests are carried out on samples.

What else you need to know

If work on monolithic housing construction is carried out in warm weather, then in order to optimize the process of keeping the mixture and gaining physical and mechanical properties, it will be necessary to keep the structure in the formwork and leave it to ripen after dismantling the fence. The schedule for curing concrete in cold weather will be different. In order to achieve brand strength, it is necessary to provide concrete heating and waterproofing. This is due to the fact that lower temperatures slow down the polymerization.

In order for the curing to occur as quickly as possible, and the exposure of concrete in time to be minimized, it is necessary to add sand concretes to the ingredients, in which the water percentage ratio is minimal. If cement and water are added in a proportion of four to one, then the time will be halved. To obtain such a result, the composition must be supplemented with plasticizers. The mixture may mature faster if the temperature is raised artificially.

Strength control

In order for the schedule of curing of concrete to be observed, for some time - up to a week - it is necessary to carry out measures to ensure conditions for curing the mortar. It needs to be heatedmoisturize and cover with moisture and heat insulating materials.

Heat guns are often used for this. Experts recommend paying special attention to surface moistening. 7 days after the completion of pouring under such conditions, if the ambient temperature varies from 25 to 30 ° C, the structure can be loaded.

Classification of concrete

If cement and traditional dense aggregates are used in the process of mixing the mortar, which make it possible to obtain heavy compositions, then these mixtures belong to the M50-M800 grades. If you have concrete of the M50-M450 grade in front of you, then porous aggregates were used for its preparation, which made it possible to obtain light compositions. Concrete has a grade within M50-M150 if it is especially light or light, as well as cellular.

The design grade of concrete must be determined at the stage of drawing up documentation for the construction of the facility. This characteristic is given based on the resistance to axial compression in cube samples. In structures under construction, axial tension is the main one, while the brand of cement is determined by it.

Concrete's strength development (tensile development curve) will take longer when the compressive strength grade increases. But in the case of high-strength materials, the increase in tensile strength slows down. Depending on the composition and area of \u200b\u200buse of the mixture, the strength class and brand are determined.

The most durable materials are those with the followingstamps:

• M50.
• M75.
• M100.

They are used in the construction of critical structures. When structures and buildings are erected that require great strength, concrete grade M300 is used. But when arranging the screed, it is best to use the composition of the M200 brand. The strongest are cements, the brand of which starts with M500.

Temperature curing

If you are going to use the mortar in construction, then you should know the graph of the dependence of the curing of concrete on temperature. As mentioned above, setting occurs during the first few days after mixing the solution. But to complete the first stage, it will take time, which is affected by the temperature of the external environment.

For example, when the thermometer is kept at 20 ° C and above, it takes an hour to set. The process starts 2 hours after the mixture is prepared and ends after 3 hours. The time and completion of the stage will shift when it gets colder, it will take more than a day to set. When the thermometer is kept at zero, the process begins 6-10 hours after the preparation of the solution, and it lasts up to 20 hours after pouring.

It is also important to know about viscosity reduction. In the first stage, the solution remains mobile. During this period, mechanical action can be exerted on it, giving the structure the required shape. The setting stage can be extended using the thixotropy mechanism,exerting a mechanical effect on the mixture. Mixing the mortar in a concrete mixer ensures the extension of the first stage.

Percentage of concrete strength from the grade depending on temperature and time

Beginning builders are usually interested in the graph of the curing of concrete at 25 ° C. In this case, everything will depend on the brand of concrete and the hardening period. If you use Portland cement grades in the range of M 400 to 500 when mixing, you will eventually be able to get concrete M200-300. In a day at the specified temperature, its percentage of compressive strength from the brand will be 23. In two, three days, this figure will increase to 40 and 50%, respectively.

After 5, 7 and 14 days, the percentage of brand strength will be 65, 75 and 90%, respectively. The curve of curing of concrete at 30 °C changes somewhat. In a day and two, the strength will be 35 and 55% of the brand, respectively. After three, five and seven days, the strength will be equal to 65, 80 and 90%, respectively. It is important to remember that the standard safe period is 50%, while work can only begin when the concrete strength has reached 72% of the branded value.

Critical strength of concrete depending on grade: an overview

Immediately after pouring, the solution will gain strength due to heat release, but after the water freezes, the process will stop. If the work is supposed to be carried out in winter or autumn, then it is important to add antifreeze mixtures to the solution. After installationAlumina cement generates 7 times more heat than regular Portland cement. This indicates that the mixture prepared on its basis will gain strength even at low temperatures.

The brand also influences the speed of the process. The lower it is, the higher the critical strength will be. The graph of the strength development of concrete, an overview of which is presented in the article, indicates that the critical strength for concrete grades from M15 to 150 is 50%. For prestressed structures made of concrete grades from M200 to 300, this value is 40% of the branded one. Concrete grades from M400 to 500 have a critical strength of 30%.

Hardening concrete in perspective

Schedule of curing concrete (SNiP 52-01-2003) is not limited to a month. It may take several years to complete the curing process. But you can determine the brand of concrete after 4 weeks. The strength of the structure will gain at different speeds. This process is most intense in the first week. After 3 months, the strength will increase by 20%, after which the process slows down, but does not stop. The indicator may double in three years, this process will be influenced by:

• time;
• humidity;
• temperature;
• concrete grade.

Quite often, novice builders wonder in which GOST the concrete strength curing schedule can be found. If you look at GOST 18105-2010, you can learn more about this in more detail. These documents mention that temperature directly affects the duration of the process. For example, at 40 ° C, the brand value is reached in a week. Therefore, it is not recommended to carry out work in winter. After all, it is problematic to heat concrete on your own, for this you need to use special equipment and first familiarize yourself with the technology. But heating the mixture by more than 90 ° C is completely unacceptable.

Conclusion

Familiarizing yourself with the curing schedule, you will be able to understand that stripping is carried out when the strength of the structure exceeds 50% of the branded value. But if the ambient temperature drops below 10 ° C, then the brand value will not be reached even after 2 weeks. Such weather conditions suggest the need to heat the poured solution.