ELAZIG GUNISIGI NEWSPAPER - December 2010
TS 1248
(Abnormal Weather Conditions)
Construction work is carried out according to one or more standards for each subject. Similarly, materials are subject to standards and regulations. Concrete is one of the most important building materials. There are rules for the production, pouring, and maintenance of concrete. In Turkish Standards, TS 1247 refers to concrete pouring under normal weather conditions, while TS 1248 refers to concrete pouring under abnormal weather conditions.
The weather is getting colder. If we say that snow has been delayed, it would not be wrong considering previous years. Construction work continues even in cold weather. In such weather, TS 1248 specifies the precautions to be taken when pouring concrete. This standard covers the rules for production, pouring, and maintenance under abnormal weather conditions to achieve the desired consistency, workability, strength, and durability in concrete.
To better express the necessary details, let us first define abnormal weather conditions. Abnormal weather conditions are those where heavy rainfall, strong winds, extreme cold and freezing, or excessive temperature rises occur during the concrete pouring period.
- Extreme cold occurs when the average temperature drops below +5°C for three consecutive days during concrete pouring.
- Extreme hot weather occurs when the average temperature rises above +30°C for three consecutive days during concrete pouring.
The average temperature is the arithmetic mean of the temperatures measured at 7:00 AM, 10:00 AM, 1:00 PM, 4:00 PM, and 7:00 PM at the concrete pouring site.
Rules for Concrete Pouring in Cold Weather
The goal of pouring concrete in cold weather is to achieve concrete with sufficient strength and durability despite freezing conditions. The protection times required for strength development should be determined by considering the possible weather conditions at the end of this period and the required strength values for the safety of the structure. In this regard, the necessary protection measures for strength should be considered before the measures for weather resistance.
Precautionary Measures
After placing fresh concrete, precautions against possible freezing and ensuring the minimum required temperature should be planned in advance. Several measures can be taken when pouring concrete in cold weather:
- The materials that make up the concrete can be heated,
- Accelerator additives can be used to speed up the setting time,
- Enclosed areas of the construction site can be heated.
Each of these precautions has its own specific characteristics. For instance, the mixing water can be heated, but it should not exceed 40°C. If it is heated beyond this temperature, the water should first be mixed with aggregates (sand and gravel), and once the temperature drops below 40°C, cement should be added to the mixture. If the hot water system is not adjusted in this way, the cement may set too quickly, leading to undesirable results.
Challenges with Concrete
Concrete is a practical yet sensitive building material. Even under normal conditions, there are many problems encountered during its production, pouring, and maintenance. When conditions worsen, extra care should be taken with concrete. If the water inside the concrete freezes, the desired load-bearing capacity will not be achieved. Therefore, extra caution is needed to avoid economic losses during concrete pouring in cold and rainy weather.
Curing Time and Form Removal
Under abnormal weather conditions, the curing time required for concrete to gain strength becomes more critical. In cold weather, form removal times should be extended. Since concrete gains strength more slowly in cold weather, formwork should remain for longer periods than under normal conditions. Additionally, even if precautions are taken during pouring, night-time concrete pouring should be avoided in cold weather.
Conclusion
Concrete and reinforced concrete are vital building materials. We are confident that by adhering to the necessary rules, we will achieve the desired strength and durability. Let us remember: a solid future is built with solid structures.