Antifreeze additive in concrete - a dry mixture or solution of chemicals for which a fairly long shelf life. The main purpose of this additive is to provide work on concreting during the winter period.
New complex antifreeze additives, in addition to adjusting the strength of concrete mix, regulate a number of its rheological properties. As a result of lowering the temperature, the setting time is shorter, the hardening process of the cement stone is accelerated, and its brand strength is increased by 2 classes.
Antifreeze additives in solution (concrete) on a chemical basis can be conditionally divided into three main groups:
- Antifreeze winter additives-accelerators.
Let us consider them in more detail.
This antifreeze additive in concrete reduces the freezing point of the liquid, accelerates or weakly inhibits the setting of the solution. At the same time, antifreeze does not change the rate of formation of structures at all.
Sulphate of iron, aluminum or other metals is a frost-free component, the addition of which will ensure the fastest formation of a dense solution. The strength is also positively affected by the active heat release, which is accompanied by the interaction of concrete with the products of hydration. Such an additive can not be used to lower the freezing point, since it completely binds to sparingly soluble compounds.
Antifreeze winter additives-accelerators
Antifreeze additives in solution (concrete) of this type contribute to increasing the degree of solubility of silicate components of cement, resulting in the formation of double or basic salts with hydration products. Most of them simultaneously reduce the freezing point.
- Potash - a strong antifreeze additive in concrete, accelerating the hardening process. In order to prevent the decrease in strength, potash is recommended to combine with sulphite-yeast mash, sodium tetraborate or other retarding agents. The concentration in the mixture should not exceed 30%.
- Sodium nitrite is a fire-hazardous poisonous antifreeze additive to concrete. In the case of combined use with lignosulfonates, the formation of poison gases is possible. The dosage should be determined experimentally and be within 0.1-0.42 l / kg of cement mortar at an ambient temperature of 0 to -25 ºC.
- Sodium formate is a frost-free accelerator. Used to improve the plasticizing, water-reducing properties. It is recommended to be used together with naphthalene lignosulfonate. This antifreeze additive to concrete consumption from the mass of cement on average has 2-6%.
To organize concrete works in winter, in addition to the above, you can choose a frost-based additive based on sodium formate on alcohol, urea, ammonia water or calcium chloride.
- Plastifies and stabilizes finished cement mixtures.
- Allows you to perform concrete work in winter.
- Promotes increased durability of the mixture during the operation of the building.
- Improves the ultimate frost resistance of the solution.
- Reduces shrinkage deformation.
- Reduces the release of water and the process of delamination.
- Reduces installation costs.
- Eliminates corrosion of the internal reinforcing mesh.
The use of antifreeze additives in concrete as a whole will lead to significant savings.
- Some additive components are considered poisonous.
- With the purpose of reliable maintenance of strength characteristics, the consumption of cement increases.
- Sometimes the regulated capacity of concrete grade falls.
Recommendations for use
Antifreeze additive is introduced into the concrete solution together with water, preferably with the last third of the liquid. It is undesirable to administer the product into a dry mixture. After the additive has been introduced into the solution, it is necessary to wait a certain time to ensure its uniform distribution.
It is very important to adhere to the requirements for installation work in the winter period:
- During the snowfall it is necessary to perform special shelters.
- The recommended solution outlet temperature is from +15 ºC to +25 ºC.
- To prepare the mixture, it is advisable to take preheated water.
- Heating aggregates should be performed immediately before use.
To obtain a solution with the necessary strength characteristics, it is recommended to observe the requirements for the care of concrete in the winter season in accordance with SNIP 3.03.01. It is desirable to perform measures to achieve strength of at least 20% of the design by the time the solution is cooled to the temperature at which the calculation of the dosage was performed.
Antifreeze additives in concrete: technical characteristics
|Pot life of solution||Not less than 3 hours|
|Bulk weight||1300-1400 kg / m 3|
|Size of aggregate||Not more than 0.3 mm|
|Temperature of use||From +5 ºC to +30 ºC|
|Density at compression at the age of 28 days||Not less than 10 MPa|
|Adhesive strength||Not less than 0,5 MPa|
|Optimum application layer||2-4 mm|
|Consumption||26-37 kg / m 3 masonry|
|Brand for frost resistance||F 50| Dosage
The dosage of antifreeze additive should be selected for each specific case by carrying out tests in production and laboratory conditions. It depends on the following:
- Conditions for care of concrete.
- The temperature of the solution at the exit from the concrete mixer.
- Ambient temperature.
- The material and chemical-mineralogical composition of the solution and the speed of recruitment strength.
- Vintage strength of cement.
When storing for a long time or using a large volume of the additive, it is recommended to periodically homogenize the solution by mixing or bubbling with compressed air. Dosage should be performed with an error of ± 2%.
|Solution hardening temperature||Consumption of antifreeze additive for warm solution in terms of dry consistency||The consumption of antifreeze additive for cold mortar in terms of dry consistency|
|Up to -5 ºC||0,8-1% of the solution mass||1-1.2% of the weight of the solution|
|-5 ºC to -10 ºC||1-1.2% of the weight of the solution||1,2-1,4% of the solution mass|
|-10 ºC to -15 ºC||1,2-1,5% of the solution mass||1.4-1.8% of the weight of the solution|
|-15 ºC to -20 ºC||1.5-1.8% of the weight of the solution||1.8-2.5% of the weight of the solution|
|-20 ºC to -25 ºC||1.8-2.2% of the weight of the solution||2.5-3.5% of the weight of the solution|
Antifreeze additive in concrete own hands
It is worth noting that the most preferable option is to purchase a ready-made additive in concrete solution in any specialized store. They are not so expensive, they have a low consumption and at the same time they provide a significant improvement in the properties of the solution in winter, with minimal negative consequences.
With a small work front and an air temperature of at least 10 ºC, this method will be optimal.
However, it happens that the antifreeze additive in concrete, made by hand, is the only option. In this scenario, attention should be paid to chlorides (salts). Chloride salts can significantly reduce the freezing point of the solution, shorten the setting time and reduce the consumption of cement. But such a frost-resistant additive in concrete (expert reviews confirm this) can only be used for unreinforced structures.
When working with this type of substance, protective gloves are recommended.
In case of contact with skin, wash with soap and water. It is unacceptable to get antifreeze additives in the eyes. In such a case, immediately flush the product with a large volume of water and consult a doctor.
The additive is disposed of in accordance with local regulations, it is strictly forbidden to pour it into the sewage system, water bodies and soil.