Frost resistance and waterproofness of concrete. Concrete grades for frost resistance and water resistance. Additives in concrete for watertightness

Despite the variety of modern buildingmaterials, concrete continues to maintain a leading position among competing options, as it has such important characteristics as strength, reliability and durability. It is an integral component of solutions for the creation of foundations, masonry walls, plaster and other construction operations.

Water resistance of concrete, as well as itsability to withstand severe weather conditions, are the main qualities that ensure a long life of finished products. These are the criteria that are the most important when choosing the brand of this building material.

Concrete, frost and water resistancewhich are at a high level, is the key to quality and excellent performance indicators of any design. These properties mean the ability of concrete products to withstand the negative effects of such natural phenomena as moisture, water and negative temperatures.

Currently there are various brandsconcrete on frost resistance and water tightness, differing in quality, the price and technological capabilities. This classification helps to select the optimally suitable material for the creation of structures intended for use in certain conditions.

Brand concrete for water resistance

Depending on the degree of water resistance,concrete is divided into ten major grades (GOST 26633). They are denoted by the Latin letter W with a certain digital value indicating the maximum water pressure that the cylindrical test concrete sample withstands a height of 15 cm during special tests.

Determination of waterproof concretecarried out by direct and indirect indicators of its interaction with water. Direct indicators are the concrete grade and its filtration coefficient, and indirect indicators are indicators of the water-cement ratio and water absorption by weight.

In private and commercial construction practice,to find out the water resistance of concrete, pay attention to its brand, and other criteria are important mainly in the production of this building material.

Characteristics of concrete grades in terms of water resistance

When choosing the required brand of concrete forperformance of a certain type of construction work is guided by digital indices, standing after the letter W, characterizing the degree of interaction of the material with moisture and water. For example, the lowest water resistance of concrete and, therefore, low quality of the brand W2. Solutions on this basis are categorically not recommended for use in environments even with a low level of humidity.

Normal degree of permeability for concretebrand W4. This means that this composition has the ability to absorb a normal amount of water, so its use is possible only if good waterproofing is provided.
On the next position in the quality scale is the brandW6, which is characterized by low water permeability. This concrete belongs to the compositions of medium quality and low price category, which explains the popularity of its use in construction.

Concrete brand W8 has a low permeability, as it absorbs moisture in the amount of only about 4.2% of its mass. It is a better and more expensive option than the W6 brand.

This is followed by concrete grades with indices 10, 12,14, 16, 18 and 20. The higher the digital value, the lower the permeability of the material. According to this classification, W20 concrete is the most waterproof, but it is not often used because of the relatively high price.

Practical use of certain grades of concrete for water resistance

A type of concrete must be chosen independing on the operating conditions of objects. For example, the W8 brand is quite suitable for pouring the foundation, provided that additional waterproofing is provided. Plastering of the walls is carried out with W8-W14 concrete. However, for arranging sufficiently wet and cold rooms, the water resistance of concrete should be maximized, therefore it is recommended to use solutions of the highest quality, and additional treatment of the walls with special soil compositions is required.

For high-quality and durable exterior finishwalls, casting of homestead plots and paths should also use concrete with maximum water resistance, as these areas will be systematically exposed to the negative impact of external weather factors.

Concrete additives for waterproofing do it yourself

The need to use high qualityconcrete mixtures in the production of certain objects or their elements is obvious, but this requires significant financial investments due to the high cost of such materials. But what to do if the budget for construction is limited, and the violation of the technological process is unacceptable? The answer is simple: you can use a compromise option, namely to increase the water resistance of the concrete yourself.

Today there are several effective waysincrease the resistance of concrete mixes to water, but the most popular won two of them: by eliminating the shrinkage of concrete and using a temporary impact on the concrete composition.

Eliminating the process of shrinkage of concrete

Concrete low and medium grades are sufficientporous materials that easily absorb moisture. This negative property is enhanced in the process of shrinkage of the solution during freezing. Thus, it is possible to improve the quality and impermeability of the concrete mixture by reducing the degree of shrinkage.

To achieve the desired result will help an integrated approach:

1. It is necessary to use special additives inconcrete for waterproofing. The principle of their action is that when the solution hardens, they form a protective film that prevents it from shrinking. Today, various concrete additives for waterproofing are presented on the market, and although the task is one, each individual variant has its own characteristics, so you should carefully read the manufacturer's instructions before buying.
2. Помимо того, что добавляют в бетон для water resistant special additives, it is also recommended to pour water. This procedure is performed during the first four days with an interval of 4 hours. Next, the concrete structure should dry in natural conditions.
3. With the rapid evaporation of moisture from the solution atFreezing also causes undesirable shrinkage. To slow down this process, after pouring the concrete structure, it is necessary to immediately cover it with a special film, under which condensate will form, which prevents shrinkage and contributes to an increase in concrete strength. The coating is positioned so that it does not touch the fill. Along the edges leave small gaps for ventilation.

Temporary effects on concrete composition

This method is to givedry solution "stale" for a certain time. The main requirement for this is compliance with proper storage conditions. The mixture should be in a warm dark room and be constantly moistened. Thus, after six months, its water resistance can increase several times.

Frost resistance of concrete

Под данным показателем подразумевается the ability of concrete mixtures to maintain their physico-mechanical properties in conditions of repeated freezing and thawing. This characteristic plays a priority role in the selection of concrete for the construction of bridge piers, airfield and pavements, hydraulic structures, buildings and other facilities operated in middle and northern latitudes.

Determination of the frost resistance of concrete is carried outby laboratory tests using two methods: basic and accelerated. If the research results diverge, the final version will be considered the data obtained using the basic method.

Study of the resistance of concrete to low temperatures

Tests are carried out using basic andcontrol samples that are made from concrete of various grades for waterproofing for serial testing. Control concrete blanks are used to determine their compressive strength. This procedure is carried out before testing the main samples, which will be subjected to alternate freezing and thawing in different modes of water saturation, which take place in natural climatic conditions.

For example:

• in the presence of the highest possible level of groundwater;
• during seasonal thawing of permafrost;
• when exposed to precipitation;
• in the absence of periodic water saturation, when the concrete is reliably protected from groundwater and precipitation.

Classification of the level of frost resistance of concrete by brands

Согласно последней редакции ГОСТ, марки бетона по frost resistance is indicated by the Latin letter F. This value characterizes the maximum number of freeze / thaw cycles maintained by samples of a certain design age, taking into account the reduction of the tensile strength and the reduction of the mass of the material by its value stipulated by the standards of the current standards.

To determine the level of frost resistance of concrete, digital indicators are used from 25 to 1000. The greater this value, the higher the quality and reliability of the material.

Concrete selection rules

Выбор необходимой марки бетонных смесей по frost-resistant properties should be carried out taking into account the climatic features of the area, as well as the number of freezing and thawing cycles during the cold period of the year. It should be noted that the most frost-resistant concrete with high density.