The possibility of artificial stone does not pass water under sufficient pressure called waterproof of concrete. Denote by the W symbol and within the even numbers from 2 to 20, denoting the pressure in MPa. 10 -1, whose concrete elements are height and a diameter of 0.15 m hold on the water and do not let it through themselves.

Few people think that the use of concrete with high waterproof rates increases the cost of construction, but it allows you to significantly reduce the cost of waterproofing the foundation. Depending on the type of object, it is worth analyzing that it is cheaper to buy concrete with a high indicator of waterproof, or waterproofing.

Due to what concrete has different waterproofability

Many factors affect waterproofability. This ability is ensured by a special capillary-porous structure of the material. Waterproof in dense concrete is much higher, as it is less than pores.

Low-profile composition, excess water and shrinkage can be causes of a large volume of pores. During drying and solidification, shrinkage and a decrease in the volume of concrete mixture occurs. From a limited reinforcement and evaporation of water under the influence of negative environmental factors, the greatest shrinkage occurs.

Air ducting additives Change the character of porosity. Pores close and become more dense.

Material on the alumina and high-strength cement composition has a higher level of waterproof. Such species attach more water molecules during hydration and form a high density stone.

The water resistance of concrete depends on the type of additives. The seal of the mixture increases, due to aluminum and iron sulfates. This happens with the help of vibration, pressing and vacuum water removal. Regarding Pozzolan Portland cement, it can be said that its impressive indicator of impermeability directly depends on the volume of pozzolanic additives and their swelling.

The age of concrete design also affects the indicators. The older cement, the greater the hydrate neoplasms becomes the reason for increasing waterproof.

Concrete brands for waterproof

The stability of concrete to the effects of water is reported by brand concrete on waterproof. The level of stability is directly proportional to the level of the coefficient.

Table 1 Approximate compliance of concrete brand for waterproof

Concrete W2 has a high permeability, it can absorb a lot of water. Without waterproofing it is impossible to use it. W4 also absorbs a large amount of fluid. Although its indicators are higher than W2, it is not recommended to be applied without waterproofing.

Concrete W6 is a mixture of reduced permeability. The most popular in construction, thanks to the average volume of the absorbed moisture.

Concrete W8 absorbs only 4.2% by weight. The permeability of the material becomes less subsequently. The W20 concrete is most resistant to water, but in fact is practically not used.

For the construction of hydraulic structures, water tanks, base storage or bunkers apply W10-W20 brands. Waterproofing is not needed when applying these brands of concrete. Also, these types of artificial stone have high frost resistance. The material is practically not applied to private construction due to a fairly high price (4500 -5300 rubles per 1 m³).

Characteristics and indicators of material permeability

Direct and indirect (indicative) parameters determine the permeability of concrete. Direct include the name of the waterproof brand and the filtering coefficient. Moisture absorption and water-cement ratio are indirect indicators.

Table 2 Indicators that affect the permeability of concrete

According to GOST 12730.5-84, the filtration coefficient is established and the waterproof mark.

Granite offers concrete delivery in Ulyanovsk with waterproof from W2 to W8. Call us, tell us for what purposes you want to buy concrete and we will tell you what brand you will suit the most. An important advantage of our delivery is that we ourselves are the manufacturer of concrete, so we can offer more favorable prices, and you can be sure that you get exactly the brand of waterproof, which we ordered.

Despite the diversity of modern building materials, concrete continues to maintain leading positions among competing options, as it has such important characteristics as durability, reliability and durability. It is an integral component of solutions for creating foundations, wall masonry, plaster and other construction operations.

The waterproofability of concrete, as well as its ability to withstand harsh weather conditions, are the main qualities that provide a long service life of finished products. It is these criteria that are basic when choosing the brand of this building material.

And the waterproof of which is at a high level, is the pledge of quality and excellent performance of any design. Under these properties implies the ability of concrete products to withstand the negative impact of such natural phenomena as moisture, water and negative temperatures.

Currently, there are various brands of concrete on frost resistance and waterproof, characterized in quality, price and technological capabilities. Such a classification helps to choose the best suitable material for creating structures designed for operation in certain conditions.

on waterproof

Depending on the degree of waterproof, the concrete is divided into ten main brands (GOST 26633). They are indicated by the Latin Latin W with a specific digital value indicating the maximum water pressure that withstands the test concrete sample of the cylindrical shape height of 15 cm during special tests.

The determination of concrete waterproof is carried out according to direct and indirect indicators of its interaction with water. The straight indicators are concrete brand and its filtering coefficient, and indirects are indicators of water-cement ratio and water absorption.

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

Characteristic features of brands of concrete in waterproof indicators

When choosing the necessary brand of concrete to perform a specific type of construction work, they are guided by digital indexes after the letter W, characterizing the degree of interaction of material with moisture and water. For example, the lowest waterproof of concrete and, therefore, low quality in the W2 brand. Solutions on this basis are categorically not recommended to be used in environments, even with a slight level of humidity.

Normal degree of water permeability in concrete brand W4. This means that this composition has the ability to absorb the normal amount of water, so its use is possible only if it is possible to ensure good waterproofing.
At the next position in the quality scale, there is a brand W6, which is characterized by a reduced water permeability. Refers to the compositions of average quality and low price category, which causes the popularity of its use in construction.

The concrete of the 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 expensive option, compared with the W6 brand.

Then follow the brands of concrete with indices 10, 12, 14, 16, 18 and 20. The higher the digital indicator, the lower the water permeability of the material. According to this classification, the waterproof is the W20 brand concrete, but it does not use it often due to a fairly high price.

Practical use of certain waterproof concrete brands

The variety of concrete should be seamless depending on the operating conditions of the objects. For example, for the fill of the foundation, the W8 brand is quite suitable under the condition of the arrangement of additional waterproofing. Wall plastered is made by concrete brands W8-W14. However, for the arrangement of sufficiently raw and cold rooms, the waterproof of concrete must be maximum, therefore it is recommended to use solutions the highest quality, and also requires additional processing of walls with special soil compositions.

For high-quality and durable external wall decoration, pouring of household platforms and tracks should also use concrete with maximum indicators of waterproof, since these sites will be systematically subjected to negative impact of external weather factors.

Additives in concrete for waterproof with your own hands

The need to use high-class 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 the compromise option, namely to increase the waterproof of concrete yourself.

Today, there are several effective ways to increase the resistance of concrete mixtures to the effects of water, but two of them won the greatest popularity: by eliminating concrete shrinkage and with the help of temporary effects on the concrete composition.

Concrete shrinkage

Concretes of low and medium grades are quite porous materials that are easily absorbed by moisture. This negative property is enhanced in the process of shrinking the solution when frozen. Thus, improving the quality and waterproofability of the concrete mix can be possible by reducing its degree of shrinkage.

A comprehensive approach will help to achieve the desired result:

1. It is necessary to use special additives to concrete for waterproof. The principle of their action lies in the fact that when solving the solution, they form a protective film that prevents its shrinkage. Today, various additives in concrete are presented on the market for waterproof, and even at least one task is one, yet each individual option has its own characteristics, so before buying should be carefully familiar with the manufacturer's instructions.
2. In addition to adding special additives to concrete for waterproof, it is also recommended to water water. This procedure is performed during the first four days at an interval of 4 hours. Next, the concrete structure should dry in natural conditions.
3. With a quick evaporation of moisture from the solution, a unwanted shrinkage also occurs during frozen. To slow down this process, after filling the concrete structure, it must be immediately covered with a special film, under which condensate will be formed, preventing shrinkage and promoting the increase in concrete strength. The coating is in such a way that it does not concern the fill. At the edges, there are small gaps for air ventilation.

Conclusion on concrete composition

This method is to give a dry solution to "climb" within a certain time. The main requirement of compliance with the right storage conditions. The mixture should be in a warm dark room and undergo permanent moisturizing. Thus, after six months, its waterproofability will be able to rise several times.

Frost resistance concrete

Under this indicator implies the ability of concrete mixtures to maintain its physicomechanical properties in conditions of multiple freezing and thawing. This characteristic plays a priority role when choosing concrete for the construction of bridge supports, airfield and road surfaces, buildings and other objects operated in medium and northern latitudes.

The definition of frost resistance of concrete is carried out by laboratory tests using two methods: basic and accelerated. If the research results differ, the final option will be considered the data obtained using the base method.

Study of concrete resistance to low temperatures

Tests are carried out using basic and control samples, which are produced from concrete of various waterproof stamps for serial testing. Control concrete blanks are used to determine their strength in compression. This procedure is carried out before testing the main samples, which will be subjected to alternate freezing and thawing in different water saturation modes that occur in natural climatic conditions.

For example:

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

Classification of the level of frost resistance of concrete by brands

According to the last edition of GOST, the brand of concrete on frost resistance is marked with the Latin letter F. This value characterizes the maximum number of freezing / thawing cycles, withstanding samples of a certain design age, taking into account the reduction of strength and reduce the mass of the material on its value provided by the norms of existing standards.

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

Concrete Mixture Selection Rules

The choice of the necessary brand of concrete mixes in frost-resistant properties should be carried out taking into account the climatic features of the area, as well as the number of cycles of freezing and thawing during the cold period of the year. It should be noted that concretes with high density indicators have the greatest frost resistance.

Concrete is the most common building material. Most facilities involving water contact are performed precisely from concrete. One of the important properties of concrete is its waterproofability.

Waterproof - The ability of concrete is not to pass water under pressure, while the pressure is raised by steps until a certain value is reached.

Methods for determining waterproof (GOST 12730.5-84):

• determination of waterproof by "wet stain" (based on measuring the maximum pressure at which water is not selected through the sample);
• determination of waterproof by the filtration coefficient (based on the determination of the filtration coefficient at constant pressure on the measured number of filtrate and filter time);
• the accelerated method for determining the filtration coefficient (filtrate);
• the accelerated method for determining the waterproof of concrete by its breathability.

Due to the fact that conventional test methods occupy a lot of time (the test of concrete brand W8 "on a wet stain" lasts about a week), in practice the accelerated methods of determining water resistance are used.

For the concrete structures to which the permeability limit requirements are imposed, the following waterproof stamps are established: W2, W4, W6, W8, W10, W12, W14, W16, W18, W20 (GOST 26633).

Brand concrete on waterproof W. Corresponds to the maximum value of water pressure (MPa · 10 -1), withstanding a concrete sample-cylinder with a height of 150 mm in a standard test (for example, the concrete of the W4 brand with a standard test should not pass water at a pressure of 0.4 MPa \u003d 4 atm).

Concrete permeability is estimated by the brand of concrete on waterproof or filtration coefficient (direct indicators), as well as concrete water absorption and water-cement ratio (indirect indicators), which are approximate and additional indicators.

What concrete to use for the foundation?

For most structures from the monolithic reinforced concrete, it is enough for its waterproof brand not lower W6.. However, even if there is a concrete with high waterproof (W6-W8), water into the construction penetrates on the seams, pairing (for example, the wall-floor, wall ceiling) and other defective sites in the design.

Therefore, to ensure reliable protection of underground structures from water impact, a device is necessary for waterproof seams.

Enhance the waterproof of concrete

Density and porosity

Concrete, being a capillary-porous body, if there is an appropriate pressure gradient permeate for water.

The waterproof of concrete depends on the set of factors, among which the mainstream is the degree and nature of the porosity of the material. The more dense concrete, the smaller the amount and the volume of pores in it, the higher its waterproof.

The main reasons for the occurrence of pores:

• insufficient concrete compaction;
• the presence of excessive water of the indion;
• reducing concrete in volume when drying (concrete shrinkage).

The required compactness of concrete is achieved by good stirring and careful vibration.

The chemical reaction of clinker components of cement with water (water connection), which occurs in concrete during the conformity of the strength, is called the hydration reaction. The reaction continues for a long period of time.

For complete hydration of cement particles, the amount of water present should be at the level of 40% of the mass of cement, which corresponds to the water-cement ratio of the / c \u003d 0.4. At the same time, only 60% of the starting water is chemically associated, which corresponds to a / c \u003d 0.25.

Theoretically, the cement hydration is sufficient to / c \u003d 0.25, however, the rigidity of concrete increases sharply, so in practice the concrete with a / c ratio of about 0.5 is used, which ensures transportation and disappointment of the concrete mix.

Water that has not entered into the reaction of cement hydration, after drying, forms a large number of pores in concrete. Some of them are closed, and the part forms through channels, for which water can subsequently penetrate.

To increase the waterproof of concrete, the amount of indion water should be minimized (value in / c \u003d 0.4 is considered as "optimal").

Reducing a water-cement ratio (for example, with a / c \u003d 0.5 to V / c \u003d 0.40, i.e. by 20%) at a given mobility of the concrete mixture achieved due to the application, with the amount and volume of the pores sharply decreases.

To obtain a particularly dense concrete with a high brand of waterproof, various.

Shrinkage concrete

The hardening and drying of concrete is accompanied by a shrinkage manifested in reducing its volume.

The intensity and magnitude of the shrinkage depends on the reinforcement (the lack of reinforcement leads to the formation of large cracks during the shrinkage), the possible flow of the process of evaporation of water surrounding the conditions and composition of the concrete mixture.

Waterproof concrete must have a minimal shrinkage.

Solving shrinkage problems:

• moisturizing freshly found concrete (every 3-4 hours) for the first three days
  (depending on the ambient temperature);
• the shelter of the concreting section is a wet burlap or film;
• the use of special film-forming compositions
  (Before use, it is necessary to study the characteristics of the composition, since some of them cannot be applied to a waterproofing or other coating after concrete aging).

For concrete with low / c ratio, the preservation of water in the body of concrete from the evaporation required for the cement hydration process is one of the main tasks.

The effect of concrete age on its waterproof

One of the features of concrete is that with an increase in its age, the waterproof of concrete rises. At the same time, intense and sustained increase in the waterproof of concrete can be achieved only with prolonged humidity care.

A significant increase in the waterproof of concrete on portland cement (with constant moisturizing of concrete or the absence of moisture loss and positive temperatures) takes place up to age 180 days.

The waterproofability of concrete that has been fucked in an air with low relative humidity and lost a significant amount of indentation water during hardening, always significantly (several times) below the waterproof of the same concrete, but those who have been constantly moisturized. Thus, the waterproof of the samples of concrete, which were after the platforms in the air with a relative humidity of about 50-60% and tested at the age of 180 days, usually turn out to be actually equal to or below the waterproof of the same samples of concrete, which have been fixed in constant moisturizing conditions - 28 days.

The most intensive increase in waterproof is observed in the hardening of concrete under conditions of constant abundant moistening (excessive humidity).

With the hardening of concrete in the conditions of possible slow evaporation of moisture from concrete (for example, when hardening in an air environment with a relative humidity of 90-95% with rare watering water or absence of irrigation), water resistant is also significantly increased (albeit somewhat less than with constant moisturizing and absorption. Water concrete from outside), reaching a maximum of 180 days -1 year, and in the future stabilizes.

With air storage, under conditions of evaporation from concrete, significant amounts of water; The growth of concrete waterproof is slowed down the greater, the more determined its dehydration. With high water loss, the growth of the waterproof of concrete is terminated and, moreover, there are cases of reducing its initial value.

Increment
Waterproof Betonov
various compositions in time
In conditions of slow evaporation of water from concrete

The ability of concrete and w / w to the resistance of moisture under certain pressure is considered one of the main characteristics and is taken into account when selecting the brand, along with the class of strength and frost resistance. Water resistant directly and indirectly affects their reliability and deadlines, the maximum requirements are put forward to the outer and underground structures - the foundations of buildings, supports of bridges, basements, wells, facades operated by roofing. The desired value is laid at the design or planning of construction work.

This indicator reflects the maximum powerful water pressure with a cylindrical sample of 15 cm height with other standard conditions. In practice, this means that concrete with water resistance W2 does not pass water at 0.2 MPa or 2 atm, W4 - at 0.4 and so on. The W4 brand complies with the building requirements for structures with normal permeability, but when the pressure increases (for example, when lifting groundwater to the basement sole), moisture begins to accumulate, which is unacceptable.

There is a direct connection between this characteristic, the class of strength and frost resistance, the correspondence is reflected in the table below:

According to the requirements of GOST 26633, with construction structures, concrete solutions from W2 to W20 are used. Of these, the mixtures to W4 are inclusive for filling objects with normal permeability (symbol - H), up to W6 - reduced (P), from W8 to W20 - especially low (o). In addition to the most direct indicator, reflecting the water resistance, the marking takes into account other additional characteristics: the filtration coefficient, water absorption and water-cement ratio. The relationship between them is reflected in the table:

Concrete indicators for frost resistance and waterproof depend on the density of its structure, on the formation of which has a comprehensive impact of a number of factors:

• The quality of the sealing mixtures when pouring and aligning, the formation of large voids and the uneven distribution of components is unacceptable.
• Structure. In addition to the extracts of the given proportions, the water resistance of the artificial stone depends on the presence or absence of air-boring additives and the ratio of binder and water.
• The parameters of the external environment at the main stages of cement hydration: temperature, air humidity, other conditions affecting the rate of evaporation of the fluid.
• Carry out proper reinforcement. In the absence of a frame or an insufficient cross section of his rods, the shrinkage of the structure increases, which in turn leads to the formation of large capillaries and the deterioration of its water resistance.

Choosing a solution for foundation

The base of the buildings is subjected to intensive humidity loads (atmospheric and primer), taking into account the indispensability of this design, concrete with a low brand of water resistance are used. This also applies to W2 and W4, their use for filling the foundations and outer walls is limited and requires the adoption of a number of expensive waterproofing measures. Purchase of expensive varieties in the construction of tape or slab systems should be justified, all factors are taken into account in order to avoid extra spending: the geological conditions of the site, weight loads, the level of precipitation and the climate of the region are taken into account.

The minimum allowable concrete brand for filling the foundation is:

• W4 - for frame and temporary buildings;
• W4 and W6 - for wooden low-rise buildings when building construction on stable and movable soils, respectively;
• W6 - under the cottage from foam blocks, W8 is made of structural aerated concrete;
• W8 - when bookmarking the bases of any type under the building of the brick or stone.

The optimal "price-result" plan for foundations and basements is considered to be a mixture of W8, which corresponds to the class by strength B25 (M350). In practice, the acquisition of this variety allows himself not every owner of the future at home, which leads to the need to enhance the water resistance to artificially. It should also be remembered that the use of concrete with a high brand of waterproof does not mean a refusal to protect against soil moisture or precipitation, the exception is made only when construction on dry areas with a low CE.

Another accounted factor is the type of work. In practice, the mixture of W2 and W4 is rather in demand when preparing a pillow under the ribbon foundation or sections under the column. When armed with iron reinforced structures, the recommended minimum is W6. When building a base, in addition to the selection of the brand, it is important to eliminate all the risks of water penetration. This type is flooded with a single monolith, without defects, in the sections of the pairing provides for the protection of seams.

Ways to improve concrete waterproof

Conditionally, all measures to protect artificial stone from moisture are divided into primary (control over the composition and stages of hydration, treatment of deep penetration soils and other processes affecting the material directly) and secondary, aimed at creating a barrier between the surface of the foundation or exterior walls and an external environment. . The maximum effect is achieved by compliance with them in the complex, including the preparation of concrete mix, its laying and sealing, providing the desired setting conditions and waterproofing. There are nuances in each case.

At the stage of kneading, it is important to adhere to the correct relationship in / c. Water is a prerequisite for cement hydration, but only 60% of its total share is entering chemical reactions. In practice, this means that the smaller the fluid in the solution, the higher its quality (but not lower than the minimum standards). The excess leads to the formation of large pores, the penetration of water in them is only a matter of time. Low in / C ratio reduces concrete mobility, which is also fraught with a deterioration of its structure and waterproof.

The correct solution is to use accurate specified proportions of water and cement and input of special additives at high mobility requirements (with conventional seals).

Substances that reduce the water consumption of building compositions have a different chemical basis. These include water-soluble aluminum and iron sulfates, mixtures of sodium salts, silicone compounds, polycarboxylate ethers and resins. The criterion for the effectiveness of additive is the degree of reduction of water consumption, most of them allow you to reduce it at least twice. But their input requires caution due to side effects and influence on performance.

Most builders to ensure good water resistance of concrete choose preventive measures, namely high-quality sealing and care. At the cooking stage, concrete mixers are necessarily involved, the solution is not stirred too long and consumed immediately, without diluting with water and re-enable equipment. Air intake is carried out with a layer pouring no more than 20 cm using vibrators or remedies. After that, the monolith of the foundation or screed is covered with a film and watering water during the first 5-7 days. The desired water resistance is achieved when creating an artificial medium - with air humidity from 60% and above and at a temperature of about 20 ° C (but not lower than +5).

If it is necessary to increase the waterproof the already operated or hardened base, the treatment with waterproofing compositions of penetrating or film type is selected. With their selection, drying speed, a method of application, washing resistance, cost and degree of protection of protection are taken into account. The best results are achieved by using multicomponent polymer primers and penetrating compounds that enhance the water resistance of the foundations of the building and the outer walls several times.

Waterproof concrete Called the ability of a hardened solution to resist the penetration of water under pressure. The permeability is estimated either by the filtration coefficient (the mass of water that passed through the sample of material at constant pressure), or the limit pressure, which can withstand the sample subjected to water under pressure for a set period of time.

Waterproof materials in SI is measured in meters (M) or Pascal (PA). Waterproof of concrete and mortar mixtures is estimated in kgf / cm 2 or MPa and means water pressure in which standard concrete samples.

To designate the waterproof of concrete and mortar mixtures, the coefficient of waterproof is used, denoted by the letter "W", which characterizes the brand of concrete on waterproof (W2 - W20).

Properties

The waterproofability of the concrete depends on the / c (water-cement ratio), the type of binder, as well as on the content in the concrete of thin-fat and chemical additives, the conditions of hardening and age of concrete. The structure of the concrete also affects the structure of pores. Runifying in C, we reduce macroporosis and increase the waterproof of concrete. In fig. 1 shows the graphical dependence of the constant constant of concrete from the / c. The greater the / c, the greater the permeability of concrete and, accordingly, below the brand of concrete on waterproof.

It is possible to reduce the consumption of cement at a constant water flow, using plasticizing additives (for example, CT throne-5) and other methods.

Increased sealing of the concrete mix and an increase in waterproof, various types of machining are promoted: vibration, pressing, centrifugation, etc., or water removal by vacuuming.

Concrete Tests for Waterproof

The determination of waterproof concrete is carried out according to GOST 12730.5-84 by the following methods:

1. method "Wet Spot"
2. determination of waterproof by the filtration coefficient;
3. the accelerated method for determining the filtration coefficient (filtrate);
4. the accelerated method for determining the waterproof of concrete by its breathability.

Example. Determination of waterproof by the "Wet Spot" method:

1. Prepare samples in the cylindrical forms inner diameter of 150 mm and a height of 150; 100; 50 and 30 mm. The height of the samples is chosen depending on the size of the aggregate grains.
2. Stored made samples in a normal hardening chamber at a temperature of 20 ° C and relative air humidity at least 95%. Before testing, samples are kept in the laboratory room during the day.
3. Apply the installation of any design, which has no less than six sockets for fastening the samples and provides the possibility of supplying water to the lower end surface of the samples with an increasing pressure, as well as the possibility of observing the state of the upper end surface of the samples.
4. Install in the installation jacks to test the samples in the clip and securely secure.
5. Increase water pressure with steps of 0.2 MPa and kept at each stage for 4-16 hours (depending on the height of the samples).
6. Tests must be carried out until signs of water filtering in the form of droplets or wet spots appear on the upper end surface of the sample. The brand of concrete on waterproof is taken for pressure, in which the signs of water filtering were not observed, according to the table: