Fast hardening concrete with water resistance from w12 to w16. What is concrete water resistance? Practical use of certain grades of concrete for water resistance

Many factors are taken into account: the expected load, the weight of the building, the presence of a basement and the type of base, geological conditions. The reliability and durability of the constructed structure is highly dependent on such soil characteristics as: mobility, freezing depth and groundwater level. As a result, when buying or preparing concrete, attention is paid to its water resistance and a set of measures is organized to waterproof the foundation. This property of the material means its ability not to let moisture into its structure, it is included in the mandatory designations of the concrete mixture (numbers from 2 to 20) and is marked with the Latin letter "W".

The exact value of this indicator is determined according to the methods specified in GOST 12730.5-84. It corresponds to the maximum withstand water pressure for a standard concrete sample, 15 cm high. Thus, the W2 grade, during a standard test in a climatic chamber, should not pass water at 2 atm (0.2 MPa). The better the water resistance of concrete, the stronger its waterproofing and resistance to soil freezing, which is important when pouring the foundation.

Indirectly, this indicator is related to the water-cement ratio, the W4 brand corresponds to 0.6 W / C, W8 - 0.45. In practice, this means that low permeability concrete sets quickly, especially when hydrophobic additives are present, but for all the advantages of such a solution, it is inconvenient to lay. The characteristic directly depends on the porosity of the artificial stone and its structure. That is, dense grades with a minimum number of pores and capillaries have high water-repellent properties. Conversely, loose low-quality compounds not only allow moisture to pass through, but also retain it in themselves; they should not be used to fill the foundation, except perhaps as a substrate.

Concrete marking

According to the degree of water resistance, grades are distinguished from W2 to W20. Each characterizes the direct interaction of the material with water and corresponds to a certain percentage of its absorption by weight, under the influence of loads. The first two grades refer to concretes with normal permeability, W6 - with reduced, W8 and above - with especially low permeability. W2 and W4 are not recommended for use in construction work in the absence of additional reliable waterproofing.

Grade W6 absorbs significantly less moisture, it is a medium quality concrete, quite suitable for pouring foundations and erecting relatively water-resistant structures. The composition of W8 is considered optimal, but this affects its cost, it sorbs no more than 4.2% moisture by weight and is used in areas with a high level of groundwater. All grades further down the scale from 8 to 20 are water resistant, W20 has minimal water resistance and is second to none in quality.

Depending on the purpose, concrete of the appropriate grade is selected, for example, mixtures from W8 to W14 are suitable for plastering, the damper the room, the more significant the requirements for their hydrophobic properties. For cladding facades or pouring sidewalk paths, the highest grade is selected, taking into account the planned budget. When preparing the foundation, a lot depends on the parameters of the soil, the weight of the future building or the material used. The minimum allowable brands for water resistance:

For frame buildings - W4.
For wooden houses - W4 on slightly heaving soils, W46 - on moving ones.
When using foam blocks or aerated concrete - W46 and W48, respectively.
For brick and monolithic walls - W8.

The mixture with water resistance from W8 is considered optimal for pouring the foundation, regardless of the brand chosen, waterproofing work is carried out.

Ways to improve water resistance

Distinguish between primary and secondary protection of concrete from moisture. In the first case, attention is paid to the structural features of the structure, the materials added to the solution, and the elimination of cracks. This also includes deep penetration primer treatment. For example, to obtain waterproof concrete for the foundation, silicate additives or hydrophobic fibers are introduced into it. Secondary protection implies the creation of a barrier between the material and the aggressive environment, surface isolation and sealing of the outer layer. For this purpose, water-repellent impregnation, thin-layer coatings or self-leveling floor technology are used. These materials most often have a polymer, epoxy or polyurethane base.

One of the reasons for the poor water resistance of concrete is the high porosity that occurs due to non-compliance with the technology of its preparation and pouring. For example: insufficient compaction, violation of proportions when mixing the solution, reduction in the volume of the structure due to shrinkage. The foundation is under the constant influence of moisture, even when choosing the right brand, there is a risk of its destruction and subsidence of the entire building. To prevent such cases, in addition to mandatory waterproofing (crushed stone embankments and roofing material flooring), such methods of influencing water resistance are used, such as:

solving shrinkage problems;
exposure time;
water repellent treatment.

1. Shrinkage control.

First of all, the ratio of loads and dimensions of the foundation is thought out, everything possible is done to prevent cracks. One of the conditions for improper shrinkage is insufficiently reliable reinforcement or an error in the thickness of the structure. To improve the water resistance of concrete, it is necessary to control the process of water evaporation from the solution, especially for grades with a minimum W / C ratio. To do this, the freshly laid foundation is moistened every 3 hours for 3 days. In hot weather, procedures are carried out more often, it is recommended to cover the surface with burlap or film. To protect against the formation of capillaries, concrete is treated with film-forming compounds, which require careful handling, depending on the brand, they are applied at different stages of cement hydration.

2. Long-term moisture care.

A feature of cement mixtures is the improvement of operational characteristics with an increase in the hardening period under certain conditions. Therefore, in order to obtain waterproof concrete for the foundation, it is recommended to organize the longest possible maintenance, ideally up to 180 days. The slower the liquid evaporates from the surface, the better. After stripping, it is desirable to ensure air humidity of at least 60%; when dried in dryness, the concrete loses its original volume. If cracks cannot be prevented, they should be treated with a waterproof sealant.

3. Waterproofing compounds.

This type of protection is necessary not only to enhance water resistance, but also to preserve the foundation when the soil freezes. After the formwork is removed, a waterproof coating for concrete of a penetrating or film type is applied to the base.

There are many varieties of water-repellent compositions, they can have a mineral or synthetic base, reinforcing fibers or other modifying substances are added to enhance their effectiveness. The best are multicomponent polymer mixtures of the dispersion type, they are easy to apply, dry quickly and increase water resistance several times.

Concrete is a versatile building material widely used in various construction works. Traditionally, floors between floors, main walls of buildings, reinforced concrete structures are made from it. The material has many positive qualities, one of the main ones is the excellent water resistance of concrete.

Conventional cement composition can pass water through itself. But there are situations when increased moisture resistance of concrete is required to ensure the necessary operational conditions of the structure. The main representatives of these structures, which are used in traditional construction, are:

floors in the building that are below zero;
basement walls;
strip foundations.

At the same time, during the construction of the basement or pouring the foundation, due to the increased water resistance of concrete, you can significantly save on the installation of waterproofing or choose a more budgetary type.

The water resistance of this material is also relevant for industrial structures in the hydraulic engineering direction. having direct contact with

water and accepting increased loads:

dams;
dams;
underwater tunnels;
special tanks.

General description of the indicator

Resistance to water ingress under pressure is determined by the water resistance index of the concrete mixture, which is denoted by the letter W simultaneously with a digital value in the range of 2–20 and changes with a multiplicity of two.

The digital designation determines the permissible water pressure in kg / cm² on the reference standard of a cubic shape, where the sides are 15 cm. For example, the water resistance of W6 concrete is the pressure of a water mass per square centimeter of 6 kg. Moreover, water does not penetrate through this building material.

With an increase in the numerical index, which describes the brand of cement composition for water resistance, the ability of the concrete mass to withstand water pressure increases.

Features of different brands

The permeability of the concrete mixture is expressed by indirect and direct parameters. The latter include the filtration coefficient and the brand of concrete for water resistance. Indirect indicators are the water-cement ratio and water absorption. In this way, there is a certain table of water resistance of concrete:

Concrete, which is marked W2, corresponds to cement M150-M250, which quickly absorbs moisture, and regardless of the thickness of the layer, it requires an indispensable application of waterproofing.
Concrete composition W4 corresponds to the brand of cement M250-M350. It is less susceptible to moisture than W2, but is quite hygroscopic. Recommended for use with a waterproofing layer. The material is used in traditional construction. The water resistance index increases during the introduction of ingredients and additives into the prepared concrete composition that cause compaction of the array, as well as the use of cements with a high expansion index.
Concrete mortar W6 (corresponds to M350) is characterized by lower moisture permeability, which makes it possible to widely use it during construction. Excellent water resistance allows the use of a composition for sealing gaps in reinforced concrete and monolithic structures for waterproofing tanks. It is also used for building underground basements where groundwater is close.
W8 concrete mix is made from high quality M400 cement. The water resistance of W8 is approximately 5% moisture by weight. Concrete proved to be excellent during the work on pouring the foundation, constructing tanks and containers that are used to store liquids, bomb shelters, and various hydraulic structures. It is used in traditional construction, if it is required to carry out work on the construction of a structure that will be operated in high humidity.
Solutions W10-20 (M450-600) are characterized by maximum water resistance, do not require a waterproofing layer during application. The sphere of use of these compositions is the construction of hydraulic structures, liquid storage tanks, as well as other special reservoirs. Concrete W20 has the highest resistance to water; it is not used in private construction. The solution is characterized by high frost resistance F250-F350, which allows it to withstand a significant temperature difference.

The water resistance of concrete composition marked "W" depends on several factors. The main points that affect this characteristic are:

Porosity and Density

The concrete composition, being a porous-capillary body, is permeable to moisture during the presence of an appropriate pressure. The water resistance is highly dependent on the porosity of the material.

Causes of pores:

reduction in the volume of concrete during drying;
the presence of an excessive volume of water in the solution;
bad seal.

The required compaction of the mortar is achieved by careful vibration and mixing of the cement composition.

The chemical reaction of concrete components with water, which takes place in the array during curing, is called hydration. In this case, the reaction lasts for a long time.

For complete hydration of cement particles, the volume of water must be at the level of 45% of the total mass of concrete, this corresponds to the water-cement ratio W / C = 0.45. Moreover, only 55% of the total amount of water in the solution is chemically bound, this corresponds to W/C=0.20.

In theory, W / C = 0.20 is enough for concrete hydration, but at the same time, the stiffness of the solution increases significantly, therefore, in practice, a concrete mix with a W / C ratio of approximately 0.5 is used, which completely ensures convenient delivery and pouring of the solution.

Water, which has not entered into a hydration reaction, after solidification of the latter, forms many pores in the array. Some of which are closed, and some create through tunnels, through which moisture begins to pass in the future.

To improve water resistance, the amount of moisture during mixing must be minimized (W / C = 0.45 is the optimal value).

A decrease in the water-cement ratio (for example, from W / C \u003d 0.6 to W / C \u003d 0.45, i.e. by 25%) with a certain mobility of the cement composition is achieved through the use of plasticizers, and the number of pores is significantly reduced.

To obtain the most dense solution with a high water resistance grade, various waterproofing additives are used.

Performance Improvement

The task of increasing the water resistance of the concrete mixture is relevant both during civil and industrial construction, and during the corresponding work in private buildings. Since not all the time, when doing concrete work, it is possible to purchase high-quality cement.

There are effective methods that make it possible to achieve increased stability, complicating the ingress of moisture through the hardened concrete:

Control methods

Options for determining indicators are indicated by GOST. This document specifies the following methods for testing the watertightness of a concrete mix:

In times of urgent need to determine water resistance, accelerated control options are used, since accurate laboratory methods will require at least one week for testing.

The choice of the required brand of concrete solutions for frost resistance and water resistance must be made taking into account the climatic conditions of your region, as well as the number of freezing and thawing cycles during the winter. It must be remembered that compositions with a high density characteristic have the best performance.

As a building material, concrete has many advantages and useful qualities, thanks to which it has received its wide distribution. One of them is water resistance, which refers to the ability not to let moisture through under pressure of a certain value. In this article, we will consider the types of concrete that can withstand moisture.

Methods for determining

According to GOST 12730.5-84, there are several methods at once to determine the water permeability of concrete W:

Since the first two methods are quite long in time (for example, W8 concrete using the “wet spot” method will have to be checked for a week), the last two options are most often used in practice.

Concrete grades for water resistance

GOST 26633 assumes 10 grades of concrete, depending on the degree of their water resistance (W2, W4, ... W18, W20).

The instructions for determining each brand are as follows:

a concrete sample-cylinder Ø150 mm is taken;
pressurized water is supplied to it;
make observations and measurements.

Each of the brands must withstand a certain pressure. For example, concrete W6 should be resistant to pressure up to 6 atmospheres (0.6 MPa), and W4 - 0.4 MPa.

Considering the characteristics of W4 concrete, it can be noted:

the production cost of the material is low;
with age, its water resistance increases, in particular, concrete B15 F150 W4 showed a 6-fold increase during the year;
material thickness of 200 mm is ideal for creating waterproofing, which allowed him to become a leader in civil engineering;
By adding expandable cements or sealing components to B15 F75 W4 concrete, the water tightness can be increased without losing the essential characteristics of the material.

To assess the permeability of concrete products, the following can be used:

direct methods(water resistance or filtration coefficient);
indirect(water-cement ratio and water absorption).

Effect of material age

An interesting fact is that as concrete ages, its waterproof qualities only increase. However, a significant and intensive increase in such indicators seems to be possible only with special care for it (constant moistening).

As an example, do-it-yourself concrete made from Portland cement can be cited. If it is constantly moistened or if a positive temperature is reached at which moisture does not evaporate, its water resistance will rapidly increase for up to six months. This will significantly increase the overall service life.

Tip: concretes that harden with constant moisture and the required temperature conditions have several times higher water resistance than concretes that harden in an environment with low relative humidity or were accompanied by significant moisture loss.

For example, if we take a material that hardened after stripping under constant moisture for a month, and compared with that which hardened after stripping under conditions of insufficient humidity (at the level of 50-60%), the latter will need about six months to achieve water resistance indicators. first.

From this we can conclude that the fastest will occur in conditions of sufficient humidity.

At the same time, even if watering is rare or completely absent, and the relative humidity of the environment approaches 100%, the waterproof qualities will also increase in the first six months or a year, then their indicator will stabilize. When moisture evaporates from concrete or it hardens in conditions of insufficient relative humidity, the increase in water resistance also decreases.

In situations where the base loses a huge amount of moisture, the process may completely stop or go in the opposite direction. This can lead to the fact that after a certain time the concrete water resistance index will become lower than the original one.

Tip: the characteristics of W8 concrete are quite adequate for the construction of a conventional foundation, but only with waterproofing work.

Ways to improve water resistance

Since concrete has a capillary-porous structure, under the influence of a certain value of water, it turns out to be permeable to it. This indicator is influenced by many factors, incl. nature and degree of porosity. In this case, the connection is as follows - with an increase in porosity, water permeability decreases, and vice versa, the more dense the material is, the higher this indicator will be.

Tip: concrete B25 W4 F75 has a frost resistance of 75 cycles.

Pores can occur in a material due to a variety of reasons, the main ones being:

weak seal;
excess mixing water;
shrinkage of concrete, which occurs after it has dried and is characterized by a decrease in volume.

To achieve the desired effect with a vibrator. It is worth remembering that the process of adding water to the cement is called hydration and it can last for a long period of time.

For complete hydration, the proportions must be strictly observed - for every 10 kg of cement, 4 liters of water must be used. However, only slightly more than half (60%) of this water enter into a direct chemical reaction with cement.

Conclusion

Each brand of concrete has its own characteristics, especially waterproof. When developing a construction plan, this parameter must be taken into account. The article went into detail about what water resistance is and how it is tested.

The video in this article will help you find more information on this topic.

Operational and technical characteristics are especially important when it comes to building materials. Any professional in the construction industry will confirm that the level of quality of products used in the process of erecting architectural and functional structures completely depends on how long the operational period of the building will be and the comfort of carrying out absolutely any activity within the walls of the building. One of the most common building materials, as practice shows, is concrete. This product has a high level of water resistance. This characteristic even underlies a certain classification of this product - these are concrete grades for water resistance.

Resistance to the harmful effects of moisture is perhaps the key property of building materials. It is due to the specific structure of the substance, which is practically devoid of any voids and is quite dense. The seams located between the blocks of material are carefully filled with a specialized composition with waterproofing characteristics. Speaking specifically about waterproof concrete, it is worth saying that its structure is very specific, which, of course, gives it many advantages and distinguishes it from analogues offered in a wide variety of domestic and world markets.

Moisture resistance is an important property for concrete

The possibility of using products of this type is determined by the structural features of the future building. For example, waterproof building materials should not be used for buildings that do not belong to the monolithic category. The fact is that in buildings, the construction of which involves mainly assembly work, there are too many seams. A large number of seams virtually eliminates the possibility of achieving water resistance.

Proposed classification

Experts in the relevant field offer a very convenient classification. We are talking about the division of various types of material into grades for water resistance. Concretes that are resistant to moisture are designated in the relevant literature by alphanumeric indices. Such an index necessarily includes the letter W, as well as a numerical range from 2 to 20, excluding odd values. Depending on the pressure that the building material is able to withstand, one or another index number is assigned to it.

Factors affecting this property

The described characteristic is influenced by a wide range of various factors, including such as:

Product lifespan. Of course, the older the material, the naturally it is more reliably protected from the harmful effects of moisture.
Environment. Everyone knows that in the environment there are a huge number of objects that can both maintain and diminish water resistance.
Additional ingredients. Experienced workers in the construction industry, through trial and error, as well as following the recommendations of successful specialists, determine which ingredients give the final solution the maximum set of positive parameters. This factor is of great importance in practice. For example, if you need to achieve a specific level of solution density, you need to supplement the standard formulation with aluminum sulfate. The proposed approach is much easier to implement than to achieve the desired performance due to the mechanical impact of the press, vibration, water removal due to vacuum techniques.

Why do pores occur?

The presence of pores in the structure of the product leaves it practically no chance in the fight against moisture. Thus, when mixing the solution, both manually and mechanically, as well as in the process of solidifying the substance, it is necessary to create all the conditions due to which pores will not appear in the finished product. However, no matter how hard you try, sometimes you still cannot create a substance of the appropriate quality. The reason for this is primarily the following:

the density level of the substance is not sufficient;
in the process of mixing the solution, more water was used than the recipe proposed by professionals suggests;
reduction in the final volume of the product due to shrinkage.

Pay attention to shrinkage

In this case, careful attention, especially for beginners, is worthy of shrinkage and the consequences that it causes. Regardless of the brand of concrete in terms of frost resistance and water resistance, its shrinkage must be the smallest. In order to minimize the risk of problems associated with excessive shrinkage of building materials, it is necessary to carry out the following types of work:

regular wetting of building materials for three days after pouring, as a rule, builders maintain a gap of about three hours between procedures;
covering the surface filled with the described material with a wet film or even burlap;
the use of specially designed agents, the use of which contributes to the formation of a film.

One way or another, before proceeding with the implementation of measures in any way related to the use of waterproof concrete, it is necessary to properly study the characteristics inherent in a particular class of goods.

Features of individual product brands

Domestic and foreign manufacturers of goods in this category offer us a wide variety of options. It is usually quite difficult for a beginner in the construction industry to determine which brand is needed specifically in his situation. Thus, before proceeding with the direct choice of material, it is worth studying the information on existing marking options, as well as on the use of individual classes in the process of erecting an architectural and functional object.

Product Requirements

With regard to water resistance, GOST, specially developed at the state level, imposes certain requirements. The accuracy of compliance with these requirements is determined by the brand of concrete for water resistance. The proposed classification distinguishes concrete grades for water resistance with the index w2 and w4, as well as w6, w8 and even w12. Indexing ends with number w20. Experienced professionals advise avoiding the use of products whose brand is lower than w6. Meanwhile, even the best categories have some limitations. However, labeling helps beginners and even more experienced workers figure out what pressure the concrete mix will be designed for.

Influencing factors

Two types of factors have the main share of influence on the quality of the interaction of the described building material with water. These are things like:

Direct. This category implies a standard filtration coefficient in perspective and a level of resistance to moisture, which directly depends on the class of concrete.
Indirect. Here we are talking about the ratio in the composition of the mixture of cement and water, as well as the absorption of moisture relative to the total mass of the substance ready for use.

No matter how significant indirect factors seem, in reality, as a rule, they are repelled exclusively from the impact of direct ones. They are at least easy to navigate for inexperienced workers. Based on this, three of the most popular and widely used brands of building materials can be distinguished:

A solution of this category passes water in minimal quantities. However, its cost is also considerable, although it is consistent with the advantages that the substance has.
The degree of resistance to penetration into the structure of the substance is slightly lower than that of the analogue mentioned above. The quality of such a composition can be called average, but due to the democratic, universally affordable cost, its operation takes place in the widest range of works.
This product is no longer suitable for specialized structures, the conditions for the future operation of which require special waterproofing properties.

A water resistance grade over w8 is even more hydrophobic. Thus, it can be argued that a completely reliable product with an indicator of w20 water resistance of concrete, water resistance of concrete in this case will cost a considerable amount of money, but it will also ensure the longest possible service life of an architectural structure of any type.

Scope of application

In order to expand the range of work, the implementation of which allows the operation of this building material, manufacturers are constantly improving its recipe. The ongoing research and experiments made it possible to add one more positive property to the number of advantages of building materials, we are talking about frost resistance. For example, products in the w8-w14 range are the basis for the construction of the most durable objects, among which are hydraulic structures, reservoirs and even bunkers.

How can I define this property myself?

Sometimes it happens that we have to face the need to independently measure, if not the waterproof mark, then at least this characteristic in general terms. Experts have developed a number of methods that can be resorted to in such a situation. They are conditionally divided into:

basic;
auxiliary.

Basic ways

Before proceeding to the consideration of auxiliary methods, the number of which exceeds their main counterparts, it is necessary to consider the fundamental methods:

Wet spot. This method involves measuring the highest level of pressure at which the surface is still not exposed to moisture.
Calculation of the filtration coefficient. Actually, here you have to do algebraic calculations of the number, which is determined by the pressure constant, as well as the period in which the filtration occurs.

Auxiliary methods

The complex of methods of the auxiliary category consists of:

Based on data about the binder that is added to the mixture. This substance, as a rule, is Portland or hydrophobic cement, which gives the solution a lot of advantages and additional parameters.
Determination of the type of additives of chemical origin, the addition of which significantly improves the performance of building materials.
Calculation of the porosity of the structure of a substance. As you know, an increased number of pores in the structure does not contribute to moisture resistance.

Additional ingredients of the composition

The value of water pressure, which is measured in MPa x 10 -1, is a factor that determines the conditions for the future operation of building materials. Of course, when developing brands for water resistance, they try to give their product the best properties in all existing parameters.

Manufacturers do not hide how many different additives they use. The waterproofing abilities of a substance are directly related to the nature of its additional components. It can be made surprisingly durable and as moisture resistant as possible. However, it is important to remember that the use of such products is relevant only in the horizontal plane. Otherwise, the solution will simply drain to the construction site. Meanwhile, if you can boast a lot of resources such as time and effort, you can put on a retaining film, which will fix the mixture in an upright position.

What is offered to non-professionals?

The domestic market is replete with additives for every taste. Speaking of taste, it is worth saying that here, first of all, the cost is implied. The most demanded products in this market segment are called:

silicate type glue;
calcium nitrate;
ferric chloride;
sodium oleate.

In order to save money, many people prefer to buy calcium nitrate. It really is the least expensive option, but at the same time, its resistance to the harmful effects of moisture is practically not inferior to its counterparts. In addition, it will actually not be difficult for you to add this ingredient to the solution, since it dissolves remarkably well in water and, most importantly, is completely safe for human health.

Waterproof concrete: grades, characteristics and application specifics updated: January 1, 2017 by: Artyom

Concrete is one of the strongest and most widely used building materials today. It is an integral part of the mortar for pouring the foundation, plastering and masonry walls, as well as other critical works. Like any other material, concrete mix has many different properties. And one of these properties is its degree of water resistance.

The degree of water resistance of any concrete is its ability to keep moisture and water under pressure.

According to water resistance, concrete is divided into several grades. And the better the brand of concrete in terms of water resistance, the more pressure it can withstand on itself, while not letting water through.

Characteristics of concrete grades for water resistance

In GOST 26633 it is said about ten main brands of water resistance of the concrete composition. Each such brand is indicated by the Latin letter W, and a certain number is indicated next to it. It is this figure that identifies how much this type of concrete corresponds to the maximum water pressure that is maintained by a standard cylindrical concrete sample, whose height is 15 cm.

Indicators of concrete on interaction with water distinguish between direct and indirect. Direct indicators include water resistance and filtration coefficient. To indirect - water-cement ratio and water absorption by weight. It should be noted that of all four indicators in everyday life and construction, it is customary to first of all pay attention to the first direct indicator of water resistance, which is considered indicative. The remaining three coefficients are in most cases used for scientific purposes and in the process of production itself. These are additional indicators for concrete compositions.

In order to better understand and navigate the characteristics of individual grades of concrete in terms of its water resistance, one should first consider the three main grades in turn. Note that those other grades that will stand in between these three will also characterize a greater or lesser degree of interaction of concrete with water and moisture.

Grade W4 has a normal degree of permeability. That is, this composition is able to absorb a normal amount of water, so it is not very suitable for work with a lack of a sufficient level of waterproofing. And the W2 grade, which is even before the W4 grade on the scale, has even greater permeability, which characterizes such concrete as a mix of the lowest quality.

W6 grade concrete is considered a low water permeability mix. It absorbs less moisture, therefore it is considered to be of average quality and is most often used in construction. At the same time, there are no more concretes in the scale interval between such concrete and concrete of grade W4.

And now for the brand W8. It is usually referred to as compositions with a low degree of permeability. It absorbs moisture only up to 4.2% by weight. This is a more expensive version of the concrete composition. This grade is followed on the scale by a number of concrete grades such as W10, W12, W14, W16, W18, W20. In these six grades of concrete, water permeability gradually decreases from beginning to end. Therefore, we can confidently say that W20 concrete is the most resistant to water. But they do not use it so often, because it is quite expensive. But the quality of such a composition today is not inferior to any other brand.

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Choosing a brand for a specific type of work

Now as for the choice of a specific brand for the device of any objects. So, for pouring a conventional foundation, concrete of the W8 brand will be quite enough. But this is the case if additional waterproofing is provided.

For plastering walls, grades from W8 to W14 will also be quite suitable. But if the room is damp or cold enough, the best option would still be to choose a concrete of a higher grade. Moreover, it will be necessary to additionally treat the wall with a soil composition.

But for the exterior of the house, it is desirable to prefer only concrete with the highest degree of water resistance. Indeed, in this case, as a rule, it will be constantly exposed to external adverse environmental factors. The same applies to filling the territory on the street.

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Principles of increasing the water resistance of the concrete composition

An urgent issue in recent years has been to increase the degree of water resistance of the concrete mix independently in the domestic environment. This is largely due to the fact that people simply do not have enough money to buy high-quality concrete. Especially if it requires a large amount to carry out certain work.

To date, several methods have been developed to increase the water resistance of concrete. Each of them has its own degree of effectiveness in certain conditions. However, two of these methods are considered the most common. This is an increase in water resistance by eliminating the shrinkage of the concrete composition and by temporarily affecting the concrete composition.

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Eradication of the shrinkage process

First you need to figure out how you can increase the water resistance by eliminating the shrinkage process. As a rule, concrete itself is a fairly porous substance. Moreover, its porosity decreases with the improvement of water resistance. The concrete composition of medium grades usually has a sufficient number of small pores through which moisture can freely penetrate into it. All these unpleasant processes are mostly associated with the gradual shrinkage of the concrete solution during solidification.

In order to minimize the degree of shrinkage and thereby increase the water resistance and quality of concrete, it is recommended to carry out the following measures. First, you need to use special formulations for such purposes. The essence of their action is that a protective film is formed on the surface of the substance, which prevents the solution from shrinking. You just need to read the instructions very carefully, as different compounds can act differently.

Secondly, it is useful, oddly enough, to water the concrete with water. This must be done every 4 hours. Only the effect of water should last only the first four days. The rest of the time the concrete should dry naturally.

And thirdly, immediately after pouring, it is useful to cover the concrete structure with a special protective greenhouse film or burlap. This protects the surface from excessive moisture and at the same time forms a slight condensate, which helps and prevents it from shrinking. It is only necessary to cover the fill so that the film does not touch the solution, and small gaps remain at the edges.