The concrete slab was poured and cracks appeared. Cracks in concrete

Concrete is indispensable in construction when laying the foundation of future houses and structures. There are often cases that it begins to crack as it dries. What could be the reasons for this not very pleasant event, we will consider in this article.

As concrete dries, structural (non-structural) cracks appear. The reason for this is the internal reactions occurring in concrete. It becomes durable and hydration occurs. If the causes are not eliminated at this moment, structural cracks will appear, which pose a threat to the entire structure as a whole. In the latter case, the concrete will continue to crack under the influence of external factors.

If the concrete began to crack when it was first poured, then it is all due to excess moisture, which forms plastic shrinkage. Moisture from the surface evaporates, the mass becomes compacted and uneven laying of the solution occurs. This is not a big deal, since the inner layers usually remain the same size, and upper layer

covered with cracks.

A much more important and serious problem is related to compaction and shrinkage, when the concrete has already set, but you did not use a vibrating tool while laying the concrete and the deformation of the structure continues under the influence of gravity. Also during the drying period due to temperature changes due to prolonged variable expansion and contraction of substances, concrete paving

becomes uneven, which leads to cracks in already hardened areas.

Corrosion cracks are associated with rusting of reinforcing bars and mesh. Steel increases in volume and this leads to concrete rupture at any stage of drying. Are important correct calculations

1. composition of the concrete mixture, inadmissibility of errors when calculating ground movements, natural disasters, impacts, etc. It is difficult to predict such reasons, but it is possible.
2. It is necessary to follow the exact recipe for preparing the solution. Often people try to save money, but this is not the case when saving will be useful.
3. Concrete must be poured in accordance with all standards, using vibration compactors, ventilation, etc.

Concrete is the basis of buildings. Foundations, floor slabs, subfloors, and load-bearing beams are made from it. In combination with steel reinforcement, it is used in all sectors of the construction industry.

Therefore, it is so important to know and be able to prevent the main problem that arises when working with this material - the formation of through and surface cracks.

What is the danger?

Errors in the design, production, pouring and maintenance of concrete lead to the appearance of cracks that:

• Significantly reduce the strength and load-bearing characteristics of the structure.
• Reduces the service life of the finished structure.
• Deteriorate appearance.

Causes

In construction theory, there are three main causes of concrete cracking:

1. Constructive failures.
2. Structural changes.
3. Action of external factors.

Constructive failures

The appearance of cracks is associated with errors at the design stage, exceeding permissible load per element or low-quality components for the production of concrete mixture. The formation of cracks as a result of design miscalculations does not depend on the filling technology, the quality of care and the qualifications of the working personnel.

Structural changes

Most of the cracks are associated with them. The influence is exerted by internal chemical processes, concrete pouring and maintenance technology.

There are three reasons:

1. Plastic shrinkage. At the beginning of the hardening cycle, the outer surface of the concrete mixture loses moisture faster and decreases in volume than the inner and lower layers. The structure is covered with a network of small, non-through cracks. Destruction occurs in a similar way under rain, as well as gravity.

2. Temperature shrinkage. Destruction of integrity as a result of hydration, chemical reaction between cement and water. Stands out thermal energy. The concrete mixture increases in volume. In the upper layers, hydration occurs faster than in the middle and lower layers. As a result, the concrete “tears” from the inside.

3. Drying. A common cause of deep cracks. The concrete sets, but continues to decrease in volume and cool. Internal stresses rupture the foundation, causing deep cracks to appear.

Action of external factors

Destruction occurs quickly and unpredictably. Heavy rain or snowfall during strengthening, earthquake or shrinkage of the old foundation. All this can cause cracking.

Construction from concrete or reinforced concrete is a responsible undertaking that requires knowledge of the specifics of the work. Not all negative factors that lead to cracking can be eliminated, but it is possible to reduce the risk of destruction.

You can purchase concrete from the manufacturer at reasonable prices from the company.

Classification of cracks in concrete

Causes

What and how to seal

How to seal it yourself

Cracks almost always appear in concrete, even in new buildings, because the pouring technology is not always followed, or a substandard mixture is used. They also happen due to age, and although it may seem that there is no salvation, everything will fall apart, you should not despair: everything can still be fixed. Cracks in concrete are the result of deformation from external loads or from the occurrence of internal stresses.

Classification of cracks in concrete

In bending: perpendicular to the axis of the reinforcement loaded in bending tension. They start from the edge and end at the zero line.

Shear cracks appear in the area of ​​shear force and arise from the occurrence of bending stresses. They usually run diagonally to the reinforcement axis.

Through faults appear during central tension and run through the cross section.

Connection failures often occur in the area where the bars are anchored and run parallel to the reinforcement. Occurs in the corners of the foundation belt type If anchored incorrectly or when low-quality concrete is used, they lead to lamination of the protective layer of the fill. Typical reasons for support deformation: heaving, soil subsidence, rise when saturated with water, etc.

Deformations due to internal stress

This stress occurs when there is a temperature difference on the surface and inside the concrete mass. The reason is the rapid cooling of the surface from cold air, water, or when a large amount of heat is radiated during the process of cement hydration. If the stresses exceed the strength of the material, surface cracks appear in the concrete. They go several cm deep. Among the causes of cracks are stresses from sudden drying of the outer layer from exposure to air temperature or sun rays with high air temperature.

According to the standards for conditions of alternating freezing-thawing, the presence of shrinkage, surface technological cracks on the surface is allowed, but their width should not exceed 0.1 mm (GOST 13015-2003). It is believed that surface cracks after pouring in concrete perpendicular to the axes of the reinforcement are up to 0.4 mm in size, or up to 0.3 mm. but running along the reinforcement, do not lead to a critical decrease in durability. You just need to control the size of their opening; it is believed that these are acceptable cracks in concrete, but they should be repaired in a timely manner.

Causes

Since concrete structures have low tensile strength, when they dry, they shrink and develop shrinkage cracks in the concrete. The reasons for their formation are divided into three categories:

1. Cracks affecting the strength of the structure(“constructive”). They don't lead to emergency condition structures. Structural cracks are often caused by:

a) Design errors;
b) errors during construction;
c) changes in maintenance conditions with overloading of the structure in excess of the design loads;
d) emergency situations, such as explosion, earthquake, etc.;

2. Fire cracks. They can be constructive or non-constructive (structural). There is always delamination of the top layer.

3. Non-structural cracks. Includes reasons not included in paragraphs. 1 and 2. Divided into several types:

a) From plastic shrinkage;
b) temperature- shrinkage cracks concrete in the initial stage;
c) shrinkage when drying;
d) cracks due to corrosion of reinforcement.

What and how to seal

For repair work, wet cement “dough”, a binder solution, a mixture of polyester or epoxy resin, and also purchased repair mixtures are usually used.

Repair of cracks (up to 3 mm) is carried out with cement “dough” or a special mixture. Mix proportions: 1 part Portland cement to 3 parts water and sand + PVA glue. Large cavities and areas with peeling concrete are sealed using crack sealant.

The most popular repair is injection. The essence of the method is that the work is carried out by “injections” polymer materials into caverns without replacing elements of the structure itself. The method is especially applicable for large volumes of work.

To repair vertical surfaces, they are coated with a mixture consisting of concrete mortar with a polymer additive. Suitable additives include furyl alcohol (0.35% of the total mass) and 0.02% sulfanol. Once dry, the frozen mixture is additionally coated with polyurethane sealant.

Repairs can also be carried out by creating a layer of the same material on the surface. However, the use of this method is not always rational, because it is labor-intensive and leads to an increase in building mass, increasing the load on the foundation.

How to seal it yourself

The cracks in the concrete foundation themselves are a source of subsequent structural destruction. To restore the monolith yourself, you must first inspect the damage and determine the method of repair.

Sealing should begin by cleaning the surface with a brush using detergent and water. Remove excess water. Remove all exfoliated fragments with a metal brush. Degrease the areas to be restored (with a product containing acid). Small cracks are cut with a spatula and deepened to 5 mm: this way the solution fills the space more easily. We strengthen the deep ones: we use a grinder to saw through the transverse grooves.

If reinforcement is visible in the depths, it must be cleaned and treated with an anti-corrosion agent. Pieces of wire with a diameter of 4 mm are placed in the cleaned furrows.

A primer is applied over the entire surface to be repaired with a brush; its thickness is 3 mm. Then, without waiting for final drying, we apply the repair mixture.

The foundation of any building is the main component of the future building. The appearance and quality of the house depends on it. This is a base that performs a load-bearing function and ensures stability and durability.

Depending on use different materials, the characteristics of the structure being built, its number of storeys, a foundation is created that is ready to provide the structure with the required load-bearing capacity.

The main task of the foundation is to evenly distribute the loads over the entire surface of the foundation, including the total weight of the structure. The durability and good performance operational capability buildings.

Cracks as a result of errors in calculations

When choosing a foundation type with the necessary indicators bearing capacity are based on two fundamental groups of factors: natural and anthropological.

The first group includes the features of the construction site: the maximum freezing depth, the presence of water and its level in the soil, the nature of these soils.

The second group is factors caused by human activity. These include all structures that are located nearby construction site and limiting the design capabilities of the future building. In this case, it is possible to limit the height and number of storeys of the structure being built.

A correctly calculated bearing capacity of the foundation will allow you to avoid partial deformation of the foundation, violation of its integrity, or even complete destruction.

This mainly happens when trying to save on constructing a foundation with a design load. If you provide a large load-bearing capacity, additional, unnecessary costs will be required.

Errors during the foundation pouring process

Sometimes the appearance of cracks in the foundation is a direct consequence of violations during foundation work. And, despite the fact that most builders do not consider a number of chips and cracks that occur to be very serious, their occurrence is by no means a norm that must be followed.

Indeed, most cracks are eliminated after repairing the base. But, in order to prevent them from appearing again, it is necessary to identify the root cause of their occurrence. Having understood the reason, you can choose the best way to solve this unpleasant problem.

Experts call the most likely reasons for this destruction of surface integrity not only incorrect calculations, but also an attempt by house owners to arrange the construction of the foundation with their own hands.

Among the miscalculations, the following errors are possible:

• incorrectly installed formwork, which does not allow the required solidity of the structure to be obtained after completion;
• poorly reinforced internal part of the foundation;
• insufficient depth of the foundation for seasonal freezing of the soil at this construction site;
• choosing the wrong quality of concrete for pouring, which does not guarantee resistance to soil influences and loads;
• discrepancy between the laid down characteristics of the foundation and changes in the structure during construction and after, for example, additional building of a floor;
• water entering the concrete base due to unmade or improperly performed drainage.

Harmful influence of external factors

Groundwater forces (1); heaving of freezing soil (2); forces on the side parts (3,4) acting on the foundation

In addition to structural violations and failure to comply with all required steps, damage to the foundation slab is possible after exposure to certain natural factors.

One of the most common and dangerous defects concrete surface is cracking. Cracks in concrete after pouring, during operation or after machining can arise due to the influence of a huge number of factors.

The cause of this defect may be hidden either in improper preparation of the solution, or in its transportation, installation, or improper care.

Causes of surface cracking

The causes of cracks in concrete can be very different.

These factors are divided into the following groups:

1. Even at the stage of preparing the solution, an error may be made in the technology for preparing the building material; for example, the ratio of such components of the solution as water and cement may be disrupted. As a result of such violations, the building material will be of a different brand and, accordingly, will not meet the stated requirements;
2. Too long a process of transporting the concrete mass can lead to the beginning of a process such as “welding” of concrete;
3. An error in calculations at the design stage can lead to the fact that an excessively high load will be placed on the finished monolith already at the operation stage finished product. The cause of cracks in in this case may become insufficient reinforcement;
4. Difficult conditions operation. So, for example, designers may not take into account the presence of heaving soils on a building site;
5. Violation of the technology for working with the mixture at the construction site:
   • You can often encounter a situation where water is added to the solution to make it more convenient to pour and level. But excess moisture interferes with the normal process of strength gain;
   • Also, cracks in reinforced concrete structures can be a consequence of improper installation steel reinforcement or insufficient compaction of the concrete mass at the pouring stage, as well as improper installation of formwork panels;
6. Construction of additional extensions to the object without taking into account the additional load on its surface.

Classification of cracks in concrete

Instructions for eliminating defects that have arisen are primarily based on the type of crack.

Distinguish following types similar defects:

1. Through. Occurs due to the influence of axial tensile forces or forces with a low level of eccentricity;
2. Cracks in the tension zone. They are a consequence of the bending of the product or are located perpendicular to the reinforcement bars;
3. Defects caused by shear force or shear cracks. Such cracks are directed at an angle to the reinforcement bars;
4. Cracks located parallel to the reinforcement bars can occur in the anchorage area due to improper production, as a result of soil heaving or uneven settlement of the monolithic structure;
5. Small cracks can occur due to temperature changes on the surface concrete product and him inner layers;
6. Hairline cracks can also occur due to temperature changes, but their depth does not exceed a couple of millimeters.

Defect elimination methods

In a freshly laid solution, defects of this kind can be eliminated without special costs, simply re-compacting the mixture.

Note! A solution is considered freshly laid if no more than 1-2 hours have passed since it was poured.

Well, in order to remove cracks in an already frozen structure, you will have to use one of the following methods:

• Injection method. A repair compound is injected into the crack under pressure;

Note! Some repair compounds can, in addition to sealing cracks, also displace water from the resulting cavity, but their price will be noticeably higher.

• Sealing method, which involves filling the defect with a concrete composition.

Repairing a crack

This method is most often used in practice, because every owner can handle it with his own hands without the help of professionals.

Advice. As a rule, to implement it, it is necessary not only to fill the void with a solution, but also to pre-treat the surfaces in order to ensure the best adhesion.

In order to repair cracks on the surface yourself, you need to prepare or purchase following materials and tools:

• Sander;
• Chisel;
• Putty knife;
• Hammer;
• Brush with hard metal rods;
• Vacuum cleaner;
• Trowel;
• Brush;
• Rake or rule;
• Pure water;
• Cement flour;
• Wire;
• Glue;
• Metal ironing board.

Now it remains to answer the questions about how to cover up the cracks and how to do it correctly?

This task involves the execution next stages repair work:

1. Preparatory activities. First you need to inspect the crack itself and identify weak spots around her. Next, using a chisel and hammer, you should widen and deepen it to at least 5 mm. This is necessary so that the repair composition is securely strengthened in its depth and does not fall out;

Advice. If necessary, you can deepen the crack using the sharp edge of a spatula.

1. Now the crack should be thoroughly washed, removing any remaining dirt and particles of cement stone. To completely remove dust from the surface, use a vacuum cleaner. Using a sponge will dry the crack and rid it of excess moisture;
2. If the reinforcement was exposed during the expansion of the crack, then before starting work with the solution, you should treat the metal using primers with anti-corrosion properties;
3. In order to seal, professionals recommend using a sand solution consisting of cement and sand in a ratio of 1 to 3. PVA glue can also be added to such a solution;

Advice. Sufficiently deep surface defects should be filled in several layers, making sure to moisten each layer to ensure high-quality filling and uniform drying of the solution.

1. In some cases, cracks should be reinforced using small pieces of reinforcing metal wire;

1. The surface of the crack filled with mortar is carefully leveled using a trowel;
2. The remaining protruding parts of the mortar should be sanded using a specialized grinding machine.

How to prevent cracking of a monolith

The most common and most common cause of cracks in concrete is non-compliance with the proportions of water and cement in the solution. It is this violation of technology that leads to a decrease in the quality of the concrete itself and subsequent intensive cracking. Exactly because of this reason Special attention When working with concrete, attention should be paid to these proportions.

In addition to this error, compaction is of considerable importance in the process of mixing concrete mixture. mortar using specialized vibrators. The importance of being correct and competent in the process of drying and hardening should also not be underestimated.

Advice. In order to prevent too much evaporation of moisture from the surface and to prevent uneven drying of the mass, the solution should be covered with a damp cloth.

Particularly dangerous can be cracks that appear on the surface, which is operated under conditions of temperature changes with frequent transitions through the 0-degree mark.

The fact is that when moisture freezes and gets into the very depths of the crack, it expands, deepening and expanding the size of the defect. The result of such processes may be the exposure metal fittings and the occurrence of corrosion, which will lead to a decrease in the strength of the entire structure.

In order to promptly identify cracking and eliminate this defect before irreparable consequences occur, you should regularly inspect concrete surfaces, record identified defects and repair them. This way, you will be able to localize cracking at a very early stage and reduce the amount of repair work required.

Advice. Under no circumstances allow yourself to be lazy and put off repairing until later, even if we are talking about very small defects.

Finally

Cracks on the concrete surface, whether they are shrinkage cracks in concrete according to SNiP or cracks in foam concrete, are the first sign that something was done wrong during the construction process. And if what has been done cannot be undone, then you should take care of it already at the operation stage, repairing the defect immediately after its occurrence and preventing the growth of cracks and an increase in their number.

And the video in this article will tell you even more about what kind of cracks there are and how to deal with them.

Cracks in the foundation after pouring concrete

A common occurrence when doing construction with your own hands or by unskilled workers is cracks in the foundation after pouring. There are many reasons for their formation, and it is quite difficult to independently identify a specific one. Below we will consider what causes cracks in a concrete structure and how you can deal with them.

The occurrence of cracks in a strip foundation in itself is not something catastrophic. Sometimes they appear as a result of natural shrinkage of the soil under monolithic design. If the preliminary soil study was carried out correctly and its results were taken into account when designing the foundation, then the grid of small depressions will not lead to critical consequences.

On the contrary, if cracks in the foundation after pouring have uneven “torn” edges and the depth of the recesses exceeds 10 cm, in this case it is urgent to take effective measures to save the situation. May require complete dismantling concrete base and replacing it with a new one, built in accordance with building regulations. Depending on the location and direction of the crack after pouring the foundation, it can be divided into the following types:

Type of foundation cracks

1. Horizontal - directed parallel to the main working reinforcement in the foundation. Most often they are the least problematic and repairable. The main reasons for their formation are shrinkage phenomena in the underlying soils or the concrete itself.
2. Vertical - perpendicular to the main reinforcing rods of the concrete structure. Quite dangerous if the size increases. Even without detecting them, home owners may encounter unpleasant manifestations of changes in the linearity of the foundation of the house in the form of jamming of doors or windows in the openings.
3. Oblique cracks are located at one angle or another to the horizon line. They are the most dangerous from the point of view of maintaining the integrity of the foundation and the structure itself as a whole. As a rule, a combination of several factors leads to their formation.

Causes of cracks in the foundation

The appearance of cracks in the foundation of a house can occur for several different reasons, most often associated with a violation of the manufacturing technology of the foundation of the house or poorly conducted studies of the condition and type of soil at the site of construction work. Below we will consider the main factors influencing the cracking of concrete.

1. Incorrect calculation of the bearing capacity of the foundation or its excess due to the use of certain building materials not taken into account can lead to the occurrence of cracks that will be almost impossible to cope with. This happens for several reasons - the production of a strip foundation with reduced linear dimensions in order to save concrete, use plastic reinforcement instead of steel, which has a low degree of longitudinal tension, and also when using concrete of the wrong grade. Important role When building a foundation, the quality of the base also plays a role. binder– cement. Exceeding the storage time, getting wet and clumping directly in bags during long-term storage - all this can cause a decrease in the quality of concrete and, as a consequence, a decrease in its strength characteristics.
2. The behavior of the soil at the site where the house is installed is also common cause, along which shrinkage cracks appear in the foundation. Raising the level groundwater as a result of excessive rainfall during the spring-autumn period, it can negatively affect soil heaving regimes. Exceeding the calculated vibrations of the base also leads to the formation of cracks, which often self-liquidate when soil conditions return to normal. Unstable temperature conditions in winter can have a similar impact. Frequent thaws alternating with severe frosts– for better conditions for the stability of the concrete foundation.
3. Violation of technology foundation works can be expressed in a whole complex of various mistakes made by private developers or teams of unskilled workers. The most common ones include the following:

Causes of cracks in the foundation

• The use of steel reinforcement with multiple traces of corrosion, which can negatively affect internal state concrete;
• Incorrect alignment of the reinforcing belt in the corners of the foundation and at the junction with partitions. It is not recommended to connect the reinforcement in these places using the end method. It is better to install rods pre-bent at an angle of 90 degrees in corners and joints.
• When pouring concrete from a mixer and there is no wooden or metal tray, the mixture is often poured into one corner of the strip foundation and spread on a stretcher or spread with shovels. In this case, the consistency of concrete and the ratio of liquid and solid fractions are disrupted. Long breaks when pouring the foundation of a house are also critical, for example, if there is not enough concrete. In the event of unexpected interference in the work, the gravel-sand-cement mixture may thicken. To save money, it is re-diluted with water without observing the required proportion, which leads to a significant decrease in the quality of concrete.
• The occurrence of internal stresses in concrete is greatly influenced by the rate of its curing from the outside and inside. The presence of frost, strong wind, rain or heat negatively affects the hardening of the mixture. It is for this purpose that the surface concrete pouring It is necessary to cover it with moistened burlap or roofing felt for the first few days to regulate the drying speed.

Investigation and measurement of cracks

If cracks appear several months or years after pouring the foundation slab, do not panic. A thorough investigation of the problem should be carried out. First, decide on the direction of the recesses, their length and depth. According to modern building regulations permissible cracks in the foundation after filling can have a width not exceeding 0.4 mm.

Even if a network of small depressions is discovered in the foundation of the house, it is not recommended to immediately begin repairing them. Builders advise monitoring the dynamics of crack behavior. A simple method is used for this. It involves installing a beacon on the crack, which is a strip of thin paper or a small plaster cake.

Investigation of foundation cracks

Before installing the beacon, the foundation surface around the crack must be thoroughly dust-free and cleared of loose concrete particles. To do this, it is convenient to use a metal brush, a brush with soft nylon bristles, and a vacuum cleaner. After this, the strip of paper is smeared along the edges with high-quality universal glue and glued to the foundation along the edges of the recess. It is better to do this in the widest part of the cracks.

Monitoring the state of the lighthouse must be carried out at intervals of 3-5 days. If the crack expands, the tape glued under tension will peel off on one side or break. This indicates expansion of the depressions in the foundation and the need to take immediate action. As cracks grow, the gypsum beacon splits, which is also a signal for immediate action.

Methods for eliminating foundation cracks

If, after pouring the foundation, cracks appear on the surface, and as a result of long-term and careful observations it was possible to establish that their growth is absent or insignificant, it is necessary to take measures to eliminate the depressions. This needs to be done for a reason negative influence on concrete moisture in all its forms - dew and fog, rain, snow and ice.

Especially harmful effects Ice is exerting pressure on the foundation of the house. From a school physics course, everyone knows about the significant expansion of water when it freezes. The moisture clogged in the crack will affect its walls, which will certainly lead to the expansion of the recess and the destruction of concrete up to a critical scale.

Currently, there are several common and available ways to remove permissible cracks in the foundation. The first of these refers to small depressions that appear an hour and a half after pouring the mixture. This usually occurs due to insufficient compaction of the concrete. In inquiries from builders, the problem most often sounds like “the foundation was poured and cracks appeared.”

If cracking is observed fresh concrete, it must be re-compacted thoroughly using a construction vibrator. To avoid the occurrence of cracks, it is recommended to perform the same operation directly when pouring the strip or slab concrete foundation of the house.

If cracks are detected after pouring and hardening of the concrete mixture on the surface of the foundation, they can be dealt with using sand-cement mortar finely dispersed composition. It is prepared before starting work, applied to the surface of the cracked foundation of the house and rubbed in with a trowel or grater. A more reliable option are special repair compounds for foundations, sold in the form of ready-made dry mixtures of complex composition.

More complex and expensive methods allow not only to get rid of cracks in the foundation, but also to significantly increase its load-bearing capacity. We are talking about the so-called injection method and the production of an additional concrete base under the existing one. The first option involves drilling inclined holes in the base and walls of the house and pumping special fastening solutions into them. In the second case, which is typical for incorrectly calculated strip foundations, a additional basis with large depth and support area.

A situation often arises when a builder cannot understand why the concrete cracked after pouring. This is a fairly common phenomenon that leads to a deterioration in the performance characteristics of the material and its gradual destruction. We want to talk about the causes of cracks and ways to prevent this phenomenon.

Cracks in concrete

Varieties

Concrete cracking is a widespread phenomenon that occurs due to a number of reasons, and for the convenience of considering this topic, individual cases of this phenomenon should be classified.

So, all cracks can be divided into three large groups:

1. Structural cracks s. They pose a threat to the integrity of the structure and its load-bearing capacity, appearing, as a rule, due to external reasons and design errors;
2. Structural or non-structural cracks. They pose a potential hazard and, if remedial measures are insufficient, lead to more serious damage and loss of quality, load-bearing capacity and structural integrity. They arise due to internal processes during the hydration reaction and the gain of concrete strength;
3. Cracks caused by fire. Includes both structural and structural damage. Distinctive feature– delamination of the top layer of concrete.

Damage of the first group includes violations of integrity caused by increased loads on parts, discrepancy between the strength of the material and the actual loads, architect’s design errors, errors in the design of the mixture composition, ground movements, natural disasters, impacts, explosions, etc.

Important!
Cracking is often observed due to mistakes when preparing concrete with your own hands.

The price of ready-mixed concrete hits the budget, but repairing a low-quality foundation is much more expensive.

Structural defects are characterized by a high opening width, great depth, end-to-end character, great length and special localization. Prevention of such damage is associated with competent design and calculation of loads, application quality materials, taking into account the peculiarities of geology and concerns mainly technical and project preparation construction.

It is almost impossible to take into account the impact of natural disasters and accidents, man-made disasters and wars, the same applies to disturbances due to fires.

The second group of defects refers to violations of the structure and integrity of the material as a result of natural physical and chemical processes occurring in concrete at all stages of its maturation, especially at the initial ones.

There is a whole range of phenomena that lead to the appearance of such defects:

• Cracks due to plastic shrinkage. They arise due to intense evaporation of moisture from the surface and as a result of uneven shrinkage and compaction of the mass;
• Temperature-shrinkage destruction. Appear due to the effect of thermal expansion and contraction of materials caused by heating and uneven cooling of the mixture;
• Shrinkage defects when the solution dries. They arise due to an uneven reduction in the volume of concrete during drying;
• Cracks due to corrosion of reinforcement. When rusting actively, the steel increases in volume and can tear apart the concrete.

Important!
Preventing cracks from occurring is a much more effective and efficient way than eliminating and repairing them.
To successfully prevent it, you must know the causes of defects.

Causes

If everything is clear about the reasons for the appearance of structural defects, then structural violations should be considered in more detail. So, let's start in order.

Plastic shrinkage is a process that occurs at the very beginning of the life of a solution. Here an effect such as intense evaporation of moisture from the open surface of the laid concrete is observed. As a result, the mass of the solution actively decreases in volume, while the lower layers remain the same size, and the upper layer is covered with a network of thin hairline cracks.

Also, during the first period of the solution's life during installation, the process of mixing under the influence of gravity begins. If compaction by a vibrating tool is insufficient, a moment arises when the concrete has already set, and its compaction continues. This leads to faults.

Temperature-shrinkage deformations appear due to the hydration reaction of cement, which occurs with the release of heat. The solution heats up, increasing in volume, and the hardening areas crack. Also affects reverse process– the upper layer cools and shrinks, while the lower one remains the same size or increases, the result is ruptures in the material.

Shrinkage cracks during drying are caused by the fact that the set material decreases in volume. This is typical for any type of concrete, glue and other hardening and drying substances. Usually observed in unreinforced structures and products of flat, extended or non-standard shape, this is how they crack concrete screed large area, plaster and similar structures.

Important!
Drying shrinkage often leads to aggravation of other types of cracks and an increase in the degree of their opening.

The penetration of moisture into a concrete structure leads to corrosion of the metal inside it. As a result, the reinforcing bars increase in volume and tear the stone.

Prevention

To avoid the appearance of defects and breaks in concrete, you should adhere to the rules contained in the concreting instructions.

For the sake of brevity, here are three main points:

1. Prepare the mixture correctly and follow the recipe. Excess water or cement has the most detrimental effect on the quality of concrete and leads to the appearance of defects;
2. Place the mortar in accordance with accepted standards: use vibration compaction, aeration and other standard procedures;
3. Maintain concrete after installation. The object can be covered with film, its surface can be moistened with water, formwork can be used if necessary, and expansion joints should be cut in large screeds.

Important! Observe concreting conditions, namely: work in the correct temperature conditions, control humidity, monitor changes weather conditions, do not violate the limits within which work can be carried out, do not neglect the technology of caring for hardening concrete and use high-quality materials.

For concreting critical components and structures, it is better to use high-quality ready-mixed concrete, since a homemade product most often demonstrates the listed phenomena, and different ones at the same time.

Important! Do not dilute concrete with water or add cement to it; this is a gross violation of technology and interference in the mixture recipe, the result of which is predictable.

Conclusion

Cracks lead to the fact that further processing and construction procedures lead to a worsening of the condition of the structure; only cutting reinforced concrete with diamond wheels and diamond drilling holes in concrete does not destroy it. To prevent such defects from occurring, the technology must be strictly followed. concrete works, which the video in this article explains in detail.

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Concrete mortar is used everywhere. Without it, it is difficult to imagine any construction, be it the construction of a multi-storey building, a bridge, the arrangement of a site or an alley in a country house. Concrete structures are strong and durable, but sometimes problems arise. Concrete can crack; it is worth considering the main reasons for this phenomenon.

• Armature

When making concrete structures, it is important to use reinforcement, which increases strength and prevents cracks. To do this, metal rods or mesh are poured with concrete mortar, it turns out that it is inside the concrete structure. If there is no reinforcement and the concrete layer is thick, then most likely cracks will appear on the surface. Armature reinforced concrete structures increases their tensile strength.

• Evaporation of moisture

Lack of moisture - during the hardening process, water evaporates from the concrete solution before it hardens. This process is similar to drying mud. Therefore, the complete hardening process of concrete takes 28-30 days; during this period it must be covered with film and periodically moistened as it dries.

• Sudden changes in temperature

In case of possible sudden changes in temperature, it is important to use frost-resistant cement and thermal insulation. As an option, you can buy royal concrete on the website of our comrades http://impbet.ru/, which has high frost resistance.

• Surface preparation

Improper surface preparation can also cause cracks in concrete. Any surface must be thoroughly cleaned of dirt and leveled before pouring concrete. To install a screed inside a building, before pouring the concrete solution, the floor is treated with a deeply penetrating primer.

• Incorrectly prepared solution

Concrete mortar is made from crushed stone, sand and cement in a ratio of 3:2:1, sometimes 4:2:1, and water is also added. If the proportions are taken incorrectly or the solution is poorly mixed, then cracks may subsequently appear. Sometimes plasticizers are added to the solution if there is a problem in a room with a concrete floor. negative impact vibrations.

• Formwork

If they do concrete pad on the street or foundation, then the formwork may be done incorrectly. Concrete mortar, if it is very liquid, can spread, and cracks will appear during the drying process. The inside of the formwork must be covered with film.

• Frost

Moisture gets into microcracks in concrete, and when it freezes, it expands, forming cracks.

How to protect concrete structures

To protect concrete structures are used different methods. If this is the foundation of a house, then various cladding and installation can help drainage systems, to rainwater did not erode the structure. Water-repellent compounds are also used to treat the surface.

Repairing cracks

If cracks have already formed, it is worth finding out the reason for this and eliminating it. The walls of old cracks are treated with a primer, and a polymer mixture or concrete mortar. If the concrete has not yet dried, the cracks can be eliminated by compaction.

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