Treatment of cracks in concrete - injection

Epoxy resin

Repair compositions for sealing cracks in concrete based on epoxy resin are used to repair small cracks in a monolithic base, this mixture can also be used to repair a foundation in a private house.

The work to eliminate defects consists of three stages:

1. Cleaning the area from small fractions.
2. Drying the problem area.
3. Filling the crack with epoxy.

Cleaning the problem area is done with a stiff metal brush. It is necessary to process the inside and the surface around the gap. Removal of fine fractions and dust is carried out by blowing, after which the area can be dried with a building hair dryer.

Before sealing cracks in concrete on the street using epoxy compounds, it is necessary to place special nozzles along the entire length of the problem area with a run-out of 30 cm. The installation of nozzles along the height of the wall begins from the lower section of the crack, stepping back from the level of the blind area 30 cm.

Epoxy adhesive is formed by mixing resin with a hardener. This mass is injected into the fracture through nozzles, starting from the lowest. The solution gains full strength within five days, after which the nozzles are removed (cut off), and the surface of the repaired area is rubbed with an epoxy solution.

Types of cracks

To know how to fix cracks in concrete, you must first determine what type it belongs to:

• Through cracks occur under tensile forces;
• Surface cracks appear after the concrete has dried due to a violation of the mortar formulation;
• Cracks in the tension zone appear during bending and are directed across to the reinforcing bars;
• Cracks located at an angle to the reinforcement, which occur under the influence of a transverse force;
• Shrinkage cracks parallel to the reinforcement, which occur due to heaving of the soil, uneven shrinkage or improper anchoring. Due to such cracks, shrinkage and deformation of the foundation and the entire building occur. Shrinkage cracks can also appear if the load calculation was not made according to the rules of SNiP;
• Small cracks that appear during temperature changes;
• Hairline cracks occur for the same reason as the previous ones, but usually their depth does not exceed a few millimeters.

Having determined the causes and types of cracks, they are determined with the type of repair work.

Equipment used and its cost

If we talk about equipment for concrete injection, then usually the following are used for this purpose:

• injection pumps. Their cost depends on the composition used. For example, a KSG-700 pump for cement mortars will cost about 82,000 rubles. For polyurethane and epoxy resins, the KSG 900 model, costing 48,000 rubles, is suitable. Also, on sale you can find manual injection pumps at a lower cost.
• Packers for injection. These elements are special tubes through which a solution is supplied to the concrete base. Now 1 injection packer costs about 50 rubles (however, everything depends on its size).

The cost of the resin is about 800 rubles per 1 kg, acrylic gel will cost about 600 rubles. Also, you will need to buy a protective tape, worth about 400 rubles per 1 roll.

After acquiring everything you need, it remains only to inject.

Causes of deformation

Cracks in concrete structures can appear due to the violation of proportions in the manufacture of concrete mix.

The occurrence of cracks in concrete structures or concrete coverings (eg floors, walls, etc.) is common and not cause for confusion. Especially often it is faced by builders who do not have enough experience.

And it does not matter where they appeared - in the floor or on the wall, in any case, repair is a prerequisite. Below are some of the main reasons that affect the appearance and nature of

The cement mixture contains an excess of water. Most often, the violation of the proportions characteristic of a particular concrete mixture occurs during its mixing by hand.Since the amount of the water component is increased, the work of workers mixing all the components of the solution is greatly facilitated. The disadvantage of such actions will be a noticeable loss of concrete qualities. With an excess of water, shrinkage occurs fairly quickly, followed by drying and hardening. It has long been known that with more water, shrinkage occurs more intensely. And the result of such a fast process is always cracks. To avoid the appearance of cracks in the concrete pavement, first of all, it is necessary to strictly observe the proportions of the solution you need.

Small cracks in the concrete may appear due to the mixture drying too quickly.

The second most common reason can be called too fast drying process. What else, besides the water component, affects the time at ? The answer is known to many, it is air temperature. At high temperatures, moisture evaporates quickly enough and, as a result, defects appear. To avoid this, it is necessary to prevent the concrete from being exposed to direct sunlight when it dries. To do this, it is necessary to make some kind of protective cover or (at high temperatures) to ensure the wetting of the concrete surface with water.

An incorrectly selected composition of the mortar components (a concrete mix unsuitable for the manufacture of a particular structure) also significantly affects the appearance of cracks.

Sharp temperature fluctuations. This is another factor contributing to the appearance of cracks in the concrete pavement. The finished concrete or reinforced concrete structure expands quite quickly under the influence of various temperatures, then contracts, etc. As a result of these impacts, cracks appear.

And the last thing: the not very stable state of the soil causes deformation of the concrete structure and, as a negative result, the appearance of defects. What to do in this case? The answer is quite simple: it is necessary to perform reinforcement with a metal frame or rods, the diameter of which corresponds to a value from 8 to 12 mm.

Self-expanding cords

This method is used to carry out repair work in the bowls of outdoor pools, to restore monolithic foundations and restore the integrity of external walls in industrial premises.

To perform work, you will need to prepare the site by cleaning it of fine fractions and dust, measure the depth and width of the crack and select a self-expanding cord or tape that is suitable in size.

A cord is laid in a pre-prepared seam and the remaining space is filled with polyurethane sealant from a mounting gun. Excess sealant is leveled with a spatula, and after the material has risen, the surface of the problem area is polished.

This method of eliminating defects in concrete surfaces allows you to choose a cord to seal any crack, which ensures complete tightness of the seam and a long service life. An important feature of the method is the possibility of performing work at low temperatures.

How to repair defects in concrete

Starting to close up cracks, first determine how you will do it. Thin cracks in concrete in most cases are simply primed, plastered or painted over.

Crack filling is carried out mainly by filling the depth with synthetic mixtures with the addition of resins that have a low viscosity. Holes are drilled along the crack, they must be placed diagonally, towards the defect. After that, bushings are placed in the holes and the working mixture is forced through them. The resin is then pressed in using an injector. This method helps to ensure good strength of the structure, and it is able to work as a whole.

Materials used

Manufacturers who make mixes for concrete injection use various components. They differ in composition and technical characteristics.

The following base is used for production: epoxy resin; polymer cement composition; polyurethane.

Injection of concrete is carried out with a properly prepared solution. It must have the right level of viscosity, high penetrating power. These properties are not depend on the size damage and cannot change depending on it. In the hot season, you do not need to make a solution that is too thin, which will not be strong after hardening.

The following similar properties of compositions that are intended for injection can be distinguished:

• low viscosity;
• can be used to repair buildings and structures if there is severe frost or hot weather outside;
• minimal shrinkage after hardening;
• adhesion to different materials, metal fittings;
• the material does not deteriorate after 5-10 years;
• no corrosion occurs.

Ways to seal a crack in concrete

To increase the operational life of a building or structure, it is important to close the resulting cracks in a timely manner.

The list of funds that are used for this purpose:

• cement-sand mixture;
• compositions containing epoxy resin;
• sealants;
• self-expanding linear products;
• solutions with the addition of liquid glass;
• ready mixes for finishing and building works, etc.

Epoxy Resin Application

If small cracks appear in the monolithic base, then you can use a repair compound made on the basis of epoxy resin. The same tool is suitable for repairing the foundation of a private house. The work is carried out as follows:

Epoxy resin.

1. Clear the area of ​​small fractions. To do this, use a hard metal brush. She needs to carefully process the inside of the crack and the surface around it. Dust and smaller particles can be removed by simple blowing. After that, dry the problem area with a building hair dryer.
2. Before proceeding with the main work, you will need to deal with the placement of special nozzles along the entire length of the problem surface. Keep a distance of about 30 cm. It is necessary to install the nozzle along the height of the wall, starting from the bottom of the crack - while stepping back 30 cm from the level of the blind area.
3. To form an epoxy adhesive, mix the resin with a hardener. The resulting mass must be injected into the crack through a special nozzle - start the process from the lowest fault. The solution will gain full strength within 5 days. After that, the nozzles must be removed (cut off), and the surface of the repaired site should be rubbed using an epoxy solution.

Use of sealants

You can effectively fill almost any crack in a concrete surface with the help of a sealant. Such an elastic material will tightly seal the defect, since it is able to increase in volume.The preparatory stage involves a thorough cleaning of the problem surface from small and large fractions. Moisten the substrate before applying the sealant. In addition, prepare small grooves to improve the adhesion of the composition to the material.

Usage .

Liquid glass to eliminate defects

If small cracks appear in the screed, try repairing them with a sealing mixture with the addition of liquid glass to it. This tool is a water-alkaline solution of sodium silicates (less often potassium and lithium). The same composition is suitable for masking the seams that exist between. Before starting repair work, prepare a solution of the following components:

• liquid glass - 20%;
• cement - 20%;
• sand - 60%

Self-expanding cords

A method that is used for surfaces in the bowls of outdoor pools, restoring the integrity of walls in industrial premises and monolithic foundations.

Self-expanding cords are widely used to seal seams and joints, which are the most vulnerable places for water penetration.

The main steps will be as follows:

1. Prepare the area to be repaired. Clean it from dust, small and large fractions.
2. Measure the width and depth of each crack to find the best self-expanding cord.
3. Lay a suitable material in the prepared seam and fill the remaining space with a sealant - give preference to a polyurethane composition. For this purpose, use a mounting gun.
4. Excess sealant must be well leveled with a spatula. Once the material has hardened, you can sand the problem surface.

Sealing self-expanding cord.

The described method fixing cracks in concrete allows you to choose a self-expanding cord to fill almost any defect. Thanks to this, it is possible to ensure complete tightness of the seam and a long service life of the structure. The peculiarity of this repair technology is that it can be used even at negative temperatures.

injection

Injection is based on the supply of special compounds under pressure into the openings that have appeared, which completely fill the voids formed and harden. The injection of the filling mixture is carried out by pneumatic, electric or mechanical pumps. Their design capabilities are designed for a clear dosage of injection components, maintaining the required pressure level. The injection material is polymer-cement materials, epoxy resin. To carry out such a procedure, holes are drilled in concrete along the crack on both sides and packers are installed through which the injection composition is supplied (Fig. 1).

Comments:

• Sealing cracks in concrete
• How to repair defects in concrete
• Sealing and injection of concrete
• What repair compounds are more popular

Repairing cracks in concrete is sometimes a high priority task. Defects and cracks are formed both in old structures and in newly built ones.

Before proceeding to get rid of cracks, you will need to choose the most convenient way.

Cracks in concrete can occur due to moisture or deformation of the concrete product, shrinkage or load.

Causes of cracks in concrete

During operation, concrete structures are exposed to a number of negative factors that can lead to the appearance of cracks.

Such factors include temperature differences, shrinkage, deformation during subsidence of soils, exposure to moisture and chemically aggressive substances, corrosion of steel reinforcement. Structural miscalculations, errors in concreting and insufficient reinforcement are essential.

As a result of the growth of internal stresses caused by the negative effects described above, cracks form in the concrete structure, which can significantly reduce the bearing capacity of the structure, as well as shorten its service life.

What is injection (injection)

Repair of cracks in concrete by injection is a technology that allows you to repair cracks in building structures by injecting special repair compounds into them, the chemical basis of which may vary depending on the material of the structure and the tasks at hand.

Injection compounds are injected into the body of building structures using special pumps through devices called packers. There are two main types of packers - adhesive and drilling. The use of one or another type of packers is determined by the type of injection composition, the thickness of the structure, the depth and width of the fracture opening.

Where is this technology applied?

• Sealing of cracks, including aquifers in concrete.
• Ensuring the tightness of the communication input zones.
• Sealing of joints and sealing of technological seams of concreting.
• Outline filling of voids behind concrete structures sunk into the ground.
• Filling cracks and voids in masonry and masonry.

Types of injection formulations

• Epoxy resins are used for structural repair of reinforced concrete structures.
• Polyurethane resins and foams are used for waterproofing cracks, including water-bearing ones.
• Microcements are used to repair masonry and concrete structures not subjected to dynamic loads.
• Acrylates - used to restore damaged foundation waterproofing.

RELATED: Concrete Waterproofing Guide

Causes of deformation

Cracks in concrete structures can appear due to the violation of proportions in the manufacture of concrete mix.

The occurrence of cracks in concrete structures or concrete coverings (eg floors, walls, etc.) is common and not cause for confusion. Especially often it is faced by builders who do not have enough experience.

And it does not matter where they appeared - in the floor or on the wall, in any case, repair is a prerequisite. Below are some of the main reasons that affect the appearance and nature of

The cement mixture contains an excess of water. Most often, the violation of the proportions characteristic of a particular concrete mixture occurs during its mixing by hand. Since the amount of the water component is increased, the work of workers mixing all the components of the solution is greatly facilitated. The disadvantage of such actions will be a noticeable loss of concrete qualities. With an excess of water, shrinkage occurs fairly quickly, followed by drying and hardening. It has long been known that with more water, shrinkage occurs more intensely. And the result of such a fast process is always cracks. To avoid the appearance of cracks in the concrete pavement, first of all, it is necessary to strictly observe the proportions of the solution you need.

Small cracks in the concrete may appear due to the mixture drying too quickly.

The second most common reason can be called too fast drying process. What else, besides the water component, affects the time when concrete dries? The answer is known to many, it is air temperature. At high temperatures, moisture evaporates quickly enough and, as a result, defects appear. To avoid this, it is necessary to prevent the concrete from being exposed to direct sunlight when it dries. To do this, it is necessary to make some kind of protective cover or (at high temperatures) to ensure the wetting of the concrete surface with water.

An incorrectly selected composition of the mortar components (a concrete mix unsuitable for the manufacture of a particular structure) also significantly affects the appearance of cracks.

Sharp temperature fluctuations. This is another factor contributing to the appearance of cracks in the concrete pavement. The finished concrete or reinforced concrete structure expands quite quickly under the influence of various temperatures, then contracts, etc. As a result of these impacts, cracks appear.

And the last thing: the not very stable state of the soil causes deformation of the concrete structure and, as a negative result, the appearance of defects. What to do in this case? The answer is quite simple: it is necessary to perform reinforcement with a metal frame or rods, the diameter of which corresponds to a value from 8 to 12 mm.

Repair with cement mortar and mixtures

This type of repair can be considered the simplest and at the same time the weakest. This is a temporary partial filling of floor, wall and foundation cracks in both dry and wet rooms.

Such filling of cracks does not seal them, but protects them from contamination for a while and prevents their further opening for a short time.

They begin repairs according to the rules of SNiP with the preparation of the disclosure itself.

It should be checked for chips, as other cracks and openings may form in them in the future. A chisel is run along the entire length of the crack to make it wider.

Next, clean the crack with water and a brush to remove various contaminants, you can also use a vacuum cleaner. The remaining water must be collected with a sponge.

Using a spatula, you should also deepen the crack to 5 mm so that the mortar holds stronger.

For repairs, a solution is made from 3 parts of sand and 1 part of cement, to which PVA glue must also be added. The solution should be thick enough.

Pour it into the crack with a trowel, and moisten it from above. If you carry out repairs using a polymer mixture, and do not use a concrete solution, you do not need to wet the composition.

Reinforcement is usually visible in medium cracks, it must be cleaned and coated with a special agent that will prevent corrosion. Next, you need to make grooves and put pieces of reinforcement 4 mm in them.

Now we apply an adhesive composition evenly over the entire surface so that the layer thickness is about 3 mm, and without waiting for drying, you need to fill it all with a solution.

The solution must be compacted so that it gets into all the recesses and irregularities, and the surface should be leveled with a wooden lath, which must be moved over the surface of the solution to the right and left and towards you.

If the gap is very deep, it is advisable to lay the mortar in several passes. At each stage, the surface needs to be sprinkled with a little water.

A special metal trowel will help to make the concrete surface perfectly smooth. When the solution has hardened, the excess must be removed with a spatula.

If you paint or cover the concrete surface with laminate, then such work can be done within a day after the repair is made, but for laying tiles should wait longer.

If, nevertheless, this did not happen, with the help of a grinding machine, the surface of the former crack is leveled to the desired level.

If you are dealing with a crack, the width and length of which are large enough, you can process it before repair with a circular with a diamond disc, after which the repair is carried out according to the scheme described above.

This method of sealing is most often used as a temporary solution, since sealing does not occur during such repairs.

The method is relevant both for dry and for rooms with high humidity, where good waterproofing is required.

Video:

Advantages and disadvantages

The presented technique has its advantages and disadvantages.

Before starting work and restoration, it is important to familiarize yourself with the following advantages:

• performance of work in different weather;
• minimal time and labor costs;
• in the process of restoration work, a monolithic waterproofing layer is created, on which there are no seams and joints;
• emergency leaks can be quickly and easily eliminated;
• the ability to use water under high pressure;
• as a result of the restoration, the bearing strength of the walls and foundation increases;
• material may come into contact with drinking water.

But there are also disadvantages that can affect the final decision when choosing. Materials and equipment are expensive, so not everyone will be able to afford the restoration work.In order for the concrete base to turn out to be strong, it is necessary to follow the sequence of technology.

If you do not contact specialists and do the restoration yourself, you can violate the integrity of the structure. Cracks and hollow structures can collapse under strong pressure. The consequences in this case will be irreparable.

Before work, it is important to remember about financial costs. Restoration and restoration work of a concrete monolith must be entrusted to qualified craftsmen

Cracks in concrete: causes

For a better understanding of crack repair technologies, it is necessary to consider the types and causes of their appearance of these defects. Cracks in concrete are classified according to the following factors:

• Depth of damage: hairy, through, superficial.
• Direction of cracks: vertical, inclined, horizontal, curvilinear and closed.
• Type of destruction of concrete: shear, shear, rupture, collapse.

The reasons why the concrete material begins to collapse:

• Shrinkage. Shrinkage cracks in concrete are the result of incorrect proportions of components in the preparation of mortar or improper care of a freshly poured structure. This type of damage appears in the absence of load and is characterized by: small opening (up to 2 mm), uniform distribution along the entire length of the structure.
• Temperature changes. With a concrete structure length of 100 meters, a change in ambient temperature by 1 degree Celsius causes a change in linear dimensions by about 1 millimeter. Due to the fact that during the day the temperature drops can reach 15 or more degrees, the concrete cracks. To eliminate this harmful phenomenon, the technology of "temperature seams" is used.In this case, the distance between the expansion joints is calculated individually, depending on the dimensions of the structure and other factors.
• Draft. Uneven settlement of concrete foundations and walls poses a serious danger to newly built structures. Settling is the cause of the most "bad" inclined cracks. To prevent uneven settlement, it is necessary to strictly observe the soil preparation technology and erect the building box (load the foundation) after natural settlement - 12 months after pouring.
• Heaving. The phenomenon of heaving of the soil occurs in winter. Frozen soil tries to "push" the building out of the ground, resulting in very serious damage. As practice shows, the linear displacement of the building as a result of heaving can reach 15 centimeters. The formation of cracks from heaving can be prevented by the correct depth of foundation embedment below the level of maximum soil freezing in the area.
• Corrosion of steel reinforcement and improper reinforcement. In accordance with the laws of chemistry, corroded metal increases in volume and, accordingly, begins to “tear” concrete. Also, incorrect calculation of the reinforcing belt can lead to the appearance of cracks.

Method 4. "Make it in advance." Additive in concrete for self-healing of cracks

It sounds unusual, tempting and incredible. However, this is a fact - Russian scientists have created a drug that forms hydrophobic crystals. Moreover, it works only in the finished structure and in contact with water. By including such an additive in the composition of concrete during the construction of a pool or foundation, you can insure yourself against the appearance of small cracks, from which major problems begin.To date, only one company produces such an additive - Penetron. Their product "Penetron Admix" is available in buckets of 10 kg and costs about 250 rubles./kg.

Whatever method you choose, remember that waterproofing is not a whim or a fad, but a constructive necessity and a vital structural element.

Vitaly Dolbinov, rmnt.ru

Conclusion

Concrete injection is a modern way of repairing concrete or brick surfaces, which is characterized by high quality, strength and durability. It should be noted that the technology has no restrictions regarding the depth or thickness of cracks.

The disadvantage of the procedure is the high cost of the materials used in the work, the need for special equipment and the skills of the performers in such work.

Sources of information:

1. SP 349.1325800.2017 (introduced on 06/13/2018).
2. GOST 32016-2012 (introduced on 01.01.2014).
3. Instructions for the installation of injection waterproofing during the construction and reconstruction of buildings and structures (updated on 01/01/2019).
4. RD 153-34.2-21.625-2003 (introduced in 2003).

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Editor: Denis Nazarov

About me: Generalist. Over 12 years of experience as an editor and author of articles as a journalist. Graduated from the Faculty of Philology of the Belarusian State University (Department of the Russian Language and Literature) and received a diploma in the specialty “Philology. Teacher of Russian language and literature.

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