Concrete is widely used in construction. Foundations, floors, walls of industrial and residential buildings are made from it. This is a very durable material. However, it has one annoying feature. It is very prone to the formation of such a defect as cracks. This is especially true for concrete that has been poured recently.
There are several types of cracks:
Before you begin to close up the sealing of cracks in concrete, you need to find the cause of their occurrence. Used to fill cracks in concrete special sealants. They are rigid and elastic.
If defects occur in finishing stage construction, then they are suitable for their elimination epoxy resins or other rigid materials. A prerequisite for such a repair is the immobility of the foundation.
Thin cracks are sealed with more elastic sealants. Serious consideration should be given to the choice of materials for eliminating voids in potable water tanks. The sealant must be non-toxic, biostable and harmless. If there are many defects or they appeared in the first 2 hours after concrete laying, then The best way their elimination - injection.
This method does not require replacement of part of the structure. The sealing of cracks in concrete is carried out by injecting special materials or solutions under pressure into voids. A small amount of voids can be repaired manually.
If vertical surfaces are damaged, they are repaired by applying sandy cement mixture . It is necessary to add a polymer to it: 0.35% furyl alcohol or 0.02% sulfanol. The percentage of additive is calculated from the mass of cement.
When the applied repair mixture hardens, a layer is applied to it. polyurethane sealant. To seal cracks in concrete with a size of not more than 3 mm, cement "dough" is used. It is made from cement, water and glue. You can use special solutions.
If there are too many voids, then a decision may be made to remove the damaged concrete. A layer of the same material is applied on top. This method is not often used, as it is very time consuming and impractical. It must be taken into account that the new layer also shrinks, and this leads to cracks.
There are several ways to self-seal cracks in concrete. The most economical and simple is filling voids with cement mortar or repair mixture.
For work you will need:
- Grinder;
- vacuum cleaner;
- putty knife;
- chisel;
- trowel;
- metal brush;
- hammer;
- mixing containers;
- wooden lath;
- brush;
- cement;
- sand;
- water;
- metal trowel;
- PVA glue;
- wire.
Stages of work on sealing cracks in concrete:
This method does not give a sealing effect. It is used as a temporary and partial solution to the problem. Suitable for use in both dry and wet areas.
Repair with epoxy
Repairs to seal cracks in concrete can be made using epoxy resin and epoxy repair compounds:
For work you will need:
- Bulgarian;
- primer for concrete;
- vacuum cleaner;
- epoxy repair compound or resin with hardener;
- fine sand packing;
- spatulas;
- repair brackets;
- mixing containers.
Progress:
- Crack patching. At this stage, the edges are aligned with a grinder and loose concrete is removed. The width must be no more than 25 mm and no less than 4 mm. Every 400 mm along the entire length of the crack, it is necessary to cut transverse grooves 150 mm long.
- Vacuum cleaner to remove small debris and dust.
- Processing seams with a primer.
- Staples should be laid in the transverse groove.
- Following the instructions, it is necessary to prepare the solution and add the hardener.
- Sand is poured into the solution and the seams are filled with the resulting mixture.
- The surface should be sprinkled with sand.
- After an hour, sand is removed with a vacuum cleaner.
This method is economical, has a high drying rate, and also prevents further crack movement. It is suitable for removing defects in dry screeds.
If the concrete will be in contact with water, then sand is not needed. The repair of water tanks, such as swimming pools, requires a more serious approach.
For work you will need:
- Bulgarian;
- vacuum cleaner;
- primer for concrete;
- cord or tape for sealing stone cracks;
- construction pistol;
- polyurethane sealant for concrete;
- brushes;
- chisel;
- brushes;
- foam rubber.
Progress:
Cracks in concrete are not a surprise, but they also do not cause positive emotions. More often defects occur when reducing the time of work or saving on materials. But even with full observance of the technology, it is not possible to avoid concrete cracking, but it can significantly reduce the number and depth of voids.
Small voids do not cause serious damage to the building, and repairing them yourself will not be difficult.
One of the initial defects that precedes all serious problems with concrete surfaces are cracks. Small cracks in concrete are often ignored, which is absolutely contraindicated.
If timely sealing of cracks in concrete is not completed, then the smallest defects can grow into serious through damages in the wall, in the presence of which the accident rate of the building increases significantly, and serious repair of the blocks is required.
Factors causing cracks in monolithic concrete, as well as inside the cinder block, heat blocks, foam blocks and expanded clay blocks, a huge number, starting with the wrong technology for making concrete mix for blocks, and ending with erroneous calculations in the design during the construction of a house.
- We overwrite the damaged concrete surface with foam glass, which allows us to clean it from accumulated dirt.
- The brush removes the dust formed during the grouting process.
- The surface with microcracks is covered with cement slurry.
- After solidification of the sludge, its excess from the heat blocks is removed by sanding with foam glass.
3.7 Features of repairing cracks on concrete surfaces (video)
Many homeowners are interested in how to repair cracks in concrete, as this is a fairly common problem for cottages and country houses.
Concrete is used in various fields - for pouring floors of apartments and houses, industrial premises, roads, for building foundations.
This material is weakly resistant to tension; in the process of drying, concrete structures narrow, which may cause various defects and disclosures.
This is especially true for concrete floors or foundations.
In addition, cracks often appear due to corrosion. metal fittings, temperature instability, various negative impacts.
This defect is very dangerous and widespread, and in order to solve the problem, you need to know why it occurs, what are the reasons for disclosure.
Experts identify such causes of cracks in concrete:
- Violation of the technology for manufacturing the mixture at the factory, when the ratio of water and cement is violated.
- Because of this, the brand of the composition does not correspond to the specified one. In addition, long-term transportation leads to "welding" of concrete;
- Errors in calculations are also common causes of crack formation. Lack of reinforcement or heavy loading damages the integrity of the concrete pavement. It is very important to adhere to the norms of SNiP in the implementation of all calculations;
- Difficult geological conditions. The calculations do not always take into account the features of the soil on the ground;
- Wrong mixture technology when laying. Often, in order to make the composition fit more conveniently, it is diluted with water, which prevents the concrete from gaining strength. In addition, improper compaction of concrete and dismantling of formwork, as well as neglect of the rules for laying reinforcement according to SNiP standards, will subsequently lead to concrete deflection and cracking;
- Violation of the rules for the care of freshly laid concrete, especially when laying in hot weather, when moisture evaporates too quickly from the coating;
- Construction of various facilities that were not taken into account in advance in the calculations;
- It is not always possible to correctly choose the type of foundation according to the rules of SNiP, which is why deflections and cracks may also occur during the operation of the building;
- One more common cause the formation of cracks is the rusting of the reinforcement, as a result of which the volume of the metal becomes larger and breaks concrete pavement from within.
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, which 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 repair work.
Repair with cement mortar and mixtures
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.
Hidden chips that appear during work should be removed immediately.
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 needs to be cleaned and covered special means which will prevent corrosion. Next, you need to make grooves and put pieces of 4 mm reinforcement 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 laminate the concrete surface, then such work can be done within a day after the repair is made, but you should wait longer for laying tiles.
It is important to know that after drying, the solution shrinks, so the casting compound is laid slightly above the floor level, and after drying it will fall into place.
If this still does not happen, use grinder the surface of the former crack is leveled to the desired level.
If you are dealing with a crack whose width and length are large enough, you can treat it before repair with a circular saw with 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.
Repair with elastic sealant
An elastic sealant will also help to close the cracks.
The most popular in this case is silicone adhesive - sealant. Such a sealant is used both for small cracks and for those whose width is large enough.
A repair process that requires the use of a sealant is no different from a repair that uses concrete composition.
First you need to clean the crack from dirt, make grooves for better bonding of the material to the surface. When applying glue - sealant to the surface, it must also be moistened.
The sealant, unlike the cement mixture, dries in a short time, which makes this material much more convenient.
However, the sealant is much more expensive, so not everyone can afford such a repair.
Epoxy repair
Epoxy resin and epoxy repair compound are also used to seal cracks in concrete.
First you need to embroider the opening and remove loose concrete and chips. The width of the groove should be no more than 25 mm and no less than 4 mm.
Every 400 mm along the crack, transverse grooves 150 mm long should be made. With the help of a vacuum cleaner, all debris and dust are collected and the seams are treated with a primer.
Metal staples for reinforcement are placed in the transverse grooves that were made earlier. Further, according to the instructions, the epoxy solution is diluted and the hardener is added to it.
Sand is also poured into the epoxy mortar and the mixture is poured into the furrows.
From above, the epoxy solution is sprinkled with sand, and after an hour the sand is removed with a vacuum cleaner.
Repairing a crack in concrete epoxy resin quite economical, and drying takes very little time. In addition, such treatment of cracks prevents their further movement.
You can use it for dry screed.
If you need to epoxy a coating for a liquid medium, you do not need to add sand to the mixture. Do not sprinkle sand on top either.
Repair with cords and ribbons
If you need to cover up cracks in a pool or water tank, in an underground section of the foundation or on the outer walls of a building where high-quality waterproofing is required, then the methods described above will not be enough for the strength of the structure.
To treat the opening in such places, a special composition is usually used. The cost of such repairs is much higher. habitual ways, but in a humid environment, it fully justifies itself.
For each task there is a special material on sale, you just have to make the right choice.
With the help of these materials, complete sealing of the crack is ensured, so that the coating will last for more than one year.
Repair is possible both indoors and outdoors, at any time of the year.
To start the repair, as in previous cases, you need to process the disclosure. After all the excess has been removed, and the surface of the furrow has been cleaned with a vacuum cleaner, the width and depth are measured.
This is done in order to choose the right self-expanding cord for repairs.
A cord is laid in the cut, which should lie freely, without compulsion.
20-30 mm should remain to the bottom and top of the furrow so that the cord expands further. Whatever type of cord you choose, you can not lay it by force.
Now a polyurethane sealant is applied on top of the cord, the surface of which is leveled with a spatula. The glue that has come out of the seam is removed with a sponge.
Usually it is written on the packaging which material is preferable for this type of cord or tape, strictly follow the recommendations.
If you will use this material in relatively dry areas where waterproofing is only for insurance, the finish can be done with cement mortar.
In order to choose a material for concrete repair, you should familiarize yourself with what these materials are and how they differ from each other.
Today, the range of such products is quite wide.
This material consists of polymer resins and modified clay, and also includes bentonite or its analogue, which binds the surfaces together and seals them.
As for the release form, they are as follows:
- Cord - the material is used to repair shallow cracks 30 - 50 mm;
- Tape - the material is placed in cracks 20 - 50 mm wide and up to 150 mm wide;
- Paste - sealant is used to process small furrows;
- Mats - fasten the layers of concrete screed, and when the old coating is laid, a new layer is laid.
Crack repair by injection
The name of this method speaks for itself - injection involves the introduction of special materials into the voids formed in concrete by "injections".
Injection allows you to repair the concrete pavement without replacing the entire concrete pavement.
This is one of the most effective ways repair of these defects, which is also quite economical.
Injection involves the introduction of a cement, epoxy or polymer mixture into a gap under pressure, due to which the mixture fills any slightest voids and cracks.
As a result, the design is very strong and reliable.
Using this method, concrete is also waterproofed, for which a different composition is used.
Crack Prevention
Even at the stage of pouring concrete, it is very important to make sure that the concrete composition of the floor and foundation is of high quality, in compliance with all proportions.
When laying the concrete composition, it is necessary to carefully compact it not only manually, but also with the help of a special tool.
To prevent moisture from freshly poured concrete from evaporating at a high rate, it can be covered with a damp cloth on top.
In addition, today there are special preparations on sale that will protect the concrete coating from the appearance of cracks and chips in contact with water.
Do not neglect these tools, as waterproofing is very important for the integrity of the concrete pavement.
Waterproofing walls and foundations with the help of such means will help prevent further opening of cracks.
A liquid solution is used for cracks less than 3 mm, and for more than 3 mm, a proprietary solution or a special mixture is used, consisting of 1 part of Portland cement, 3 parts of water and sand, and PVA glue.
Concrete coating is very durable, so it is used in various areas: for floors in the residential sector, in production shops, on highways. This material has a low tensile strength, and as it dries, structures made of it shrink and shrink, so defects appear in concrete, which are a common problem, for example, concrete floors. They can also appear due to mechanical and chemical damage, temperature changes, corrosion of reinforcement. Regardless of the reasons for the appearance of cracks, they must be repaired.
Embedding in concrete becomes the main task and serves to prevent further destruction of the entire structure.
In this article, we will consider the question of how to repair cracks in concrete. There are several ways to repair.
Repair methods
The solution is prepared from 3 parts of sand and 1 part of cement. Be sure to add PVA glue.
The first way is injection. To do this, polymeric materials are introduced into the voids using "injections". This method eliminates the need for partial replacement of the concrete structure. The second way is to apply a special mixture to the damaged surface, which consists of a polymer additive and cement-sand mortar. The polymer additive is sulfanol and furyl alcohol. When the mixture applied to the concrete dries and hardens, a polyurethane sealant is applied to it. The third method of elimination is the shotcrete method using a concrete mixture, that is, applying an additional layer of the same material to the repaired areas. This mixture consists of fractionated sand, water, cement and an organic additive, which can be used as resin, bitumen, latex. This method is not always convenient to use, since it entails an increase in the mass of the structure, and, accordingly, the load on the foundation increases.
All this applies to industrial repair. If you need to repair at home, then they use liquid cement "dough", epoxy resin mortars, proprietary repair mixtures. Liquid "dough" is used for defects less than 3 mm, and for more than 3 mm, a proprietary solution or a special mixture is used, consisting of 1 part of Portland cement, 3 parts of water and sand, and PVA glue. There is also such a thing as self-healing. It implies spontaneous filling. Such self-healing is only suitable for very small ones, the size of which does not exceed 0.1 mm. Consider the process of embedding in concrete using the example of repairing a concrete floor. For work you will need the following materials and tools:
When applying an elastic sealant, moisture is also required without fail.
- chisel;
- hammer;
- sand;
- cement;
- PVA glue;
- putty knife;
- brush;
- mittens;
- water;
- paint brush;
- trowel;
- wooden rail;
- pieces of wire;
- metal trowel;
- grinder.
Reconstruction Options
Cement-lime mortar
Before starting work on the elimination of cement-lime mortar, preliminary preparation is necessary. To begin with, the crack itself is checked, whether there are any chips next to it, since in the future they can turn into shallow pits. Next, with the help of a chisel and a hammer, we pass along the entire length in order to embroider it. If during this work a hidden chip appeared, then this piece of concrete must be removed immediately. Then it is necessary with the help of water, brush and detergent clean the surface. In order to remove dust and debris, it is also better to use a vacuum cleaner. Remove the remaining water with a sponge. In order for the cement-lime mortar to fill the entire space and hold firmly and for a long time, we deepen them with a spatula up to 5 mm. We prepare the solution itself from 3 parts of sand and 1 part of cement. Be sure to add PVA glue. In this case, the solution should not be liquid, but thick. Pour the solution with a trowel, and then moisten it with water. Such a procedure with water is not needed if you use a polymer composition instead of a solution.
If the crack in the floor is medium in size and reinforcement is visible in it, it must be cleaned and treated with a special solution that will protect against corrosion. To strengthen the grooves, you need to put pieces of wire of the same length, the diameter of which is about 4 mm. Then we apply the adhesive composition with a brush and distribute it over the surface of all irregularities. The layer thickness should be approximately 3 mm. Then we fill everything with a solution, without waiting for the composition to dry. It is necessary to pour gradually so that the solution settles tightly. With the help of a wooden lath, we level the surface, moving it towards ourselves from right to left. When the hole is very deep and large, you need to apply the solution in several layers, with each layer should be wetted with a little water. The surface is perfectly leveled with a metal trowel. After hardening, the excess solution is removed with a spatula. Already a day after the repair, the concrete floor can be painted or laminated, but it’s too early to glue the tiles and you have to wait more.
It is important to remember that the pouring layer of the solution must be above the floor surface, since the solution will shrink after drying. We bring the former crack to the floor level with a grinder. If the crack in the floor is large, then you will need a circular saw with diamond disc. Further, the repair process will be the same as in the case of medium-sized cracks.
Elastic sealant
You can also seal a crack in concrete floors with an elastic sealant. The most widespread among them is silicone sealant. It is suitable for sealing both small and large cracks. The repair process using these materials does not differ from that described above. In the same way, initial cleansing is required, and if necessary, grooves are made. When applying the material, moisture is also required without fail. Dignity modern materials for embedding in concrete floor, unlike cement lime mortar, is their ability to dry quickly. Although, compared to the solution, this method of repair will cost you more.
It is advisable to start repairing the concrete floor as soon as cracks appear, otherwise the destruction will continue and in the future it may be necessary not to repair a separate section, but to completely replace the concrete surface. As you can imagine, it won't be cheap.
Repair of existing screeds
A simple calculation of conventional M150 sandstone shows that it is suitable for modern floor coverings.
For example, pieces of parquet rivets measuring 40 × 250 mm, laid on screeds, must reach a static pressure of 15 tons, so that the screed breaks under it.
To tighten the female heel clamp, the female must weigh 150 kg and at the same time stand on one foot only on the heel.
If your apartment in Soviet times is made of cement, sand screed or light aggregate and at the moment when it is in a normal condition and does not need to be touched: it is very suitable for modern floors.
The highest value you need for this is adjusting it to "nothing" and then not always. The dust of the top layer of the screeds is not a sign of its destruction, it is natural process release of particles - it is eliminated by filling, and not by replacing the screed.
However, it should be kept in mind that, despite the static calculations in the previous century, heel deviations are actually possible on M150 coils. Elegant dancing women can easily damage the heels of their hair with an ester of this strength, for example, if you put linoleum or carpet on it.
Khaira is a terrible weapon! If the house usually does not fit the shoes, in this case, when moving heavy furniture, the tie comes out. For the same reason, parquet rivets from the “gutter” locks and adhesive rivets in the screed are drawn on uneven screeds.
Therefore, flooring of all types on the M150 screed is best positioned above the redistribution underlay. Do not place underlay under ceramic tiles.
To determine the safety of an existing screed, first carefully remove adhesive, paint, and other contaminants. Perform a visual inspection while cleaning the screed. Ideally, the screed should have a uniform, uniform light gray color. The inspection reveals cracks and screeds.
Then the screed is hung by a hug wooden stick. The impact sound should be the same throughout the connector area - solid and sonorous. If there are “bows” in places, the sound is deaf (empty), and then the tie screws from the plates.
First, the "digging" of the screed is canceled. There are several ways to eliminate the screed scaling, but it will not be available to the house builder, which is only one option for you: define the boundary of the "buhteniya" eavesdropping and cut the screed to cover the bouncer and hammer, hammer, switch to "".
If the tie is "wrinkled" in important areas, it must be completely removed and removed. The layer that is being cleared from the bottom, though still holding on, will eventually remain, fill the void that has arisen below it, and pull the veil with it. In other words, the floor covering, installed on "uneven" screeds, will become a little more beautiful, and then it will fall apart sooner or later.
A small area of the screed can be repaired (Fig.
32). For this purpose, the screed is covered at the point of its removal from the floor.
How to repair cracks in a concrete base - step by step instructions
Then the screed pieces are removed from the broken hole, the hole is smeared and powdered. Before applying mortar to the mortar cavity, the edges of the pit and the exposed surface of the slab must be covered.
The preparation can be carried out in several ways: with water, cement milk or powders.
When filled with water, the entire surface of the cavity is wet with plenty of water, but without the formation of a pig.
The preparation with water is intended for wet mortar of the old screed around cellular concrete and concrete panels to preserve their openings. Otherwise, these materials will "dry out" the water from the cleaned repair solution. Instead of participating in the process of taking the repair solution, the water will come out of its intended destination. In addition, dusting with water removes dust from the cavity that the vacuum cleaner does not remove (if the vacuum cleaner is damaged, you can do this by cleaning with water).
Capturing the pores with water with cement milk and binds dust.
Roasted cement laitance from cement and water in a ratio of 1:2. For dusting with water or cement laitance, the repair mortar should be used immediately after the base coat, without waiting for it to dry (using the wet method). Cooking with cement milk is better for filling with water. Thanks to this method, the cement that is in the base coat is combined with the repair mortar and the old screed.
Preparation with special cases has a slightly different character.
These samples are in the path of adhesives that react at the molecular level with old coatings and stains. For example, some samples penetrate into the pores of the old screed and into the pores of the cover plate and crystallize there, thus stopping the water from the plaster. The example that does not fall into the pores remains on top and also crystallizes, covering the surface on which it belongs to the multiscale scales.
The modern construction market offers wide choose samples.
They are divided into dust for absorbent, weakly absorbent and non-absorbent substrates. The cement screed and the top of the reinforced concrete are covered with weak absorbent substrates.
Stickers of numerous comparisons read: "for concrete surfaces, plasters and screeds.
Use for expensive expensive dry mixes with high strength does not make sense since the screed itself was made from M150 mortar.
This solution is best characterized by sand and cement, or we use cheap dry mixed mixed dried foods. For the patch, it is better not to use the "M150 Universal Dry Mix" because it reads the specification mixture (some manufacturers), see: It has acquired a capacity of 10 MPa (100 kg / cm²), which does not match the slime.
It is better to buy a dry mix M300 ( sandblasting) - its strength after hardening is not very high, but it is specially designed for fasteners made according to relevant national standards. The dilution of the dry mixture must be exactly according to the instructions written on the bag, namely, if the manufacturer says that the amount of water required for mixing is about 0.15-0.2 liters per 1 kg of the mixture, the amount of water and should not be poured. more and no less.
In simple domestic mixtures, in addition to great advantages - low prices are not serious defects - they do not contain polymer additives.
This means that the top mix is the untouched amount of water recommended by the manufacturer, you will get a heavy mix that is hard to lay down and will also set on the screeds for almost a month (28 days). Therefore, the mixture should also be purchased with a plasticizer and curing accelerator. It is not necessary to buy plastic patches, because the area of repair bindings is small, and try, you can place a non-packing mixture, but it requires the purchase of a hardening accelerator.
Otherwise, the humidity will be more than the floor covering. Of course, it is possible to ignore the hardeners and dry the patch with heaters, which will disrupt the normal setting of the mortar. The solid solution does not speed up the bonding time, they only form a crust on the surface, which allows it to do further work, and the setting itself is "not exhausted by the material" and does not yet take time.
Artificial drying of the material removes water from the material, which becomes insufficient for the normal reaction of the chemical plant. On the contrary, during the care of the patch, cover with polyethylene, which does not allow early evaporation of water, and sometimes spray water from a spray bottle.
The simplest and most affordable accelerator - liquid glass(office glue).
However, this accelerator accelerates the solid solution even longer and reduces the lifetime to 1-2 minutes. For optimal performance, it is better to purchase an installation accelerator, such as "Plytonite Agent, Accelerator", which has the properties of lamination, which not only speeds up the bonding time, but also makes the solution easier, but is also a complex solution.
For example, if the screed is made with fillings, for example, the screed is made of foamed clay, and then expanded clay beads in Pesqueconcrete.
The ratio of dry mix to expanded clay is 1:2. To prevent glaciers from floating, apply a plaster to a sheet of tin.
After installation on the screed, work with cracks. If the entire screed is full of numerous cracks, then it is better not to repair it, but to completely remove it. If the cracks are small and the ties do not break into pieces, they can be repaired. The technology of repairing cracks is almost identical to the technology of patches on "puffy" sections of the screed.
Cracks along the entire length are widespread (extended with a crowbar or perforator), they are removed from the dirt and prepared.
Then repair the mortar and use it in the cracks. By the way, cracks cracking with a sharp or perforator immediately show the condition of the screed. On a reliable screed work with percussion instruments will only be interrupted by fast moving spots, and bad ties will be broken up into large pieces.
After installing patches and repairing cracks, we expect 9 days.
Next, we conduct a geodetic survey of the connector. We test its balance with the "rule of space" and tilt with a laser or normal level. If the tie is normal flat and loose, the screed may not be suitable for all types of flooring, laminate, solid float boards, linoleum and carpets. However, they must all be installed on the ground, as the old clips made during the Soviet Union do not exceed the strength of modern flooring.
Under tiled floors the repaired screed is suitable in a state in which the substrate is not needed.
If the screed is not horizontal or has a deviation that exceeds the standard, it must be leveled. Geodetic survey with laser level should show the unevenness of the screed, and the result of the control is recorded directly on the screed. If we compare the difference between heights between hills and caves, you must decide on the method of leveling the screed.
Connected can coordinate rough levelers, since a layer of 10 - 50-80 mm is laid out or final rovinites ("self-raised"), the so-called dry mixture of layers, laid from 1 to 10-20 mm.
If you use it on a mixture bag for a bundle thickness of 10 to 50 mm, then the screed from them must be exactly the same so that it cannot be pulled out “nothing”: the thickness of the thinner part must be at least 10 mm, and the thickness should not be more 50 mm mm.
If the inscription is an addition, "and holes up to 80 mm", this addition must be read literally, that the height of the screed must be at least 10 and not more than 50 mm, but more deep holes height up to 80 mm, but this height is allowed, but the main one is 50 mm.
The same applies to the final levels.
The difference between rough roughing and finishing in the amount of fill grains is ultimately more subtle. Rough roving patterns are denser, they need to be "stretched" by placing a rule, determining the thickness of the screed from rocks or guides. With the possibility of using these screeds, you can create a floor slope.
Finish levels are liquid, about like syrup or kefir, stretched without lamps and shelving. Set the thickness of the screed with a wide spatula. This type of material is quite liquid and can come out unevenly at a low angle. There should be no holes at the bottom of the end level.
Based on the results of the survey of the existing repaired ester, you must decide which of the "levels" will be used for leveling: coarse or final, or both.
In most cases, only the final mix should be used, as the coarse mix is removed from a room height of 30-50 mm. However, the final mixture is rather limited by the height of the screed. Therefore, with old screeds, it is necessary to remove the open seas mechanically. This can be done in two ways: old grandfather - weld the ax to thick reinforcement or steel waste and clean the sediment; Buy grinding machine, abrasive wheels and grinding.
After removing the holes, clean the entire upper layer(old cement "milk") to the filler for the screed "cut" or mill from the old screed.
Practice shows that the best adhesion (adhesion) of the top layer to the bottom surface of the rough surface. First, on a rough surface, the grip surface increases. Secondly, when sanding old screeds, cement particles are removed and the filler (sand particles, foamed alumina, fine gravel) is exposed. After that, the closed cement of the upper screed not only interacts with the filler, but also with the filling of the lower screed.
Thirdly, the bottom screed must be free from dirt, which is possible only by grinding (removing the top layer) of the surface. If braces were allowed to marry and the top layer of the screed was distributed, then of course sucking was necessary.
After grinding, the esters should be wiped off and sucked up.
It is then treated with "cement" cement coatings for weak absorption surfaces or with general purpose primers. For best use cement screed cement-based "self-melting" when using plaster, then buy a type of release coat against "cement-gypsum plaster" such as "Primer 2" (Plitonite).
The preparation of the old screed is best done in half. The screed lies on the ground for a long time and is likely to be dried, the first coating, which simply "despises" such a screed, does not leave marks on the surface. Therefore, when the first coating crystallizes in the screeds, it must be covered with another coating.
The time between the first and second application is read in the reading instructions as some powder manufacturers require the first coat to dry completely, others allow the primer to be "wet on wet".
Separate us in accordance with the instructions for leveling the lessons ("self-straight"). When mixing the mixture, it is preferable to pour the mixture into water (80% of the total volume) and stir, and then no elbows are formed, and the remaining water is added during mixing.
If you are working with a drilling machine with a mixing nozzle, do not turn on the high speed drills, mix it on average speed, or the mixer blades will trap air and bring it into the solution.
Start charging the coupler (fig. 33) with the far corner of the space with lines along the far wall, back to front door. We installed a temporary door at the door. Two people work because the coupler must be thrown in one step over the entire area.
One closes the mixture, the other pours out and scatters it with a tent. When laying the mixture does not go on a new screed, spray it with a spatula on the side and on it, but not under the feet.
After filling the tape with screed (width by touch of hands), twist it with a needle roller or lift it up by drilling or with a hard brush to release the air trapped in the solution.
Leave it for a few hours after applying the screed (recommended by the manufacturer).
After this time, he is allowed to walk along the front. Yard should cover it with plastic foil so it doesn't dry out before time. When cleaning the screed and during the sliding process in the room, it is necessary to maintain a stable temperature in the room, and there should be no drafts, that is, the windows should be closed. Screed trees usually do not exceed three days, they are read on the bag, from different manufacturers different hands to install the screed.
In rooms with an area of more than 20 m² or on one side of the screed with a length of more than 8 m, expansion joints must be left in the screeds.
The fact is that when comparing closed and dry adjacent mixtures with the ground, an internal expansion of the solution occurs, which can destroy the screed. To do this, the space of the large part is divided into half or four parts and fits into these places with wooden planks. In fact, not two, but four screeds are poured into space. When the ties are tightened and you can walk around them, the plates are removed and you can fill in the places where the boards were removed from.
If for some reason you forgot to leave the extension clips, you can still make them once the zip tie allows you to bypass it. In this case, the top layer becomes hard in the screed, but it is still soft in it. When using an old file or similar tools, the top layer of the screed must be cut to the depth of the old screed.
In fact, you create artificial cracks on the screed and relieve internal stress inside. If this is not done, or we don't have time to create warp stitches, it will lead them to one, i.e., needless to say, the cracks won't be where they will be. After setting and hardening of the inner layer of the screed, the internal stresses in it are destroyed, but you can grab the cracks.
Once hardened, the screed is ready for all types of floor coverings, with or without a foundation.
The power of self-levelling compounds is usually at least 20-25 MPa (200-250 kg/cm2), which is in line with world standards.
Sealing cracks in concrete
To protect the concrete floor from destruction and increase its service life, it is equipped with expansion joints. As you know, under the influence of various loads or as a result of changes temperature regime, the concrete web can expand or contract.
This causes the coating to move, the energy of which must be directed somewhere, since such an effect leads to the appearance of cracks in the concrete surface and other serious consequences.
It is the expansion joints that take on the main load. To avoid more expensive procedures aimed at restoring the concrete floor, it is necessary to monitor their condition and repair expansion joints in a timely manner if defects are found.
Types of damage to concrete joints
- wear
- destruction
- edge chipping
- loss of tightness
Features of the repair of expansion joints in concrete floors
Recovery activities include several stages:
- Expansion of a damaged seam using a diamond disc
- Removal of concrete residues and other construction debris from recesses
- Dedusting
- Epoxy primer treatment
- Applying a repair compound to the seam
- Marking with a steel marker along the seam
- After the final polymerization, grinding to equalize with the concrete surface
- Removing markers and cutting at the mark of a new expansion joint
- Cleaning with a construction vacuum cleaner
- Laying the sealing cord
- Application of silicone sealant for a final impermeability of the surface
It should be noted that for any type of repair of concrete joints, whether it is loss of tightness or complete restoration, strict adherence to technology is required.
If you do not have the necessary knowledge and equipment, we recommend entrusting the repair activities to the specialists of our company. We have everything you need to carry out high-quality repair of expansion joints in concrete floors.
Ways to repair and restore concrete
Concrete was invented and used for a long time. Despite the increased strength, this material is subject to destruction over time.
How to close a gap in concrete on the street. How to fix a crack in a foundation
Carrying out the restoration of its damaged surface is always more cost-effective than dismantling and installing a new one.
Types of materials for repair and requirements for them
To perform the repair and restoration of concrete, "repair" compositions are used. Before performing work and choosing a material, it is necessary to clarify the type of damage, find out the characteristics of the surface being repaired. Separately, we draw your attention to the fact that on the website http://emaco-spb.ru specialists offer repair mixes for the restoration of concrete and its waterproofing.
All modern repair mixtures are subject to a number of requirements, compliance with which will allow the restoration of concrete surfaces with high quality and reliability:
- non-shrinkage;
- good fluidity;
- low ratio of water and cement;
- high degree of mobility;
- high thixotropy;
- good adhesion to the surface;
- complete lack of drainage.
According to the conditions for the use of the mixture, they differ:
- Cement - non-shrinking dry one-component mixtures having a liquid (for filling horizontal cavities) or thick (for a vertical surface) consistency.
They are used more often for the restoration of road, airfield surfaces and concrete structures.
- Epoxy - mixtures having a liquid two-component composition. They are used in the repair of cracks, to restore the bearing capacity of the material, to create adhesive layers.
- Polyurethane - liquid mixtures, having a two - three-component composition.
They are used to repair damage that has certain properties (localization of leaks under pressure, water inflow).
The cost and quality of all compounds depend on their ability to securely adhere to the repaired surface (adhesion), viscosity and thickening rate.
Which of the methods of repair and restoration of concrete to choose
All types of damage are repaired with their obligatory reconstruction to the sizes provided by the project.
Any repaired surface is prepared before performing restoration work: it is cleaned of dust, dirt, oils, foreign inclusions. In the presence of weak concrete at the repair site, it is chipped to a solid layer without leaving sharp corners and protrusions. Rust is removed from bare fittings, if necessary.
The choice of restoration method and type of material is directly related to the conditions of work and the size of the damaged area.
To perform repair and restoration work, the following methods are used:
injection- is the most popular way to repair damage with an opening of up to 0.1 mm.
The essence of this method is that the restoration is performed without replacing the structure itself. Cracks, chips and voids are filled with "injections" of polymer or water-cement compositions. This method is recommended when performing repairs with a large amount of damage.
Before starting work, all defects are blown with a strong air stream.
Further, the entire surface around the crack is processed with a rag moistened with acetone. To avoid leakage of the solution from the cracks, they are treated with an epoxy adhesive from the outside. To speed up the process of its hardening, it is possible to use heating with a burner, provided that the flame and glue do not come into contact.
The composition of the mixture used should have a viscous consistency.
Defects are filled under pressure of 100 kgf/cm². Ready-made polymer or water-cement mixtures must be used within the first 3 hours after preparation. Their complete hardening occurs at a temperature of 17-20°C for 8-10 days.
Grout- a method of applying a special dry mixture to the repaired surface with a defect opening value of more than 2 mm, and their number should not be large. This technique is also suitable for restoring vertical surfaces.
High quality, strength, frost resistance, high adhesion of these mixtures makes it possible to repair and restore roads and runways. In its composition, the dry mix has Portland cement, dried sand and mineral fillers.
To prepare a grouting solution for 1 kg of dry mix, you need to take about 200 ml of water, brought to 200 ° C.
The mixture is added to the water in small portions with constant stirring. The solution prepared in this way should be kept for about 5 minutes and used within 2 hours.
To repair a surface of 1m², 1.8 kg of dry mix will be required with a maximum allowable thickness of 50 mm.
If the cracks are up to 1 mm wide, then polymer cement paints are used to repair them. If the size of the defect exceeds 2 mm, polymer dough is used. The applied mixture contains polymer additives (0.02% sulfanol, furyl alcohol) and a cement-sand mortar. After the mixture has dried sufficiently well, the concrete should be coated with a polyurethane-based sealant.
Shotcrete- a way to create an additional layer of the same material on top of the old one.
The technology of this method consists in throwing with compressed air concrete mortar. The composition of the mixture includes: cement, water, additives organic species, sand.
Shotcrete can be: "dry" and "wet". The difference lies in the moment at which the mixtures are mixed with water.
With “dry” shotcrete, mixing is performed at the outlet of the mixture from the pipe, with “wet” shotcrete, it is prepared in advance. This method is good in that it is possible for them not only to carry out repairs, but also to increase the stability of the structure to low temperatures, to perform structural reinforcement.
But it is considered time-consuming and always leads to a weighting of the structure and an increase in the load on the foundation.
The solution is applied to the repaired concrete in 1-2 layers. To perform the work, it is recommended to take cement M - 400 and above, the fraction of the aggregate used is not more than 8 mm.
The ongoing work on the restoration and repair of concrete surfaces should be carried out at an air temperature index of at least + 5 ° C in dry weather.
Regardless of the cause and nature of the damage, their elimination should be carried out only after the stabilization of the disclosure process and the elimination of the cause of the appearance.
Concrete screeds are classified as hidden types of work; the normal operation of the floor structural elements laid on them depends on their quality.
Defects in concrete screeds appear on the surface of the coating in the form of cracks, irregularities, dips.
Opening damaged floor covering concrete screed possible in the following cases:
- the screed was laid with lean concrete (with insufficient cement);
- laying and subsequent care (moisture treatment) were carried out in violation of the technology;
- the screed under the coating has been exposed to aggressive liquids (acidic, alkaline);
- the insulation sank, the leveling screed was deformed and cracked;
- the screed cracked due to shrinkage deformations (lack of expansion joints, expansion joints).
A concrete floor with a cement coating is usually arranged in utility rooms- in basements, storerooms and garages.
When repairing floors, it is necessary to find out from the drawings or local probing which structural layers are located under the coating. During operation, abrasion of the coating occurs, sometimes after 1-2 years its repair is required.
Such coatings must be kept clean, regularly cleaned so that individual grains of sand do not scratch the surface.
When examining the floors, various defects can be identified.
Cracks in the pavement may be caused by the poor quality of the concrete screed laid under the cement pavement; poorly prepared concrete base surface.
In order to avoid the appearance of cracks during the application of the front coating, the substrate is thoroughly cleaned from contamination.
Contamination with gypsum residues is unacceptable, which, even in a small amount, can gradually destroy a 5-6 cm layer of concrete screed.
Blisters, cracks in the cement coating, dusting of the surface may occur as a result of hard mortar coating; plastic composition of the solution (water release on the surface); excess cement and the appearance of shrinkage deformations, causing cracks in the coating.
Repair depends on the nature of the defect and the extent of damage to the coating.
Restricted to repairs:
- for defects in small area surfaces;
- if the purpose of the room where the floors are laid is preserved;
- at low labor costs for the repair of communications associated with their termination.
The device of a new coating is advisable:
- if the cost of repair corresponds to the cost of a new coating;
- when the purpose of the room changes and it becomes necessary to install floors of a different design.
Concrete floor repair is designed to eliminate local scuffs and cracks.
At the same time, a layer of cement mortar cannot be applied to the concrete coating in defective places, since such repairs are short-lived.
What can be done to repair cracks in concrete?
The defective place is cut down with a chisel and replaced for the entire thickness with a new coating. Cracks in the coating are sealed with epoxy mastic ED-20 with a hardener-aminophonol AF-2. Potholes for better adhesion are sealed with cement mortar using synthetic materials (polyvinyl acetate dispersion).
Repair of concrete floors according to traditional technology.
After examining the floor and determining the amount of damage, the coating is pierced to the entire depth of the layer, trying to find out the cause of the defect (for example, deformation or contamination of the base).
For the installation of a concrete floor for 1 m of a rigid concrete mix, 200 kg of cement grade 300 is required.
With a smaller amount of work, 1 bucket of gravel (16 kg) requires 2 kg of cement. The measured volumes of materials are mixed dry, after which the mixture is moistened with water from a watering can; while continuing to mix, with each full shoveling, add water from a watering can.
The prepared concrete is leveled with a rail, and then overwritten. Care of freshly laid concrete involves moistening with water sprays (every 6 hours), 1 day after laying.
Concrete floors are laid at temperatures above +5°C.
Another way of constructing the floor is possible, when a layer of cement mortar 1.5–3 cm thick is spread over the rough surface of the concrete screed and grout is made.
Reliable adhesion of the mortar layer to concrete is ensured 3-24 hours after laying the concrete screed. To prepare the cement mortar of the front layer for grouting, 250 kg of cement grade 400 is required per 1 m of sand (2.5 kg of cement is needed for a bucket of sand 18 kg).
The solution is prepared in such an amount that it can be used up within 2 hours.
To obtain a colored floor covering, dyes (pigment) are added to the solution. Dry pigments are mixed with cement or pigments in the form of a paste are preliminarily diluted in water.
The surface of the front cover is rubbed with a metal trowel, sprinkled with dry cement to obtain smooth surface gender.
Repair of concrete surfaces with mastic based on epoxy resin ED-20. The hardened mastic is waterproof and waterproof, weather and frost resistant, resistant to cleaning agents. This mastic is applied to a dry and wet (but not wet!) Base. The mastic is applied with a steel spatula on both horizontal and vertical surfaces.
Mastic based on epoxy resins repair cracks, potholes in concrete surfaces.
Along the cracks, holes with a diameter of 15-20 mm are hollowed out, into which the mastic is pressed. The distances between the holes depend on the depth and length of the crack. Where two or more cracks converge, a hole must be drilled.
Preparation of epoxy mastic.
Epoxy resin ED-20 and Portland cement are mixed with a hardener - aminophenol AF-2 in a ratio of 1:10. The components are thoroughly mixed with a drill with a stirrer attachment at a speed of 300-400 rpm (Fig.
Stirring in a water bath at a temperature of 60 ° C is continued for 4-5 minutes until the mixture becomes homogeneous. After that, the mixture is transferred to a flat dish and mixed again to make sure that the prepared mastic is homogeneous. It is necessary to prepare such an amount of mastic that it can be used up before hardening begins.
The terms of laying epoxy mastic depend on the ambient temperature: at 10°C - 2 hours, 20°C - 3/4 hours, 30°C - 1/2 hour.
The material consumption for puttying is 1.2-2 kg/m.
Upon completion of work, wash tools and dishes with a brush or sponge dipped in acetone.
Synthetic resin ED-20 can be used to prepare solutions with the addition of quartz sand as a filler.
The repair solution is made in the following proportion:
h synthetic resin ED-20 and 4 - 5 wt. h quartz sand. Such a solution is used for horizontal concrete surfaces, primarily for repairing floor coverings.
Material consumption is about 1.8 - 2.2 kg-m2 with a layer thickness of 1 mm.
Occupational Safety and Health.
The hardened synthetic resin solution is physiologically harmless. ED-20 resin sometimes causes allergic reactions in some people. Aminophenol AF-20, when it comes into contact with the skin or with air into the lungs, causes irritation and is dangerous to the eyes. Work with epoxy mastic is carried out with rubber gloves.
The skin of the body and eyes are protected from mastic. Splashes of mastic from the skin are washed off with a cotton swab dipped in acetone. Then the contaminated area is washed with warm water and soap or a 3% solution of acetic acid.
After finishing work, the hands are smeared with a greasy cream.
If splashes of mastic get into the eyes, they are immediately washed with water (for 15 minutes), and then rinsed with an aqueous solution of boric acid.
Mandatory compliance the following rules labor protection:
- during work, the room should be intensively ventilated; it is necessary to protect the skin and eyes from mastic splashes;
- when ventilating enclosed spaces, it is necessary to use respirators that exclude the inhalation of vapors;
- the workplace must be kept clean;
- care should be taken to create conditions for washing;
- it is necessary to provide workers with protective gloves, work clothes, aprons, goggles.
Added: 08/27/2017 04:22:31 PM
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Repair of industrial concrete floors
Dozens and even hundreds of people walk on the floors of industrial premises every day, machinery drives around, deforming them and scratching them. Loads are piled on these floors and heavy objects are dropped, which sometimes break off whole pieces from the coating.
Temperature fluctuations, not uncommon in production shops, cause cracks to appear. Finally, even daily cleaning is damaging - it's not just washing with detergent, but serious chemical exposure. All this together is a very significant load, causing the often occurring need for local repairs.
What causes defects in floors?
Most often, the formation of defects during the operation of floors in workshops, warehouses and other premises of industrial buildings is due to the fact that the following damage occurs:
- the floor is cracking;
- chips and potholes appear;
- the top coat peels off;
- the edges of the joints are destroyed;
- when the screed is tapped, an “empty” sound is heard (in other words, the screed “blows”).
How to repair?
How to solve all these problems?
Repairing cracks in concrete
First of all - promptly. It is necessary to eliminate problems with the floor covering quickly, until they worsen and there is no need to completely replace it.
Chips, potholes, static cracks
Potholes, chips and static (surface) cracks are the easiest to repair.
They are sealed with a special cement-based compound or a mixture of epoxy resin and quartz sand. But processing even a shallow crack is more difficult than a regular recess in the floor, and consists of several stages:
- expansion of the crack with an angle grinder;
- spilling to the full depth with epoxy without impurities;
- after drying - sealing the upper part with a filling composition;
- after the outer filling has dried, grinding and surface coating with epoxy resin.
Mobile cracks
A mobile crack is more insidious than a static one and is fraught with more serious consequences.
Therefore, it is necessary to approach the elimination of this defect more thoroughly. The path of least resistance in this case is the treatment with an elastic sealant. A more reliable method is a two-stage filling following the pattern of repairing a static crack, after which a deformation seam is cut.
At the final stage, the seam is treated with a sealing polymer composition.
Finally, the optimal method of repairing a mobile crack (but at the same time the most time-consuming and expensive) includes the following steps:
- dismantling of the floor area adjacent to the deformed area;
- installation of a profile framing the expansion joint;
- monolithic sealing of the dismantled area with a cement or polymer-based repair compound.
The latter method best suits the goals and objectives of repairing the floor in industrial premises, since the damaged area after processing is completely ready for normal operation.
Under any load, the defect is guaranteed not to recur.
Coating failure
Peeling of the coating, as a rule, occurs if the laying technology has been violated. When using a hardened coating (topping), an alarming signal is the appearance on its surface of tortuous cracks resembling craquelure.
If the coating peels off locally, the damaged area should be removed, and then the floor should be treated with a repair compound.
If its destruction is noticeable over the entire area, it makes sense to completely replace the coating.
Seam edge failure
Joint edges between floor slabs usually suffer for two reasons:
- shrinkage of the building;
- regular passage of industrial machinery.
Both the scale of destruction and the method of repair, as a rule, are determined precisely by the cause of the defect.
With its one-time occurrence (primary shrinkage, shifts due to seasonal temperature fluctuations), it is permissible to limit ourselves to the dismantling of the destroyed area (to a depth of at least one centimeter) with its subsequent sealing with a cement-based repair compound or a polymer composition. After the seal dries, a new one is cut along the line of the old seam, which is treated with a sealant.
If the defect arose as a result of a regular and intense traffic load, it would be more advisable to use a combined method, which involves the installation of a framing profile around the area of the expansion joint.
This method provides the possibility of long-term operation of the repaired area without any restrictions.
Voids in the screed ("bubble")
The reason for the so-called "whipping" is the formation of voids in the concrete floor screed. This defect can be fixed in two ways:
- injection of the damaged area;
- complete dismantling of the site and pouring from scratch.
The first method, although it often gives positive results, involves a “by eye” diagnosis, which makes it impossible to draw up an accurate estimate of the work.
Therefore, pouring the floor again seems to be a more reasonable solution.
Finally
Any problems with the floors of industrial premises cannot be left for later - delay is fraught with the fact that minor damage with constant mechanical, thermal and chemical exposure will grow to the extent of a major overhaul.
And this, in turn, will entail downtime of the entire production and serious financial losses. Therefore, at the slightest defect, you need to contact specialists who will be able to diagnose, localize and eliminate the danger in a timely manner.
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Repairing cracks in concrete with cement-lime mixture or elastic sealant
Everyone knows about the strength of concrete, which is why the material is so popular with consumers. It is used in the manufacture of floors, and in the laying of roads, and in other construction. But for all positive qualities concrete and it can crack over time.
Such a defect may be the result of:
Decrease in the strength of the material caused by shrinkage of the structure; - mechanical or chemical violation of integrity; - a sharp change in air temperature;
Rebar rusting.
The sooner we close the cracks, the more likely it is to prevent the subsequent destruction of the structure.
Wall termination options
1) Injection - polymers are injected into cracks and voids in small injections, this allows you to postpone or completely eliminate the problem of replacing the concrete structure.
2) Sealing with a special composition - when the damaged surface area is treated with cement mortar and a polymer additive of furyl alcohol and sulfanol, and a layer of polyurethane sealant is applied on top.
3) Shotcrete - when the damage is treated with the same special composition, and a layer of cement mortar and an organic additive of bitumen, resin and latex is applied to it.
In the conditions of private housing construction, they use:
1) "Dough" of cement for sealing small cracks. 2) Compounds with epoxy.
3) Construction mixtures.
Repair technology
Before starting work, a set is prepared necessary tools, it includes:
- hammer;
- chisel;
- metal brush;
- putty knife;
- brush;
- trowel;
- rail;
- wire;
- trowel;
- Sander.
See also: The ratio of water and cement in the manufacture of concrete
Reconstruction of a crack in the walls
CIS (cement - lime mixture)
A springboard for work is being prepared: the area around the crack is checked for the absence of chips, if they are found, a chisel with a hammer is picked up, each chip noticed is knocked off, and these places and the crack itself slightly expands along its entire length.
Then the dust is removed from the groove with a vacuum cleaner, followed by cleaning it with a brush, water mixed with detergent.
With a spatula, the groove is deepened by approximately 5 mm so that the CIS fills the recesses and is well fixed in them.
If the defect is not very large, of medium size, and reinforcement is visible in it, then this area is cleaned and treated with an anti-corrosion solution, and then the CIS is poured. For greater fixation, a wire with a diameter of 4 millimeters is laid in the furrow. The surface is leveled with a rail.
If the defect is deep, then the solution is applied in several layers.
The floor covering is allowed to be laid on concrete in a day, just like painting, but with the laying out of ceramic tiles you will have to wait a bit.
It should be remembered that the fill must exceed the level of the main plane - after drying, the solution shrinks. At the end, the surface is processed with a grinding machine.
silicone sealant
The crack can be repaired with elastic silicone sealant. It is suitable for repairing defects of any size.
In the process of work, the crack is cleaned in the same way, grooves are made and the embedding site is moistened.
The main advantage of the method is the drying speed. The sealant dries much faster than the cement-lime mortar, but at the same time, it costs a little more.
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Cracks in concrete: causes and methods of sealing
Cracks in concrete are one of the most dangerous and common defects. Their appearance is due to many factors, starting with violations during the preparation of the mixture at the plant, its transportation, and ending with non-compliance with the laying technology and the care of fresh concrete. The causes of cracks in concrete can be divided into the following groups:
- At the stage of production of the mixture, at the plant, a violation of the preparation technology is possible (the water-cement ratio may be violated), as a result, the brand of concrete will not correspond to the declared one. Too long transport can lead to the so-called "welding" of the concrete.
- Calculation error (or excessive load during operation). Insufficient reinforcement can cause cracking.
- Difficult soil and geological conditions (for example, the presence of unaccounted for heaving soils in the construction zone).
- Violation of the mixture technology at the facility. Quite often, it is diluted with water to increase workability, but excess water prevents the concrete from normal curing. The cause of cracks can also be a violation of the location of the reinforcement and insufficient compaction of the concrete mixture, improper dismantling of the formwork.
- Failure to comply with the rules for the care of fresh concrete. It is characteristic mainly for construction in hot weather. Cracks are caused by too rapid evaporation of water.
- Construction of additional extensions to the object without taking into account their joint work.
Crack classification
Depending on the type of cracks, the methods for their elimination also differ. There are such types of cracks in concrete as:
- Through. Occur when excessive axial tensile forces (or forces with a small eccentricity).
- Cracks in the tensile zone. They occur during bending and are directed perpendicular to the reinforcing bars.
- Cracks caused by the action of a transverse force (shear cracks) are directed at an angle to the reinforcing bars.
- In the area of reinforcement anchoring, cracks may appear parallel to the reinforcing bars. The reason for this may be incorrect anchoring, heaving of the soil, uneven settlement of the structure.
- Small cracks caused by the temperature difference between the surface of the concrete and its inner layers.
- Hairline cracks are also caused by temperature differences, but their depth does not exceed a few millimeters.
Ways to seal cracks in concrete
In freshly laid concrete (within 1-2 hours from the moment of laying), cracks can be eliminated by re-compacting the mixture. To eliminate cracks in hardened concrete, the following methods are used:
- Injection - under pressure, a repair compound is injected into the crack. Some compounds allow you to displace moisture from cracks.
- The walls of the crack are treated with a composition to increase adhesion, then it is filled with a mixture with the addition of a polymer.
- To repair the cracks, a concrete mixture is used, after the crack is cleared and cleaned, it is filled with a fresh concrete mixture.
When sealing cracks in concrete with your own hands, the cracks are prepared and filled with a repair compound. To do this, you will need materials and equipment such as:
- grinder;
- chisel;
- putty knife;
- hammer;
- metal brush;
- vacuum cleaner;
- brush;
- trowel;
- wooden rail;
- water;
- cement;
- sand;
- small pieces of wire;
- glue;
- metal spatula.
Sealing cracks in concrete is carried out in several stages:
- Preparatory stage. It is necessary to identify weak spots in the concrete near the crack. The crack itself is embroidered with a chisel and a hammer, its depth should be about 5 mm (so that the repair compound does not fall out), if necessary, deepen the crack with a spatula.
- Then the crack must be thoroughly cleaned with water (a vacuum cleaner can be used to remove dust). The sponge will allow you to slightly dry the crack and remove excess moisture.
- If the reinforcement is bare, then before filling the crack with a repair compound, it is necessary to treat the reinforcement with an anti-corrosion solution.
- To fill the crack, it is recommended to use a sand mortar prepared in the proportion of 1 part of cement to 3 parts of sand. You can add PVA glue to it. Deep defects are filled gradually with the obligatory moistening of each layer of the repair composition.
- In some cases, the crack is reinforced with small pieces of wire.
- The surface is leveled with a trowel.
- The protruding part of the hardened mortar is removed with a grinder.
The best way to deal with cracks in concrete is to prevent them from occurring.
Violation of the water-cement ratio is a very common cause of quality deterioration and subsequent intense cracking. That's why Special attention should be given to the observance of proportions during the preparation of the cement concrete mixture.
During the laying of the mixture, it is necessary to carefully compact it with the help of vibrators. It is equally important to ensure that fresh concrete is properly cared for. To prevent too intense evaporation of moisture, fresh concrete can be covered with a cloth.
Especially dangerous are cracks in concrete operating under conditions characterized by frequent transitions through 0°C. When freezing, moisture trapped in a crack expands, thereby enlarging the crack. As a result, the reinforcement is exposed, its corrosion begins and the strength of the structure decreases.
For the timely detection of cracks and their elimination, it is necessary to regularly inspect the concrete surface and fix the identified defects. This will allow to localize cracks at an early stage of their development and thereby reduce the amount of repair work. In no case should you postpone the repair of even minor defects in concrete.
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Cracks in concrete - no reason to be upset
Almost all concrete and reinforced concrete structures during the drying process, they shrink and shrink. And due to the fact that this material has a low tensile strength, cracks appear in the structure. In addition, cracks in concrete can form:
- because of mechanical damage material (accidents, excessive loads, vibrations, seismic activity, water wear);
- “due to” chemical damage (from exposure to alkalis, salts and acids);
- from physical processes (fluid leaks, temperature changes, erosion);
- from corrosion of fittings, due to carbonization, exposure to salts, humidity, and carbon dioxide.
However, whatever the causes, as well as the nature of the damage, they must be immediately eliminated, because. these cracks themselves serve as a source for further destruction of the structure. In order to carry out the restoration of concrete, it is necessary to visually inspect the damage and select the right way repair.
One of the most popular repair concrete foundations is injection. The essence of this method is that restoration work are carried out without partial replacement of the concrete structure, but thanks to "injections" into cracks and voids of polymeric materials. This type of repair is especially recommended for large volumes of damage.
To repair vertical concrete surfaces, you can use the method of applying a special mixture to the repaired surface. The repair mixture for concrete consists of a cement-sand mortar and a polymer additive. Furyl alcohol (0.35% by weight of cement) and sulfanol (0.02%) are used as this additive. After drying, the cured concrete repair mix is covered with polyurethane sealant.
Also, concrete repair and restoration can be carried out by creating an additional layer of the same material on the surface (by shotcrete using a concrete mixture). The composition of the mixture for concrete includes: cement, water, fractionated sand and an organic additive (bitumen, latex, resin, etc.). But the use of such a method is not always advisable, because. it is quite laborious and at the same time leads to an increase in the mass of the structure, which entails an increase in the load on the foundation of the building.
In addition, when the additional layer dries, its shrinkage will appear, which can lead to a gap between the new and old layer, and the structure will not be restored.
Often from private developers you can hear the question, how to repair cracks in concrete? When carrying out repair work at home, liquid cement "dough", cement mortar with a special binder, mortars with polyester or epoxy resin, as well as proprietary repair mixtures are usually used.
Repair of cracks in concrete up to 3 mm is carried out with a liquid cement "dough" or a proprietary mixture. Wider cavities, as well as places where the concrete has peeled off, are repaired with a proprietary mortar or a special mixture. The proportions of the mixture for concrete: 1 part of Portland cement, 3 parts of sand and water, as well as PVA glue.
Filling cracks in concrete requires pre-training. First you need to clean the surface with water, brush and detergent. Excess water is removed with a sponge. Small cracks are embroidered with a spatula and deepened to 5 mm so that the cement-lime mortar fills the entire space well. We strengthen deeper and larger cracks with a “grinder”, for this we saw through the transverse furrows.
If exposed reinforcement is visible in the crack, then it must be cleaned and treated with a special preparation that protects against corrosion. Pieces of wire with a diameter of about 4 mm are placed in the previously cleaned furrows.
Using a brush, apply a primer, its thickness is approximately 3 mm. Carefully and evenly distribute it over the entire repair surface. After that, we apply the repair mixture (the primer has not yet dried out).
When the cement-lime mixture is applied, it must be moistened periodically, but if the joints were filled with polymer compounds, then moistening is not necessary. The surface is leveled with a spatula. A day later, it is desirable to cover the repaired surface with paint.
