How and what to seal cracks and holes in concrete

Concrete cracks and holes are frequent problems that can result from a variety of circumstances, including bad weather, large loads, or normal wear and tear. If ignored, these flaws in the concrete can cause more significant structural issues in addition to affecting its aesthetic.

To keep your concrete surfaces long-lasting and intact, you must seal these holes and cracks. The good news is that this task can be simple and efficient if the proper tools and methods are used.

We will examine the various tools and techniques for fixing concrete in this post. There are workable ways to get your concrete surfaces back to their original state, regardless of the size of the holes or tiny hairline cracks you are facing.

Additionally, we will provide you detailed instructions to help you navigate the repair process so that, even if you are a do-it-yourself enthusiast, you can achieve professional-quality results. Let’s get into the specifics and discover how to handle concrete repairs quickly and skillfully.

Material Application
Concrete Patch Best for small cracks and holes; easy to use and durable.
Epoxy Resin Ideal for structural repairs; bonds well and is very strong.
Polyurethane Foam Useful for larger gaps and holes; expands to fill voids.
Hydraulic Cement Perfect for stopping water leaks; sets quickly and is waterproof.
Acrylic Caulk Good for minor cracks; flexible and paintable.

Concrete must have its holes and cracks sealed in order to retain its strength and beauty. To ensure a long-lasting repair, this process entails selecting the appropriate materials, such as epoxy, polyurethane, or latex-based sealants, and adhering to a simple procedure. Your concrete surfaces can be kept from further deterioration and have their lifespan increased by taking quick care of these imperfections. Adhering to appropriate sealing techniques can greatly improve the integrity and visual appeal of your concrete projects, be they outdoor structures, floors, or walls.

Types of cracks in concrete

Some inexperienced or dishonest builders would rather just use mortar or putty to hide the hole or any other flaw. However, it’s important to identify the precise cause of any problems before filling in a hole or crack in a concrete wall or other foundation.

Defects come in various forms:

  • Superficial. Such cracks often appear after pouring the foundation during the drying of the sand-cement mortar, if the mixture was prepared without observing the required proportions of the components, low-quality components were used, or there was not enough water in the mixture.
  • Shrinkage (also called hairline cracks). Defects of this type are considered the most dangerous, since they cause not only deformation of the foundation, but also of the entire building as a whole. This leads to a decrease in strength. Defects of this type appear with uneven load on the foundation and with improper selection of cement composition.

  • Temperature-shrinkage. Cracks of this type appear during the hardening of the concrete base due to the exothermic reaction that occurs between cement and water. Very often, when erecting walls and ceilings, novice builders do not take into account the freedom of deformation, as a result of which temperature stress occurs in the concrete mass and defects appear on the surface.
  • Cracks and holes that appear due to poor reinforcement. If the frame for strengthening the structure is too weak, it will bend under loads, which will also lead to the formation of defects. In addition, the reinforcing rods can begin to oxidize. Due to the appearance of corrosion, the material increases in size, tearing the concrete mass from the inside.

Outdoor concrete surfaces are also prone to cracking. Chemically active materials can be found in the external environment, which can lead to the formation of defects.

Furthermore, abrupt temperature variations can cause damage to the concrete’s surface as well as its actual thickness. Nevertheless, UV light also has a negative impact in addition to cold air.

It is also important to consider the cracks’ width because, in certain situations, these flaws are not serious.

Permissible crack sizes

Within the construction sector, DBN B.2.6-98:2009 establishes the admissible crack width, which is contingent upon operating conditions.

  • The size of the cracks should not exceed 0.5 mm if the concrete surface is not exposed to weather conditions. That is, it is not affected by moisture, low temperatures and ultraviolet radiation.
  • The permissible crack width cannot be more than 0.4 mm, provided that the structure is exposed to weather.
  • The crack width should not exceed 0.3 mm if the concrete base is in an aggressive environment.
  • It is not recommended to allow cracks larger than 0.2 mm to form if we are talking about reinforced structures that are characterized by reduced resistance to corrosion.

Small-opening horizontal cracks, which frequently occur in columns made of reinforced concrete, are likewise regarded as innocuous.

But it’s crucial to remember that there are some operating environments in which cracking is completely prohibited:

  • if we are talking about reinforced concrete structures that constantly interact with liquids and gases (that is, they must be impenetrable and airtight);
  • when using structures that are subject to more stringent requirements for their durability.

It is far simpler to make a decision than to fix holes in a wall or any other concrete surface once the type of defect and the necessity of correction have been established.

Cement mortars

Because of their affordability and capacity to patch small shrinkage cracks in concrete, these compounds are highly well-liked.

Repairing a crack

Check for chips surrounding the crack before starting to seal it. It is essential to remove any peeling concrete pieces because if there are any, they could soon become holes. Following this, you’ll need:

  • Perform jointing. To do this, using a chisel and hammer, you need to walk along the entire length of the crack so that its depth is at least 5 mm. If necessary, you can use a spatula to create a depression.

  • remove dust using a vacuum cleaner and rinse the resulting depression with water.
  • Remove excess water and cover the crack with cement mortar (3 parts sand to 1 part cement with the addition of PVA). In this case, you need to ensure that the composition covers the entire space of the recess.
  • Moisten the poured cement with water.

Filling the hole

The following procedures can be used to fix the issue if a hole has developed in the concrete surface where the reinforcement is visible:

  • Clean the hole in the concrete and treat its surface with an anti-corrosion compound.
  • Place pieces of steel wire with a diameter of about 4 mm into the recess.
  • After this, the recess is covered with a primer, evenly applying it to the entire surface. In this case, the thickness of the mixture layer should be about 3 mm.
  • Without waiting for the mixture to dry, fill the hole with a cement composition for sealing cracks in concrete and make sure that it fills the entire hole. If the hole is too deep, then the cement is poured in several stages. In this case, each subsequent layer must be moistened with water from a sprayer.
  • Level the surface with a rail (metal or wooden), moving the tool from right to left.

  • After the mixture has hardened, excess cement composition must be removed with a spatula and the surface must be plastered. If the crack was too deep, then leveling is performed using a grinding machine.

Practical! It is necessary to pour the cement mixture with a reserve so that it is just barely above the floor. In the course of hardening, the mixture will condense.

The concrete floor is ready for painting or applying any type of finishing material after a full day.

It is important to keep in mind, though, that this type of concrete crack sealing won’t have a sealing effect and isn’t appropriate for surfaces with higher waterproofing requirements. Furthermore, one could think of the composition of cement as a stopgap measure. The flaws will eventually resurface. Resins, specialty repair compounds made from them, or sealants can be used to seal the defects if your goal is to "completely patch up" the holes and prevent them from happening again.

Long-term sealing of defects

This defect processing technique is worth considering when determining how to permanently seal concrete cracks. For the restoration of screeds, blind areas, and other concreted areas or horizontal surfaces, resin and sealing mixtures based on it are appropriate.

There are several benefits to using such compositions to repair concrete cracks. This is primarily due to the mixtures’ low cost and quick drying times. However, resin makes it possible to consistently seal the seams and prevent future expansion.

Therefore, in order to remove flaws, you must get ready:

  • angle grinder and diamond-coated discs;
  • vacuum cleaner;
  • spatulas and trough for mixing the composition;
  • primer for concrete;
  • epoxy (base A and hardener B);
  • fine-grained sifted sand.

Dust and dirt must be removed from the crack before sealing it. Following that, we carry out the sealing in the order listed below:

  • We make expansion of the crack. In this case, the width of the resulting depression should be at least 5 mm.
  • Using a grinder, we cut transverse seams in the concrete with a step of 400 mm (the length of the grooves is about 100-150 mm).
  • We remove the loose layer of concrete and remove dust from the surface with a vacuum cleaner.
  • We treat the surface of the defect with a primer, and fix the transverse grooves with repair staples.
  • We prepare a solution from resin (base), hardener and sand according to the instructions on the package with the composition.
  • We seal the defect with the resulting mixture and quickly level the surface, since the setting time of the resin is only 10 minutes.

The next step is to apply sand to the surface, which needs to be vacuum-cleaned before filling the base or covering it with finishing material.

The best epoxy compounds

The most efficient materials available today for fixing cracks in concrete walls and other surfaces are:

  • Epoxy resin of domestic production ED-16 and ED-20 costing about 2,000 for 3 kg. The hardener will have to be purchased separately (costs about 300-500 rubles).
  • Epoxy 520 resin from the Czech manufacturer Spolchemie costing 3,500 rubles for 5 kg.
  • German compound UZIN KR 416, which will cost 2,700 rubles for 0.75 kg.

Sika, an Italian manufacturer, also produces highly sought-after compositions.

It is important to keep in mind, though, that this type of defect correction is not appropriate for processing holes that develop in concrete foundations under intense water pressure. It makes sense to use a sealant in this situation.

Use of sealants and self -expanding ribbons

It is important to note up front that this method of defect sealing is highly costly, and as such, it is typically employed for repairing concrete pool bowls in suburban settings. But even though sealant is expensive, using self-expanding cords has advantages over it.

  • the possibility of processing a defect of any type;
  • complete tightness;
  • the possibility of installing installation work in conditions of cold weather.

For work, you’ll need the following in addition to a basic toolkit:

  • mounting gun;
  • self -expanding tape or cord;
  • chisel and brushes;
  • Hermatic for concrete.

However, measure the cracks’ dimensions and buy the appropriate type of sealant and tapes based on them before smearing the flaw. For instance, an 18 x 23 mm cord would be appropriate if the hole is 60 mm deep.

The following action needs:

  • Expand the cracks and dust them.
  • Install the cord in the recess.
  • Fill the remaining space with sealant.
  • Smooth out the protruding composition with a spatula.

You won’t have to wing it when it comes to caulking or puttying the surface after the work is finished. Just applying the composition and leveling it is sufficient.

When it comes to the best compositions of this kind, the most well-known ones are:

  • Domestic ELASTOSIL PU 20 at a cost of 280 rubles for 600 ml.
  • Composition from the French manufacturer Rubberflex, which is now sold at a price of 300 rubles for 310 ml.
  • PLUG tape of Russian production at a cost of about 260 rubles per linear meter.

Injection

It’s important to consider this approach when determining the best way to seal holes in a concrete wall, particularly if water is seeping through the wall in addition to the crack.

With injection technology, a unique compound—such as microcement, epoxy resin, polyurethane, or waterproofing mixture—is injected into the concrete’s thickness using powerful injection pumps.

In order to carry out this kind of defect restoration, it is required to:

  • Make holes in a checkerboard pattern on both sides of the gap.
  • Install packers in them (special tubes through which the solution is supplied, reminiscent of a dowel) at an angle.

  • Pour in the solution.
  • Pull out the tubes and cover the surface with a building compound.

We have already examined the process of independently caulking a hole in a concrete wall, but what happens if the concrete in question is aerated?

Any concrete structure that wants to remain sturdy and long-lasting needs to have its holes and cracks repaired. It is possible to stop additional damage and future expensive repairs by taking care of these problems as soon as they arise. A strong and long-lasting repair depends on using the proper tools and materials.

Concrete holes and cracks can be sealed using a variety of techniques and materials, each of which is appropriate for a particular kind and extent of damage. Depending on the particular requirements of your project, the best solution may range from basic patching compounds to sophisticated epoxy injections. To get the best results, always make sure the surface is adequately prepared before applying any repair material.

Concrete surfaces must be regularly inspected and maintained to remain in good condition. You can guarantee the long-term resilience and aesthetic appeal of your concrete structures by being watchful and taking care of minor problems as they come up. Recall that in the long run, spending time and energy on appropriate concrete repair today will save you hassle, money, and time.

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Anna Vasilieva

Journalist with a technical education, specializing in construction topics. I can explain complex technical topics in simple and accessible language.

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