Filling and sealing cracks in masonry and concrete

Recommendation points

• Method 1. Cement mortar and repair mixtures
• Method 2. Epoxy resin and epoxy repair compounds
• Operating procedure
• Method 3. Cords and tapes for seams and crack repair
• Operating procedure
• Method 4. “Make in advance”. Additive to concrete for self-healing cracks

How to repair cracks in brick or concrete? What materials to use in this case? What are the ways for each of the cases? Our article will tell you about these everyday situations that every owner of a country house faces..

A crack is a “friend of man”. She is the first to inform the owner about problems in element stability or material wear. It provides a signal before more serious destruction occurs. In these cases, the movement that caused the crack must be stopped and the crack repaired and masked. We talked about how to stop and hide it in previous articles. In this we will discuss methods of sealing cracks and technological joints..

The causes of occurrence, “global” and camouflage measures to stop them have already been described in detail in the articles “What are the cracks in buildings and their causes” and “How to stop the formation of cracks in the walls of a house.” Such defects can occur, for example, in the basin of a pool, foundations or external walls exposed to atmospheric influences. Such a crack, after taking measures against further development, must be sealed to avoid moisture ingress, which contributes to the development of any defect..

Cement-based repair mortars are a good way for dry and in some cases damp rooms, but do not give the desired effect when used outdoors and in water tanks. This will require special tools. So, the crack was found, stopped and is waiting for repair..

Attention! The described methods are applied in the case of a stable surface (non-through) crack. Sealing a through crack will only give an unreliable and temporary result..

Method 1. Cement mortar and repair mixtures

The simplest and cheapest of the existing methods, while the weakest. Suitable for partial temporary filling of cracks in floors and walls in dry and damp rooms. As a rule, it does not give a sealing effect, protecting only from clogging. The method is described in detail in the article “Repair mixtures for concrete”.

Method 2. Epoxy resin and epoxy repair compounds

Much more effective than cement mixes, but only suitable for horizontal joints – floor and screed. The epoxy is sold ready-made with a hardener or separately.

Applications: screeds and concrete floors, interior work.

Benefits:

1. Low price.
2. Fast drying.
3. Reinforces seams, preventing further movement.

What you need:

1. Grinder with diamond disc.
2. Dust removal tool (vacuum cleaner, syringe, pump).
3. Concrete primer.
4. Hardener Resin or Epoxy Repair.
5. Fine sand, packed.
6. Spatulas, containers, etc..

Note.The first three points will be needed for any chosen method.

Operating procedure

1. First of all, we make the crack jointing in order to level the edges, along the way we remove the loose layer of concrete. In this case, its dimensions should not increase significantly (4–25 mm in width). We cut transverse grooves for a power tie (length 150 mm, step 400 mm).

2. Dust the seam.

3. We process the seam with a primer.

Note.The first 3 points will be required for any selected method (except grooves).

4. We put the repair brackets in the transverse grooves

5. Prepare the solution according to the instructions, adding the hardener to the resin.

Attention! Setting time of epoxy mortar 10 minutes.

6. Add fine sand to the resulting solution and fill the seams.

7. Fall asleep on top with a thin layer of sand.

8. After about an hour, remove the sand from the surface with a vacuum cleaner.

The described sand method is good for dry screeds. When used under a liquid medium (water), sand is excluded from the composition (including dusting). The possibility of using sand as part of branded repair mixtures of kits (resin + hardener) is indicated in the instructions.

Epoxy crack repair compounds:

Name, manufacturer	Release form	Unit price, rub.	Price 1 kg, rub.	Consumption kg / liter of cavity	Note
Epoxy resin ED-16, Russia	Bucket 5-20 kg	900 (5 kg)	180	1.28	Hardener Etal-45M (160 rubles / kg) is purchased separately
Epoxy resin ED-20, Russia	Bucket 5-20 kg	1100 (5 kg)	220	1.28
Resin Epoxy 520, Spolchemie, Czech Republic	Bucket 5 kg	1400	280	1.28
UZIN KR 416, Germany	Can 750 g + hardener 42 g	1000	1200	1.21	Fast hardening
Repair Technokolla, (Sika), Italy	Can 1800 g + hardener 200 g	3600	1800	1.35	The widest scope

Method 3. Cords and tapes for seams and crack repair

To solve the problem in more critical areas – in the bowl of the pool or tank, in the walls of the underground part of the foundation or the outer walls of the house – serious measures and special tools will be needed. Such repairs, although expensive against the background of the “good old” methods described above, are many times superior to them in terms of functions, reliability and scope.

Benefits:

1. Variety of products – there is a special material for each task.
2. Tightness, durability, wide range of applications.
3. For outdoor use and harsh conditions. Installation possible in winter.

Disadvantage: high material cost.

What you need:

1. The first 3 items of the list of the previous method.
2. Tape or cord for “stone” cracks (selected depending on the requirements).
3. Polyurethane sealant for concrete, gun.
4. Chisel, brushes, brushes, foam rubber.

Operating procedure

See points 1, 2, 3 described above.

4. At this stage, you should take measurements of the depth and width of the space to be filled in order to choose the right self-expanding cord.

5. Install the cord (tape) in the cut. With a depth of 60 mm, an 18×23 mm tape is ideal. It should be held in the gap without tension, naturally. To the bottom and to the top of the crack, there should be 20-30 mm for expansion.

Attention! No type of self-expanding cord should be caulked or any other type of reinforced installation. He himself will fill the entire space during the expansion process..

6. Fill the outer part with polyurethane sealant, smooth the surface with a spatula. We remove the remnants of raw sealant with foam rubber. As a rule, the names of the preferred brands are placed on the packaging of materials requiring careful selection. Follow the manufacturer’s recommendations.

In case of application in relatively dry rooms (basement, basement), where waterproofing measures are of a safety nature, finishing with cement mortar or cement repair mixture is allowed.

Polyurethane sealants:

Sealant	Release form	Unit price, rub.	Price kg, rub.
ELASTOSIL PU 20, Russia	600 ml tube, 500 g	250	500
3M PU 575, Russia	600 ml tube, 500 g	275	550
Rubberflex Pro PU-15, France	600 ml tube, 500 g	300	600

Crack repair cords are of particular interest, and we will tell you more about them..

Concrete renovation materials are a huge range of products, different in price and purpose, that have appeared over the past 15 years. These are the results of scientific progress in the service of the national economy. These materials are mainly binders and come in the form of a cord, tape or solid mat. The main components are modified clay, polymer resins and bentonite material (or an analogue). The purpose of their application is to bind two surfaces, or to seal them.

According to the release form, they are:

1. Cord. For filling designed cracks of small depth (30-50 mm).
2. Tape. For crevices, cracks and technological joints 20-50 mm wide and 50-150 mm deep.
3. Mats. For interconnecting the layers of cement (concrete) screed when laying a new one on an old one.
4. Water-reactive sealant paste. For grouting small cracks.

Cords and tapes are called hydrophilic and have a special property – to fill the space in which they are installed, without creating excessive forces (without crushing the seam). This happens in contact with water. That is, a dry cord laid in a crack remains dry until water appears. In contact with it, it swells and detains it, becoming a “plug”. When water is removed, it returns to its original state. Such cords and tapes are capable of increasing in volume up to 8 times within 48 hours.

Binder mats are resin-impregnated bentonite webs. Resins are activated in contact with liquid concrete (mortar).

The paste has properties similar to the cord, but is available in tubes. Especially for hard-to-reach places.

Hydrophilic crack fillers:

Name, manufacturer	Release form	Withstands pressure, atm	Expansion coefficient, times	Price 1 rm. m
“PLUG”, Russia	Ribbon, cord	5.5	2.5	190
G-Flex GX-7615, Alchimica, Ukraine	Tape 18×23 mm	6	2.5	200
Waterstop 1520, Greece	Cord Tape 18×23 mm,	7	3.5	245
FUMAX, China	Tape 18×23 mm	6	2.5	320
Hydrotite CJ-0720-2K, Japan	Tape 18×23 mm	8	4	360

Method 4. “Make in advance”. Additive to concrete for self-healing cracks

It sounds strange, tempting and incredible. However, this is a fact – Russian scientists have created a drug that forms hydrophobic crystals. Moreover, it works only in a 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 produced in buckets of 10 kg and costs about 250 rubles / kg.

Whichever method is chosen, remember that waterproofing is not a fad or a tribute to fashion, but a constructive necessity and a vital structural element..