Repair mixtures for concrete

Recommendation points

• Types of repair compounds
• How to choose a repair compound
• Leveling the floor
• Repair of potholes on the floor
• Crack repair

Potholes, chips, cracks – all these can happen to any concrete surface. In this article we will tell you how and with what mixtures you can repair concrete.

Types of repair compounds

Concrete is known for its strength, reliability, and durability. However, under the influence of various factors, it begins to deteriorate over time. The reason for this may be poor-quality styling, non-observance of the proportions of the components, an aggressive external environment, mechanical damage. Defects can be eliminated with the help of special repair compounds..

In order to prepare the composition, you need to mix the dry repair mixture with water. An option is possible with the use of special additives that improve some of the characteristics of concrete. Ready-made compounds are used to repair floors, walls, stairs, bridges, roads and other concrete structures.

All repair mixtures can be conditionally divided according to their purpose:

• for the repair of load-bearing concrete structures such as columns, beams, floor slabs;
• for the repair of roads and concrete floors;
• to protect concrete structures from corrosion.

There is a fairly wide range of repair compounds with different properties on the market from various domestic and world manufacturers. Accordingly, their quality and price category can differ quite significantly..

Repair mortars must ensure high adhesion to concrete, non-shrinkage and absolute compatibility with it. With their help, the bearing capacity of structures is restored, water resistance, frost resistance and concrete strength are increased. In addition, they must be affordable and economically feasible..

According to world and domestic experience, it has been proven that the use of repair mixtures is more effective than the use of traditional cement-sand mortars.

Repair mixes for concrete are divided into thixotropic and cast. The former are used for vertical surfaces, the latter for horizontal ones. It is possible to increase the reinforcing properties with the help of fiber.

How to choose a repair compound

Several factors influence the choice of the repair composition:

• type of damage
• defect size
• Operating conditions

There are three main types of repair work:

• strengthening the concrete surface
• leveling the concrete surface
• crack repair

To strengthen concrete, which carries heavy loads and has a fragile surface (screed, floor slabs), deep penetration primers are usually used.

The most common type of concrete repair is unevenness leveling. Sealing of vertical surfaces is carried out using thixotropic dry mixes. They adhere perfectly to the surface, adhere well to them and do not blur. They have minimal shrinkage and high characteristics in terms of strength, water and frost resistance..

Particularly critical areas require the addition of fiber-reinforced fiber. Fast repairs are provided with special compounds. Their solidification time is up to 6 hours. But they have a limitation on the layer thickness – up to 30-40 mm.

Horizontal surfaces are leveled with molding mixtures. They are more liquid and, due to this, they are simply poured onto the surface. The mixture sets quickly, has minimal shrinkage and is quite durable. One layer can be laid up to 10 cm thick.

Leveling mixes are also used to repair cracks in concrete.

The choice of the repair composition is influenced by the operating conditions of the structure. If necessary, components can be added to the mixture that enhance various properties, for example, water resistance or fast solidification.

The most famous manufacturers of repair mixes – BASF, MAPEI, SIKA, from the Russian – “Lakhta”, “Alit”, “Consolit”, “SpetsRemSmes”.

Leveling the floor

To level the floor, it is necessary to prepare a cement-sand screed. The concrete surface is pre-cleaned of dust and treated with a primer. After that, they are determined with the point at which the floor will be leveled, beacons are installed according to the laser level.

Next, the screed is poured. Its maximum height should not exceed 35–40 mm. The pre-mixed mortar is poured onto the surface and leveled with a spatula. On the second day, the beacons are removed and the seams are sealed with a rubbing solution..

The screed must dry well. This may take up to 2 weeks. The screed is covered with a film, and the surface itself is periodically moistened with water. Thanks to this, it will become stronger and will not crack..

Horizontal surfaces can be repaired using a self-leveling compound. They are used in the presence of small defects and uneven areas. The result of use is a perfectly flat surface.

For leveling the floor I use the following mixtures: VOLMA-Leveling Express (cost – 14 rubles / kg), Vetonit-2000 (17 rubles / kg), KESTONIT 97 (39 rubles / kg).

Repair of potholes on the floor

At the beginning of work, small cuts are made around the damage with a diamond disc or grinder. Then the remains of damaged concrete are removed with a chisel and perforator, the surface is cleaned of dust. For better adhesion of the composition to concrete, a special epoxy primer is applied to the surface.

After applying the mortar, it is necessary to remove its excess and level the surface using a strip. After complete drying, the composition becomes as strong as possible. The sealed area is sanded.

The following mixtures are suitable for sealing potholes: IVSIL EXPRESS-BASIS (cost – RUB 10 / kg), Thomsit RS 88 (RUB 30 / kg), LAKHTA Rapid Repair (RUB 80 / kg).

Crack repair

Cracks appear in concrete for various reasons. Over time, they can grow, destroying the whole structure. This defect must be repaired..

Vertical cracks are repaired by injection. When using the injection method, the composition is pumped into the fracture using special equipment – a packer.

Surface cracks, which usually form on inclined and horizontal surfaces, are repaired by saturation. In this case, the cracks are impregnated with a mixture without pressure..

There is another method for eliminating cracks. At the beginning of the work, the crack is sawn 25-50 mm deep and 10-20 mm wide. Excess concrete must be removed and the crack blown out of dust and dirt. The kerf is filled with repair mortar. In the event that the concrete crumbles, it is worth using a better mixture, if it practically does not produce dust, a cheaper product will do..

To repair cracks, the following mixtures can be used: LAKHTA basic repair compound (cost – 57 rubles / kg), BASF MasterEmaco S 488 (33 rubles / kg), Sika Monotop 612 (86 rubles / kg).

Comparative table of technical characteristics of dry repair mixes:

Parameters	“LAKHTA basic repair composition”	BASF MasterEmaco S 488	Sika Monotop 612
Material consumption, kg / dm3	1.6-1.7	1.9	2.11
Water consumption, l / kg	0.13	0.145-1.6	0.1-0.115
Bond strength to concrete after 28 days, MPa, not less	1.5	2.5	1.5-2.5
Flexural strength after 28 days, MPa, not less	8	8	7-9
Waterproof mark not less than	W12	W16	W16
Application temperature, ° C	from +5 to +35	from +5 to +50	from +5 to +35
Cost, rub / kg	57	33	86

The main technical characteristics presented in this table will help you choose the best repair mix for your needs..

Correctly selected concrete repair mix and quality work guarantee an excellent end result.