How to repair a concrete floor?

Nahaufnahme eines sanierungsbedürftigen Betonbodens mit freigelegten Kabeln

A concrete floor is robust and durable. This is why this building material is often chosen for garages, car parks and industrial areas. Over time, however, also concrete floors can suffer minor or major damages which must be repaired. We explain how the repair works best.


1.    When must a concrete floor be repaired?

2.    Which material is suitable for repairing a concrete floor?

3.    What must be considered during substrate preparation?

4.    How does the processing work?

5.    Conclusion

1.    When must a concrete floor be repaired?

If the concrete floor shows holes, cracks or chipped areas, it should be repaired. A quick repair prevents further damage due to moisture ingress and subsequently corrosion and frost damage. As soon as corrosion damage of the steel reinforcement occurs, the statics of the building might be in danger.

Finding out the causes of the damages

Concrete damage should always be examined and repaired by a professional. 

He first determines the cause and extent of the damage. This includes checking the state of corrosion, chloride content and strength of the concrete.

Concrete floors are damaged over time by weathering, chemical processes and mechanical loads. The reinforcing steel inside the concrete is then no longer sufficiently protected. In addition to structural defects, inadequate maintenance and upkeep also promote corrosion damages.

Example: multi-storey car park and underground garage

In multi-storey car parks and underground garages, the most frequent damage to reinforced concrete floors is due to corrosion, which is usually triggered by carbonation. This is when carbon dioxide in the air changes the concrete over the years and eliminates the natural corrosion protection. Another cause is entrained chlorides. The salts introduced by car tyres migrate via cracks into the floor structure and the steel reinforcement.

What is concrete made of?

Cement, water and aggregates are mixed for the production of concrete. During drying, the individual components combine through chemical processes so that the end product "concrete" has a high compressive strength.

2.    Which material is suitable for repairing a concrete floor?

For professional repair of concrete substrates, specialists rely on concrete replacement mortars. The unique pumpable and flow-grade concrete replacement mortar weber.floor 4640 Outdoor RepFlow can be used in statically relevant exterior and interior areas, as it is resistant to frost and de-icing salts. This means it can be used in underground garages, warehouses, production areas as well as on courtyard surfaces and bridges. It is rated in the highest class R4 according to EN 1504-3 (ʺProducts and systems for protection and repair of concrete structures, part 3: Static and non-static relevant repair worksʺ), fulfills the guideline "Technical Rule for Maintenance of Concrete Structures" (Germany), and can also be used directly as final wear layer in case of medium loads.

Large floor areas

A major advantage of the concrete replacement mortar weber.floor 4640 Outdoor RepFlow is its processing. Thanks to modern pump technology it can be easily mixed and quickly conveyed to the target location, so that even large areas can be placed in just a few hours.

Small floor repairs

The new concrete repair mortar is also suitable for smaller renovation projects, such as courtyard driveways or garage floors. The material is simply mixed by hand and applied on the damaged and well-prepared areas. In this way, all unevenness can be repaired in no time and holes and cracks can be filled.

3.    What must be considered during substrate preparation?

For a perfect result, accurate substrate preparation is crucial. In case of large floor surfaces the damaged areas must be first removed by shot blasting or milling. Depending on the extent of the damages due to chlorides or corrosion, these areas must be removed at an appropriate depth so that the biggest grain contained in the aggregates of the old concrete is exposed. Afterwards the exposed surfaces must be thoroughly cleaned. Subsequently, damaged reinforcing steel must be free from dust and covered with a corrosion protection coating.

In the case of minor damages in courtyard entrances, it may also be sufficient to clean the damaged areas by suitable measures (for ex. chiselling of small, severely damaged areas, vacuuming of loose residues and using of high-pressure water jet), so that the biggest grain is exposed in such damaged areas. In this case, the removal of larger areas is not necessary.

In all cases, the application of a bond coat is mandatory to improve the adhesive bond and to optimize the absorbency between the substrate and concrete repair mortar.

4.    How does the processing work?

First, the concrete replacement mortar is mixed. In the conventional method, the material in bag must first be brought to the job site and then mixed by hand, little by little, with water. Afterwards, skilled workers place the material while kneeling. This is very laborious and time-consuming, especially for large areas.

Quicker processing with mobile silo

For larger areas, it is much more practical and easier to mix the replacement mortar on site in a mobile silo or a weber.floor MixMobil with modern machine technology and to pump it directly to the target place. In this way, eight to twelve tons of material per hour can be processed by hose. The rehabilitation of more than a thousand square meters per day can be done trouble-free. This considerably shortens critical processes on the job site.

Bring in standing position

How does it work exactly? Workers apply the pumped replacement mortar by swinging the casting hose back and forth in a comfortable standing position at the target location. The layer thickness depends on the depth of the damaged floor areas. After pouring, the skilled workers only need to beat the cast surface crosswise with a wobbling bar, in order to bring a good levelling and aerating effect.

5.    Conclusion

The repair of a damaged concrete floor with the help of a pumpable and flow-grade concrete replacement mortar is extremely efficient. It saves a lot of time and staff, especially for large areas up to 90%, depending on the area type. This is an important aspect, especially in times of a shortage of skilled workers. Another advantage is that the utilization of the repair floor surface is only interrupted for a short time thanks to the fast repair method.