Project Description

Durability issue due to concrete cracks in balconies, solved with Basilisk ER7

During an inspection in one of the LUMC hospital buildings, hairline cracks were found in the concrete of the balconies. At first sight, the concrete damage was limited, but on closer inspection it appeared that the damage could cause a durability problem in the future. Spraying the balconies with Basilisk Liquid Repair System ER7 prevents these problems and secures the design life of the building.

“Safety and sustainability are paramount in the maintenance policy of LUMC hospital. After we discovered hairline cracks in the concrete during an inspection, there was no doubt in my mind whether the concrete should be repaired. I did want to weigh up the alternatives carefully though,” says Frans Hogervorst, maintenance manager at LUMC hospital. “I had two real options: applying a coating or working with Basilisk Self-Healing Repair System ER7. The cracks were too small for concrete repair with injections, so that method could be discarded almost immediately.”

LUMC building balcony repair concrete

Crack formation in concrete balconies: prevention is the best cure

Before we explore both solutions, we look at some more project details. The concrete cracks had a width of 0.2 mm and were located at the top side of the balconies. This hasn’t caused any problems yet, but it will in the future. On the one hand, due to frost damage, whereby the concrete surface can flake off due to a combination of moisture and freezing cold. On the other hand, due to moisture that penetrates the concrete via shrinkage cracks and reaches the reinforcement. The reinforcement can then corrode and expand causing even more damage to the concrete. Once the reinforcement corrodes, substantial costs have to be incurred to repair this damage. Prevention is therefore the best cure, in this and similar situations.

Coating versus Basilisk ER7 for concrete repair

If the application of a coating would be chosen, the treatment could still be postponed for some time. That was a clear advantage for LUMC hospital. However, the disadvantages outweighed: applying a coating requires a larger investment and has to be repeated every 10 to 15 years. In addition, a coating changes the appearance of the concrete surface.

The transparent Basilisk ER7 spray penetrates the cracks. Then the self-healing system produces limestone in those places, inside the cracks. This seals the cracks and gives the concrete permanent waterproof properties. Periodic repetition of the treatment is not required.

Concrete repair with Basilisk ER7 spray

After the cracks have been repaired, the concrete surface looks the same. However, the properties of the concrete are different: moisture no longer penetrates and the reinforcement is well protected again.

Quick and easy to apply

“I had never used Basilisk Liquid Repair System ER7 before, but I found it was very easy and fast to work with,” commented John Zoutenbier, contractor at HKZ. “The product was easy to handle and conveniently packaged. What I also really liked is that it is a bio-based product and therefore does not smell chemically and does not give off harmful fumes.” In total, HKZ worked on this project with two people for about two weeks. Within that time, the total area of 2 000 m2, spread over seven floors, was treated. Does he want to work with Basilisk ER7 again in the future? “Yes, this is a good and easy to apply solution for repairing small cracks in various concrete surfaces.”

Main benefits of self-healing concrete

An overview of the benefits of using Basilisk Liquid Repair System ER7 for this project:

  • Design life secured by reinforcement protection
  • Unchanged concrete appearance
  • 40% cheaper than a coating
  • 90% CO2 savings
Project details
Location Leiden, the Netherlands
Total surface 2 000 m2 (7 floors)
Object type Balconies
Product Basilisk ER7
Year 2022
Partners HKZ Specialisatie (contractor) and LUMC Hospital (client)
Main product benefits Suitability for hairline cracks in concrete and optically unchanged appearance of concrete
Cost savings* 40%
CO2 reduction* 90%

* Compared to the application of a coating

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