‘Concrete Cancer’ can seriously damage the building structure if not promptly repaired. Concrete cancer is rust within the concrete in its reinforcement steel and can quickly cause a lot of structural damage if not remedied. How does it happen? What to look for? How can you stop it?
How does it happen?
You need a combination of Iron, Water and Oxygen. A dangerous cocktail!
When moisture comes into contact with steel reinforcement it combines with carbon dioxide in the air to form weak carbonic acid. As this acid forms it dissolves the iron in the reinforcement, some water starts breaking down into its components, hydrogen and oxygen, and the oxygen and iron combine and iron oxide freeing electrons form. This is called rusting.
Some buildings are more likely than others to suffer concrete cancer.
- Buildings built before July 1997 generally have less concrete to protect the reinforcement.
- Buildings near salt water – salt in the air helps to accelerate rates of oxidization.
- Buildings near high smog areas near busy roads or industrial areas.
- Buildings that are not regularly painted. Painting at least every eight years is recommended to maintain waterproofing levels.
What to look for?
- Reddish stains adjacent to cracked concrete.
- Reddish stains running down any surface on the building.
- Concrete lifting or exploding often means that the reinforcing steel is rusting.
- Cracks in the concrete showing white crystals (fluorescence) indicates that oxidisation is occurring.
In all these cases, it is important for experts such as, FCS Concrete Repairs, to investigate, find the cause and recommend a solution. Any delay can be very costly because it is essential to stop the rust and re-seal the surrounding concrete before more serious damage occurs.
How can you stop it?
- The spalling concrete around the reinforcing bar is removed.
- A rust inhibitor is applied to the reinforcing steel.
- An epoxy, mortar epoxy and/or cementitious material is used to patch the area.
- Cracks are repaired using a technique called ‘crack injection’ where suitable epoxy resins or special mortars are injected.
- Treatment of concrete cancer may include waterproofing.
- The area should be re-painted/re-coated.
Important: Be aware that the problem is very likely to be much more extensive than is visible on the surface. The cancer may have spread along the reinforcing in each direction. It is difficult to know the extent until the concrete is chiselled away.
If the signs are there that concrete cancer is starting in your building, act quickly. The most important fact is that once more than 30% of a reinforcing bar is eaten away the bar is structurally worthless and full replacement will be necessary. Fixing concrete cancer is expensive but replacing reinforcing is a much larger expense. Some buildings have been condemned because the owners did not act quickly enough. So be advised.
Act quickly, act now! Always choose a contractor who you can trust!