Concrete Cancer and Spalling Repair
Concrete cancer is caused when the steel reinforcing within a concrete slab begins to rust. As steel rusts it can expand up to 7 times its original size causing the surrounding concrete to be displaced and become flakey. As the steel pushes the concrete away, more water gets to the steel expediting the process. The process is often referred to as concrete spalling.
Telltale signs of Spalling Concrete
Unless you are a structurral engineer, or have seen the signs before, chances are you will not know what the signs of spalling are, nor when it's time to organise concrete cancer repair work. Here are a few key signs your structure is in need of repair:
- Flaking and cracking concrete (concrete spalling)
- Rust stains which seem to leak out from within the concrete
- Bubbling of concrete render or
- Leaks which appear in the roof or internal walls
As often as not, people mistake these signs as general weathering and delapidation, caused by the elements; but whilst this is true to some extent and may play a part in exacerbating the problem, the real problem lies within the concrete itself.
Risks of Spalled Concrete
Whilst most people would agree that spalled concrete is an eye-sore, what many people fail to realise is that as time goes on, concrete cancer also represents a potential OH&S hazard. Over time, and with increased exposure to the elements, untreated pieces of concrete may fall from your structure. If these fall from heights in high traffic areas, then passers-by will be at risk of injury, and other buildings in proximity, at risk of damage as well.
Spalling and delaminated concrete should be repaired immediately, as deffering the decision to treat it will inevitably lead to increased problems into the future.
How Concrete Cancer Begins
The process can start in many ways, but generally it is due to one of the following:
- Poorly treated reinforcing steel being used when the slab is poured
- The ends of the reinforcing being too close to the surface. As water seeps through the concrete it picks up limestone and other chemicals.
- When it hits the steel it causes oxidation to occur in the form of rust
- Incompatible metals being used in close proximity to each other, thus causing a reaction which allows water into the slab
- Stress fractures from bearing weight or general wear and tear allow water to penetrate the concrete and react with the steel
- Poorly installed window and door lintels are exposed to the elements causing rusting to occur
Furthermore, any attempts to fix the problem for the short-term (such as rendering over the problem) will only exascerbate the issue. Despite, potentially looking better, the rusting process will continue below the surface causing the steel to again displace the concrete and in some cases rust so badly the steel eventually needs replacement. Treatment and repair of the concrete is the best solution.
Concrete Cancer Repairs
For over 40 years, Remedial Building Services have offered comprehensive concrete cancer repairs. Sydney and Brisbane are where our main operating hubs are located, however, we have and will provide repair services up the entire Eastern Seaboard of Australia. Our staff are trained in the identification of the underlying issues causing your visible and strutural defects.
Once these are identified we will tender to you a scope of works, a repair methodology and an estimate. We then begin the process of repairing your concrete. In summary we remove all drummy concrete and brick work, grind back the reinforcing steel to remove all rust and treat the steel with anti-corrosive membranes (or replace the steel if required). Once the steel underneath has been treated we reinstate the visual component (bricks or render) to restore the original facade.
Where the issue has originated in the slab on the roof of the building structure, it is likely that waterproofing will need to be undertaken. In this instance we will jackhammer the surface to expose the problem before treating it. Once the rusted reinforcing has been repaired, application of a waterproofing membrane will help prevent the ingress of moisture to the slab and prolong the life of the steel and therefore the structure itself.
Services we Offer
Sadly, as often as not, fixing concrete cancer is just one part of the problem. Depending on the nature of your building, its age or the cause of the original problem, you may need more than just spalling repair. We offer a range of related repair services which may need to be engaged for your job, including:
- Application of Carbon Fibre - Used when your structure needs increased load bearing capacity
- Heritage work - If your building is heritage listed, or if you just want to preserve its facade, our experience with heritage listed structures means we can help you too
- Protective Coatings
- Fire Rating Solutions - With changes to the BCA you may be required to update your fire rating compliance. Ask us for more details
Beating Concrete Cancer
If you would like any more information on concrete cancer, or would like to arrange someone to help solve your concrete problems, whatever the nature, please contact your closest Remedial Building Services office today.
Or for more information, please read our glossary of structural repair terms or request our latest brochure.