Strata properties throughout Australia are facing major repair costs and potentially life threatening damage due to concrete cancer.
What is Concrete Cancer?
Concrete Cancer is the layman’s term used to explain cracking, spalling and damage to concrete caused by rusting of the reinforcing steel.
The initial cause of concrete cancer is usually from water penetration through the concrete. When calcium oxide reacts with water it produces a solution of calcium hydroxide which reacts with carbon dioxide in the air, thus transforming into calcium carbonate which causes cracks to the concrete surface, which allow more water to penetrate.
The water penetration causes the reinforcing steel to rust which expands with the rust, causing more cracking and spalling of the concrete. This additional cracking results in more water penetration and the accompanying rusting of the reinforcing steel.
How to Identify Concrete Cancer?
The signs of are easy to see as all concrete cancers start with water penetration into the concrete. However, most people just see staining or a white powder. In severe cases of water penetration calcium stalactites are formed on the underside of concrete slabs.
Once water has penetrated for a time, the reinforcing steel will commence to rust which provides the best evidence of concrete cancer.
- Water seepage through walls or floors;
- White staining of concrete walls and floors;
- Calcium stalactites on underside of concrete slabs;
- Flaking and cracking concrete
- Rust stains that seem to leak out from within the concrete
- Bubbling of concrete render
- Leaks that appear in the roof or internal walls
Treatments for Concrete Cancer
In the early stages when there is only evidence of water penetration, the best treatment is to repair/replace the water proofing membrane. Although this is costly, it will rectify the problem before the reinforcing and concrete are severely damaged.
Replacing the waterproofing may seem costly, but when compared to the cost of future repairs, or the demolition of the building, it then seems only a minor expense.
Once damage has occurred, cracks can be injected with an epoxy resin to stop water penetration. However, such methods may just push the problem to other parts of the concrete.
But when concrete is chipping and spalling, the repairs involve cutting into the concrete and repairing the reinforcing and concrete.
What is involved to repair Concrete Cancer?
The repair process for chipped and spalling concrete will depend upon the extent of damage and the location in any structural component.
The process though, generally follows the following principals.
- Remove all loose and damaged concrete;
- Expose the reinforcing steel;
- Clean reinforcing steel of all rust;
- Treat reinforcing steel with rust inhibitor;
- Patch the concrete with an epoxy or structural mortar material to suit the structural capacity of the areas being repaired;
- Repair / replace waterproofing membranes;
How to prevent Concrete Cancer?
Waterproofing membranes must be maintained and repaired at the first signs of water penetration.
If the waterproofing is adequate, water should not penetrate the concrete and reach the reinforcing steel, unless the steel is fitted to close to the concrete surface. In this case you will not know until damage has occurred.
The major problems of tomorrow though will occur in basement car parks. Unfortunately the external walls are treated as “wet walls” which means that water can pass through these walls and not be classed as a building defect.
This sounds good in design, especially if drains are correctly installed along the walls, but as water passes through these walls, the reinforcing steel in the concrete or masonry structure will eventually start to rust.
Currently there is no proven method to seal these walls due to hydrostatic pressure. I envisage major and catastrophic failures of these walls in the future.
Budgeting for future Concrete repairs
The first part of the budgeting process is to identify the current condition of the building through a condition audit. The next will be to identify the extent of waterproofing membranes within the building or complex.
The cost to replace waterproofing membrane would start at $100 /m2 plus the cost to remove and replace tiling, gardens, etc. Thus, repairs will result in substantial expenditure.
It is critical that your Sinking Fund is updated to include allowances for replacements to waterproofing from the first day of the complex. Plus allowance for concrete cancer repairs could be many hundreds of thousands of dollars.
Allowing funds in the Sinking Fund for future repairs is critical to good budgeting.
Gold Coast high rise cancer epidemic sparks concerns someone will be killed
June 13, 2015 9:20am – JACK HOUGHTON Gold Coast Bulletin
Gold Coast high rise cancer epidemic sparks concerns
June 14, 2015 2:04pm – JACK HOUGHTON Gold Coast Bulletin
Gold Coast high rise Focus Apartments may need $2.7m worth of repairs due to concrete cancer
June 15, 2015 12:00am – JACK HOUGHTON Gold Coast Bulletin
From these headlines, it would seem that concrete cancer is only a problem on the Gold Coast. However, this is not the fact, as all buildings may suffer from this costly scourge.
Sydney buildings suffer just as much as the Gold Coast but get less headlines.
But as can be seen, the cost of repairs can, and regularly does run into the millions of dollars.
ABOUT QBM (QUALITY BUILDING MANAGEMENT)
Quality Building Management (QBM) formed by Donald Pitt, has been an active professional within the Building and Strata Industries since 1970.
QBM have completed thousands of building inspections and have successfully identified all concrete cancer cases and the reasons behind it in all cases it is present.
Specialising in everything to keep Commercial, Industrial and Residential Complexes safe and legally compliant, QBM provide the full range of Asbestos, Fire and Building inspections, reporting and training services for Property Owners and Managers, as well Real Estate Agents.
By doing all the required services and investing in systems and our people, we can confidently give cost saving guarantees where you will save money.