A common defect in steel-reinforced concrete constructions, concrete cancer should be attended to immediately on detection to prevent further structural damage to the building. Prevention is, however, the best solution for concrete cancer.
How does concrete cancer occur?
Concrete buildings are reinforced with bars or mesh made of steel during the construction process. Any exposure to air and water can cause this steel to corrode, forcing it to expand, and the surrounding concrete to crack. This condition, known as spalling, impacts the strength of the building. The term ‘cancer’ is used because the cracks further expose the steel to the elements, speeding up the level of corrosion, and the deterioration of the building.
Though enveloped in concrete, steel can corrode because concrete is a porous material, constantly absorbing the elements around it. A good waterproofing job can prevent or delay concrete cancer. Buildings that have not been waterproofed, or are poorly waterproofed, are likely to suffer from concrete cancer as they do not have sufficient protection in place. Additionally, exposure to a marine environment can cause chlorides from salt water to enter the concrete and corrode the steel. Defects in construction can also leave the concrete and the supporting steel vulnerable to corrosion.
Even environmental factors, such as the natural movement of the earth underneath the building can cause natural cracks in the structure, exposing the steel to the elements, and allow water to enter the building from the ground. Weather can also be a factor, especially in colder climates, as water can freeze on the surface and then melt, allowing the water to easily enter the concrete.
Construction quality is another major cause of concrete cancer, especially in older buildings where the materials used in the concrete may not meet the relevant standards applicable today. Also, the environment and climate have changed since these older buildings were built, and the materials and concrete used then may no longer be appropriate to handle current conditions.
Signs of concrete cancer
Most structural engineers will be able to spot the visible signs of concrete cancer in a building but since they’re not always on hand, it helps to know the tell-tale signs so that experts can be consulted before it’s too late.
Typical signs of concrete cancer include cracking or crumbling concrete, rust stains seeping out from the concrete, bubbling in the concrete render, and leaks in the roof or internal walls. Often mistaken for general wear and tear, they can be signs of something much more sinister.
Prevention, the best cure
The best cure for concrete cancer is preventing the issue entirely. However, early detection and quick remedial action can arrest the condition and prevent the problem from deteriorating further.
Waterproofing is the best preventative measure to protect the building against concrete cancer. High quality Wolfin or Cosmofin waterproofing membranes are extremely resistant to tears and punctures, minimising water leakage into the structure while their exceptional elongation properties prevent any leakage condition from building movement.
Both waterproofing membranes have a long lifespan with the durability to withstand extreme weather conditions. When waterproofing is not in place, or has not been executed to high quality standards, the building will be more susceptible to concrete cancer, leading to serious structural damage.
Regular and timely maintenance
Fix any standing water issues, internal leaks and drips immediately. Water entering the building is most likely to do so through the concrete layer, and cannot be ignored. Quick remedial action will prevent further damage.
Cracks in the building’s structure must be dealt with immediately. Consult with a professional on an appropriate sealing solution that would prevent the crack from developing to such an extent that it exposes the steel to the elements.
Buildings need regular maintenance, especially to seal the concrete and prevent water damage and general wear and tear.
Builders are constantly exploring solutions that would completely prevent concrete cancer including changing internal reinforcements to a material that’s resistant to corrosion, such as bamboo. Another solution being implemented in some markets involves painting the concrete using paints specifically formulated to resist chloride. This is especially recommended for buildings near the ocean, as it will lower the risk of saltwater-related corrosion.
Fixing the issue
While prevention is the best cure, concrete cancer may show up regardless of the precautions implemented during the building’s construction.
Cost-effective remedial solutions include removing the rusted steel by chipping away the spoiled concrete and clearing out the loose material. The rusted steel is then removed and new steel welded to the undamaged old steel. New concrete is poured with extra thickness so the new steel is reinforced. The new concrete is then coated with waterproofing membranes for added protection.
Wolfin and Cosmofin waterproofing membranes are available in Australia from the Projex Group.