Concrete cancer, also known as specific cancer, is a serious problem that can cause extensive and costly property damage. It occurs when steel reinforcement within a concrete slab begins to rust, expand and displace the surrounding concrete, causing it to become brittle and crack. The process cycle of exposure, corrosion and further degradation allows for greater exposure, making the condition always worsen. Six common causes of concrete cancer are poor waterproofing, formation of saltwater chlorides in buildings near the sea, construction defects, weather, poor quality concrete and insufficient concrete cover, and ground movement under construction that causes cracking.
Once steel begins to rust, it expands and deforms, often breaking or blowing concrete parts off. This is known as “chipping” and increases the exposure of the steel, compounding the problem. The steel bars in concrete resist tensile forces and their cross-sectional area works hard to withstand the load it has to bear. As the steel oxidizes, its effective cross-sectional area decreases until there is not enough intact steel left to withstand the forces.
At this point, the slab (or beam, column or ladder) is weakened and risks sudden failure or collapse. Signs of concrete cancer include concrete chips, rust spots that seem to leak from inside the concrete, bubbles from concrete plaster or leaks that appear in raised concrete. If you have detected signs of concrete cancer in your building, consult a professional and get advice on the type of repair work to be done. Poor waterproofing can cause much more than concrete cancer, such as health risks from mold, allergies and fungal infections. Cracking accelerates the concrete cancer process by exposing more steel, significantly weakening the building.
While it may initially seem like an aesthetic or cosmetic concern, it is possible to correct the particular cancer in some cases. Be sure to check if they have experience treating concrete cancer and if they know you want to repair rather than replace damaged concrete if possible. Naturally, this increases the cost of concrete so consider high-quality options such as Wolfin or Cosmofin waterproofing membranes to seal new horizontal concrete surfaces. Plastering the concrete is not enough to hide the oxidized steel as the oxidation process will continue underneath. If chloride pollution is the problem in buildings near the ocean, you may need specialized repair work to treat concrete cancer. Contrary to popular belief, specific cancer is not always caused by poor craftsmanship; there are numerous reasons that contribute to it.
If reinforcing steel bars are too close to the surface they are more likely to come into contact with any moisture that causes rust. Unfortunately, this awareness of the durability of concrete and the risk of corrosion is something that the construction industry did not understand well in past decades. Watch for signs such as concrete chips, rust spots that seem to leak from inside the concrete, bubbles from concrete plaster or leaks that appear in raised concrete. For situations where concrete carbonation and low concrete coverage are the problem, engineers might recommend using a polymer-modified repair system. Consider high-quality options such as Wolfin or Cosmofin waterproofing membranes to seal new horizontal surfaces. Plastering alone is not enough to hide oxidized steel as oxidation will continue underneath. If chloride pollution is a problem in buildings near the ocean, specialized repair work may be needed to treat concrete cancer.
Be sure to check if they have experience treating it and if they know you want to repair rather than replace damaged concrete if possible.
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