Concrete cancer occurs when moisture or water is mixed with metals that reinforce the concrete. Rusting is a process that happens in metals in the presence of moisture and air. When the steel reinforcing the concrete get in contact with moisture, in the presence of air, it rusts. Rust causes expansion hence the steel used in reinforcing concrete expands due to the rusting process. While this metal expands, it displaces the concrete around it, causing the concrete to become brittle. This process causes cracks in the concrete.
There are signs associated with concrete cancer, these signs indicate potential or existing concrete cancer. Concrete cracking which is technically referred to as concrete spalling signifies the existence of concrete cancer. The concrete sheet begins to remove in crumbs and fragments. This extrication can graduate into larger fragments causing an obvious defacement to structures. Concrete cancer can also be seen in concrete structures having rust stains. The rust stain leaks out from within the concrete with rusting steel.
Bubbling of concrete render is also a sign of concrete cancer. When there is a lump-like coarseness in the surface of a concrete render, it is as a result of rusted steel in the concrete. Leaks which appear in overhead concrete surface also occurs when there is brittleness in concrete as a result of steel rust. All these are signs of degradation in the concrete strengths.
There are reasons attached to concrete cancer. It is a popular belief that concrete cancer is caused by poor craftsmanship, however, contrary is the case. The following are the causes of concrete cancer:
Poorly poured concrete: Water leaks from improper sealing of concrete after being poured. This water comes in contact with steel used in reinforcing the concrete lab. The steel rusts and expands; this expansion causes cracks and displacement in surrounding concrete. There is feeling of brittleness underfoot, cracking while walking on it, signs of rust and discoloration are the signs of an early stage of concrete cancer. These signs spread and can start from deep within a slab rather than surface.
Poor waterproofing: The process of making concrete slab water resistant is called waterproofing. This control process is done in order to avoid rain, moisture and leaking into the slab causing concrete cancer and hindering the structural integrity of the building. Poor waterproofing can hence open loopholes for intrusion of moisture into the internal structure of concrete slab.
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Incompatible reinforcing steel: Electrolysis occurs when incompatible metals come in contact with electrolyte such as water. Corrosion occurs on the weaker metal when galvanic reaction from electrolysis in dissimilar metals is set off. As the corrosion progresses, expansion occurs hence concrete cancer.
Reinforcing bars too close to the surface: When reinforcing bar is close to the surface of the concrete slab, there is tendency of more intrusion of moisture. Concrete absorbs water, expands while it heats up and retract while it cools down. While at the expansion state, moisture seeps quickly to contact reinforcing bar close to surface. Rusting occurs, hence concrete cancer.
Excessive weight: Stress fractures occur when concrete bears more weight than it is designed for. When stress fractures happen, it opens path for water and moisture to flow and contact the reinforcing steel. This is an instant risk of concrete cancer.
Identifying a potential concrete cancer can be done by anyone but it is advisable to enquire for professional opinion for rectification. Immediate steps are required at the appearance of slight sign of concrete cancer.