Concrete Cancer
Introduction
What is Concrete Cancer?
Concrete cancer is a structural issue that occurs when the steel reinforcing bars (rebar) inside the concrete start to corrode.
This corrosion is primarily caused by the exposure of the steel to water and air, leading to the expansion of the metal. As the steel expands, it creates cracks in the surrounding concrete, a process known as spalling. Over time, these cracks worsen, allowing more air and water to reach the steel, further accelerating the corrosion and weakening the structural integrity of the building.
Signs of Concrete Cancer
- Cracking or crumbling concrete: Visible cracks or crumbling sections.
- Rust stains: These may appear as brown or orange discoloration on the surface of the concrete.
- Outward expansion: Sections of concrete may appear to push out or expand due to the growing corrosion inside.
- Bubbling in concrete render: The surface may look uneven or "bubbly" as the rebar corrodes underneath.
- Leaks in roofs or internal walls: Water seeping through cracks caused by concrete cancer.
Common causes
- Poor waterproofing: Inadequate sealing allows moisture to penetrate and reach the steel reinforcing.
- Building defects: Flaws during construction can leave the structure vulnerable to water and air.
- Weather conditions: Particularly relevant for coastal properties exposed to salt water.
- Low-quality concrete: Poorly mixed or weak concrete is more susceptible to cracking and water infiltration.
- Ground movement: Shifts in the earth can cause cracks that expose rebar to moisture.
Prevention tips for Scout Groups
- Regular Inspections: Conduct visual checks for signs of spalling, rust stains, and leaks, particularly in buildings near the coast or areas prone to ground movement.
- Waterproofing Maintenance: Ensure that roofs, walls, and foundations are properly sealed to prevent water penetration.
- Addressing Cracks Quickly: Even minor cracks should be sealed as soon as they appear to prevent water from reaching the steel reinforcement.
Treatment options
The type of treatment needed depends on the severity and cause of the concrete cancer:
- Polymer Modified Repair System: This is a less invasive treatment and is ideal when the damage is limited, often due to carbonation (where the concrete absorbs carbonic acid from the atmosphere).
This involves removing the damaged concrete, treating the corroded steel, and applying a specialized polymer-modified material. - Electrochemical Treatment: This is more complex and may be necessary for more severe cases, such as when chloride contamination (often from salt water) is the root cause.
This process uses an electric current to stop the corrosion and restore the concrete’s integrity.
When to call in the professionals
Conclusion
Concrete cancer, if detected early, can be addressed before it causes major structural damage. Scout groups should stay vigilant, conduct regular inspections, and prioritize waterproofing and crack repair. For severe cases, professional help is essential to ensure the safety and longevity of Scout properties.
By keeping these steps in mind, Scout groups can protect their properties and minimize the risks associated with concrete cancer.
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