Short Answer:

Corrosion of reinforcement occurs when steel bars inside concrete start rusting due to moisture, air, or chemicals reaching them through cracks or porous concrete. This rust expands, causing cracks, spalling, and weakening of the structure, which can lead to serious damage or failure.

To prevent corrosion, it is important to use good quality concrete, provide enough cover to steel, use coated bars, apply waterproofing, and maintain proper drainage and repair systems. Prevention helps in increasing the life and safety of RCC structures.

Detailed Explanation:

Corrosion of reinforcement and its prevention

Corrosion of reinforcement in RCC structures is a serious issue in civil engineering. It refers to the chemical or electrochemical reaction that damages the steel bars embedded in concrete. When steel corrodes, it forms rust, which occupies more volume than the original metal. This causes internal pressure, leading to cracks and breaking of the surrounding concrete. Over time, the load-carrying capacity of the structure reduces, and in extreme cases, it may collapse.

This problem is most commonly found in structures exposed to moisture, coastal environments, poor construction practices, or chemical attacks. Early signs include cracks, rust stains, and flaking (spalling) of concrete.

How Corrosion Occurs

• Moisture and oxygen enter through cracks or porous concrete.
• In coastal or polluted areas, chlorides and sulfates accelerate the corrosion process.
• In the presence of carbon dioxide, the protective alkaline layer around steel breaks down (called carbonation), making it prone to rust.
• Once corrosion starts, rust expands and pushes the concrete outward, leading to visible damage.

How to Prevent Corrosion of Reinforcement

1. Provide Adequate Concrete Cover

• Keep enough distance between reinforcement and surface.
• This prevents moisture or chemicals from reaching the steel.

2. Use Quality Concrete Mix

• Proper water-cement ratio and compaction lead to dense and low-permeability concrete.
• Reduces chances of water entry into concrete.

3. Apply Surface Coatings

• Use epoxy, waterproof paints, or sealants on concrete surfaces.
• These block moisture and protect against weathering.

4. Use Coated or Stainless Steel Bars

• Epoxy-coated, galvanized, or stainless steel rebars resist corrosion better.
• Suitable for coastal, industrial, or humid areas.

5. Cathodic Protection

• Electrical method that protects steel by making it the cathode in an electrochemical cell.
• Often used in bridges, marine structures, or pipelines.

6. Control Construction Quality

• Ensure proper curing, compaction, and vibration during construction.
• Avoid honeycombing and cracks.

7. Repair Cracks and Joints Timely

• Sealing cracks early avoids entry of water or chemicals.
• Grouting or crack injection methods are commonly used.

8. Use Corrosion Inhibitors

• Chemicals added to concrete mix that reduce corrosion rate of embedded steel.

Effects of Corrosion if Not Prevented

• Cracks in concrete surface
• Peeling or spalling of concrete
• Reduction in load capacity
• Safety risks and possible collapse
• Increased repair and maintenance cost

Conclusion:

Corrosion of reinforcement is a hidden danger that weakens RCC structures over time. It starts with the entry of moisture and chemicals and results in rust, cracks, and damage to concrete. Prevention through good construction practices, protective coatings, and timely maintenance ensures a longer life and safety of concrete buildings and infrastructure.