2. The 5 Main Types of Concrete Failure
1. CORROSION
2. CHEMICAL
3. FIRE
4. MECHANICAL
5. STRAY CURRENTS
3. Corrosion of reinforcement is a significant issue in concrete structures, particularly those exposed to harsh environmental
conditions.
Corrosion occurs when the protective layer in concrete steel reinforcement is destroyed
1. Mechanism:
* Initiation : carbonation or chloride ions penetrate the concrete cover, reaching the steel reinforcement .
* Electrochemical Reaction : In the presence of moisture and oxygen, an electrochemical cell forms on the steel
surface, leading to the corrosion process.
2. Influencing Corrosion:
* Chloride Exposure : Chloride ions from de-icing salts or marine environments accelerate corrosion.
* Moisture Content : Corrosion requires the presence of water to facilitate the electrochemical reactions.
4. 3. Effects of Corrosion:
* Expansion : As corrosion products (rust) form, they occupy a larger volume, exerting pressure on the surrounding
concrete and causing cracking.
* Loss of Bond : Corroded reinforcement loses its bond with the surrounding concrete, diminishing structural
integrity.
* Reduction in Cross-Sectional Area : Corroded steel loses its original strength, further compromising the
structure’s load-bearing capacity.
4. Preventive Measures:
* Concrete Cover : Adequate concrete cover thickness shields the
reinforcement from external elements.
* Corrosion Inhibitors : Chemical additives can be included in the concrete
mix to inhibit the corrosion process.
* Coatings and Sealants : Applied on the concrete surface to create a
protective barrier against moisture and aggressive substances.
* Cathodic Protection : An electrochemical method where a sacrificial
anode or impressed current system is used to counteract the corrosion
process.
5. 5. Detection and Monitoring:
* Non- Destructive Testing : Techniques like electrochemical methods, half-cell potential measurements, can assess
the condition of reinforcement.
* Visual Inspection : Regular inspections for signs of rust stains, cracking, or delamination.
6. Repair and Rehabilitation:
* Removal of Corroded Concrete : Eliminate the corroded portion and expose sound reinforcement.
* Application of Corrosion Inhibitors : As a part of the repair process to prevent further corrosion.
* Reapplication of Protective Coatings : Enhance the durability of repaired structures.
6. Although an initial chemical reaction is required to create a reliable, load-bearing concrete, other chemical
reactions such as ASR and contaminants from soil such as sulphates can weaken the cement matrix.
2. CHEMICAL
1. Chemical Mechanism:
• Acid Attack: Exposure to acids can lead to the dissolution of cement paste, weakening the concrete structure.
• Sulfate Attack: Sulfates in soil or water can react with concrete components, causing expansion and cracking
• Chloride Ion Penetration: Chloride ions can corrode reinforcing steel, compromising the structural integrity.
2. Influencing Factors:
• Exposure Conditions: Harsh environments with high acidity, sulfate content, or chloride presence accelerate
chemical deterioration
• Concrete Mix Design: The choice of materials and proportions in the mix can impact resistance to chemical
attacks
7. 3. Effects:
• Cracking: Chemical reactions can lead to cracks, reducing the strength and durability of concrete.
• Corrosion of Reinforcement: Weakened concrete allows for the corrosion of embedded steel, further compromising
structural integrity.
4. Preventive Measures:
• Proper Mix Design: Optimize concrete mix to enhance resistance to specific chemical exposures.
• Protective Coatings: Apply coatings to shield concrete from aggressive chemicals.
• Quality Construction Practices: Ensure proper curing, sealing, and drainage to minimize exposure.
5. Detection and Monitoring:
• Non-destructive Testing: Use methods like ultrasonic testing or ground-penetrating radar to assess concrete
integrity.
• Visual Inspection: Regularly inspect for surface degradation, cracks, or discoloration.
6. Repair and Rehabilitation:
• Remove Damaged Sections: Cut out and replace deteriorated areas.
• Corrosion Mitigation: Treat corroded reinforcement and apply corrosion inhibitors
• Surface Coatings: Apply protective coatings to prevent further chemical ingress.Regular maintenance, timely
repairs, and a proactive approach to addressing chemical exposure can significantly extend the lifespan of
concrete structures.
