In the first article of this series, we introduced the challenges faced by cementitious structures located in coastal areas. These structures are continuously exposed to harsh marine environments, making them vulnerable to severe deterioration. This article focuses on the impact of chloride attack on such structures and explores measures to mitigate its effects.
Impact of Chloride Attack on Concrete Structures
Chloride intrusion is one of the most severe threats to concrete structures in coastal regions. Its high aggressiveness systematically deteriorates cementitious materials by reacting with the cement content, weakening the binding properties of the matrix. This leads to heterogeneity in the concrete structure, causing decomposition-like damage to structural elements.
For structures in coastal areas, the allowable chloride content in concrete is limited to 0.03% by weight of cement. However, in actual conditions, chloride concentration can rise close to 1.0%, severely compromising the structural integrity of the matrix.
Mitigation Measures for Chloride Attack
Various strategies have proven effective in mitigating the adverse effects of chloride exposure on concrete structures. The key measures include:
1. Surface Protection with Coatings
Applying suitable coatings on the concrete surface is one of the most effective ways to prevent chloride ingress. These coatings seal the surface porosity, significantly restricting the penetration of chloride salts into the core concrete. Proper selection and application of these coatings enhance durability and reduce the rate of deterioration.
2. Maintaining Alkalinity of Core Concrete
Chloride-induced deterioration accelerates when the pH of the concrete drops below 7, whereas the natural pH of concrete is around 12. Maintaining the pH level between 10 and 12 effectively prevents chloride salts from reacting with the cement matrix.
Methods to Maintain Alkalinity:
- Injection of Polymerized Cement Slurry: This technique helps in sustaining the required pH level within the core concrete, preventing chloride-induced degradation.
- Avoiding Epoxy Injection: While epoxy injection is useful for sealing cracks, it is not effective in combating chloride attack. The polymerized cement slurry method is preferred for ensuring long-term durability.
Conclusion
Chloride attack poses a significant risk to concrete structures in coastal areas, leading to extensive deterioration if not adequately managed. The application of protective coatings and maintaining core alkalinity are among the most effective strategies to mitigate this risk. Future articles will continue exploring advanced methods for enhancing the longevity of structures in coastal environments.
About the author;
Er. Chirag K. Baxi is the Director of Prudent Forensic Consultancy Private Limited and General Manager of K K Retroflex Solutions. He specializes in Corrosion Control Measures for concrete and steel surfaces, Damage assessment with the FORENSIC ENGINEERING approach and Structural rehabilitation of concrete and steel structures in the Industrial environment. He holds a degree in BE (Civil Engineering) and has completed MBA (Construction Management).
The author has invented CONCARE B 14 (which has been granted a patent) that makes concrete structures sustainable even with salty, saline, untreated or even seawater without deterioration in any of the end properties of constructed elements. He has written (two) drafts of IS Codes on the topic of “Carbon brick lining” and “PolyPropylene Glass lining” which are under the final stage of approval at BIS.
About 40 Technical papers on National and International platforms are authored, published and presented by the author. He has been recognized by several Institutes for his significant contribution to the Civil Engineering Industry.
