Repair and Strengthening of Corrosion-Damaged Buildings
Introduction
Corrosion of reinforcement steel is a primary cause of deterioration in reinforced concrete structures. It occurs due to the penetration of moisture, oxygen, chlorides, and carbon dioxide into the concrete. Corrosion causes the expansion of steel, leading to cracking, spalling, reduction in bond strength, and loss of load-carrying capacity. Proper repair and strengthening are essential to restore structural safety and durability.
Background of the Case Study
A 25-year-old reinforced concrete residential building located in a coastal area showed severe signs of deterioration due to reinforcement corrosion. Continuous exposure to a marine environment and inadequate concrete cover accelerated the corrosion process.
Damage Observed
The following defects were identified during inspection:
- Longitudinal cracks along reinforcement bars
- Spalling of concrete cover
- Exposure of corroded reinforcement
- Rust stains on concrete surfaces
- Reduction in reinforcement diameter
- Leakage and dampness in slabs and beams
- Reduced load-carrying capacity of structural members
Assessment of Damage
A detailed structural assessment was carried out using:
- Visual Inspection: Mapping of cracks and spalled areas; identification of exposed reinforcement.
- Rebound Hammer Test: Assessment of surface hardness and concrete quality.
- Ultrasonic Pulse Velocity (UPV) Test: Detection of internal cracks and voids.
- Half-Cell Potential Test: Determination of the probability of reinforcement corrosion.
- Carbonation Test: Measurement of carbonation depth in concrete.
- Core Testing: Evaluation of the actual compressive strength of concrete.
Repair Measures Adopted
- Removal of Damaged Concrete: Loose and deteriorated concrete was removed using chipping hammers to expose sound concrete.
- Cleaning of Reinforcement: Corroded steel bars were cleaned by wire brushing and sandblasting to remove rust and scale.
- Application of Rust Eliminator: Chemical rust removers were applied to reinforcement bars.
- Anti-Corrosion Coating: A protective epoxy-based coating was applied to the steel reinforcement.
- Concrete Repair: Damaged portions were repaired using polymer-modified repair mortar; micro-concrete was used in heavily damaged areas.
- Crack Repair: Structural cracks were repaired by epoxy injection.
Strengthening Measures Adopted
- Reinforced Concrete Jacketing: Additional reinforcement and concrete were provided around columns and beams to increase load-carrying capacity and stiffness.
- Fibre Reinforced Polymer (FRP) Wrapping: Carbon fibre wraps were applied around columns to improve strength, ductility, and durability.
- Protective Surface Coating: Waterproof and anti-carbonation coatings were applied to concrete surfaces.
- Cathodic Protection System: Installed to prevent future corrosion of reinforcement.
Results of Rehabilitation
- Structural strength significantly improved.
- Corrosion activity was reduced.
- Cracks and leakage were eliminated.
- Service life of the building was extended.
- Safety and durability of the structure were restored.