Case 2

Introduction

Type of Building: Public Residential Flats

Deteriorated concrete is not just unsightly—it can compromise structural integrity. A spall is a section of concrete that is breaking away or has broken away from the original structure. Usually corrosion of reinforcement would present symptoms of cracks initially.

In this case, spalling of concrete has taken place due to the corrosion of reinforcement bars as a result of insufficient concrete cover.

Concrete cover refers to the thickness of concrete covering the reinforcement (such as steel bars or mesh) within a concrete structure. It plays a crucial role in ensuring the durability, strength, and corrosion resistance of reinforced concrete elements.

The lack of concrete cover (less than 5mm in many locations) in this case give little corrosion protection to the reinforcement as aggressive agents (e.g. CO₂ and Cl^–) can reach the level of reinforcement easily. Concrete cover (both quantity and quality) are essential to serve the following purposes:

Corrosion Protection: Concrete cover shields the reinforcement from environmental factors such as moisture, chloride ions (from saltwater or de-icing salts), and carbonation, which can lead to corrosion of the steel.

Fire Resistance: Adequate concrete cover provides a layer of protection against fire, preventing rapid heating and potential failure of the reinforcement.

Strength and Durability: Proper concrete cover helps maintain the structural integrity and durability of concrete elements by preventing premature deterioration of the reinforcement.