Corrosion Damage In Reinforced Concrete - Damages & Causes

Damages Caused by Corrosion in Concrete Structure

The corrosion of steel can be termed as “creeping disaster” for a reinforced concrete structure. It begins with signs of weakness in the structure progresses with time causing the structure to exhibit unsightly cracks and finally causes the collapse of the structure.

Bridge Corrored ready for repalcement: Image Courtesy Phil's 1stPix/Flickr.com, CC BY-NC

The following are the damages observed in concrete structures:

1. Formation of White Patches

2. Occurrence of Cracks

3. Formation of Multiple Cracks

4. Spalling of cover concrete

5. Bulging

6. Delamination

Formation of White Patches in Concrete

The carbon dioxide reacts with Ca(OH)2 in the cement paste to form CaCO3. The free movement of water carries the unstable CaCO3 towards the surface and form white patches. This indicates the occurrence of carbonation.

Fig.2.Formation of White Patches in Concrete

Occurrence of Cracks in Concrete

The increase in the volume of corrosion products exerts considerable bursting pressure on the surrounding concrete resulting in cracks. Hairline cracks on the concrete surface directly above the reinforcement above the reinforcement and running parallel to it are a positive visible indication that the embedded reinforcement in corroding. These cracks indicate that the expanding rust grown is enough to split the concrete.

Fig.3. Crack Formed in Concrete

Formation of Multiple Cracks in Concrete

As the corrosion progresses, multiple layers of rust are formed on the reinforcement which in turn exert considerable pressure on the surrounding concrete resulting in the widening of hairline cracks. The bond between concrete and the reinforcement is considerably reduced.

Spalling of Cover Concrete in Concrete

Due to the loss in the bond between steel and concrete and the formation of multiple layers of cracking and the cover concrete starts peeling off. At this stage, the size of the bars is reduced.

Fig.4.Spalling in Concrete

Bulging in Concrete

The spalling of the cover concrete and snapping of ties causes the main bars to buckle. This results in the bulging of concrete in that region. This is followed by the collapse of the structure.

Delamination in Concrete

The delamination in concrete is the formation of layers of the reinforcement.

Fig.5. Delamination in Concrete