Concrete Damage

Damage on concrete structure after construction may happen during the construction or building operational process. Damage happened during the construction will trigger damage on the operation process. The damage may be caused by:
1. Planning error
2. Implementation error
3. Inappropriate use
4. External causes, such as earthquake, fire, landslide, tsunami, etc.

Types of concrete damage are cracks, voids, spalling, scaling, erosion, drumminess, chemical causes (sulphate penetrations, salt, chloride acid, etc) and physical causes (volume change due to concrete fluctuation, difference of settlement, temperature change, fire, overloading, earthquake, cyclical load, fatigue, etc).

Crack is a damage commonly found within concrete structure, where there is a separation between long and narrow concrete masses. Fracture on concrete structure is happened before or after ossification (plastic condition). Crack may also happened in the early stage, when concrete not ossified yet, concrete mortar still in plastic condition and cannot hold maximum load. Kind of cracks like this is caused by solidification due to cold weather (in the region with cold weather), shrinkage, and settlement.

Shrinkage crack is happened due to uneven concrete shrinkage among its parts. It is commonly found in floor plate. There is mass movement within concrete of plastic condition, water with lighter masses will move upwards. Water will be trapped on the lower surface of aggregate or big-sized frame, yielding water bags. After concrete ossified and water slowly evaporated, water bags become empty or vacant. If it receives load, this part will potentially create early fracture.

Complex crack will be created after concrete solidified, which is caused by physical reason, chemical, thermal, or overloading. Crack created after construction on the element of beam structure is usually termed with structural fracture. Wide, length, location and orientation of the crack can indicate its type and causes, thus it can be quickly and appropriately anticipated.

Voids are deep holes or hollows that usually caused by:

1. Condensation during improper implementation thus mortar cannot fill hollows among aggregates.

2. Frame concrete that extremely dense.

3. Leakages on begisting which make water or cement pasta come out.

4. Water excess in the mixture.

5. Improper gradation of the mixture.

Kind of voids are honey combing, sand streaking, bugholes, and form scabbing.

Spalling is extrication of concrete surface in form of small fragments or chunks. This kind of damage is caused by frame corrosion, overloading, fire, etc. when there is corrosion on frame concrete, its volume will be doubled and triggers tension on concrete around the frame. If this tension exceeds concrete capacity surround it, then it will cause fracture followed by spalling. In the condition of fire, spalling is caused by expansion difference between aggregate and mortar that working in contradictive manner. Scalling is exfoliation of some parts of concrete surface due to solidification and liquefaction, which happened in cold area..

Erosion is extrication of small / soft grain from concrete surface due to abrasion; if the process is dry then it is called dusting. Abrasion happened due to wave is called water erosion.

Drumminess is a term used for concrete with low quality. It is called drumminess because when part of concrete surface is bumped into a hammer, it yields a high-pitched sound like a drum. Drumminess can be caused by corrosion on concrete frame, improper patching (material used for patching cannot properly patched on the concrete).

Source: Types and Causes of Damage on Concrete Structure (Andreas Triwiyono), irc.nrc-cnrc.gc.ca/pubs/ctus/8_e.html, www.phys.tue.nl/nfcmr/damage-crys.html, www.wsdot.wa.gov/Projects/US2/Eb...otos.htm, www.concrete.org/Troubleshooting,