An occurrence of the cracks is often a subject that raises numerous questions. Cracks may appear in structures, either at the initial stage or with time and it should be accepted that some types of cracking are unavoidable in the house.
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Cracks may be big or small, structural or non-structural, or in various shapes, various width, & various patterns.
All of them can be a nuisance by way of either damage to the structure in appearance or in function as a passage for atmospheric polluting gases and moisture to the body of concrete causing distress.
Types of Cracking and Appearance of Cracks at Various Ages:
As cracking in concrete is inherent, what really matters is the type of structure and the nature of cracking.
The table below represents the types of cracking in general:
01. Plastic Shrinkage Cracks:
- Plastic Shrinkage Cracks appear in first few minutes or hours after concreting.
- Plastic shrinkage cracking occurs when fresh concrete is subjected to a very rapid loss of moisture. It is caused by a combination of factors such as air and concrete temperature, relative humidity, and wind velocity at the surface of the concrete. These factors can cause high rates of evaporation in either hot or cold weather.
02. Plastic Settlement Cracks:
- Plastic Settlement Cracks appear in first few minutes or hours after concreting.
- Plastic settlement cracks appear in freshly laid/placed cement concrete in reinforced structure, sometimes they also occur on the surface before the concrete has set, when there is the relatively high amount of bleeding & there is some form of obstruction (i.e. reinforcement bars) to the downward sedimentation of the solids.
03. Cracks due to Corrosion:
- Corrosion cracks usually appear after one year or even after many years.
- Corrosion cracks appear along the line of reinforcement and expand with time.
- It is mostly manifested by discolouration of paint or stains of rust.
04. Cracks due to Loads:
- After loads are imposed and during the first time duration of loading.
05. Cracks due to Dead Weights:
- Just after formwork supports are removed.
- If Section has the inadequate size or reinforcement bars that cannot carry own dead weight then this type of crack appears.
06. Cracks due to chemical changes in Hardened Concrete:
- After one or even after many years depending on the chemical attack from outside (sulphate) or chemical reaction from within (ASR).
Together above all,
Types of Cracks
|01.||Plastic Shrinkage||First few minutes or hours after concreting|
|02.||Plastic Settlement||First few minutes or hours after concreting|
|03.||Cracks due to corrosion||After one year or even after many years|
|04.||Cracks due to loads||After loads are imposed and during first time duration of loading|
|05.||Cracks due to dead weights||Just after formwork supports are removed|
|06.||Cracks due to chemical changes in hardened concrete||After one or even after many years depending on the chemical attack from outside (sulphate) or chemical reaction from within (ASR)|