We all know cracking is one of the major problems experienced in concrete building and it should be considered with utmost seriousness. It's important we know the sources which can cause cracking in concrete. Here is a list of sources of cracking in concrete;

1. Use of low-grade materials:
One of the major sources is the use of lower quality materials which include both concrete and steel in reinforced concrete structures.
2. Shrinkage:
Shrinkage can cause cracking if not controlled during mix design and curing stage. Shrinkage can become critical in high strength concrete because of low water/cement ratio and also because of use of Mineral Admixtures.
3. Quality and Type Of Aggregate:
The quality of aggregate used in concrete determines the overall strength of concrete. If the aggregate is of poor quality it will not make a proper bond with cement.
4. Overloading of structure:
Overloading of structure especially at younger age is a common source of cracking. This can happen if formwork is removed before time or more construction load is present.
5. Mistakes at design stage in office:
If there are errors at design stage then it is obvious that problems will occur at site. concrete cracking is one of them.
Improper Curing:
6. Another major cause of concrete cracking. If curing is not done appropriately for given time span then one should expect cracking.
7.Early Formwork Removal:
If formwork is removed before concrete has achieved strength, there will be cracking.
8.Use of Congested Reinforcement in Lean Concrete:
If you use heavy reinforcement in average quality concrete then stress distribution between steel and concrete can become non-linear causing cracking.
9. Mistakes at Site or during erection:
Proper and trained labour and workmanship are necessary for any site work. Lack of it during concreting can cause cracking.
10. Unqualified/inexperienced site Engineer:
It is often said that the building communicates with the builder. The site engineer must be qualified and experienced enough to handle the structure. Most mistakes that causes cracking on a building can easily be avoided by a good engineer.

Very good articles.

Hajji M.