Cracking:
Cracking can be the result of one or a combination of factors, such as drying shrinkage, thermal contraction, restraint to shortening, subgrade settlement, and applied loads. The major factor influencing the drying-shrinkage properties of concrete is the total water content of the concrete. As the water content increases, the amount of shrinkage increases proportionally.

Steps to reduce cracking:

1. Use proper subgrade preparation, including uniform support and proper subbase material at adequate moisture content.
2. Minimize the mix water content by maximizing the size and amount of course aggregate and use low-shrinkage aggregate.
3. Use the lowest amount of mix water required for workability; do not permit overly wet consistencies.
4. Avoid calcium chloride admixtures.
5. Provide contraction joints at reasonable intervals,
6. Properly place, consolidate, finish, and cure the concrete.
7. Consider using synthetic fibers to help control plastic shrinkage cracks.
   

Concrete Links

National Ready Mixed Concrete Association

Tilt-Up Concrete Association

The Portland Cement Association

American Concrete Institute

American Society of Testing Materials

Concrete.com

Effingham Area Home Builders Association