Deterioration

This includes cracking, scaling, spalling and delamination. 

Cracking 

A crack is an incomplete separation of concrete into one or more parts to a variable depth, but visible at the surface. Plastic shrinkage cracks result from rapid drying of the concrete in its plastic state. Map cracking is a term describing a network of closely spaced cracks that are usually due to chemical reactions between the mineral aggregates and the cement paste. Drying shrinkage cracks result from the drying of restrained concrete after it has hardened.  Settlement of cracks can result from the settlement of the formwork as well as from settlement of the foundation. Structural cracks result from under reinforced or over stressed tension zones in the concrete.  Corrosion induced cracks are caused by corrosion of reinforcing steel within the concrete.  Much surface cracking seems primarily due to volume changes in concrete caused by poor construction practices, such as concrete that is too wet, placed too slowly, poorly finished or improperly cured. 

Scaling 

Scaling is the process of flaking away or disintegration of the surface mortar of concrete, exposing, and eventually loosening coarse aggregate. A weak surface layer of mortar may result from poor finishing and curing practice. Scaling is caused primarily by freeze-thaw action. 

Spalling 

Spalling is more serious and more common place than cracking.  The predominate cause is corrosion of reinforcing steel in the concrete. Spalling is local disintegration of a portion of the concrete surface. 

Delamination 

Delamination is a form of scaling which occurs over large areas of corroding reinforcing steel (rather than being localized over a few reinforcing steel bars) and results in a plane of separation within the concrete immediately over the plane of the reinforcing steel.