Concrete has a natural tendency to crack because it's usually relatively weak in tension. When tension resulting from applied loads, restrained shrinkage, or temperature drops exceeds the strength of the concrete, a crack forms. Concrete can crack while plastic and after hardening. Cracking can be controlled during construction, however, by using quality materials, following proper construction practices, and using reinforcement and jointing.
During the summer of 1992, a group of 21 U.S. highway and pavement experts including contractors, engineers, and representatives of government and trade organizations observed the condition and construction of highways in western Europe. Called the U.S. Tour of European Concrete Highways (U.S. TECH), the group visited 5 countries and met with experts from 4 more to learn about portland-cement-concrete highway pavements in those countries.
In most building construction, concrete effectively protects reinforcement from damage caused by environmental factors or exposure to fire. In severe environments found in some industrial plants, marine structures, bridge decks and parking structures, destructive effects of reinforcement corrosion have been a problem. With proper design, mix selection, and construction practices, reinforced concrete structures can perform well in corrosive environments. Concrete cover makes an important contribution to this performance.