Define the term "Durability" and how to be considered in RC concrete design?

Durability is ability of concrete to resist weathering action, chemical attack, and abrasion.

 For RC design it defined as the capacity of the concrete elements of resistance to climatic conditions and chemical materials and sulfur salts, the fact that this salt within the favorable conditions caused the deterioration in the concrete, leading to rust of rebar, leading to the consequences of the lack of efficiency of the facilities in the achievement of the functional role and reduce the life, these negative effects must be reduced to promote sustainability, injured in strengthening the property of sustainability.