DURABILITY OF CONCRETE STRUCTURES

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INTRODUCTION
During the recent past , the problem of early deterioration of concrete structure has posed a serious problem all over the world. In India also, this problem is being witnessed in the past few years, especially in coastal and industrial area as well as in other aggressive environments


CAUSES OF DETERIORATION 
Concrete normally provides excellent corrosion protection to embedded reinforcement. The high alkalinity of concrete, i.e. above pH 12.5, results in the formation of protective oxide film on steel bars. causes for deterioration of concrete structures are,


DESIGN FOR DURABILITY OF CONCRETE STRUCTURES 
The procedure for control of deflection is to control span to effective depth ratio. It assumes that the deflection of beam and slab will depend on the following factors.
1.The span/effective depth ratio
2.Type of supports as to whether simply supported , fixed or continuous
3.Percentage of tension steel or the stress level in the steel level at service loads if more than the necessary steel is provided at the section.
4.Percentage of compression steel provided.

CRACKING 
A crack is a complete or incomplete separation of concrete into two or more parts produced by breaking or fracturing. The crack in concrete is one, which cannot be completely prevented but can only be controlled and minimized.


CONCLUSION
Durability of concrete structures should be considered as a significant aspect of structural design. A designer should be aware of the constructional aspects of structures, as well as, in order to foresee durability problems due to any peculiarities of structural loads, layout as well as environment