03-01-2013, 04:44 PM
DURABILITY OF CONCRETE STRUCTURES
1DURABILITY OF CONCRETE.ppt (Size: 1.41 MB / Downloads: 304)
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.
WHAT IS DURABLE CONCRETE ?
Durable concrete can be defined as one that is designed, constructed and maintained to perform satisfactorily in the expected environment for the specified designed life.
BEHAVIOUR OF CONCRETE
The behaviour of concrete depends on several processes.
Physical
Chemical
Biological
1.Physical process
Physical processes lead to gradual deterioration of concrete, and govern its long-term behaviour.
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 limit state of deflection
Excessive deflection of beams and slab is not only an eyesore in itself but it can also cause cracking of portion.As given in IS 456(2000) the commonly accepted limits of allowable deflection are,
1 A final deflection of span/250 for the deflection of horizontal bending members like slabs and beam due to all load so as to be noticed by the eye.
2 A deflection of span/350 or 20mm which is less for these members after the construction of the partitions and finishes etc,to prevent damages to finishes and partitions.
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.