Corrosion of Rebars, Types, Methods, Process, Evaluation and conclusion is presented in this Powerpoint Presentation

1. Rishabh Lala
Dual Degree
RGPV, Bhopal
CORROSION OF RE-BARS

2. INTRODUCTION
CORROSION PROCESS
CORROSION EVALUATION
TYPES OF CORROSION
PROTECTION METHODS
CONCLUSION
OUTLINE

3. Serious problem called rust – Bridges of steel
22.6$ Billions – average cost in 2009 – US
Corrosion in India – Railways, Dilapidated
Buildings
Reduces the strength of material
CORROSION A SERIOUS PROBLEM

5.  CHLORIDE INDUCED
REINFORCEMENT CORROSION
IN CONCRETE EXPOSED TO
SEAWATER
Corroded rebar from cracked concrete of a
parking structure exposed to de-icing salts

6.  ASTM terminology (G 15) defines corrosion as “The chemical
or electrochemical reaction between a material, usually a
metal, and its environment that produces a deterioration of
the material and its properties.”
 For steel embedded in concrete, corrosion results in the
formation of rust which has two to four times the volume of
the original steel and none of the good mechanical properties.
Corrosion also produces pits or holes in the surface of
reinforcing steel, reducing strength capacity as a result of the
reduced cross-sectional area.
DEFINITION

7. VOLUME CHANGE
VOLUME

8. Yes if:
 (a) For dry Concrete – no H2O to form rust. Also aggressive
agents cannot easily diffuse into dry concrete.
 (b) Avoiding Oxygen Contact – Sufficient Cover
 (d) A Polymeric Coating is applied to the concrete member to
keep out aggressive agents. These are expensive and not
easy to apply and maintain.
CAN CORROSION BE AVOIDED ?

9.  (e) A polymeric coating is applied to the reinforcing bars to
protect them from moisture and aggressive agents. This is
expensive and there is some debate as to its long- term
effectiveness.
 (f) Stainless steel is used in lieu of conventional bars. This is
much more expensive than conventional bars.
CAN CORROSION BE AVOIDED ?

10.  No, Not entirely !
 Concrete is not usually under water or continuously dry.
Aggressive agents such as carbon dioxide, de-icing agents
and/or sea water can diffuse into the best of moist concrete,
and corrosion will eventually result.
CAN WE AVOID CORROSION?

11.  Depth of carbonation can be detected using
an indicator.
 A chemical such as Phenolphthalein sprayed
on to freshly broken concrete.
 Areas remaining alkaline will turn in a bright
purply-pink color.
 Carbonated areas of concrete will remain
unchanged in color.
DETECTING CARBONATION

12.  Best method to detect corrosion of rebars
 Measuring the potential of embedded bars relative to
reference of the potential half cell placed on the
concrete surface
 Concrete functions as the electrolyte
 Corrosion is calibrated to the measured potential
difference
HALF POTENTIAL CELL

13. CORROSION EFFECTS

14. Abandoned Electric Pole
(Shyamla Hills)

15. REBAR COATING
FLY ASH
HOT-DIP GALVANIZING
SENSORS FOR MONITORING CORROSION
EFFECTIVE COVER
PREVENTION OF CORROSION

16.  CORROSION IS UNDESIRABLE FOR THE DURABILITY OF THE
STRUCTURE
 CAUSES INCLUDE MOISTURE + CO2 FROM ATMOSPHERE,
CHLORINATION AND CARBONATION
 MEASURES SHOULD BE TAKEN TO PREVENT CORROSION AT
RIGHT TIME
KEY TAKE-WAYS