Case Studies

Corrosion of Steel Reinforcement due to Aggressive Marine Environment 

One of the projects constructed at Portland. which is a highly corrosive Lone demanded special treatment to the steel reinforcement bars against corrosion. For the construction  no pit sand or river said is available and hence only sea sand from sea coast is used tor construction. 

As is known, the chloride content it the sea sand is about 4000 ppm, whereas IS:456- 1978 imposes a restriction on chlorides at 2000 ppm for plain concrete aid 1000 reinforced concrete and 500 ppm of sulphate, in the maxing water. 

The sea sand is collector and thoroughly washed with potable water in a specially constructed talk and the washed said is used for the works.  As a measure of abundant precaution against corrosive atmosphere prevailing there (from causing corrosion of reinforcement)  and also lo prevent corrosion of reinforcement by the chlorides in sand, the method developed by Central Electro Chemical Research Institute (CECRI) Karaikudi has been deployed.  This method basically involved acid pickling on reinforcement rods (for removing rust) rinsing with good copious water applying phosphate jelly immediately and 

applying  the sealing compound  as a corrosion inhibitor. The various processes involved are indicated In the flow diagram. 

Different tanks necessary for carrying out all the above three treatment have been constructed aid the treatment of rods done and used in the work. 

The precautions to be taken are: 

All the rods before treatment shall be cut aid bent to required shapes, treated and used in work without danging lo treatment done at the earliest. While handling, fixing, tying and other operations if anywhere the treatment gets affected the inhibitor is applied with brushes and then only used. 

This treatment has been followed in recent constructions like Pam ban Road Bridge Rameswaram, North Madras Thermal Scheme and other important works.

Flow Diagram