Corrosion is another issue that is bogging the civil structures of Mumbai Monorail because adequate measures required were not taken during the construction phase.
Corrosion is another issue that is bogging the civil structures of Mumbai Monorail because adequate measures required were not taken during the construction phase.
Corrosion happens to the reinforcement bars and it happens due to extreme weather conditions and pollution. "Audit observed that protective coating (anti-carbonation paint) was not done by LTSE (by November 2014) though phase I had already been commissioned from February 2014," noted the CAG report.
The MMRDA had withheld the payment for this violation but immediately released it after LTSE gave an assurance for compliance.
The CAG has found that several piles, pier caps and piers were not given anti-corrosive treatment. "The LTSE had been carrying out the work of anti-corrosive treatment to reinforcement bars without cleaning the steel by sandblasting, as provided for in the contract, till March 2011," reads the report.
But by that time 1,046 piles, 286 pier caps and 271 piers were already ready without proper anti-corrosive treatment and "the situation is irretrievable now".
Another factor that can damage the reinforcement bars inside the concrete structure is presence of chloride in soil. A soil investigation report submitted by LTSE to MMRDA in January 2011 showed a chloride content ranging between 20,050 and 89,000 parts per million (PPM) in 22 out of 31 locations between Wadala Depot and Bhakti Park – chloride level found in sea is 19,400 PPM.
"The use of concrete of reduced strength may lead to corrosion of reinforcement bars during the designed life of concrete structures in this section thus, resulting in their early deterioration," says the CAG report.
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