RAMANATHAPURAM: A recent structural audit by the National Highways Authority of India (NHAI) found severe deterioration, corrosion, and concrete damage in 12 bridges along the Nagapattinam-Ramanathapuram stretch of NH 32, prompting authorities to initiate rehabilitation works at a cost of Rs 10.57 crore.
The distressed bridges are located at Palliodaivayal, Marudangavayal, Vallikkollaikadu, Maravanvayal, Manamelkudi, Kottaipattinam, Periyamadaippaychchal, Nattanipurasakudi, Kanatangudi, A Manakudi and Chitturuvadi.
Senior official sources said structural audits conducted by a private consultancy for the NHAI’s Ramanathapuram Project Implementation Unit identified extensive deterioration of concrete and reinforcement at several locations. The inspections included non-destructive tests such as Ultrasonic Pulse Velocity, Rebound Hammer, and Half-Cell Potential tests.
The reports flagged low and doubtful ultrasonic pulse velocity readings in several bridge components, indicating internal cracks, voids, and loss of concrete integrity. Half-Cell Potential tests also indicated a high probability of reinforcement corrosion at several locations, while chemical tests detected carbonation of concrete.
Physical inspections further revealed exposed and heavily corroded reinforcement, loss of rebar cross-section due to rusting, cracked and debonded protective concrete layers, and spalling. Bearings at some bridges were also found to be corroded and seized, officials said.
Expansion joints at several locations were clogged with debris and vegetation, affecting drainage and resulting in water seepage, efflorescence and salt deposits on bridge components. Cracks and localised damage were also observed in concrete railings and other structural elements.
Based on the audit findings, the NHAI has floated a tender for the repair, rehabilitation and structural strengthening. The proposed works include removing deteriorated concrete, treating and strengthening corroded reinforcement, pressure-grouting cracks, concrete jacketing of piers and other structural components, and applying carbon fibre reinforced polymer (CFRP) to strengthen vulnerable members.
The consultants have recommended temporary structural propping before major repair works begin, particularly while removing damaged concrete from load-bearing members.
They have also recommended static deflection load testing after completion of the rehabilitation works, before the bridges are cleared for heavy traffic.