Ahmedabad: Back in March 2021, when the first pothole appeared on the Hatkeshwar bridge costing Rs. 39 crores, the documents show a meeting involving the consultant, contractor, and civic body engineers for the flyover. They had opined a set of non-destructive tests (NDT) to be performed on the flyover to comprehend the quality of concrete and whether the flyover was a danger to public safety. The march was resisted by the civic body's engineering department for over one and half years till reams of concrete began to fall off in three separate instances recorded in 2022 - in February, June, and August.
NDT tests are conducted for evaluating compressive strength, estimating the concrete quality concerning standard requirements, detecting the presence of voids, cracks, and other imperfections, and identifying areas of the flyover with lower integrity than other parts.
The contractor, Ajay Engineering Infra Pvt Ltd, began the flyover construction work in 2015 and was open to the public in 2017. Initially, in May 2021, after two months when the first pothole had appeared, a private lab CIMEC executed a standard NDT test called the hammer rebound test. The test revealed that the concrete quality was four times less than the standard meant for M45 concrete. However, only after five potholes were sighted in 2022; did the state roads and buildings department demand a comprehensive set of NDT in September 2022.
These tests included the ultrasonic pulse velocity tester, rebound hammer, pull-off, pull-out and break-off, core-drilling, and permeability tests. "Recently, after four private consultants submitted their reports on the concrete compression strength, IIT Roorkee too had been approached to conduct tests on the flyover," reveals a senior AMC official.
Even after the private consultants advised that another set of NDT tests would be performed, the opinion was resisted again in 2022. The private labs engaged by the AMC, which included CIMEC, e-cube, KCT, and SVNIT-Surat, had referred that the web, top and bottom slabs of the pre-stressed concrete (PSC) box of the 45-meter span did not have enough concrete strength. Instead of an M45 grade, the PSC had quality as low as M10 to M15. The repairs which had begun were stopped.
