Is Ahmedabad's Mumatpura bridge safe with a new deck?

AHMEDABAD: Fifteen months after a deck on the Mumatpura flyover collapsed, the engineers placed a new deck on Sunday.
But Ahmedabad Urban Development Authority (Auda) is yet to certify whether flyover itself is safe for commuters or not.
After the flyover deck collapsed in December 2021, samples were collected for quality checks by the high-powered committee (HPC), only for the collapsed portion of the flyover and not the whole.
The results for the collapsed portion clearly indicated "poor quality concrete" as the cause. "It is true. A detailed non-destructive testing (NDT) of the entire flyover, to check its quality, is yet to be carried out," admitted a senior Auda official.
A detailed quality check involves the rebound hammer test to ascertain the compressive strength of the concrete; a cover meter test to determine the concrete cover required; checking moisture content and depth of carbonation; and chloride and half-cell tests to monitor corrosion. These tests ascertain whether a flyover meets the Bureau of Indian Standards (BIS) norms or not.
The HPC, led by GAD secretary Rakesh Shankar, had clearly observed that in case of the collapsed portion of the Mumatpura flyover, seven of the 11 concrete samples tested did not meet the BIS norms.
"Failure of even one concrete core sample is disastrous to the overall strength of the girder and samples 2399 and 2402 from the crash site had failed the tests. Besides, the collapse of the flyover was due to cumulative effects of poor concrete, negligence in quality assurance, quality control and workmanship," the HPC report had observed.
The report later said, "In sensitive public works, highly standardized concrete quality is put to use. But this standardization was missing in Mumatpura flyover samples." In January last year, Auda had written to the state government to carry out independent load-bearing tests for all 113 girder boxes.
In case of the Hatkeshwar flyover, the Ahmedabad Municipal Corporation (AMC) had employed five labs including IIT Roorkee, which had tested compressive strength for the entire flyover before it was closed for traffic eight months ago.
The work order for the Mumatpura flyover was issued by Auda to Ranjit Buildcon at a cost of Rs 78.47 crore.
The construction, which began on March 5, 2019, was to be completed by September 4, 2021. The HPC submitted its first report on the deck collapse on March 8, 2022.