Concrete deficiency damaged flyover in 2018: IIT-B report

The spot that was damaged on Wednesday is located around 10-15 feet from the spot where concrete had fallen off last year.

Following damage to the Hero Honda Chowk flyover for the second time in 13 months, it has been revealed that a team of experts from the Indian Institute of Technology, Bombay (IIT-B) had blamed the “deficient strength of concrete” for the damage caused last April.

Workers repair a damaged portion of Hero Honda Chowk flyover.

The spot that was damaged on Wednesday is located around 10-15 feet from the spot where concrete had fallen off last year.

Although the expert team had concluded last year that the problem with the quality of concrete was local, it had pointed out that any defect in other parts of the flyover is difficult to detect. “Based on core tests, it may be concluded that the problem of quality of concrete is local, though such problems are difficult to identify in other parts of the bridge, if they exist, and cannot be ruled out,” wrote Ajay Goyal, a professor with the department of civil engineering, IIT-B, in a letter to the National Highways Authority of India (NHAI) project director on June 2, 2018.

“In our opinion, no immediate action is required in other parts of the bridge,” he had added.

The team of experts had found that extra water was added to the concrete mix used at the spot and this might have affected the strength of the material. “The concreting time-log of the suspect area indicates ‘extra’ waiting time of the dumper truck of the order of one- to one-and-half hours. Most probably, extra water was added to maintain the slump, and it may be the main reason for showing very low strength for samples C11, C12, C13 in the suspect patch area,” Goyal stated in the letter (a copy of which is with HT).

The committee had recommended that the concrete must be replaced with a higher-grade concrete and additional steel be added to the top and bottom for more strength. It was further mentioned that tests on other samples revealed that their strength was acceptable.

Goyal, who led the IIT-B team, declined to comment on the matter when contacted on Thursday. The NHAI is now constituting a team of experts again to look into the incident, which it has called “a matter of serious concern”.

K Madhusudan Rao, former general manager, Valecha Engineering, who oversaw the construction of the flyover, said that all the recommendations made by experts were followed in repairing the flyover. “The damage on Wednesday has also been caused in the same concrete span and is localised. The flyover has no structural fault and it was mentioned in the report. Further action would be initiated based on probe of the NHAI technical committee,” said Rao, who has since left the project.

A senior NHAI official in the Union transport ministry said that their intervention is limited at present due to the model code of conduct. “The NHAI has set up a technical committee of experts to study the matter in detail and prevent a repeat of such incidents in the future. A comprehensive check-up would be done and remedial action taken,” he said.

DD Sarode, an expert with the Institute of Chemical Technology, Mumbai, said that the pictures of the damaged surface portray a serious problem. “There is need to test the concrete strength to know the exact problem as iron bars have been exposed completely,” he said.