Many roads in the city have bumps and undulations even after repairs, mayor Firhad Hakim acknowledged on Saturday morning, about 12 hours after he inspected the condition of roads in the city ahead of Durga Puja.
Hakim promised The Telegraph over the phone that the civic body would take up repairs in winter that would flatten the roads.
“There are bumps on the roads and that is why we will repair the roads with mastic asphalt in winter. The layer of mastic asphalt makes roads more durable,” he said.
Mastic asphalt is a bituminous mixture that has more bitumen content than other mixtures. The mastic asphalt mix is poured over a road to create a fresh top layer.
Engineers said the top mastic asphalt layer was impervious, which prevented water from seeping down to the underlying layers and thus arrested the damage to the road.
“We have not been able to use mastic asphalt after an order by the National Green Tribunal (NGT) a few years ago. This time we will procure the materials for repairs from a plant and bring it to the repair site for the work,” he said.
Engineers of the Kolkata Municipal Corporation (KMC) said that the use of mastic asphalt to repair roads stopped after the NGT imposed a ban on the practice of on-site heating of the bituminous mix — also called hot mix — because of the immense air pollution it caused. The order said the mixture has to be prepared outside city limits, said an engineer.
The KMC lacked the technology to prepare the material elsewhere and then bring it to a road and pour the mixture over the road. But it will now adopt this method to undertake repairs.
However, external experts said that merely pouring mastic asphalt as the top layer will not improve the condition of roads.
If required, the damage in underlying layers has to be fixed.
Many of Kolkata’s roads remained battered and broken through monsoon and the KMC took up repairs with the aim of covering the potholes before Puja.
A layer of bitumen was hastily poured over the potholes to cover them and the new layer rose above the surrounding road surface. The hasty repairs have thus created more undulations.
Hakim inspected roads across the city on Saturday night. His visit was limited to arterial roads only. He went through CR Avenue, APC Road, Sealdah, Ballygunge Circular Road, Southern Avenue and Diamond Harbour Road, among others. All the roads had bumps caused by patch repairs over the years.
He broached the point of using mastic asphalt on Sunday after being told that the roads have multiple bumps and undulations.
Partha Pratim Biswas, a professor of construction engineering at Jadavpur University, agreed that mastic asphalt was a more durable top layer, but added that the KMC should look into why a road was damaged and do repairs accordingly.
“Pouring an overlaying mastic asphalt layer on in-service roads is a practice that has paid good results. But the existing top layer has to be removed (scarped off) if the bumps and undulations have to go,” he said.
“The condition of a road can also worsen if there is damage to underlying layers of a road. If that is the reason why potholes and craters formed, then merely pouring a new top layer will not give a long-term solution,” Biswas added.