Work was suspended in November after defects were detected
Road: Resurfacing of around 4km of the Trashigang-Rangjung road stretch between Godi and Mithidrang town, which was suspended after defects were found is yet to resume.
Resurfacing is slated to restart only in February. The roads department regional office in Trashigang suspended the resurfacing work five days after it began following glaring quality defects being detected, Rangjung sub-division executive engineer Karma Tshewang explained.
The Nu 7 million (M) worth resurfacing work, which started on November 7, became an issue after the bitumen surface started disintegrating.
The premix carpet and tract coat started disintegrating soon after being laid.
While resurfacing of the road began in 2014, it is being carried out in stretches given budget availability. The resurfacing of the Trashigang to Godi stretch, above the new crematorium started in November last year.
The roads department has decided to change the required ratio of bitumen to aggregates. “We are switching to bitumen immersions 80/100 from 40/60,” Karma Tshewang said.
The quality of the bitumen works is expected to improve with the use of increased bitumen immersions. The 80/100 bitumen mix will be used without lacing it with water. The 40/60 percent bitumen immersion contains 40 percent water. It takes longer for the mix to set as the water has to evaporate.
With 80/100 bitumen immersions, damage from traffic is expected to be reduced. “But we are going to regulate the traffic since there are still chances of the premix carpet and tract coat being scoured by the tyres of moving cars,” the engineer said.
The roads department is also planning to resurface the road at night to mitigate the impact from traffic. But there are disadvantages to such a move. The engineer explained that as the temperature drops, the most suitable temperature at which the bitumen and aggregate mix can be laid and rolled is not met, which could compromise quality.
The possibility of this occurring is further increased as the mix is being ferried from Rolong, which is 17km from Trashigang.
The poor quality of work was attributed to mechanical issues specifically the wrong calibration of the hot-mix plant and not because of the contractor. “There was some problem in the ratio of bitumen and aggregates since the auto calibration was damaged, which probably led to disintegration of the blacktop since the right ratio could not be struck,” Karma Tshewang said.
Heavy traffic also added to the problem. The engineer said that the tract coat after being laid needs at least 48 hours of setting time but in this case, vehicle movement has to be allowed almost immediately as the road is a single lane.
The change in bitumen immersion will not increase costs as the contract is still in its liability period. The contractor has until May this year to complete the road.
Meanwhile, road users are increasingly frustrated with the condition of the road given loose aggregates. “I nearly went off the road last time because of aggregates which has made the road slippery,” a civil servant said. Drivers say that the road should be fixed as soon as possible to prevent an accident.
Tempa Wangdi | Trashigang