'Water knife' to cut road repair time, pollution

Workers prepare fast-setting concrete being used with the "water knife" cutting machine at a construction site on Tongji Elevated Road in Baoshan District yesterday. — Yang Yi

Shanghai's road construction authority is to employ innovative "water knife" technology to repair elevated highways, bridges and tunnels across the city from next year to help cut down on noise and dirt.

Water jet cutting machinery will replace traditional pile-driving machines to dig holes and remove the old surface of roads, tunnels and bridges undergoing repairs, the Shanghai Urban Construction Group said yesterday.

Using the water knife will cut the noise from more than 100 decibels to around 70, while also avoiding clouds of dust and acrid smoke, said Pan Wei, general manager of the project management department with the group.

Many of the city's elevated roads and tunnels — such as the Inner Ring Road and Yan'an Road E. Tunnel — are scheduled for major renovations next year and the water cutting technology will be employed.

Last July, the group began using the technology on Tongji Elevated Road renovation project in Baoshan District in a test operation.

Six water jet cutters were deployed to remove the original surface of the road.

Employing the technology also helped cut the schedule of the project from 280 days down to 100 days, Pan added.

A fast-setting concrete will be used along with the water jet cutting machines, which workers will lay immediately after the water knives have removed the old surface.

The concrete dries within two hours, after which vehicles can drive on the new surface.

The combination of water jet cutting technology and fast-setting concrete can reduce the impact on local traffic during road, bridge and tunnel repairs, Pan said.